Anatomy_Gray

Anatomy_Gray. Surgery was planned. A small transverse incision was made below the level of the inguinal ligament where the great saphenous vein passes through the saphenous ring in the deep fascia. This can be easily palpated as a small circular defect in the fascia. The saphenofemoral junction was identified and the great saphenous vein was ligated, at its anastomosis with the femoral vein. The great saphenous vein was stripped using special surgical techniques and removed. The patient was placed prone for the second part of the operation. A small incision was made transversely at the level of the skin crease in the popliteal fossa. However, the surgeon had difficulty identifying the junction between the small saphenous vein and the popliteal vein. After considerable time the surgeon located what he thought was the small saphenous vein and the structure was ligated and the wound closed.


Anatomy_Gray

Anatomy_Gray. The following day the patient was sent home, but returned to the clinic after 2 weeks complaining of problems walking. On examination there was absence of dorsiflexion, a sensory disturbance over the lateral aspect of the leg and foot, and obvious wasting of the fibular muscles. As the patient walked, the foot was dragged between steps. A clinical diagnosis of footdrop was made and a common fibular nerve injury was diagnosed. The injury occurred at the time of surgery.


Anatomy_Gray

Anatomy_Gray. Within the popliteal fossa are the popliteal artery, popliteal vein, and sciatic nerve (and its divisions). The popliteal artery is the deepest structure. The popliteal vein is superficial to the artery and the sciatic nerve is superficial to the vein (eFig. 6.142). Importantly, the sciatic nerve divides at the apex of the popliteal fossa. The tibial nerve continues into the lower popliteal fossa. The common fibular nerve passes laterally adjacent to the biceps femoris muscle to become superficial and wrap around the fibula neck. It was concluded that the surgeon had accidentally ligated the common fibular nerve rather than the small saphenous vein, thus producing this patient’s symptoms. A 72-year-old woman was admitted to the emergency room after falling at home. She complained of a severe pain in her right hip and had noticeable bruising on the right side of the face. On admission it was noted that the patient’s right leg was shorter than her left leg and externally rotated.


Anatomy_Gray

Anatomy_Gray. On admission it was noted that the patient’s right leg was shorter than her left leg and externally rotated. An initial series of investigations was carried out, including a plain radiograph of the pelvis. The plain radiograph of the pelvis demonstrated a displaced fracture through the right neck of the femur.


Anatomy_Gray

Anatomy_Gray. The plain radiograph of the pelvis demonstrated a displaced fracture through the right neck of the femur. The apparent shortening and external rotation of the leg on clinical examination were accounted for by spasm of the muscles connecting the pelvis to the trochanters and proximal femur. Of the muscles that surround the hip joint the largest group is the adductor group (adductor longus, brevis, and magnus) and the psoas major. The psoas major inserts onto the lesser trochanter and its action is to externally rotate and flex the hip. The fulcrum of action of the psoas major is the femoral head in the acetabulum. However, when the femoral neck is detached its overriding action pulls the femur proximally and into external rotation. The external rotation is exacerbated by the spasm in the adductor muscles. Extensive medical testing was necessary before surgery. It is important to remember that elderly patients may have a number of coexisting diseases.


Anatomy_Gray

Anatomy_Gray. Extensive medical testing was necessary before surgery. It is important to remember that elderly patients may have a number of coexisting diseases. The patient then underwent a hemiarthroplasty. Hemiarthroplasty is a surgical procedure in which the femoral head is removed from the acetabulum. The femoral neck is trimmed close to the trochanters and the medullary cavity of the femoral shaft is reamed. A metal hip prosthesis is inserted into the medullary cavity of the femur and the head of the prosthesis is placed into the acetabulum, in which it articulates. Importantly, the acetabulum is not replaced in straightforward cases, though a prosthetic acetabulum may be inserted if clinically appropriate. An arthroplasty was the only procedure that could be performed.


Anatomy_Gray

Anatomy_Gray. An arthroplasty was the only procedure that could be performed. The blood supply to the femoral head is from three sources—the artery within the ligament of the head of the femur, vessels in the medullary cavity, and vessels deep to the synovium running in the retinacula of the fibrous capsule of the hip joint. With increasing age, the medullary cavity undergoes fatty replacement of the normal red marrow, thus attenuating the medullary blood supply. The artery within the ligament of the head of the femur also becomes attenuated and this is often associated with atherosclerotic arterial disease.


Anatomy_Gray

Anatomy_Gray. Unfortunately for this patient, the sole blood supply to the head of the femur was via the vessels in the retinacula fibers, which were transected at the time of the fracture. If the patient had an intertrochanteric fracture instead, the vessels of the retinacula fibers would not have been damaged and a different approach to surgical fixation could be undertaken without the need for a hemiarthroplasty. The patient has osteoporosis. Osteoporosis is a common condition affecting older people, but is significantly more frequent in postmenopausal women. Many fractures of the femoral neck in elderly patients occur because the strength of the bone is significantly reduced when it is osteoporotic. Other common sites for osteoporotic fractures include the distal radius and the thoracic and lumbar vertebrae.


Anatomy_Gray

Anatomy_Gray. A 28-year-old woman was seen by her family practitioner for a routine pregnancy checkup at 36 weeks’ gestational age. Neither the patient nor the family physician had any concerns about the pregnancy. However, the patient did complain of unilateral swelling of her left leg, which had gradually increased over the previous 2 days. Furthermore, the evening before her visit she developed some sharp chest pain, which was exacerbated by deep breaths. The family physician ordered a duplex ultrasound scan of the left leg venous system. Ultrasound scanning of the vascular tree can demonstrate flow and occlusion of arteries and veins.


Anatomy_Gray

Anatomy_Gray. The family physician ordered a duplex ultrasound scan of the left leg venous system. Ultrasound scanning of the vascular tree can demonstrate flow and occlusion of arteries and veins. The probe was placed over the left femoral vein and no flow was demonstrated. Furthermore, the vein could not be compressed, and no alteration of flow with breathing could be demonstrated. Some flow was demonstrated in the deep femoral vein and in the great saphenous vein. No flow was demonstrated throughout the length of the left femoral vein, the popliteal vein, and the tibial veins. The technician scanned the opposite side, where excellent flow was demonstrated within the right femoral venous system. In addition, when the calf was gently massaged an augmentation to the flow was noted. It was possible to demonstrate alteration of flow with respiratory excursion and venous compression was satisfactory. A diagnosis of extensive left-sided deep vein thrombosis was made.


Anatomy_Gray

Anatomy_Gray. Certain patients are more prone to deep vein thrombosis. Three major factors predispose a patient to thrombosis: reduced or stagnant blood flow in the veins—significant stasis of blood (which may be due to lack of movement), reduced muscular calf pump effect, and obstruction to flow may occur; injury to the vein wall—venous trauma may damage the vessel walls, promoting thrombus formation; hypercoagulability of the blood—hypercoagulable states are often associated with abnormal levels of certain clotting factors, such as antithrombin III, protein C, and protein S. In this patient, compression of the left external iliac veins by the gravid uterus was the likely cause of stasis, which led to the deep vein thrombosis. The chest pain was due to pulmonary emboli.


Anatomy_Gray

Anatomy_Gray. In this patient, compression of the left external iliac veins by the gravid uterus was the likely cause of stasis, which led to the deep vein thrombosis. The chest pain was due to pulmonary emboli. Small emboli were thrown off from the leading edge of the thrombus through the heart to lodge in the lungs. Small emboli cause typical pleuritic chest pain, which is exacerbated by breathing. In isolation these small pulmonary emboli may affect respiratory function, but they may be the precursor to a large and potentially fatal pulmonary embolus (eFig. 6.143). Anticoagulation was instituted and the patient had an uneventful delivery. A 45-year-old man had recently taken up squash. During a game he attempted a forehand shot and noticed severe sudden pain in his heel. He thought his opponent had hit him with his racket. When he turned, though, he realized his opponent was too far away to have hit him.


Anatomy_Gray

Anatomy_Gray. Within minutes there was marked swelling of the ankle. The patient was unable to plantarflex his foot and had to stop the game. Afterward an appreciable subcutaneous hematoma developed in the ankle. The diagnostic possibilities include a bone or soft tissue injury. A bony injury was excluded because there was no bone tenderness. The patient had a significant soft tissue injury. On examination he had significant swelling of the ankle with a subcutaneous hematoma. He was unable to stand on tiptoe on the right leg, and in the prone position a palpable defect was demonstrated within the calcaneal tendon. A diagnosis of calcaneal tendon rupture was made. This patient has a typical history of ruptured calcaneal tendon and the clinical findings support this. Magnetic resonance imaging was carried out and confirmed the diagnosis (eFig. 6.144). The patient underwent an operative repair. The tendon healed well, though the patient has not gone back to playing squash.


Anatomy_Gray

Anatomy_Gray. The patient underwent an operative repair. The tendon healed well, though the patient has not gone back to playing squash. A 67-year-old man was noted to have a mass at the back of his knee. The mass measured approximately 4 cm in transverse diameter. The patient was otherwise fit and well and had no other history of note. The mass was arising from one of the structures in the popliteal fossa. Within the popliteal fossa there is a neurovascular bundle that contains the sciatic nerve (and its two divisions), the popliteal artery and the popliteal vein. There are also numerous small bursae associated with the posterior aspect of the knee joint and the muscles and tendons in this region. It is possible that this mass is arising from the posterior structures of the knee joint, which include synovial outpouchings, the menisci, and the muscles and tendons of this region.


Anatomy_Gray

Anatomy_Gray. The commonest masses demonstrated within the popliteal fossa are a popliteal cyst, a popliteal aneurysm, and an arterial adventitial cyst. Further clinical examination revealed that this mass was pulsatile and demonstrated a bruit (an audible rumbling made by turbulent blood flow) on auscultation. A diagnosis of popliteal artery aneurysm was made. A popliteal artery aneurysm is an abnormal dilation of the popliteal artery. It is unusual for it to be greater than 5 cm because symptoms usually develop before it reaches this size. Unlike aneurysms elsewhere in the body, the natural history of popliteal aneurysms is to embolize, with the mural thrombus producing ischemia distal to the lesion, rather than rupture. It is mandatory to examine the rest of the arterial tree in patients with a popliteal aneurysm because aneurysms may be bilateral and there is an association with abdominal aortic aneurysms.


Anatomy_Gray

Anatomy_Gray. The other diagnostic possibilities include a popliteal cyst and an adventitial cyst. A popliteal cyst (Baker’s cyst) is a synovial outpouching that arises from the posteromedial aspect of the knee joint. The synovial membrane of the knee joint outpouches between the medial head of the gastrocnemius and the semimembranosus tendon to lie medially within the popliteal fossa. Occasionally it tracks inferiorly to lie in and around the tendons that form the pes anserinus (sartorius, gracilis, and semitendinosus). An arterial adventitial cyst is an uncommon cystic structure that arises from the wall of the artery. An ultrasound investigation was carried out. Using real-time ultrasound the dimensions of the popliteal aneurysm were characterized and the flow in the vessels was demonstrated. Furthermore, a popliteal cyst and adventitial cyst were completely excluded. The patient underwent a surgical excision and graft interposition and has made an uneventful recovery.


Anatomy_Gray

Anatomy_Gray. The patient underwent a surgical excision and graft interposition and has made an uneventful recovery. A young long-distance runner came to her physician with acute swelling around the lateral aspect of her ankle. This injury occurred directly after accidentally running into a pothole in the pavement. A fractured ankle was suspected. Plain anteroposterior and lateral radiographs of the ankle revealed no evidence of any bone injury to account for the patient’s soft tissue swelling. The patient was given a pair of crutches and analgesics and told to rest. A diagnosis of a simple sprain was made. Over the ensuing weeks the swelling and edema within the soft tissue of the ankle decreased and the patient began to run, but noted that the ankle kept “giving way.” She went to an orthopedic surgeon for further assessment. There was a positive anterior drawer test of the ankle joint.


Anatomy_Gray

Anatomy_Gray. There was a positive anterior drawer test of the ankle joint. At this stage it is important to review the mechanism of injury. Typically when running on a hard surface the final phase of push-off involves supination of the foot. If the foot is caught in a pothole or divot, this supinating maneuver continues and inverts the ankle joint in plantarflexion. This puts significant strain on the lateral ligament complex and, given the appropriate circumstances, disruption (in order) of the ligament structures occurs from anterior to posterior. First, the anterior talofibular ligament is disrupted, followed by the calcaneofibular ligament, and then the posterior talofibular ligament. As each of these ligaments is disrupted, the severity of the soft tissue injury is significantly enhanced and the chance of permanent ankle instability is increased.


Anatomy_Gray

Anatomy_Gray. On examination any positive anterior drawer test of the ankle (4–5 mm compared to the opposite side) suggests an injury to the anterior talofibular ligament. The anterior talofibular ligament can be assessed by placing the foot in marked plantarflexion. If there is over 10° of difference between the affected foot and nonaffected foot, an anterior talofibular ligament disruption is suspected. It is extremely rare for all three ligaments to be disrupted, and if so there are usually other significant ankle injuries. Magnetic resonance imaging (MRI) was carried out to assess ligament damage. MRI is excellent for demonstrating the medial and lateral ligament complexes of the ankle as well as the soft tissues that support the bones of the posterior foot. Unfortunately for this patient there was a tear of the anterior talofibular ligament (eFig. 6.145), which had to be repaired surgically. 670.e2 670.e1 In the clinic—cont’d


Anatomy_Gray

Anatomy_Gray. Unfortunately for this patient there was a tear of the anterior talofibular ligament (eFig. 6.145), which had to be repaired surgically. 670.e2 670.e1 In the clinic—cont’d Table 6.1 Branches of the lumbosacral plexus associated with the lower limb—cont’d Regional Anatomy • Deep Fascia and the Saphenous Opening Fig. 6.73, cont’d Surface Anatomy • Avoiding the Sciatic Nerve Surface Anatomy • Identifying Structures Around the Knee Surface Anatomy • Finding the Tarsal Tunnel—the Gateway to the Foot Surface Anatomy • Approximating the Position of the Plantar Arterial Arch Anterior compartment of the forearm 766 Posterior compartment of the forearm 775 Carpal tunnel and structures at the wrist 788 Bony landmarks and muscles of the posterior scapular region 810 Visualizing the axilla and locating contents and related structures 811 Locating the brachial artery in the arm 812 The triceps brachii tendon and position of the radial nerve 813


Anatomy_Gray

Anatomy_Gray. Visualizing the axilla and locating contents and related structures 811 Locating the brachial artery in the arm 812 The triceps brachii tendon and position of the radial nerve 813 Identifying tendons and locating major vessels and nerves in the distal forearm 815 Normal appearance of the hand 816 Position of the flexor retinaculum and the recurrent branch of the median nerve 817 Motor function of the median and ulnar nerves in the hand 817 Visualizing the positions of the superficial and deep palmar arches 818 The upper limb is associated with the lateral aspect of the lower portion of the neck and with the thoracic wall. It is suspended from the trunk by muscles and a small skeletal articulation between the clavicle and the sternum—the sternoclavicular joint. Based on the position of its major joints and component bones, the upper limb is divided into shoulder, arm, forearm, and hand (Fig. 7.1A).


Anatomy_Gray

Anatomy_Gray. The shoulder is the area of upper limb attachment to the trunk (Fig. 7.1B). The arm is the part of the upper limb between the shoulder and the elbow joint; the forearm is between the elbow joint and the wrist joint; and the hand is distal to the wrist joint. The axilla, cubital fossa, and carpal tunnel are significant areas of transition between the different parts of the limb (Fig. 7.2). Important structures pass through, or are related to, each of these areas. The axilla is an irregularly shaped pyramidal area formed by muscles and bones of the shoulder and the lateral surface of the thoracic wall. The apex or inlet opens directly into the lower portion of the neck. The skin of the armpit forms the floor. All major structures that pass between the neck and arm pass through the axilla.


Anatomy_Gray

Anatomy_Gray. The cubital fossa is a triangularly shaped depression formed by muscles anterior to the elbow joint. The major artery, the brachial artery, passing from the arm to the forearm passes through this fossa, as does one of the major nerves of the upper limb, the median nerve. The carpal tunnel is the gateway to the palm of the hand. Its posterior, lateral, and medial walls form an arch, which is made up of small carpal bones in the proximal region of the hand. A thick band of connective tissue, the flexor retinaculum, spans the distance between each side of the arch and forms the anterior wall of the tunnel. The median nerve and all the long flexor tendons passing from the forearm to the digits of the hand pass through the carpal tunnel. Positioning the hand Unlike the lower limb, which is used for support, stability, and locomotion, the upper limb is highly mobile for positioning the hand in space.


Anatomy_Gray

Anatomy_Gray. Positioning the hand Unlike the lower limb, which is used for support, stability, and locomotion, the upper limb is highly mobile for positioning the hand in space. The shoulder is suspended from the trunk predominantly by muscles and can therefore be moved relative to the body. Sliding (protraction and retraction) and rotating the scapula on the thoracic wall changes the position of the glenohumeral joint (shoulder joint) and extends the reach of the hand (Fig. 7.3). The glenohumeral joint allows the arm to move around three axes with a wide range of motion. Movements of the arm at this joint are flexion, extension, abduction, adduction, medial rotation (internal rotation), lateral rotation (external rotation), and circumduction (Fig. 7.4).


Anatomy_Gray

Anatomy_Gray. The major movements at the elbow joint are flexion and extension of the forearm (Fig. 7.5A). At the other end of the forearm, the distal end of the lateral bone, the radius, can be flipped over the adjacent head of the medial bone, the ulna. Because the hand is articulated with the radius, it can be efficiently moved from a palm-anterior position to a palm-posterior position simply by crossing the distal end of the radius over the ulna (Fig. 7.5B). This movement, termed pronation, occurs solely in the forearm. Supination returns the hand to the anatomical position. At the wrist joint, the hand can be abducted, adducted, flexed, extended, and circumducted (Fig. 7.6). These movements, combined with those of the shoulder, arm, and forearm, enable the hand to be placed in a wide range of positions relative to the body. The hand as a mechanical tool


Anatomy_Gray

Anatomy_Gray. The hand as a mechanical tool One of the major functions of the hand is to grip and manipulate objects. Gripping objects generally involves flexing the fingers against the thumb. Depending on the type of grip, muscles in the hand act to: modify the actions of long tendons that emerge from the forearm and insert into the digits of the hand, and produce combinations of joint movements within each digit that cannot be generated by the long flexor and extensor tendons alone coming from the forearm. The hand as a sensory tool The hand is used to discriminate between objects on the basis of touch. The pads on the palmar aspect of the fingers contain a high density of somatic sensory receptors. Also, the sensory cortex of the brain devoted to interpreting information from the hand, particularly from the thumb, is disproportionately large relative to that for many other regions of skin.


Anatomy_Gray

Anatomy_Gray. The bones of the shoulder consist of the scapula, clavicle, and proximal end of the humerus (Fig. 7.7). The clavicle articulates medially with the manubrium of the sternum and laterally with the acromion of the scapula, which arches over the joint between the glenoid cavity of the scapula and the head of the humerus (the glenohumeral joint). The humerus is the bone of the arm (Fig. 7.7). The distal end of the humerus articulates with the bones of the forearm at the elbow joint, which is a hinge joint that allows flexion and extension of the forearm. The forearm contains two bones: The lateral bone is the radius. The medial bone is the ulna (Fig. 7.7). At the elbow joint, the proximal ends of the radius and ulna articulate with each other as well as with the humerus. In addition to flexing and extending the forearm, the elbow joint allows the radius to spin on the humerus while sliding against the head of the ulna during pronation and supination of the hand.


Anatomy_Gray

Anatomy_Gray. In addition to flexing and extending the forearm, the elbow joint allows the radius to spin on the humerus while sliding against the head of the ulna during pronation and supination of the hand. The distal portions of the radius and the ulna also articulate with each other. This joint allows the end of the radius to flip from the lateral side to the medial side of the ulna during pronation of the hand. The wrist joint is formed between the radius and carpal bones of the hand and between an articular disc, distal to the ulna, and carpal bones. The bones of the hand consist of the carpal bones, the metacarpals, and the phalanges (Fig. 7.7). The five digits in the hand are the thumb and the index, middle, ring, and little fingers. Joints between the eight small carpal bones allow only limited amounts of movement; as a result, the bones work together as a unit. The five metacarpals, one for each digit, are the primary skeletal foundation of the palm (Fig. 7.7).


Anatomy_Gray

Anatomy_Gray. The five metacarpals, one for each digit, are the primary skeletal foundation of the palm (Fig. 7.7). The joint between the metacarpal of the thumb (metacarpal I) and one of the carpal bones allows greater mobility than the limited sliding movement that occurs at the carpometacarpal joints of the fingers. Distally, the heads of metacarpals II to V (i.e., except that of the thumb) are interconnected by strong ligaments. Lack of this ligamentous connection between the metacarpal bones of the thumb and index finger together with the biaxial saddle joint between the metacarpal bone of the thumb and the carpus provide the thumb with greater freedom of movement than the other digits of the hand. The bones of the digits are the phalanges (Fig. 7.7). The thumb has two phalanges, while each of the other digits has three.


Anatomy_Gray

Anatomy_Gray. The bones of the digits are the phalanges (Fig. 7.7). The thumb has two phalanges, while each of the other digits has three. The metacarpophalangeal joints are biaxial condylar joints (ellipsoid joints) that allow abduction, adduction, flexion, extension, and circumduction (Fig. 7.8). Abduction and adduction of the fingers is defined in reference to an axis passing through the center of the middle finger in the anatomical position. The middle finger can therefore abduct both medially and laterally and adduct back to the central axis from either side. The interphalangeal joints are primarily hinge joints that allow only flexion and extension.


Anatomy_Gray

Anatomy_Gray. Some muscles of the shoulder, such as the trapezius, levator scapulae, and rhomboids, connect the scapula and clavicle to the trunk. Other muscles connect the clavicle, scapula, and body wall to the proximal end of the humerus. These include the pectoralis major, pectoralis minor, latissimus dorsi, teres major, and deltoid (Fig. 7.9A,B). The most important of these muscles are the four rotator cuff muscles—the subscapularis, supraspinatus, infraspinatus, and teres minor muscles—which connect the scapula to the humerus and provide support for the glenohumeral joint (Fig. 7.9C). Muscles in the arm and forearm are separated into anterior (flexor) and posterior (extensor) compartments by layers of fascia, bones, and ligaments (Fig. 7.10).


Anatomy_Gray

Anatomy_Gray. Muscles in the arm and forearm are separated into anterior (flexor) and posterior (extensor) compartments by layers of fascia, bones, and ligaments (Fig. 7.10). The anterior compartment of the arm lies anteriorly in position and is separated from muscles of the posterior compartment by the humerus and by medial and lateral intermuscular septa. These intermuscular septa are continuous with the deep fascia enclosing the arm and attach to the sides of the humerus. In the forearm, the anterior and posterior compartments are separated by a lateral intermuscular septum, the radius, the ulna, and an interosseous membrane, which joins adjacent sides of the radius and ulna (Fig. 7.10). Muscles in the arm act mainly to move the forearm at the elbow joint, while those in the forearm function predominantly to move the hand at the wrist joint and the fingers and thumb.


Anatomy_Gray

Anatomy_Gray. Muscles in the arm act mainly to move the forearm at the elbow joint, while those in the forearm function predominantly to move the hand at the wrist joint and the fingers and thumb. Muscles found entirely in the hand, the intrinsic muscles, generate delicate movements of the digits of the hand and modify the forces produced by tendons coming into the fingers and thumb from the forearm. Included among the intrinsic muscles of the hand are three small thenar muscles, which form a soft tissue mound, called the thenar eminence, over the palmar aspect of metacarpal I. The thenar muscles allow the thumb to move freely relative to the other fingers.


Anatomy_Gray

Anatomy_Gray. The upper limb is directly related to the neck. Lying on each side of the superior thoracic aperture at the base of the neck is an axillary inlet, which is formed by: the lateral margin of rib I, the posterior surface of the clavicle, the superior margin of the scapula, and the medial surface of the coracoid process of the scapula (Fig. 7.11). The major artery and vein of the upper limb pass between the thorax and the limb by passing over rib I and through the axillary inlet. Nerves, predominantly derived from the cervical portion of the spinal cord, also pass through the axillary inlet and the axilla to supply the upper limb. Muscles that attach the bones of the shoulder to the trunk are associated with the back and the thoracic wall and include the trapezius, levator scapulae, rhomboid major, rhomboid minor, and latissimus dorsi (Fig. 7.12).


Anatomy_Gray

Anatomy_Gray. The breast on the anterior thoracic wall has a number of significant relationships with the axilla and upper limb. It overlies the pectoralis major muscle, which forms most of the anterior wall of the axilla and attaches the humerus to the chest wall (Fig. 7.13). Often, part of the breast known as the axillary process extends around the lateral margin of the pectoralis major into the axilla. of the breast is predominantly into lymph nodes in the axilla. Several arteries and veins that supply or drain the gland also originate from, or drain into, major axillary vessels. Innervation of the upper limb is by the brachial plexus, which is formed by the anterior rami of cervical spinal nerves C5 to C8, and T1 (Fig. 7.14). This plexus is initially formed in the neck and then continues through the axillary inlet into the axilla. Major nerves that ultimately innervate the arm, forearm, and hand originate from the brachial plexus in the axilla.


Anatomy_Gray

Anatomy_Gray. As a consequence of this innervation pattern, clinical testing of lower cervical and T1 nerves is carried out by examining dermatomes, myotomes, and tendon reflexes in the upper limb. Another consequence is that the clinical signs of problems related to lower cervical nerves—pain; pins-and-needles sensations, or paresthesia; and muscle twitching—appear in the upper limb. Dermatomes of the upper limb (Fig. 7.15A) are often tested for sensation. Areas where overlap of dermatomes is minimal include the: upper lateral region of the arm for spinal cord level C5, palmar pad of the thumb for spinal cord level C6, pad of the index finger for spinal cord level C7, pad of the little finger for spinal cord level C8, and skin on the medial aspect of the elbow for spinal cord level T1. Selected joint movements are used to test myotomes (Fig. 7.15B): Abduction of the arm at the glenohumeral joint is controlled predominantly by C5.


Anatomy_Gray

Anatomy_Gray. Selected joint movements are used to test myotomes (Fig. 7.15B): Abduction of the arm at the glenohumeral joint is controlled predominantly by C5. Flexion of the forearm at the elbow joint is controlled primarily by C6. Extension of the forearm at the elbow joint is controlled mainly by C7. Flexion of the fingers is controlled mainly by C8. Abduction and adduction of the index, middle, and ring fingers is controlled predominantly by T1. In an unconscious patient, both somatic sensory and motor functions of spinal cord levels can be tested using tendon reflexes: A tap on the tendon of the biceps in the cubital fossa tests mainly for spinal cord level C6. A tap on the tendon of the triceps posterior to the elbow tests mainly for C7. The major spinal cord level associated with innervation of the diaphragm, C4, is immediately above the spinal cord levels associated with the upper limb.


Anatomy_Gray

Anatomy_Gray. The major spinal cord level associated with innervation of the diaphragm, C4, is immediately above the spinal cord levels associated with the upper limb. Evaluation of dermatomes and myotomes in the upper limb can provide important information about potential breathing problems that might develop as complications of damage to the spinal cord in regions just below the C4 spinal level. Each of the major muscle compartments in the arm and forearm and each of the intrinsic muscles of the hand is innervated predominantly by one of the major nerves that originate from the brachial plexus in the axilla (Fig. 7.16A): All muscles in the anterior compartment of the arm are innervated by the musculocutaneous nerve.


Anatomy_Gray

Anatomy_Gray. All muscles in the anterior compartment of the arm are innervated by the musculocutaneous nerve. The median nerve innervates the muscles in the anterior compartment of the forearm, with two exceptions—one flexor of the wrist (the flexor carpi ulnaris muscle) and part of one flexor of the fingers (the medial half of the flexor digitorum profundus muscle) are innervated by the ulnar nerve. Most intrinsic muscles of the hand are innervated by the ulnar nerve, except for the thenar muscles and two lateral lumbrical muscles, which are innervated by the median nerve. All muscles in the posterior compartments of the arm and forearm are innervated by the radial nerve. In addition to innervating major muscle groups, each of the major peripheral nerves originating from the from patches of skin quite different from dermatomes (Fig. 7.16B). Sensation in these areas can be used to test for peripheral nerve lesions:


Anatomy_Gray

Anatomy_Gray. The musculocutaneous nerve innervates skin on the anterolateral side of the forearm. The median nerve innervates the palmar surface of the lateral three and one-half digits, and the ulnar nerve innervates the medial one and one-half digits. The radial nerve supplies skin on the posterior surface of the forearm and the dorsolateral surface of the hand. Nerves related to bone Three important nerves are directly related to parts of the humerus (Fig. 7.17): The axillary nerve, which supplies the deltoid muscle, a major abductor of the humerus at the glenohumeral joint, passes around the posterior aspect of the upper part of the humerus (the surgical neck). The radial nerve, which supplies all of the extensor muscles of the upper limb, passes diagonally around the posterior surface of the middle of the humerus in the radial groove.


Anatomy_Gray

Anatomy_Gray. The radial nerve, which supplies all of the extensor muscles of the upper limb, passes diagonally around the posterior surface of the middle of the humerus in the radial groove. The ulnar nerve, which is ultimately destined for the hand, passes posteriorly to a bony protrusion, the medial epicondyle, on the medial side of the distal end of the humerus. Fractures of the humerus in any one of these three regions can endanger the related nerve. Large veins embedded in the superficial fascia of the upper limb are often used to access a patient’s vascular system and to withdraw blood. The most significant of these veins are the cephalic, basilic, and median cubital veins (Fig. 7.18). The cephalic and basilic veins originate from the dorsal venous network on the back of the hand.


Anatomy_Gray

Anatomy_Gray. The cephalic and basilic veins originate from the dorsal venous network on the back of the hand. The cephalic vein originates over the anatomical snuffbox at the base of the thumb, passes laterally around the distal forearm to reach the anterolateral surface of the limb, and then continues proximally. It crosses the elbow, then passes up the arm into a triangular depression—the clavipectoral triangle (deltopectoral triangle)—between the pectoralis major muscle, deltoid muscle, and clavicle. In this depression, the vein passes into the axilla by penetrating deep fascia just inferior to the clavicle. The basilic vein originates from the medial side of the dorsal venous network of the hand and passes proximally up the posteromedial surface of the forearm. It passes onto the anterior surface of the limb just inferior to the elbow and then continues proximally to penetrate deep fascia about midway up the arm.


Anatomy_Gray

Anatomy_Gray. At the elbow, the cephalic and basilic veins are connected by the median cubital vein, which crosses the roof of the cubital fossa. Orientation of the thumb The thumb is positioned at right angles to the orientation of the index, middle, ring, and little fingers (Fig. 7.19). As a result, movements of the thumb occur at right angles to those of the other digits. For example, flexion brings the thumb across the palm, whereas abduction moves it away from the fingers at right angles to the palm. Importantly, with the thumb positioned at right angles to the palm, only a slight rotation of metacarpal I on the wrist brings the pad of the thumb into a position directly facing the pads of the other fingers. This opposition of the thumb is essential for normal hand function. The shoulder is the region of upper limb attachment to the trunk.


Anatomy_Gray

Anatomy_Gray. The shoulder is the region of upper limb attachment to the trunk. The bone framework of the shoulder consists of: the clavicle and scapula, which form the pectoral girdle (shoulder girdle), and the proximal end of the humerus. The superficial muscles of the shoulder consist of the trapezius and deltoid muscles, which together form the smooth muscular contour over the lateral part of the shoulder. These muscles connect the scapula and clavicle to the trunk and to the arm, respectively. The clavicle is the only bony attachment between the trunk and the upper limb. It is palpable along its entire length and has a gentle S-shaped contour, with the forward-facing convex part medial and the forward-facing concave part lateral. The acromial (lateral) end of the clavicle is flat, whereas the sternal (medial) end is more robust and somewhat quadrangular in shape (Fig. 7.20).


Anatomy_Gray

Anatomy_Gray. The acromial end of the clavicle has a small oval facet on its surface for articulation with a similar facet on the medial surface of the acromion of the scapula. The sternal end has a much larger facet for articulation mainly with the manubrium of the sternum, and to a lesser extent, with the first costal cartilage. The inferior surface of the lateral third of the clavicle possesses a distinct tuberosity consisting of a tubercle (the conoid tubercle) and lateral roughening (the trapezoid line), for attachment of the important coracoclavicular ligament. In addition, the surfaces and margins of the clavicle are roughened by the attachment of muscles that connect the clavicle to the thorax, neck, and upper limb. The superior surface is smoother than the inferior surface.


Anatomy_Gray

Anatomy_Gray. The scapula is a large, flat triangular bone with: three angles (lateral, superior, and inferior), three borders (superior, lateral, and medial), two surfaces (costal and posterior), and three processes (acromion, spine, and coracoid process) (Fig. 7.21). The lateral angle of the scapula is marked by a shallow, somewhat comma-shaped glenoid cavity, which articulates with the head of the humerus to form the glenohumeral joint (Fig. 7.21B,C). A large triangular-shaped roughening (the infraglenoid tubercle) inferior to the glenoid cavity is the site of attachment for the long head of the triceps brachii muscle. A less distinct supraglenoid tubercle is located superior to the glenoid cavity and is the site of attachment for the long head of the biceps brachii muscle. A prominent spine subdivides the posterior surface of the scapula into a small, superior supraspinous fossa and a much larger, inferior infraspinous fossa (Fig. 7.21A).


Anatomy_Gray

Anatomy_Gray. A prominent spine subdivides the posterior surface of the scapula into a small, superior supraspinous fossa and a much larger, inferior infraspinous fossa (Fig. 7.21A). The acromion, which is an anterolateral projection of the spine, arches over the glenohumeral joint and articulates, via a small oval facet on its distal end, with the clavicle. The region between the lateral angle of the scapula and the attachment of the spine to the posterior surface of the scapula is the greater scapular notch (spinoglenoid notch). Unlike the posterior surface, the costal surface of the scapula is unremarkable, being characterized by a shallow concave subscapular fossa over much of its extent (Fig. 7.21B). The costal surface and margins provide for muscle attachment, and the costal surface, together with its related muscle (subscapularis), moves freely over the underlying thoracic wall.


Anatomy_Gray

Anatomy_Gray. The lateral border of the scapula is strong and thick for muscle attachment, whereas the medial border and much of the superior border is thin and sharp. The superior border is marked on its lateral end by: the coracoid process, a hook-like structure that projects anterolaterally and is positioned directly inferior to the lateral part of the clavicle; and the small but distinct suprascapular notch, which lies immediately medial to the root of the coracoid process. The spine and acromion can be readily palpated on a patient, as can the tip of the coracoid process, the inferior angle, and much of the medial border of the scapula. The proximal end of the humerus consists of the head, the anatomical neck, the greater and lesser tubercles, the surgical neck, and the superior half of the shaft of the humerus (Fig. 7.22). The head is half-spherical in shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula.


Anatomy_Gray

Anatomy_Gray. The head is half-spherical in shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula. The anatomical neck is very short and is formed by a narrow constriction immediately distal to the head. It lies between the head and the greater and lesser tubercles laterally, and between the head and the shaft more medially. The greater and lesser tubercles are prominent landmarks on the proximal end of the humerus and serve as attachment sites for the four rotator cuff muscles of the glenohumeral joint. The greater tubercle is lateral in position. Its superior surface and posterior surface are marked by three large smooth facets for muscle tendon attachments: The superior facet is for attachment of the supraspinatus muscle. The middle facet is for attachment of the infraspinatus. The inferior facet is for attachment of the teres minor.


Anatomy_Gray

Anatomy_Gray. The superior facet is for attachment of the supraspinatus muscle. The middle facet is for attachment of the infraspinatus. The inferior facet is for attachment of the teres minor. The lesser tubercle is anterior in position and its surface is marked by a large smooth impression for attachment of the subscapularis muscle. A deep intertubercular sulcus (bicipital groove) separates the lesser and greater tubercles and continues inferiorly onto the proximal shaft of the humerus (Fig. 7.22). The tendon of the long head of the biceps brachii passes through this sulcus. Roughenings on the lateral and medial lips and on the floor of the intertubercular sulcus mark sites for the attachment of the pectoralis major, teres major, and latissimus dorsi muscles, respectively.


Anatomy_Gray

Anatomy_Gray. The lateral lip of the intertubercular sulcus is continuous inferiorly with a large V-shaped deltoid tuberosity on the lateral surface of the humerus midway along its length (Fig. 7.22), which is where the deltoid muscle inserts onto the humerus. In approximately the same position, but on the medial surface of the bone, there is a thin vertical roughening for attachment of the coracobrachialis muscle.


Anatomy_Gray

Anatomy_Gray. In approximately the same position, but on the medial surface of the bone, there is a thin vertical roughening for attachment of the coracobrachialis muscle. One of the most important features of the proximal end of the humerus is the surgical neck (Fig. 7.22). This region is oriented in the horizontal plane between the expanded proximal part of the humerus (head, anatomical neck, and tubercles) and the narrower shaft. The axillary nerve and the posterior circumflex humeral artery, which pass into the deltoid region from the axilla, do so immediately posterior to the surgical neck. Because the surgical neck is weaker than more proximal regions of the bone, it is one of the sites where the humerus commonly fractures. The associated nerve (axillary) and artery (posterior circumflex humeral) can be damaged by fractures in this region. The three joints in the shoulder complex are the sternoclavicular, acromioclavicular, and glenohumeral joints.


Anatomy_Gray

Anatomy_Gray. The three joints in the shoulder complex are the sternoclavicular, acromioclavicular, and glenohumeral joints. The sternoclavicular joint and the acromioclavicular joint link the two bones of the pectoral girdle to each other and to the trunk. The combined movements at these two joints enable the scapula to be positioned over a wide range on the thoracic wall, substantially increasing “reach” by the upper limb. The glenohumeral joint (shoulder joint) is the articulation between the humerus of the arm and the scapula.


Anatomy_Gray

Anatomy_Gray. The glenohumeral joint (shoulder joint) is the articulation between the humerus of the arm and the scapula. The sternoclavicular joint occurs between the proximal end of the clavicle and the clavicular notch of the manubrium of the sternum together with a small part of the first costal cartilage (Fig. 7.23). It is synovial and saddle shaped. The articular cavity is completely separated into two compartments by an articular disc. The sternoclavicular joint allows movement of the clavicle, predominantly in the anteroposterior and vertical planes, although some rotation also occurs. The sternoclavicular joint is surrounded by a joint capsule and is reinforced by four ligaments: The anterior and posterior sternoclavicular ligaments are anterior and posterior, respectively, to the joint. An interclavicular ligament links the ends of the two clavicles to each other and to the superior surface of the manubrium of the sternum.


Anatomy_Gray

Anatomy_Gray. An interclavicular ligament links the ends of the two clavicles to each other and to the superior surface of the manubrium of the sternum. The costoclavicular ligament is positioned laterally to the joint and links the proximal end of the clavicle to the first rib and related costal cartilage. The acromioclavicular joint is a small synovial joint between an oval facet on the medial surface of the acromion and a similar facet on the acromial end of the clavicle (Fig. 7.24, also see Fig. 7.31). It allows movement in the anteroposterior and vertical planes together with some axial rotation.


Anatomy_Gray

Anatomy_Gray. The acromioclavicular joint is surrounded by a joint capsule and is reinforced by: a small acromioclavicular ligament superior to the joint and passing between adjacent regions of the clavicle and acromion, and a much larger coracoclavicular ligament, which is not directly related to the joint, but is an important strong accessory ligament, providing much of the weight-bearing support for the upper limb on the clavicle and maintaining the position of the clavicle on the acromion—it spans the distance between the coracoid process of the scapula and the inferior surface of the acromial end of the clavicle and comprises an anterior trapezoid ligament (which attaches to the trapezoid line on the clavicle) and a posterior conoid ligament (which attaches to the related conoid tubercle).


Anatomy_Gray

Anatomy_Gray. The glenohumeral joint is a synovial ball and socket articulation between the head of the humerus and the glenoid cavity of the scapula (Fig. 7.25). It is multiaxial with a wide range of movements provided at the cost of skeletal stability. Joint stability is provided, instead, by the rotator cuff muscles, the long head of the biceps brachii muscle, related bony processes, and extracapsular ligaments. Movements at the joint include flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction. The articular surfaces of the glenohumeral joint are the large spherical head of the humerus and the small glenoid cavity of the scapula (Fig. 7.25). Each of the surfaces is covered by hyaline cartilage.


Anatomy_Gray

Anatomy_Gray. The glenoid cavity is deepened and expanded peripherally by a fibrocartilaginous collar (the glenoid labrum), which attaches to the margin of the fossa. Superiorly, this labrum is continuous with the tendon of the long head of the biceps brachii muscle, which attaches to the supraglenoid tubercle and passes through the articular cavity superior to the head of the humerus. The synovial membrane attaches to the margins of the articular surfaces and lines the fibrous membrane of the joint capsule (Fig. 7.26). The synovial membrane is loose inferiorly. This redundant region of synovial membrane and related fibrous membrane accommodates abduction of the arm.


Anatomy_Gray

Anatomy_Gray. The synovial membrane protrudes through apertures in the fibrous membrane to form bursae, which lie between the tendons of surrounding muscles and the fibrous membrane. The most consistent of these is the subtendinous bursa of the subscapularis, which lies between the subscapularis muscle and the fibrous membrane. The synovial membrane also folds around the tendon of the long head of the biceps brachii muscle in the joint and extends along the tendon as it passes into the intertubercular sulcus. All these synovial structures reduce friction between the tendons and adjacent joint capsule and bone.


Anatomy_Gray

Anatomy_Gray. In addition to bursae that communicate with the articular cavity through apertures in the fibrous membrane, other bursae are associated with the joint but are not connected to it. These occur: between the acromion (or deltoid muscle) and supraspinatus muscle (or joint capsule) (the subacromial or subdeltoid bursa), between the acromion and skin, between the coracoid process and the joint capsule, and in relationship to tendons of muscles around the joint (coracobrachialis, teres major, long head of triceps brachii, and latissimus dorsi muscles). The fibrous membrane of the joint capsule attaches to the margin of the glenoid cavity, outside the attachment of the glenoid labrum and the long head of the biceps brachii muscle, and to the anatomical neck of the humerus (Fig. 7.27).


Anatomy_Gray

Anatomy_Gray. On the humerus, the medial attachment occurs more inferiorly than the neck and extends onto the shaft. In this region, the fibrous membrane is also loose or folded in the anatomical position. This redundant area of the fibrous membrane accommodates abduction of the arm. Openings in the fibrous membrane provide continuity of the articular cavity with bursae that occur between the joint capsule and surrounding muscles and around the tendon of the long head of the biceps brachii muscle in the intertubercular sulcus.


Anatomy_Gray

Anatomy_Gray. The fibrous membrane of the joint capsule is thickened: anterosuperiorly in three locations to form superior, middle, and inferior glenohumeral ligaments, which pass from the superomedial margin of the glenoid cavity to the lesser tubercle and inferiorly related anatomical neck of the humerus (Fig. 7.27); superiorly between the base of the coracoid process and the greater tubercle of the humerus (the coracohumeral ligament); and between the greater and lesser tubercles of the humerus (transverse humeral ligament)—this holds the tendon of the long head of the biceps brachii muscle in the intertubercular sulcus (Fig. 7.27). Joint stability is provided by surrounding muscle tendons and a skeletal arch formed superiorly by the coracoid process and acromion and the coraco-acromial ligament (Fig. 7.28).


Anatomy_Gray

Anatomy_Gray. Joint stability is provided by surrounding muscle tendons and a skeletal arch formed superiorly by the coracoid process and acromion and the coraco-acromial ligament (Fig. 7.28). Tendons of the rotator cuff muscles (the supraspinatus, infraspinatus, teres minor, and subscapularis muscles) blend with the joint capsule and form a musculotendinous collar that surrounds the posterior, superior, and anterior aspects of the glenohumeral joint (Figs. 7.28 and 7.29). This cuff of muscles stabilizes and holds the head of the humerus in the glenoid cavity of the scapula without compromising the arm’s flexibility and range of motion. The tendon of the long head of the biceps brachii muscle passes superiorly through the joint and restricts upward movement of the humeral head on the glenoid cavity. Vascular supply to the glenohumeral joint is predominantly through branches of the anterior and posterior circumflex humeral and suprascapular arteries.


Anatomy_Gray

Anatomy_Gray. Vascular supply to the glenohumeral joint is predominantly through branches of the anterior and posterior circumflex humeral and suprascapular arteries. The glenohumeral joint is innervated by branches from the posterior cord of the brachial plexus, and from the suprascapular, axillary, and lateral pectoral nerves. The two most superficial muscles of the shoulder are the trapezius and deltoid muscles (Fig. 7.35 and Table 7.1). Together, they provide the characteristic contour of the shoulder: The trapezius attaches the scapula and clavicle to the trunk. The deltoid attaches the scapula and clavicle to the humerus. Both the trapezius and deltoid are attached to opposing surfaces and margins of the spine of the scapula, acromion, and clavicle. The scapula, acromion, and clavicle can be palpated between the attachments of the trapezius and deltoid.


Anatomy_Gray

Anatomy_Gray. Deep to the trapezius the scapula is attached to the vertebral column by three muscles—the levator scapulae, rhomboid minor, and rhomboid major. These three muscles work with the trapezius (and with muscles found anteriorly) to position the scapula on the trunk. The trapezius muscle has an extensive origin from the axial skeleton, which includes sites on the skull and the vertebrae, from CI to TXII (Fig. 7.36). From CI to CVII, the muscle attaches to the vertebrae through the ligamentum nuchae. The muscle inserts onto the skeletal framework of the shoulder along the inner margins of a continuous U-shaped line of attachment oriented in the horizontal plane, with the bottom of the U directed laterally. Together, the left and right trapezius muscles form a diamond or trapezoid shape, from which the name is derived. The trapezius muscle is a powerful elevator of the shoulder and also rotates the scapula to extend the reach superiorly.


Anatomy_Gray

Anatomy_Gray. The trapezius muscle is a powerful elevator of the shoulder and also rotates the scapula to extend the reach superiorly. Innervation of the trapezius muscle is by the accessory nerve [XI] and the anterior rami of cervical nerves C3 and C4 (Fig. 7.36). These nerves pass vertically along the deep surface of the muscle. The accessory nerve can be evaluated by testing the function of the trapezius muscle. This is most easily done by asking patients to shrug their shoulders against resistance. The deltoid muscle is large and triangular in shape, with its base attached to the scapula and clavicle and its apex attached to the humerus (Fig. 7.36). It originates along a continuous U-shaped line of attachment to the clavicle and the scapula, mirroring the adjacent insertion sites of the trapezius muscle. It inserts into the deltoid tuberosity on the lateral surface of the shaft of the humerus. The major function of the deltoid muscle is abduction of the arm.


Anatomy_Gray

Anatomy_Gray. The major function of the deltoid muscle is abduction of the arm. The deltoid muscle is innervated by the axillary nerve, which is a branch of the posterior cord of the brachial plexus. The axillary nerve and associated blood vessels (the posterior circumflex humeral artery and vein) enter the deltoid by passing posteriorly around the surgical neck of the humerus. The levator scapulae originates from the transverse processes of CI to CIV vertebrae (Fig. 7.36). It descends laterally to attach to the posterior surface of the medial border of the scapula from the superior angle to the smooth triangular area of bone at the root of the spine. The levator scapulae muscle is innervated by the dorsal scapular nerve and directly from C3 and C4 spinal nerves. The levator scapulae elevates the scapula.


Anatomy_Gray

Anatomy_Gray. The levator scapulae muscle is innervated by the dorsal scapular nerve and directly from C3 and C4 spinal nerves. The levator scapulae elevates the scapula. The rhomboid minor and major muscles attach medially to the vertebral column and descend laterally to attach to the medial border of the scapula inferior to the levator scapulae muscle (Fig. 7.36). The rhomboid minor originates from the lower end of the ligamentum nuchae and the spines of CVII and TI vertebrae. It inserts laterally into the smooth triangular area of bone at the root of the spine of the scapula on the posterior surface. The rhomboid major originates from the spines of vertebrae TII to TV and from the intervening supraspinous ligaments. It descends laterally to insert along the posterior surface of the medial border of the scapula from the insertion of the rhomboid minor to the inferior angle. The rhomboid muscles are innervated by the dorsal scapular nerve, which is a branch of the brachial plexus.


Anatomy_Gray

Anatomy_Gray. The rhomboid muscles are innervated by the dorsal scapular nerve, which is a branch of the brachial plexus. The rhomboid minor and major retract and elevate the scapula. The posterior scapular region occupies the posterior aspect of the scapula and is located deep to the trapezius and deltoid muscles (Fig. 7.37 and Table 7.2). It contains four muscles, which pass between the scapula and proximal end of the humerus: the supraspinatus, infraspinatus, teres minor, and teres major muscles. The posterior scapular region also contains part of one additional muscle, the long head of the triceps brachii, which passes between the scapula and the proximal end of the forearm. This muscle, along with other muscles of the region and the humerus, participates in forming a number of spaces through which nerves and vessels enter and leave the region. The supraspinatus, infraspinatus, and teres minor muscles are components of the rotator cuff, which stabilizes the glenohumeral joint.


Anatomy_Gray

Anatomy_Gray. The supraspinatus, infraspinatus, and teres minor muscles are components of the rotator cuff, which stabilizes the glenohumeral joint. The supraspinatus and infraspinatus muscles originate from two large fossae, one above and one below the spine, on the posterior surface of the scapula (Fig. 7.37). They form tendons that insert on the greater tubercle of the humerus. The tendon of the supraspinatus passes under the acromion, where it is separated from the bone by a subacromial bursa, passes over the glenohumeral joint, and inserts on the superior facet of the greater tubercle. The tendon of the infraspinatus passes posteriorly to the glenohumeral joint and inserts on the middle facet of the greater tubercle. The supraspinatus participates in abduction of the arm. The infraspinatus laterally rotates the humerus.


Anatomy_Gray

Anatomy_Gray. The supraspinatus participates in abduction of the arm. The infraspinatus laterally rotates the humerus. The teres minor muscle is a cord-like muscle that originates from a flattened area of the scapula immediately adjacent to its lateral border below the infraglenoid tubercle (Fig. 7.37). Its tendon inserts on the inferior facet of the greater tubercle of the humerus. The teres minor laterally rotates the humerus and is a component of the rotator cuff. The teres major muscle originates from a large oval region on the posterior surface of the inferior angle of the scapula (Fig. 7.37). This broad cord-like muscle passes superiorly and laterally and ends as a flat tendon that attaches to the medial lip of the intertubercular sulcus on the anterior surface of the humerus. The teres major medially rotates and extends the humerus. Long head of triceps brachii


Anatomy_Gray

Anatomy_Gray. Long head of triceps brachii The long head of the triceps brachii muscle originates from the infraglenoid tubercle and passes somewhat vertically down the arm to insert, with the medial and lateral heads of this muscle, on the olecranon of the ulna (Fig. 7.37). The triceps brachii is the primary extensor of the forearm at the elbow joint. Because the long head crosses the glenohumeral joint, it can also extend and adduct the humerus. The importance of the triceps brachii in the posterior scapular region is that its vertical course between the teres minor and teres major, together with these muscles and the humerus, forms spaces through which nerves and vessels pass between regions. Gateways to the posterior scapular region


Anatomy_Gray

Anatomy_Gray. Gateways to the posterior scapular region The suprascapular foramen is the route through which structures pass between the base of the neck and the posterior scapular region (Fig. 7.37). It is formed by the suprascapular notch of the scapula and the superior transverse scapular (suprascapular) ligament, which converts the notch into a foramen. The suprascapular nerve passes through the suprascapular foramen; the suprascapular artery and the suprascapular vein follow the same course as the nerve, but normally pass immediately superior to the superior transverse scapular ligament and not through the foramen (Fig. 7.38).


Anatomy_Gray

Anatomy_Gray. The quadrangular space provides a passageway for nerves and vessels passing between more anterior regions (the axilla) and the posterior scapular region (Fig. 7.37). In the posterior scapular region, its boundaries are formed by: the inferior margin of the teres minor, the surgical neck of the humerus, the superior margin of the teres major, and the lateral margin of the long head of the triceps brachii. The axillary nerve and the posterior circumflex humeral artery and vein pass through this space (Fig. 7.38). The triangular space is an area of communication between the axilla and the posterior scapular region (Fig. 7.37). When viewed from the posterior scapular region, the triangular space is formed by: the medial margin of the long head of the triceps brachii, the superior margin of the teres major, and the inferior margin of the teres minor. The circumflex scapular artery and vein pass through this gap (Fig. 7.38).


Anatomy_Gray

Anatomy_Gray. The circumflex scapular artery and vein pass through this gap (Fig. 7.38). The triangular interval is formed by: the lateral margin of the long head of the triceps brachii, the shaft of the humerus, and the inferior margin of the teres major (Fig. 7.37). Because this space is below the inferior margin of the teres major, which defines the inferior boundary of the axilla, the triangular interval serves as a passageway between the anterior and posterior compartments of the arm and between the posterior compartment of the arm and the axilla. The radial nerve, the profunda brachii artery (deep artery of arm), and associated veins pass through it (Fig. 7.38). The two major nerves of the posterior scapular region are the suprascapular and axillary nerves, both of which originate from the brachial plexus in the axilla (Fig. 7.38).


Anatomy_Gray

Anatomy_Gray. The two major nerves of the posterior scapular region are the suprascapular and axillary nerves, both of which originate from the brachial plexus in the axilla (Fig. 7.38). The suprascapular nerve originates in the base of the neck from the superior trunk of the brachial plexus. It passes posterolaterally from its origin, through the suprascapular foramen to reach the posterior scapular region, where it lies in the plane between bone and muscle (Fig. 7.38). It innervates the supraspinatus muscle and then passes through the greater scapular (spinoglenoid) notch, between the root of the spine of the scapula and the glenoid cavity, to terminate in and innervate the infraspinatus muscle. Generally, the suprascapular nerve has no cutaneous branches.


Anatomy_Gray

Anatomy_Gray. Generally, the suprascapular nerve has no cutaneous branches. The axillary nerve originates from the posterior cord of the brachial plexus. It exits the axilla by passing through the quadrangular space in the posterior wall of the axilla, and enters the posterior scapular region (Fig. 7.38). Together with the posterior circumflex humeral artery and vein, it is directly related to the posterior surface of the surgical neck of the humerus. The axillary nerve innervates the deltoid and teres minor muscles. In addition, it has a cutaneous branch, the superior lateral cutaneous nerve of the arm, which carries general sensation from the skin over the inferior part of the deltoid muscle. Three major arteries are found in the posterior scapular region: the suprascapular, posterior circumflex humeral, and circumflex scapular arteries. These arteries contribute to an interconnected vascular network around the scapula (Fig. 7.39).


Anatomy_Gray

Anatomy_Gray. The suprascapular artery originates in the base of the neck as a branch of the thyrocervical trunk, which, in turn, is a major branch of the subclavian artery (Figs. 7.38 and 7.39). The vessel may also originate directly from the third part of the subclavian artery. The suprascapular artery normally enters the posterior scapular region superior to the suprascapular foramen, whereas the nerve passes through the foramen. In the posterior scapular region, the vessel runs with the suprascapular nerve. In addition to supplying the supraspinatus and infraspinatus muscles, the suprascapular artery contributes branches to numerous structures along its course. The posterior circumflex humeral artery originates from the third part of the axillary artery in the axilla (Figs. 7.38 and 7.39).


Anatomy_Gray

Anatomy_Gray. The posterior circumflex humeral artery originates from the third part of the axillary artery in the axilla (Figs. 7.38 and 7.39). The posterior circumflex humeral artery and axillary nerve leave the axilla through the quadrangular space in the posterior wall and enter the posterior scapular region. The vessel supplies the related muscles and the glenohumeral joint. The circumflex scapular artery is a branch of the subscapular artery that also originates from the third part of the axillary artery in the axilla (Figs. 7.38 and 7.39). The circumflex scapular artery leaves the axilla through the triangular space and enters the posterior scapular region, passes through the origin of the teres minor muscle, and forms anastomotic connections with other arteries in the region. Veins in the posterior scapular region generally follow the arteries and connect with vessels in the neck, back, arm, and axilla.


Anatomy_Gray

Anatomy_Gray. Veins in the posterior scapular region generally follow the arteries and connect with vessels in the neck, back, arm, and axilla. The axilla is the gateway to the upper limb, providing an area of transition between the neck and the arm (Fig. 7.40A). Formed by the clavicle, the scapula, the upper thoracic wall, the humerus, and related muscles, the axilla is an irregularly shaped pyramidal space with: four sides, an inlet, and a floor (base) (Fig. 7.40A,B). The axillary inlet is continuous superiorly with the neck, and the lateral part of the floor opens into the arm. All major structures passing into and out of the upper limb pass through the axilla (Fig. 7.40C). Apertures formed between muscles in the anterior and posterior walls enable structures to pass between the axilla and immediately adjacent regions (the posterior scapular, pectoral, and deltoid regions).


Anatomy_Gray

Anatomy_Gray. The axillary inlet is oriented in the horizontal plane and is somewhat triangular in shape, with its apex directed laterally (Fig. 7.40A,B). The margins of the inlet are completely formed by bone: The medial margin is the lateral border of rib I. The anterior margin is the posterior surface of the clavicle. The posterior margin is the superior border of the scapula up to the coracoid process. The apex of the triangularly shaped axillary inlet is lateral in position and is formed by the medial aspect of the coracoid process. Major vessels and nerves pass between the neck and the axilla by crossing over the lateral border of rib I and through the axillary inlet (Fig. 7.40A). The subclavian artery, the major blood vessel supplying the upper limb, becomes the axillary artery as it crosses the lateral margin of rib I and enters the axilla. Similarly, the axillary vein becomes the subclavian vein as it passes over the lateral margin of rib I and leaves the axilla to enter the neck.


Anatomy_Gray

Anatomy_Gray. At the axillary inlet, the axillary vein is anterior to the axillary artery, which, in turn, is anterior to the trunks of the brachial plexus. The inferior trunk (lower trunk) of the brachial plexus lies directly on rib I in the neck, as does the subclavian artery and vein. As they pass over rib I, the vein and artery are separated by the insertion of the anterior scalene muscle (Fig. 7.40A). The anterior wall of the axilla is formed by the lateral part of the pectoralis major muscle, the underlying pectoralis minor and subclavius muscles, and the clavipectoral fascia (Table 7.3). The pectoralis major muscle is the largest and most superficial muscle of the anterior wall (Fig. 7.41). Its inferior margin underlies the anterior axillary fold, which marks the anteroinferior border of the axilla. The muscle has two heads: The clavicular head originates from the medial half of the clavicle.


Anatomy_Gray

Anatomy_Gray. The clavicular head originates from the medial half of the clavicle. The sternocostal head originates from the medial part of the anterior thoracic wall—often, fibers from this head continue inferiorly and medially to attach to the anterior abdominal wall, forming an additional abdominal part of the muscle. The muscle inserts into the lateral lip of the intertubercular sulcus of the humerus. The parts of the muscle that have a superior origin on the trunk insert lower and more anteriorly on the lateral lip of the intertubercular sulcus than the parts of the muscle that originate inferiorly. Acting together, the two heads of the pectoralis major flex, adduct, and medially rotate the arm at the glenohumeral joint. The clavicular head flexes the arm from an extended position, whereas the sternocostal head extends the arm from a flexed position, particularly against resistance.


Anatomy_Gray

Anatomy_Gray. The pectoralis major is innervated by the lateral and medial pectoral nerves, which originate from the brachial plexus in the axilla. The subclavius muscle is a small muscle that lies deep to the pectoralis major muscle and passes between the clavicle and rib I (Fig. 7.42). It originates medially, as a tendon, from rib I at the junction between the rib and its costal cartilage. It passes laterally and superiorly to insert via a muscular attachment into an elongate shallow groove on the inferior surface of the middle third of the clavicle. The function of the subclavius is not entirely clear, but it may act to pull the shoulder down by depressing the clavicle and may also stabilize the sternoclavicular joint by pulling the clavicle medially. The subclavius muscle is innervated by a small branch from the superior trunk of the brachial plexus.


Anatomy_Gray

Anatomy_Gray. The subclavius muscle is innervated by a small branch from the superior trunk of the brachial plexus. The pectoralis minor muscle is a small triangular-shaped muscle that lies deep to the pectoralis major muscle and passes from the thoracic wall to the coracoid process of the scapula (Fig. 7.42). It originates as three muscular slips from the anterior surfaces and upper margins of ribs III to V and from the fascia overlying muscles of the related intercostal spaces. The muscle fibers pass superiorly and laterally to insert into the medial and upper aspects of the coracoid process. The pectoralis minor muscle protracts the scapula (by pulling the scapula anteriorly on the thoracic wall) and depresses the lateral angle of the scapula. The pectoralis minor is innervated by the medial pectoral nerve, which originates from the brachial plexus in the axilla.


Anatomy_Gray

Anatomy_Gray. The pectoralis minor is innervated by the medial pectoral nerve, which originates from the brachial plexus in the axilla. The clavipectoral fascia is a thick sheet of connective tissue that connects the clavicle to the floor of the axilla (Fig. 7.42). It encloses the subclavius and pectoralis minor muscles and spans the gap between them. Structures travel between the axilla and the anterior wall of the axilla by passing through the clavipectoral fascia either between the pectoralis minor and subclavius muscles or inferior to the pectoralis minor muscle. Important structures that pass between the subclavius and pectoralis minor muscles include the cephalic vein, the thoraco-acromial artery, and the lateral pectoral nerve. The lateral thoracic artery leaves the axilla by passing through the fascia inferior to the pectoralis minor muscle.


Anatomy_Gray

Anatomy_Gray. The lateral thoracic artery leaves the axilla by passing through the fascia inferior to the pectoralis minor muscle. The medial pectoral nerve leaves the axilla by penetrating directly through the pectoralis minor muscle to supply this muscle and to reach the pectoralis major muscle. Occasionally, branches of the medial pectoral nerve pass around the lower margin of the pectoralis minor to reach and innervate the overlying pectoralis major muscle. The medial wall of the axilla consists of the upper thoracic wall (the ribs and related intercostal tissues) and the serratus anterior muscle (Fig. 7.43 and Table 7.4, and see Fig. 7.40).


Anatomy_Gray

Anatomy_Gray. The medial wall of the axilla consists of the upper thoracic wall (the ribs and related intercostal tissues) and the serratus anterior muscle (Fig. 7.43 and Table 7.4, and see Fig. 7.40). The serratus anterior muscle originates as a number of muscular slips from the lateral surfaces of ribs I to IX and the intervening deep fascia overlying the related intercostal spaces (Fig. 7.43). The muscle forms a flattened sheet, which passes posteriorly around the thoracic wall to insert primarily on the costal surface of the medial border of the scapula. The serratus anterior pulls the scapula forward over the thoracic wall and facilitates scapular rotation. It also keeps the costal surface of the scapula closely opposed to the thoracic wall.


Anatomy_Gray

Anatomy_Gray. The serratus anterior pulls the scapula forward over the thoracic wall and facilitates scapular rotation. It also keeps the costal surface of the scapula closely opposed to the thoracic wall. The serratus anterior is innervated by the long thoracic nerve, which is derived from the roots of the brachial plexus, passes through the axilla along the medial wall, and passes vertically down the serratus anterior muscle on its external surface, just deep to skin and superficial fascia. The only major structure that passes directly through the medial wall and into the axilla is the intercostobrachial nerve (Fig. 7.43). This nerve is the lateral cutaneous branch of the second intercostal nerve (anterior ramus of T2). It communicates with a branch of the brachial plexus (the medial cutaneous nerve of the arm) in the axilla and supplies skin on the upper posteromedial side of the arm, which is part of the T2 dermatome.


Anatomy_Gray

Anatomy_Gray. The lateral wall of the axilla is narrow and formed entirely by the intertubercular sulcus of the humerus (Fig. 7.44). The pectoralis major muscle of the anterior wall attaches to the lateral lip of the intertubercular sulcus. The latissimus dorsi and teres major muscles of the posterior wall attach to the floor and medial lip of the intertubercular sulcus, respectively (Table 7.5). The posterior wall of the axilla is complex (Fig. 7.45 and see Fig. 7.50). Its bone framework is formed by the costal surface of the scapula. Muscles of the wall are: the subscapularis muscle (associated with the costal surface of the scapula), the distal parts of the latissimus dorsi and teres major muscles (which pass into the wall from the back and posterior scapular region), and the proximal part of the long head of the triceps brachii muscle (which passes vertically down the wall and into the arm).


Anatomy_Gray

Anatomy_Gray. Gaps between the muscles of the posterior wall form apertures through which structures pass between the axilla, posterior scapular region, and posterior compartment of the arm. The subscapularis muscle forms the largest component of the posterior wall of the axilla. It originates from, and fills, the subscapular fossa and inserts on the lesser tubercle of the humerus (Figs. 7.45 and 7.46). The tendon crosses immediately anterior to the joint capsule of the glenohumeral joint. Together with three muscles of the posterior scapular region (the supraspinatus, infraspinatus, and teres minor muscles), the subscapularis is a member of the rotator cuff muscle group, which stabilizes the glenohumeral joint. The subscapularis is innervated by branches of the brachial plexus (the superior and inferior subscapular nerves), which originate in the axilla.


Anatomy_Gray

Anatomy_Gray. The subscapularis is innervated by branches of the brachial plexus (the superior and inferior subscapular nerves), which originate in the axilla. The inferolateral aspect of the posterior wall of the axilla is formed by the terminal part of the teres major muscle and the tendon of the latissimus dorsi muscle (Fig. 7.45). These two structures lie under the posterior axillary fold, which marks the posteroinferior border of the axilla. The flat tendon of the latissimus dorsi muscle curves around the inferior margin of the teres major muscle on the posterior wall to insert into the floor of the intertubercular sulcus of the humerus, anterior to and slightly above the most distal attachment of the teres major muscle to the medial lip of the intertubercular sulcus. As a consequence, the inferior margin of the teres major muscle defines the inferior limit of the axilla laterally.


Anatomy_Gray

Anatomy_Gray. The axillary artery becomes the brachial artery of the arm as it crosses the inferior margin of the teres major muscle. Long head of the triceps brachii The long head of the triceps brachii muscle passes vertically through the posterior wall of the axilla, and, together with surrounding muscles and adjacent bones, results in the formation of three apertures through which major structures pass through the posterior wall: the quadrangular space, the triangular space, and the triangular interval (Fig. 7.45). Gateways in the posterior wall (See also “Gateways to the posterior scapular region,” pp. 706–710, and Figs. 7.37 and 7.38.)


Anatomy_Gray

Anatomy_Gray. Gateways in the posterior wall (See also “Gateways to the posterior scapular region,” pp. 706–710, and Figs. 7.37 and 7.38.) The quadrangular space provides a passageway for nerves and vessels passing between the axilla and the more posterior scapular and deltoid regions (Fig. 7.45). When viewed from anteriorly, its boundaries are formed by: the inferior margin of the subscapularis muscle, the surgical neck of the humerus, the superior margin of the teres major muscle, and the lateral margin of the long head of the triceps brachii muscle. Passing through the quadrangular space are the axillary nerve and the posterior circumflex humeral artery and vein. The triangular space is an area of communication between the axilla and the posterior scapular region (Fig. 7.45). When viewed from anteriorly, it is formed by: the medial margin of the long head of the triceps brachii muscle, the superior margin of the teres major muscle, and the inferior margin of the subscapularis muscle.


Anatomy_Gray

Anatomy_Gray. The circumflex scapular artery and vein pass into this space. This triangular interval is formed by: the lateral margin of the long head of the triceps brachii muscle, the shaft of the humerus, and the inferior margin of the teres major muscle (Fig. 7.45). The radial nerve passes out of the axilla traveling through this interval to reach the posterior compartment of the arm. The floor of the axilla is formed by fascia and a dome of skin that spans the distance between the inferior margins of the walls (Fig. 7.47 and see Fig. 7.40B). It is supported by the clavipectoral fascia. On a patient, the anterior axillary fold is more superior in position than is the posterior axillary fold. Inferiorly, structures pass into and out of the axilla immediately lateral to the floor where the anterior and posterior walls of the axilla converge and where the axilla is continuous with the anterior compartment of the arm. Contents of the axilla


Anatomy_Gray

Anatomy_Gray. Contents of the axilla Passing through the axilla are the major vessels, nerves, and lymphatics of the upper limb. The space also contains the proximal parts of two muscles of the arm, the axillary process of the breast, and collections of lymph nodes, which drain the upper limb, chest wall, and breast. The proximal parts of the biceps brachii and coracobrachialis muscles pass through the axilla (Table 7.6). The biceps brachii muscle originates as two heads (Fig. 7.48): The short head originates from the apex of the coracoid process of the scapula and passes vertically through the axilla and into the arm where it joins the long head.


Anatomy_Gray

Anatomy_Gray. The short head originates from the apex of the coracoid process of the scapula and passes vertically through the axilla and into the arm where it joins the long head. The long head originates as a tendon from the supraglenoid tubercle of the scapula, passes over the head of the humerus deep to the joint capsule of the glenohumeral joint, and enters the intertubercular sulcus where it is held in position by a ligament, the transverse humeral ligament, which spans the distance between the greater and lesser tubercles; the tendon passes through the axilla in the intertubercular sulcus and forms a muscle belly in the proximal part of the arm. The long and short heads of the muscle join in distal regions of the arm and primarily insert as a single tendon into the radial tuberosity in the forearm.


Anatomy_Gray

Anatomy_Gray. The long and short heads of the muscle join in distal regions of the arm and primarily insert as a single tendon into the radial tuberosity in the forearm. The biceps brachii muscle is primarily a powerful flexor of the forearm at the elbow joint and a powerful supinator in the forearm. Because both heads originate from the scapula, the muscle also acts as an accessory flexor of the arm at the glenohumeral joint. In addition, the long head prevents superior movement of the humerus on the glenoid cavity. The biceps brachii muscle is innervated by the musculocutaneous nerve. The coracobrachialis muscle, together with the short head of the biceps brachii muscle, originates from the apex of the coracoid process (Fig. 7.48). It passes vertically through the axilla to insert on a small linear roughening on the medial aspect of the humerus, approximately midshaft. The coracobrachialis muscle flexes the arm at the glenohumeral joint.


Anatomy_Gray

Anatomy_Gray. The coracobrachialis muscle flexes the arm at the glenohumeral joint. In the axilla, the medial surface of the coracobrachialis muscle is pierced by the musculocutaneous nerve, which innervates and then passes through the muscle to enter the arm. The axillary artery supplies the walls of the axilla and related regions, and continues as the major blood supply to the more distal parts of the upper limb (Fig. 7.49). The subclavian artery in the neck becomes the axillary artery at the lateral margin of rib I and passes through the axilla, becoming the brachial artery at the inferior margin of the teres major muscle. The axillary artery is separated into three parts by the pectoralis minor muscle, which crosses anteriorly to the vessel (Fig. 7.49): The first part is proximal to the pectoralis minor. The second part is posterior to the pectoralis minor. The third part is distal to the pectoralis minor. Generally, six branches arise from the axillary artery:


Anatomy_Gray

Anatomy_Gray. The second part is posterior to the pectoralis minor. The third part is distal to the pectoralis minor. Generally, six branches arise from the axillary artery: One branch, the superior thoracic artery, originates from the first part. Two branches, the thoraco-acromial artery and the lateral thoracic artery, originate from the second part. Three branches, the subscapular artery, the anterior circumflex humeral artery, and the posterior circumflex humeral artery, originate from the third part (Fig. 7.50). The superior thoracic artery is small and originates from the anterior surface of the first part of the axillary artery (Fig. 7.50). It supplies upper regions of the medial and anterior axillary walls.


Anatomy_Gray

Anatomy_Gray. The thoraco-acromial artery is short and originates from the anterior surface of the second part of the axillary artery just posterior to the medial (superior) margin of the pectoralis minor muscle (Fig. 7.50). It curves around the superior margin of the muscle, penetrates the clavipectoral fascia, and immediately divides into four branches—the pectoral, deltoid, clavicular, and acromial branches, which supply the anterior axillary wall and related regions. Additionally, the pectoral branch contributes vascular supply to the breast, and the deltoid branch passes into the clavipectoral triangle where it accompanies the cephalic vein and supplies adjacent structures (see Fig. 7.41).


Anatomy_Gray

Anatomy_Gray. The lateral thoracic artery arises from the anterior surface of the second part of the axillary artery posterior to the lateral (inferior) margin of the pectoralis minor (Fig. 7.50). It follows the margin of the muscle to the thoracic wall and supplies the medial and anterior walls of the axilla. In women, branches emerge from around the inferior margin of the pectoralis major muscle and contribute to the vascular supply of the breast. The subscapular artery is the largest branch of the axillary artery and is the major blood supply to the posterior wall of the axilla (Fig. 7.50). It also contributes to the blood supply of the posterior scapular region. The subscapular artery originates from the posterior surface of the third part of the axillary artery, follows the inferior margin of the subscapularis muscle for a short distance, and then divides into its two terminal branches, the circumflex scapular artery and the thoracodorsal artery.


Anatomy_Gray

Anatomy_Gray. The circumflex scapular artery passes through the triangular space between the subscapularis, teres major, and long head of the triceps muscle. Posteriorly, it passes inferior to, or pierces, the origin of the teres minor muscle to enter the infraspinous fossa. It anastomoses with the suprascapular artery and the deep branch (dorsal scapular artery) of the transverse cervical artery, thereby contributing to an anastomotic network of vessels around the scapula. The thoracodorsal artery approximately follows the lateral border of the scapula to the inferior angle. It contributes to the vascular supply of the posterior and medial walls of the axilla. The anterior circumflex humeral artery is small compared to the posterior circumflex humeral artery, and originates from the lateral side of the third part of the axillary artery (Fig. 7.50). It passes anterior to the surgical neck of the humerus and anastomoses with the posterior circumflex humeral artery.


Anatomy_Gray

Anatomy_Gray. This anterior circumflex humeral artery supplies branches to surrounding tissues, which include the glenohumeral joint and the head of the humerus. The posterior circumflex humeral artery originates from the lateral surface of the third part of the axillary artery immediately posterior to the origin of the anterior circumflex humeral artery (Fig. 7.50). With the axillary nerve, it leaves the axilla by passing through the quadrangular space between the teres major, teres minor, and long head of the triceps brachii muscle and the surgical neck of the humerus. The posterior circumflex humeral artery curves around the surgical neck of the humerus and supplies the surrounding muscles and the glenohumeral joint. It anastomoses with the anterior circumflex humeral artery and with branches from the profunda brachii, suprascapular, and thoraco-acromial arteries.


Anatomy_Gray

Anatomy_Gray. The axillary vein begins at the lower margin of the teres major muscle and is the continuation of the basilic vein (Fig. 7.51), which is a superficial vein that drains the posteromedial surface of the hand and forearm and penetrates the deep fascia in the middle of the arm. The axillary vein passes through the axilla medial and anterior to the axillary artery and becomes the subclavian vein as the vessel crosses the lateral border of rib I at the axillary inlet. Tributaries of the axillary vein generally follow the branches of the axillary artery. Other tributaries include brachial veins that follow the brachial artery and the cephalic vein.


Anatomy_Gray

Anatomy_Gray. The cephalic vein is a superficial vein that drains the lateral and posterior parts of the hand, the forearm, and the arm. In the area of the shoulder, it passes into an inverted triangular cleft (the clavipectoral triangle) between the deltoid muscle, pectoralis major muscle, and clavicle. In the superior part of the clavipectoral triangle, the cephalic vein passes deep to the clavicular head of the pectoralis major muscle and pierces the clavipectoral fascia to join the axillary vein. Many patients who are critically ill have lost blood or fluid, which requires replacement. Access to a peripheral vein is necessary to replace the fluid. The typical sites for venous access are the cephalic vein in the hand or veins that lie within the superficial tissues of the cubital fossa.


Anatomy_Gray

Anatomy_Gray. The brachial plexus is a somatic nerve plexus formed by the anterior rami of C5 to C8, and most of the anterior ramus of T1 (Fig. 7.52). The plexus originates in the neck, passes laterally and inferiorly over rib I, and enters the axilla. The parts of the brachial plexus, from medial to lateral, are roots, trunks, divisions, and cords. All major nerves that innervate the upper limb originate from the brachial plexus, mostly from the cords. Proximal parts of the brachial plexus are posterior to the subclavian artery in the neck, while more distal regions of the plexus surround the axillary artery.


Anatomy_Gray

Anatomy_Gray. The roots of the brachial plexus are the anterior rami of C5 to C8, and most of T1. Close to their origin, the roots receive gray rami communicantes from the sympathetic trunk (Fig. 7.52). These carry postganglionic sympathetic fibers onto the roots for distribution to the periphery. The roots and trunks enter the posterior triangle of the neck by passing between the anterior scalene and middle scalene muscles and lie superior and posterior to the subclavian artery. The three trunks of the brachial plexus originate from the roots, pass laterally over rib I, and enter the axilla (Fig. 7.52): The superior trunk is formed by the union of C5 and C6 roots. The middle trunk is a continuation of the C7 root. The inferior trunk is formed by the union of the C8 and T1 roots. The inferior trunk lies on rib I posterior to the subclavian artery; the middle and superior trunks are more superior in position.


Anatomy_Gray

Anatomy_Gray. The inferior trunk is formed by the union of the C8 and T1 roots. The inferior trunk lies on rib I posterior to the subclavian artery; the middle and superior trunks are more superior in position. Each of the three trunks of the brachial plexus divides into an anterior and a posterior division (Fig. 7.52): The three anterior divisions form parts of the brachial plexus that ultimately give rise to peripheral nerves associated with the anterior compartments of the arm and forearm. The three posterior divisions combine to form parts of the brachial plexus that give rise to nerves associated with the posterior compartments. No peripheral nerves originate directly from the divisions of the brachial plexus. The three cords of the brachial plexus originate from the divisions and are related to the second part of the axillary artery (Fig. 7.52):


Anatomy_Gray

Anatomy_Gray. The three cords of the brachial plexus originate from the divisions and are related to the second part of the axillary artery (Fig. 7.52): The lateral cord results from the union of the anterior divisions of the upper and middle trunks and therefore has contributions from C5 to C7—it is positioned lateral to the second part of the axillary artery. The medial cord is medial to the second part of the axillary artery and is the continuation of the anterior division of the inferior trunk—it contains contributions from C8 and T1. The posterior cord occurs posterior to the second part of the axillary artery and originates as the union of all three posterior divisions—it contains contributions from all roots of the brachial plexus (C5 to T1).


Anatomy_Gray

Anatomy_Gray. Most of the major peripheral nerves of the upper limb originate from the cords of the brachial plexus. Generally, nerves associated with the anterior compartments of the upper limb arise from the medial and lateral cords and nerves associated with the posterior compartments originate from the posterior cord. Branches (Table 7.7) Branches of the roots In addition to small segmental branches from C5 to C8 to muscles of the neck and a contribution of C5 to the phrenic nerve, the roots of the brachial plexus give rise to the dorsal scapular and long thoracic nerves (Fig. 7.53). The dorsal scapular nerve: originates from the C5 root of the brachial plexus, passes posteriorly, often piercing the middle scalene muscle in the neck, to reach and travel along the medial border of the scapula (Fig. 7.54), and innervates the rhomboid major and minor muscles from their deep surfaces.


Anatomy_Gray

Anatomy_Gray. The long thoracic nerve: originates from the anterior rami of C5 to C7, passes vertically down the neck, through the axillary inlet, and down the medial wall of the axilla to supply the serratus anterior muscle (Fig. 7.54), and lies on the superficial aspect of the serratus anterior muscle. Branches of the trunks The only branches from the trunks of the brachial plexus are two nerves that originate from the superior trunk (upper trunk): the suprascapular nerve and the nerve to the subclavius muscle (Fig. 7.53). The suprascapular nerve (C5 and C6): originates from the superior trunk of the brachial plexus, passes laterally through the posterior triangle of the neck (Fig. 7.54) and through the suprascapular foramen to enter the posterior scapular region, innervates the supraspinatus and infraspinatus muscles, and is accompanied in the lateral parts of the neck and in the posterior scapular region by the suprascapular artery.


Anatomy_Gray

Anatomy_Gray. The nerve to the subclavius muscle (C5 and C6) is a small nerve that: originates from the superior trunk of the brachial plexus, passes anteroinferiorly over the subclavian artery and vein, and innervates the subclavius muscle. Branches of the lateral cord Three nerves originate entirely or partly from the lateral cord (Fig. 7.53). The lateral pectoral nerve is the most proximal of the branches from the lateral cord. It passes anteriorly, together with the thoraco-acromial artery, to penetrate the clavipectoral fascia that spans the gap between the subclavius and pectoralis minor muscles (Fig. 7.55), and innervates the pectoralis major muscle.


Anatomy_Gray

Anatomy_Gray. The musculocutaneous nerve is a large terminal branch of the lateral cord. It passes laterally to penetrate the coracobrachialis muscle and pass between the biceps brachii and brachialis muscles in the arm, and innervates all three flexor muscles in the anterior compartment of the arm, terminating as the lateral cutaneous nerve of the forearm. The lateral root of the median nerve is the largest terminal branch of the lateral cord and passes medially to join a similar branch from the medial cord to form the median nerve (Fig. 7.55). Branches of the medial cord The medial cord has five branches (Fig. 7.55).


Anatomy_Gray

Anatomy_Gray. Branches of the medial cord The medial cord has five branches (Fig. 7.55). The medial pectoral nerve is the most proximal branch. It receives a communicating branch from the lateral pectoral nerve and then passes anteriorly between the axillary artery and axillary vein. Branches of the nerve penetrate and supply the pectoralis minor muscle. Some of these branches pass through the muscle to reach and supply the pectoralis major muscle. Other branches occasionally pass around the inferior or lateral margin of the pectoralis minor muscle to reach the pectoralis major muscle.


Anatomy_Gray

Anatomy_Gray. The medial cutaneous nerve of the arm (medial brachial cutaneous nerve) passes through the axilla and into the arm where it penetrates deep fascia and supplies skin over the medial side of the distal third of the arm. In the axilla, the nerve communicates with the intercostobrachial nerve of T2. Fibers of the medial cutaneous nerve of the arm innervate the upper part of the medial surface of the arm and floor of the axilla. The medial cutaneous nerve of the forearm (medial antebrachial cutaneous nerve) originates just distal to the origin of the medial cutaneous nerve of the arm. It passes out of the axilla and into the arm where it gives off a branch to the skin over the biceps brachii muscle, and then continues down the arm to penetrate the deep fascia with the basilic vein, continuing inferiorly to supply the skin over the anterior surface of the forearm. It innervates skin over the medial surface of the forearm down to the wrist.


Anatomy_Gray

Anatomy_Gray. The medial root of the median nerve passes laterally to join with a similar root from the lateral cord to form the median nerve anterior to the third part of the axillary artery.


Anatomy_Gray

Anatomy_Gray. The ulnar nerve is a large terminal branch of the medial cord (Fig. 7.55). However, near its origin, it often receives a communicating branch from the lateral root of the median nerve originating from the lateral cord and carrying fibers from C7 (see Fig. 5.73B). The ulnar nerve passes through the arm and forearm into the hand where it innervates all intrinsic muscles of the hand (except for the three thenar muscles and the two lateral lumbrical muscles). On passing through the forearm, branches of the ulnar nerve innervate the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus muscle. The ulnar nerve innervates skin over the palmar surface of the little finger, medial half of the ring finger, and associated palm and wrist, and the skin over the dorsal surface of the medial part of the hand.