section 34 of Grey's Anatomy part 1 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Morgan Scorpion anatomy of the human body part 1 by Henry Grey the interior of the skull part 2 differences in the skull due to age at birth the skull is large in proportion to the other parts of the skeleton but its facial portion is small and equals only about one eighth of the bulk of the cranium as compared with one half in the adult the frontal and parietal eminence is a prominent and the greatest width of the skull is at the level of the latter on the other hand the glabella supercillary arches and mastoid processes are not developed ossification of the skull bones is not completed and many of them e.g. the occipital, temporal, sphenoid, frontal and mandible consist of more than one piece unossified membranous intervals termed fontanelles are seen at the angles of the parietal bones these fontanelles are six in number two an anterior and a posterior are situated in the middle line and two an anterolateral and a posterior lateral on either side the anterior or bregmatic fontanelle is the largest and is placed at the junction of the sagittal, coronal and frontal sutures it is lozen shaped and measures about four centimeters in its anteroposteria and 2.5 centimeters in its transverse diameter the posterior fontanelle is triangular in form and is situated at the junction of the sagittal and mandoidal sutures the lateral fontanelles are small irregular in shape and correspond respectively with the sphenoidal and mastoidal angles of the parietal bones an additional fontanelle is sometimes seen in the sagittal suture at the region of the obelion the fontanelles are usually closed by the growth and extension of the bones which surround them but sometimes they are the sites of separate ossific centers which develop into stutual bones the posterior and lateral fontanelles are obliterated within a month or two after birth but the anterior is not completely closed until about the middle of the second year the smallness of the face at birth is mainly accounted for by the rudimentary condition of the maxillae and mandible the non-eruption of the teeth and the small size of the maxillary air sinuses and nasal cavities at birth the nasal cavities lie almost entirely between the orbits and the lower border of the anterior nasal aperture is only a little below the level of the orbital floor with the eruption of the deciduous teeth there is an enlargement of the face and jaws and these changes are still more marked after the second dentition the skull grows rapidly from birth to the seventh year by which time the foramen magnum and petrus parts of the temperals have reached their full size and the orbital cavities are only a little smaller than those of the adult growth is slow from the seventh year until the approach of puberty when a second period of activity occurs this results in an increase in all directions but it is especially marked in the frontal and facial regions where it is associated with the development of the air sinuses obliteration of the sutures of the vault of the skull takes place as age advances this process may commence between the ages of 30 and 40 and is first seen on the inner surface and some 10 years later on the outer surface of the skull the dates given are however only approximate as it is impossible to state with anything like accuracy that time at which the sutures are closed obliteration usually occurs first in the posterior part of the sagittal suture next in the carnal and then in the lambdoidal in old age the skull generally becomes thinner and lighter but in a small proportion of cases it increases in thickness and weight owing to an hypertrophy of the inner table the most striking feature of the old skull is the diminution in the size of the maxillae and mandible consequent on the loss of the teeth and the absorption of the aldeola processes this is associated with a marked reduction in the vertical measurement of the face and with an alteration in the angles of the mandible sexual differences in the skull until the age of puberty there is little difference between the skull of the female and that of the male the skull of an adult female is as a rule lighter and smaller and its cranial capacity about 10% less than that of the male its walls are thinner and its muscular ridges less strongly marked the glabella supercillary arches and mastoid processes are less prominent and the corresponding air sinuses are small or rudimentary the upper margin of the orbit is sharp the forehead vertical the frontal and parietal eminence is prominent and the vault somewhat flattens the contour of the face is more rounded the facial bones are smoother and the maxillae and mandible and their contained teeth smaller from what has been said it will be seen that more of the infantile characteristics are retained in the skull of the adult female than in that of the adult male a well marked male or female skull can easily be recognised as such but in some cases the respective characteristics are so indistinct that the determination of the sex may be difficult or impossible craniology skulls vary in size and shape and the term craniology is applied to the study of these variations the capacity of the cranial cavity constitutes a good index of the size of the brain which it contained and is most conveniently arrived at by filling the cavity with shot and measuring the contents in a graduated vessel skulls may be classified according to their capacities followed 1 microcephalic with a capacity of less than 1,350 cubic centimetres e.g. those of native Australians and Andaman Islanders 2 mesocephalic with a capacity of from 1,350 cubic centimetres to 1,450 cubic centimetres e.g. those of African Negroes and Chinese 3 mega cephalic with a capacity of over 1,450 cubic centimetres e.g. those of Europeans Japanese and Eskimos in comparing the shape of one skull with that of another it is necessary to adopt some definite position in which the skulls should be placed during the process of examination they should be so placed that a line carried through the lower margin of the orbit and upper margin of the external acoustic me at us is in the horizontal plane the norm I of one skull can then be compared with those of another and the differences in contour and surface form noted further it is necessary that the various linear measurements used to determine the shape of the skull should be made between definite and easily localized points on its surface the principal points may be divided into two groups one those in the median plane and two those on either side of it the points in the median plane are the mental point the most prominent point of the chin alveolar point of Prostion the central point of the anterior margin of the upper alveolar arch subnasal point the middle of the lower border of the anterior nasal aperture at the base of the anterior nasal spine nausea on the central point of the front of nasal suture glabella the point in the middle line at the level of the superciliary arches of rion the point in the middle line of the forehead at the level where the temporal lines most nearly approach each other bregma the meeting point of the coronal and sagittal sutures or beleon a point in the sagittal suture on a level with a parietal parameter lambda the point of junction of the sagittal and lamedoidal sutures occipital point the point in the middle line of the occipital bone farthest from the glabella inion the external occipital protubulance opistion the midpoint of the posterior margin of the forearm and magnum bastion the midpoint of the anterior margin of the forearm and magnum the points on either side of the median plane are the gonion the outer margin of the angle of the mandible daquian the point of union of the antosuperior angle of the lacrimal with the frontal bone and the frontal process of the maxilla stephanion the point where the temporal line intersects the coronal suture pterion the point where the great wing of the sphenoid joins the sphenoidal angle of the parietal auricular point the center of the orifice of the external acoustic meatus asterion the point of meeting of the lamedoidal master occipital and master parietal sutures the horizontal circumference of the cranium is measured in a plane passing through the glabella toner or the ophion flower in front and the occipital point behind it averages about 50 centimeters in the female and 52.5 centimeters in the male the occipital frontal or longitudinal arc is measured from the nasion over the middle line of the vertex to the opistion while the basin nasal length is the distance between the basion and the nasion these two measurements plus the antero-posterior diameter of the foramen magnum represent the vertical circumference of the cranium the length is measured from the glabella to the occipital point while the breadth or greatest transverse diameter is usually found near the external acoustic meatus the proportion of breadth to length breadth times a hundred divided by length is termed the cephalic index or index of breadth the height is usually measured from the basion to the breadma and the proportion of height to length height times a hundred divided by length constitutes the vertical or height index in studying the face the principal points to be noted are the proportion of its length and breadth the shape of the orbits and of the anterior nasal aperture and the degree of projection of the jaws the length of the face may be measured from the ophion or nasion to the chin or if the mandible be wanting to the alveolar point while its width is represented by the distance between the zygomatic arches by comparing the length with the width of the face skulls may be divided into two groups dolecofacial or leptoprosopae long-faced and brachyfacial or chemoprosopae short-faced the orbital index signifies the proportion which the orbital height bears to the orbital width thus orbital height times a hundred divided by orbital width the nasal index expresses the proportion which the width of the anterior nasal aperture bears to the height of the nose the latter being measured from the nasion to the lower margin of the nasal aperture thus nasal width times a hundred divided by nasal height the degree of projection of the jaws is determined by the gnastic or alveolar index which represents the proportion between the basial viola and basan nasal lengths thus basial viola length times a hundred divided by basan nasal length the following table modified from that given by duckworth illustrates how these different indices may be utilized in the classification of skulls index one cephalic classification below 75 nomenclature dolecocephalic examples capis and native australians index one cephalic classification between 75 and 80 nomenclature mesatiscephalic examples europeans and chinese index one cephalic classification above 80 nomenclature brachycephalic examples mongolians and andamans index two orbital classification below 84 nomenclature microceme examples tazmanians and native australians index two orbital classification between 84 and 89 nomenclature mesosem examples europeans index two orbital classification above 89 nomenclature megasem examples chinese and polynesians index three nasal classification below 48 nomenclature leptorine examples europeans index three nasal classification between 48 and 53 nomenclature mesorine examples japanese and chinese index three nasal classification above 53 nomenclature platirine examples negros and native australians index four ganathic classification below 98 nomenclature orthognathus examples europeans index four ganathic classification between 98 and 103 nomenclature mesognathus examples chinese and japanese index four ganathic classification above 103 nomenclature prognathus examples native australians the chief function of the skull is to protect the brain and therefore those portions of the skull which are most exposed to external violence are thicker than those which are shielded from injury by overlying muscles thus the skull cap is thick and dense whereas the temporal squami being protected by the temporalis muscles and the inferior occipital fossae being shielded by the muscles at the back of the neck are thin and fragile fracture of the skull is further prevented by its elasticity its rounded shape and its construction of a number of secondary elastic arches each made up of a single bone the manner in which vibrations are transmitted through the bones of the skull is also of importance as regards its protective mechanism at all events as far as the base is concerned in the vault the bones being of a fairly equal thickness and density vibrations are transmitted in a uniform manner in all directions but in the base owing to the varying thickness and density of the bones this is not so and therefore in this situation there are special buttresses which serve to carry the vibrations in certain definite directions at the front of the skull on either side is the ridge which separates the anterior from the middle fossa of the base and behind the ridge or buttress which separates the middle from the posterior fossa and if any violence is applied to the vault the vibrations would be carried along these buttresses to the cellar turkica where they meet this part has been termed the center of resistance and here there is a special protective mechanism to guard the brain the subarachnoid cavity at the base of the brain is dilated and the cerebral spinal fluid which fills it acts as a water cushion to shield the brain from injury in like manner when violence is applied to the base of the skull as in falls upon the feet the vibrations are carried backwards through the occipital quest and forward through the basilar part of the occipital and body of the sphenoid to the vault of the skull in connection with the bones of the face a common malfunction is cleft palate the cleft usually starts posteriorly and its most elementary form is a bifid uvula or the cleft may extend through the soft palate or the posterior part of the whole of the hard palate may be involved the cleft extending as far forward as the incisive foramen in the severest form the cleft extends to the alveolus and passes between the incisive or premaxillary bone and the rest of the maxilla that is to say between the lateral incisor and canine teeth in some instances the cleft runs between the central and lateral incisor teeth and this has induced some anatomists to believe the premaxillary bone is developed from two centers and not from one as was stated on page 163 the medial segment bearing a central incisor is called an endognathion the lateral segment bearing the lateral incisor is called a mesognathion the cleft may affect one or both sides if the latter the central part is frequently displaced forward and remains united to the septum of the nose the deficiency in the alveolus being complicated with the cleft in the lip hair lip on examining a cleft palate in which the alveolus is not implicated the cleft will generally appear to be in the median line but occasionally is unilateral and in some cases bilateral to understand this it must be borne in mind that three processes are concerned in the formation of the palate the palatine processes of the tumaxilli which grow in horizontally and unite in the middle line and the esmavomorine process which grows downward from the base of the skull and frontal nasal process to unite with the palatine processes in the middle line in those cases where the palatine processes fail to unite with each other and with the medial process the cleft of the palate is median where one palatine process unites with the medial septum the other failing to do so the cleft in the palate is unilateral in some cases where the palatine processes fail to meet in the middle the esmavomorine process goes downward between them and thus produces a bilateral cleft occasionally there may be a hole in the middle line of the hard palate the anterior part of the hard and soft palate being perfect this is rare because as a rule the union of the various processes progresses from before backward and therefore the posterior part of the palate is more frequently defective than the anterior end of section 34 section 35 of Grey's Anatomy part one this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Steve Foreman anatomy of the human body part one by Henry Gray the extremities the bones by which the upper and lower limbs are attached to the trunk constitute respectively the shoulder and pelvic girdles the shoulder girdle or girdle of the superior extremity is formed by the scapula and clavicles and is imperfect in front and behind in front however it is completed by the upper end of the sternum with which the medial ends of the clavicle articulate behind it is widely imperfect the scapula being connected to the trunk by muscles only the pelvic girdle or girdle of the inferior extremity is formed by the hip bones which articulate with each other in front at the symphysis pubis it is imperfect behind but the gap is filled in by the upper part of the sacrum the pelvic girdle with the sacrum is a complete ring massive and comparatively rigid in marked contrast to the lightness and mobility of the shoulder girdle the clavicle the clavicle forms the anterior portion of the shoulder girdle it is a long bone curved somewhat like the italic letter F and placed nearly horizontally at the upper and anterior part of the thorax immediately above the first rib it articulates medially with the manubrium sterni and laterally with the acromion of the scapula footnote the clavicle acts especially as a fulcrum to enable the muscles to give lateral motion to the arm it is accordingly absent in those animals whose forelimbs are used only for progression but is present for the most part in animals whose anterior extremities are clawed and used for prehension though in some of them as for instance in a large number of carnivora it is merely a rudimentary bone suspended among the muscles and not articulating with either the scapula or sternum end of footnote it presents a double curvature the convexity being directed toward the sternal end and the concavity at the scapular end its lateral third is flattened from above downward while its medial two-thirds is of a rounded or prismatic form lateral third the lateral third has two surfaces an upper and a lower and two borders an anterior and a posterior surface the upper surface is flat rough and marked by impressions for the attachments of the deltoidus in front and the trapezius behind between these impressions a small portion of the bone is subcutaneous the under surface is flat at its posterior border near the point where the prismatic joins with the flattened portion is a rough eminence the coracoid tuberosity this in the natural position of the bone surmounts the coracoid process of the scapula and gives attachment to the conoid ligament from this tuberosity an oblique ridge the oblique or trapezoid ridge runs forward in lateral word and afford attachment to the trapezoid ligament borders the anterior border is concave thin and rough and gives attachments to the deltoidus the posterior border is convex rough thicker than the anterior and gives attachment to the trapezius medial two-thirds the medial two-thirds constitute the prismatic portion of the bone which is curved so as to be convex in front concave behind and is marked by three borders separating three surfaces borders the anterior border is contiguous with the anterior margin of the flat portion its lateral part is smooth and corresponds to the interval between the attachments of the pectoralis major and deltoidus its medial part forms the lower boundary of an elliptical surface for the attachment of the clavicular portion of the pectoralis major and approaches the posterior border of the bone the superior border is continuous with the posterior margin of the flat portion and separates the anterior from the posterior surface smooth and rounded laterally it becomes rough towards the medial third for the attachment of the sternocleidomestoidus and ends at the upper angle of the sternal extremity the posterior or subclavian border separates the posterior from the inferior surface and extends from the coracoid tuberosity to the costal tuberosity it forms the posterior boundary of the groove for the subclavius and gives attachment to the layer of cervical fascia which envelops the omohioideus surfaces the anterior surface is included between the superior and anterior borders its lateral part looks upward and is continuous with the superior surface of the flattened portion it is smooth convex and nearly subcutaneous being covered only by the platysma medially it is divided by a narrow subcutaneous area into two parts a lower elliptical inform and directed forward for the attachment of the pectoralis major and an upper for the attachment of the sternocleidomestoidus the posterior or cervical surface is smooth and looks backward toward the root of the neck it is limited above by the superior border below by the subclavian border medially by the margin of the sternal extremity and laterally by the coracoid tuberosity it is concave medialaterally and is in relation by its lower part with the transverse scapular vessels this surface at the junction of the curves of the bone is also in relation to the brachial plexus of nerves and the subclavian vessels it gives attachment near the sternal extremity to part of the sternohioidius and presents near the middle an oblique foramen directed lateral word which transmits the chief nutrient artery of the bone sometimes there are two foramini on the posterior surface or one on the posterior and another on the inferior surface the inferior or subclavian surface is bounded in front by the anterior border behind by the subclavian border it is narrowed medially but gradually increases in width laterally and is continuous with the upper surface of the flat portion on its medial part is a broad rough surface the costal tuberosity rather more than two centimeters in length for the attachment of the costoclavicular ligament the rest of this surface is occupied by a groove which gives attachment to the subclavius the coricoclavicular fascia which splits to enclose the muscle is attached to the margins of the groove not infrequently this groove is subdivided longitudinally by a line which gives attachment to the intramuscular septum of the subclavius the sternal extremity extremitas sternalis internal extremity the sternal extremity of the clavicle is triangular in form directed medial word and a little downward and forward it presents an articular facet concave from before backward convex from above downward and articulates with the manubrium sterni through the intervention of an articular disc the lower part of the facet is continued on to the inferior surface of the bone as a small semi oval area for articulation with the cartilage of the first rib the circumference of the articular surface is rough for the attachment of numerous ligaments the upper angle gives attachment to the articular disc the acromial extremity extremitas acromialis outer extremity the acromial extremity presents a small flattened oval surface directed obliquely downward for articulation with the acromion of the scapula the circumference of the articular facet is rough especially above for the attachment of the chromio clavicular ligaments in the female the clavicle is generally shorter thinner less curved and smoother than in the male in those persons who perform considerable manual labor it becomes thicker and more curved and its ridges for muscular attachment are prominently marked structure the clavicle consists of cancerous tissue enveloped by a compact layer which is much thicker in the intermediate part than at the extremities of the bone ossification the clavicle begins to ossify before any other bone in the body it is ossified from three centers two primary centers a medial and lateral for the body which appears during the fifth or sixth week of fetal life and a secondary center for the sternal end which appears about the 18th or 20th year and unites with the rest of the bone about the 25th year end of section 35 section 36 of gray's anatomy part one this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Steve Foreman anatomy of the human body part one by Henry Gray the scapula the scapula forms the posterior part of the shoulder girdle it is a flat triangular bone with two surfaces three borders and three angles surfaces the costal or ventral surface presents a broad concavity the superscapular fossa the medial two-thirds of the fossa are marked by several oblique ridges which run lateral word and upward the ridges give attachment to the tenderness insertions and the surfaces between them to the fleshy fibers of the subscapularis the lateral third of the fossa is smooth and covered by the fibers of this muscle the fossa is separated from the vertebral border by smooth triangular areas at the medial and inferior angles and in the interval between these by a narrow ridge which is often deficient these triangular areas and the intervening ridge afford attachment to the seratus anterior at the upper part of the fossa is a transverse depression where the bone appears to be bent on itself along a line at right angles to and passing through the center of the glenoid cavity forming the considerable angle called the subscapular angle this gives greater strength to the body of the bone by its arched form while the summit of the arch serves to support the spine in a chromium the dorsal surface is arched from above downward and is subdivided into two unequal parts by the spine the portion above the spine is called the supraspinatus fossa and that below it is the infraspinatus fossa the supraspinatus fossa the smaller of the two is concave smooth and broader at its vertebral than at its humeral end its medial two-thirds is origin to the supraspinatus the infraspinatus fossa is much larger than the preceding toward its vertebral margin a shallow concavity is seen at its upper part its center presents a prominent convexity while near the axillary border is a deep groove which runs from the upper towards the lower part the medial two-thirds of the fossa give origin to the infraspinatus the lateral third is covered by this muscle the dorsal surface is marked near the axillary border by an elevated ridge which runs from the lower part of the glenoid cavity downward and backward to the vertebral border about 2.5 centimeters above the inferior angle the ridge serves for the attachment of a fibrous septum which separates the infraspinatus from the teres major and teres minor the surface between the ridge and the axillary border is narrow in the upper two-thirds of its extent and is crossed near the center by a groove for the passage of the scapular circumflex vessels it affords attachment to the teres minor its lower third presents a broader somewhat triangular surface which gives origin to the teres major and over which the latissimus dorsi glides frequently the ladder muscle takes origin by a few fibers from this part the broad and narrow portions above alluded to are separated by an oblique line which runs from the axillary border downward and backward to meet the elevated ridge to it is attached a fibrous septum which separates the teres muscle from each other the spine spina scapulae the spine is a prominent plate of bone which crosses obliquely the medial four-fifths of the dorsal surface of the scapula at its upper part and separates the supra from the infraspinatus fossa it begins at the vertical border by a smooth triangular area over which the tendon of insertion of the lower part of the trapezius glides and gradually becoming more elevated ends in the acromion which overhangs the shoulder joint the spine is triangular and flattened from above downward its apex being directed towards the vertebral border it presents two surfaces and three borders its superior surface is concave it assists in forming the supraspinatus fossa and gives origin to part of the supraspinatus its inferior surface forms part of the infraspinatus fossa gives origin to a portion of the infraspinatus and presents near its center the orifice of a nutrient canal of the three borders the anterior is attached to the dorsal surface of the bone the posterior or crest of the spine is broad and presents two lips and an intervening rough interval the trapezius is attached to the superior lip and a rough tubercle is generally seen on the portion of the spine which receives the tendon of the insertion of the lower part of this muscle the deltoidus is attached to the whole length of the inferior lip the interval between the lips is subcutaneous and partly covered by the tendinous fibers of these muscles the lateral border or base the shortest of the three is slightly concave its edges thick and round is continuous above within the under surface of the acromion below the neck of the scapula it forms the medial boundary of the great scapular notch which serves to connect the supran infraspinatus fossa the acromion the acromion forms the summit of the shoulder and is a large somewhat triangular or oblong process flattened from behind forward projecting it first lateral word and then curving upward and forward so as to overhang the glenoid cavity its superior surface directed upward backward and lateral word is convex rough and gives attachment to some fibers of the deltoidus and in the rest of its extent is subcutaneous its inferior surface is smooth and concave its lateral border is thick and irregular and presents three or four tubercles for the tendinous origins of the deltoidus its medial border shorter than the lateral is concave gives attachment to a portion of the trapezius and presents about its center a small oval surface for articulation with the acromial end of the clavicle borders of the three borders of the scapula the superior is the shortest and thinnest it is concave and extends from the medial angle to the base of the coracoid process at its lateral part is a deep semicircular notch the scapular notch formed partly by the base of the coracoid process this notch is converted into a foramen by the superior transverse ligament and serves for the passage of the superscapular nerve sometimes the ligament is ossified the adjacent part of the superior border forwards attachment to the omohiodius the axillary border is the thickest of the three it begins above at the lower margin of the glenoid cavity and inclines obliquely downward and backward to the inferior angle immediately below the glenoid cavity is a rough impression the infraglenoid tuberosity about 2.5 centimeters in length which gives origin to the long head of the triceps brachii in front of this is a longitudinal groove which extends as far as the lower third of this border and affords origin to part of the subscapularis the inferior third is thin and sharp and serves for the attachment of a few fibers of the teres major behind and of the subscapularis in front the vertebral border is the longest of the three and extends from the medial to the inferior angle it is arched intermediate in thickness between the superior and axillary borders and the portion of it above the spine forms an obtuse angle with the part below this border presents an anterior and a posterior lip and an intermediate narrow area the anterior lip affords attachment to the seratus anterior the posterior lip to the supraspinatus above the spine the infraspinatus below the area between the two lips to the levator scapulae above the triangular surface at the commencement of the spine to the rhomboidius minor on the edge of that surface and to the rhomboidius major below it this last is attached by means of the fibrous arch connected above to the lower part of the triangular surface at the base of the spine and below to the lower part of the border angles of the three angles the medial formed by the junction of the superior and vertebral borders is thin smooth rounded inclined somewhat lateral word and gives attachment to a few fibers of the levator scapulae the inferior angle thick and rough is formed by the union of the vertebral and axillary borders its dorsal surface affords attachment to the teres major and frequently to a few fibers of the latissimus dorsi the lateral angle is the thickest part of the bone and is sometimes called the head of the scapula on it is a shallow piriform articular surface the glenoid cavity which is directed lateral word and forward and articulates with the head of the humerus it is broader below than above and its vertical diameter is the longest the surface is covered with cartilage in a fresh state and its margins raised slightly give attachment to a fibrocartinal agilist structure the glenoid labrum which deepens the cavity at its apex is a slight elevation the supraglenoid tuberosity to which the long head of the biceps brachii is attached the neck of the scapula is the slightly constricted portion which surrounds the head and is more distinct below and behind than above and in front the coracoid process processes coracoidius the coracoid process is a thick curved process attached by a broad base to that upper part of the neck of the scapula it runs at first upward and medial word then becoming smaller it changes its direction and projects forward in lateral word the ascending portion flattened from before backwards presents in front a smooth concave surface across which the superscapularis passes the horizontal portion is flattened from above downward its upper surface is convex and irregular and gives attachment to the pectoralis minor under its surface is smooth its medial and lateral borders are rough the former gives attachment to the pectoralis minor and the latter to the coracochromial ligament the apex is embraced by the conjoined tendon of origin of the coraco brachialis and the short head of the biceps brachii and gives attachment to the coraco clavicular fascia on the medial part of the root of the coracoid process is a rough impression for the attachment of the conoid ligament and running from it obliquely forward and lateral word onto the upper surface of the horizontal portion is an elevated ridge for the attachment of the trapezoid ligament structure the head processes and the thickened part of the bone contains cancelous tissue the rest consists of a thin layer of compact tissue the central part of the supraspinatus fossa and the upper part of the infraspinatus fossa but especially the former are usually so thin as to be semi-transparent occasionally the bone is found wanting in this situation and the adjacent muscles are separated only by fibrous tissue ossification the scapulae is ossified from seven or more centers one for the body two for the coracoid process two for the acromion one for the vertebral border and one for the inferior angle ossification of the body begins about the second month of fetal life by the formation of an irregular quadrilateral plate of bone immediately behind the glenoid cavity this plate extends so as to form the chief part of the bone and spine growing up from the extorsal surface about the third month at birth a large part of the scapulae is osseous but the glenoid cavity the coracoid process the acromion the vertebral border and the inferior angle are cartilaginous from the 15th through the 18th month after birth ossification takes place in the middle of the coracoid process which as a rule becomes joined with the rest of the bone about the 15th year between the 14th and 20th years ossification of the remaining parts take place in quick succession and usually in the following order first in the root of the coracoid process in the form of a broad scale secondly near the base of the acromion thirdly in the inferior angle and contiguous part of the vertebral border fourthly near the extremity of the acromion fifthly in the vertebral border the base of the acromion is formed by an extension from the spine the two separate nuclei of the acromion unite and then join with the extension from the spine the upper third of the glenoid cavity is ossified from a separate center sub coracoid which makes its appearance between the 10th and 11th years and joins between the 16th and the 18th further an epiphyseal plate appears for the lower part of the glenoid cavity while the tip of the coracoid process frequently presents a separate nucleus these various epiphyces are joined to the bone by the 25th year failure of the bony union between the acromion and spine sometimes occurs the junction being affected by fibrous tissue or by an imperfect articulation in some cases of supposed fracture of the acromion with ligamentous union it is probable that the detached segment was never united to the rest of the bone end of section 36 section 37 of gray's anatomy part one this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Steve Foreman anatomy of the human body part one by Henry Gray section 37 the humerus the humerus is the longest and largest bone of the upper extremity it is divisible into a body and two extremities upper extremity the upper extremity consists of a large rounded head joined to the body by a constricted portion called the neck and two immenences the greater and lesser tubercles the head or kaput humeri the head nearly hemispherical in form footnote though the head is nearly hemispherical in form its margins as Humphrey has shown is by no means a true circle its greatest diameter is from the top of the inner tubercular groove in a direction downward mediaward and backwards hence it follows that the greatest elevation of the arm can be obtained by rolling the articular surface in this direction that is to say obliquely upward lateral word and forward into footnote is directed upward mediaward and a little backward and articulates with the glenoid cavity of the scapula the circumference of its articular surface is slightly constricted and is termed the anatomical neck in contradistinction to a constriction below the tubercles called the surgical neck which is frequently the seat of fracture fracture of the anatomical neck rarely occurs the anatomical neck or column anatomical is obliquely directed forming an obtuse angle with the body it is best marked in the lower half of its circumference in the upper half it is represented by a narrow groove separating the head from the tubercles it affords attachment to the articular capsule of the shoulder joint and is perforated by numerous vascular foramini the greater tubercle or tuberculum magis or greater tuberosity the greater tubercle is situated lateral to the head and lesser tubercle its upper surface is rounded and marked by three flat impressions the highest of these gives insertion to the supraspinatus the middle to the infraspinatus the lowest one and the body of the bone for about 2.5 centimeters below it to the teres minor the lateral surface of the greater tubercle is convex rough and continuous with the lateral surface of the body the lesser tubercle or tuberculum minus or lesser tuberosity the lesser tubercle although smaller is more prominent than the greater it is situated in front and is directed mediaward and forward above and in front it presents an impression for the insertion of the tendon of the subscapularis the tubercles are separated from each other by a deep groove the inter tubercular groove or bicepital groove which lodges the long tendon of the biceps brachii and transmits a branch of the anterior humeral circumflex artery to the shoulder joint it runs obliquely downward and ends near the junction of the upper with the middle third of the bone in the fresh state its upper part is covered with a thin layer of cartilage lined by a prolongation of the synovial membrane of the shoulder joint its lower portion gives insertion to the tendon of the latissimus dorsi it is deep and narrow above and becomes shallow and a little broader as it descends its lips are cold respectively the crest of the greater and lesser tubercles or bicepital ridges and forms the upper part of the anterior and medial borders of the body of the bone the body or shaft or corpus humeri the body is almost cylindrical in the upper half of its extent prismatic and flattened below and has three borders and three surfaces borders the anterior border runs from the front of the greater tubercle above to the coronoid fossa below separating the anterior medial from the anterolateral surface its upper part is a prominent ridge the crest of the greater tubercle it serves for the insertion of the tendon of the pectoralis major about its center it forms the anterior boundary of the deltoid tuberosity below it is smooth and rounded affording the attachment to the brachialis the lateral border runs from the back part of the greater tubercle to the lateral epicondyle and separates the anterolateral from the posterior surface its upper half is rounded and indistinctly marked serving for the attachment of the lower part of the insertion of the teres minor and below this giving origin to the lateral head of the triceps brachii its center is traversed by a broad but shallow oblique depression the radial sulcus or musculospiral groove its lower part forms a prominent rough margin a little curved from behind forward the lateral supracondylar ridge which presents an anterior lip for the origin of the brachioradialis above the extensor carbiradialis longus below a posterior lip for the triceps brachii and an intermediate ridge for the attachment of the lateral intermuscular septum the medial border extends from the lesser tubercle to the medial epicondyle its upper third consists of a prominent ridge the crest of the lesser tubercle which gives insertion to the tendon of the teres major about its center is a slight impression for the insertion of the coracle brachialis and just below this is the entrance of the nutrient canal directed downward sometimes there is a second nutrient canal at the commencement of the radial sulcus the inferior third of this border is raised into a slight ridge the medial supracondylar ridge which becomes very prominent below it presents an anterior lip for the origins of the brachialis and pronator teres a posterior lip for the medial head of the triceps brachii and an intermediate ridge for the attachment of the medial intramuscular septum surfaces the enteral lateral surface is directed lateral word above where it is smooth rounded and covered by the deltoidius forward and lateral word below where it is slightly concave from above downward and gives origin to part of the brachialis about the middle of this surface is a rough triangular elevation the deltoid tuberosity for the insertion of the deltoidius below this is the radial sulcus directed obliquely from behind forward and downward and transmitting the radial nerve and profunda artery the enteral medial surface less extensive than the enteral lateral is directed medial word above forward and medial word below its upper part is narrow and forms the floor of the inter tubercular groove which gives insertion to the tendon of the latissimus dorsi its middle part is slightly rough for the attachment of some of the fibers of the tendon of insertion of the coracle brachialis its lower part is smooth concave from above downward and gives origin to the brachialis footnote a small hook shape process of bone the supracondylar process varying from two to 20 millimeters in length is not infrequently found projecting from the enteral medial surface of the body of the humerus five centimeters above the medial epicondyle it is curved downward and forward and its pointed end is connected to the medial border just above the medial epicondyle by a fibrous band which gives origin to a portion of the pronator teres through the arch completed by this fibrous band the median nerve and brachial artery pass when these structures deviate from their usual course sometimes the nerve alone is transmitted through it or the nerve may be accompanied by the owner artery in cases of high division of the brachial a well marked groove is usually found behind the process in which the nerve and artery are lodged this arch is the homologue of the supracondylar foramen found in many animals and probably serves in them to protect the nerve and artery from compression during the contraction of the muscles in this region end of footnote the posterior surface appears somewhat twisted so that its upper part is directed a little medial word its lower part backward and a little lateral word nearly the whole of this surface is covered by the lateral and medial heads of the triceps brachii the former arising above and the latter below the radio sulcus the lower extremity the lower extremity is flattened from before backward and curves slightly forward it ends below in a broad articular surface which is divided into two parts by a slight ridge projecting on either side of the lateral and medial epicondyles the articular surface extends a little lower than the epicondyles and is curved slightly forward its medial extremity occupies a lower level than the lateral the lateral portion of this surface consists of a smooth rounded eminence named the capitellum of the humerus it articulates with the cup shaped depression on the head of the radius and is limited to the front and lower part of the bone on the medial side of this eminence is a shallow groove in which is received the medial margin of the head of the radius above the part of the capitellum is a slight depression the radial fossa which receives the anterior border of the head of the radius when the forearm is flexed the medial portion of the articular surface is named the trochlea and presents a deep depression between the two well marked borders it is convex from before backward concave from side to side and occupies an anterior lower and posterior parts of the extremity the lateral border separates it from the groove which articulates with the margin of the head of the radius the medial border is thicker of greater length and consequently more prominent than the lateral the grooved portion of the articular surface fits accurately within the semilunar notch of the ulna it is broader and deeper on the posterior than on the anterior aspect of the bone and is inclined obliquely downward and forward towards the medial side above the front part of the trochlea is a small depression the coronoid fossa which receives the coronoid process of the ulna during flexion of the forearm above the back part of the trochlea is a deep triangular depression the electronon fossa in which the summit of the electronon is received in extension of the forearm these fossa are separated from one another by a thin transparent lamina of bone which is sometimes perforated by the super trochlea foramen they are lined in the fresh state by the synovial membrane of the elbow joint and their margins afford attachment to the anterior and posterior ligaments of this articulation the lateral epicondyle is a small tuberculated eminence curved a little forward and giving attachment to the radial collateral ligament of the elbow joint and to a tendon common to the origin of the supinator and some of the extensor muscles the medial epicondyle larger and more prominent than the lateral is directed a little backward it gives attachment to the ulnar collateral ligament of the elbow joint to the pronator teres and to a common tendon of origin of some of the flexor muscles of the forearm the ulnar nerve runs in a groove on the back of this epicondyle the epicondyles are continuous above with the supracondylar ridges structure the extremities consist of tensilis tissue covered with a thin compact layer the body is composed of a cylinder of compact tissue thicker at the center than towards the extremities and contains a large medullary canal which extends along its whole length ossification the humerus is ossified from eight centers one for each of the following parts the body the head the greater tubercle the lesser tubercle the capitellum the trochlea and one for each epicondyle the center for the body appears near the middle of the bone in the eighth week of fetal life and soon extends towards the extremities at birth the humerus is ossified in nearly its whole length only the extremities remaining cartilaginous during the first year sometimes before birth ossification commences in the head of the bone and during the third year the center for the greater tubercle and during the fifth that for the lesser tubercle making their appearance by the sixth year the centers for the head and tubercles have joined so as to form a single large epithesis which fuses with the body about the 20th year the lower end of the humerus is ossified as follows at the end of the second year ossification begins in the capitellum and extends medial word to form the chief part of the articular end of the bone the center for the medial part of the trochlea appears about the age of 12 ossification begins in the medial epicondyle about the fifth year and in the lateral about the 13th or 14th year about the 16th or 17th year the lateral epicondyle and both portions of the articulating surface having already joined unite with the body and at the 18th year the medial epicondyle becomes joined to it end of section 37 section 38 of gray's anatomy part one this is a libra vox recording all libra vox recordings are in the public domain for more information or to volunteer please visit libra vox.org recorded by Laurie Ann Walden anatomy of the human body part one by Henry gray section 38 the ulna elbow bone footnote in the anatomical position the forearm is placed in extension and supination with the palm looking forward and the thumb on the outer side end footnote the ulna is a long bone prismatic in form placed at the medial side of the forearm parallel with the radius it is divisible into a body and two extremities its upper extremity of great thickness and strength forms a large part of the elbow joint the bone diminishes in size from above downward its lower extremity being very small and excluded from the wrist joint by the interposition of an articular disc the upper extremity proximal extremity the upper extremity presents two curved processes the alecronon and the carnoid process and two concave articular cavities the semilunar and radial notches the alecronon alecronon process the alecronon is a large thick curved eminence situated at the upper and back part of the ulna it is bent forward at the summit so as to present a prominent lip which is received into the alecronon fossa of the humerus an extension of the forearm its base is contracted where it joins the body and the narrowest part of the upper end of the ulna its posterior surface directed backward is triangular smooth subcutaneous and covered by a bursa its superior surface is of quadrilateral form marked behind by a rough impression for the insertion of the triceps brachii and in front near the margin by a slight transverse groove for the attachment of part of the posterior ligament of the elbow joint its anterior surface is smooth concave and forms the upper part of the semilunar notch its borders present continuations of the groove on the margin of the superior surface they serve for the attachment of ligaments that is the back part of the ulnar collateral ligament medially and the posterior ligament laterally from the medial border a part of the flexor carpi ulnarus arises while to the lateral border the anconeus is attached the caranoid process processes caranoidius the caranoid process is a triangular eminence projecting forward from the upper and front part of the ulna its base is continuous with the body of the bone and of considerable strength its apex is pointed slightly curved upward and inflection of the forearm is received into the caranoid fossa of the humerus its upper surface is smooth concave and forms the lower part of the semilunar notch its antero inferior surface is concave and marked by a rough impression for the insertion of the brachialis at the junction of this surface with the front of the body is a rough eminence the tuberosity of the ulna which gives insertion to a part of the brachialis to the lateral border of this tuberosity the oblique cord is attached its lateral surface presents a narrow oblong articular depression the radial notch its medial surface by its prominent free margin serves for the attachment of part of the ulnar collateral ligament at the front part of this surface is a small rounded eminence for the origin of one head of the flexor digitorum sublimus behind the eminence is a depression for part of the origin of the flexor digitorum profundus descending from the eminence is a ridge which gives origin to one head of the pronator teres frequently the flexor polisus longus arises from the lower part of the caranoid process by a rounded bundle of muscular fibers the semilunar notch incisura semilunaris greater sigmoid cavity the semilunar notch is a large depression formed by the alecranon and the caranoid process and serving for articulation with the trochlea of the humerus about the middle of either side of this notch is an indentation which contracts it somewhat and indicates the junction of the alecranon and the caranoid process the notch is concave from above downward and divided into a medial and a lateral portion by a smooth ridge running from the summit of the alecranon to the tip of the caranoid process the medial portion is the larger and is slightly concave transversely the lateral is convex above slightly concave below the radial notch incisura radialis lesser sigmoid cavity the radial notch is a narrow oblong articular depression on the lateral side of the caranoid process it receives the circumferential articular surface of the head of the radius it is concave from before backward and its prominent extremities serve for the attachment of the annular ligament the body or shaft corpus ulnae the body at its upper part is prismatic in form and curved so as to be convex behind and lateral word its central part is straight its lower part is rounded smooth and bent a little lateral word it tapers gradually from above downward and has three borders and three surfaces borders the volar border margot volaris anterior border begins above at the prominent medial angle of the caranoid process and ends below in front of the styloid process its upper part well defined and its middle portion smooth and rounded give origin to the flexor digitorum profundus its lower fourth serves for the origin of the pronator quadratus this border separates the volar from the medial surface the dorsal border margot dorsalis posterior border begins above at the apex of the triangular subcutaneous surface at the back part of the elecronon and ends below at the back of the styloid process it is well marked in the upper three fourths and gives attachment to an aponeurosis which affords a common origin to the flexor carpi ulnaeus the extensor carpi ulnaeus and the flexor digitorum profundus its lower fourth is smooth and rounded this border separates the medial from the dorsal surface the interosseous crest crista interossea external or interosseous border begins above by the union of two lines which converge from the extremities of the radial notch and enclose between them a triangular space for the origin of part of the supinator it ends below at the head of the ulna its upper part is sharp its lower fourth smooth and rounded this crest gives attachment to the interosseous membrane and separates the volar from the dorsal surface surfaces the volar surface faciace volaris anterior surface much broader above than below is concave in its upper three fourths and gives origin to the flexor digitorum profundus its lower fourth also concave is covered by the pronator quadratus the lower fourth is separated from the remaining portion by a ridge directed obliquely downward and medial word which marks the extent of origin of the pronator quadratus at the junction of the upper with the middle third of the bone is the nutrient canal directed obliquely upward the dorsal surface faciace dorsalis posterior surface directed backward and lateral word is broad and concave above convex and somewhat narrower in the middle narrow smooth and rounded below on its upper part is an oblique ridge which runs from the dorsal end of the radial notch downward to the dorsal border the triangular surface above this ridge receives the insertion of the anconeus while the upper part of the ridge affords attachment to the supinator below this the surface is subdivided by a longitudinal ridge sometimes called the perpendicular line into two parts the medial part is smooth and covered by the extensor carpi onaris the lateral portion wider and rougher gives origin from above downward to the supinator the abductor policies longest the extensor policies longest and the extensor indices proprio the medial surface faciace medialis internal surface is broad and concave above narrow and convex below its upper three fourths give origin to the flexor digitorum profundus its lower fourth is subcutaneous the lower extremity distal extremity the lower extremity of the ulna is small and presents two immanences the lateral and larger is a rounded articular immanence termed the head of the ulna the medial narrower and more projecting is a non-articular immanence the styloid process the head presents an articular surface part of which of an oval or semi lunar form is directed downward and articulates with the upper surface of the triangular articular disc which separates it from the wrist joint the remaining portion directed lateral word is narrow convex and received into the ulnar notch of the radius the styloid process projects from the medial and back part of the bone it descends a little lower than the head and its rounded end affords attachment to the ulnar collateral ligament of the wrist joint the head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disc and behind by a shallow groove for the tendon of the extensor carpy ulnaris structure the long narrow medullary cavity is enclosed in a strong wall of compact tissue which is thickest along the interosseous border and dorsal surface at the extremities the compact layer thins the compact layer is continued onto the back of the alecronon as a plate of close spongy bone with lamellae parallel from the inner surface of this plate and the compact layer below it trabeculi arch forward toward the alecronon and coronoid and cross other trabeculi passing backward over the medullary cavity from the upper part of the shaft below the carnoid below the carnoid process there is a small area of compact bone from which trabeculi curve upward to end obliquely to the surface of the semilunar notch which is coated with a thin layer of compact bone the trabeculi at the lower end have a more longitudinal direction ossification the ulna is ossified from three centers one each for the body the inferior extremity and the top of the alecronon ossification begins near the middle of the body about the eighth week of fetal life and soon extends through the greater part of the bone at birth the ends are cartilaginous about the fourth year a center appears in the middle of the head and soon extends into the styloid process about the tenth year a center appears in the alecronon near its extremity the chief part of this process being formed by an upward extension of the body the upper epithesis joins the body about the sixteenth the lower about the twentieth year articulations the ulna articulates with the humerus and radius end of section 38 section 39 of gray's anatomy part one this is a libravox recording all libravox recordings are in the public domain for more information or to volunteer please visit libravox.org recorded by larry ann walden anatomy of the human body part one by henry gray the radius the radius is situated on the lateral side of the ulna which exceeds it in length and size its upper end is small and forms only a small part of the elbow joint but its lower end is large and forms the chief part of the wrist joint it is a long bone prismatic in form and slightly curved longitudinally it has a body and two extremities the upper extremity proximal extremity the upper extremity presents a head neck and tuberosity the head is of a cylindrical form and on its upper surface is a shallow cup or phobia for articulation with the capitulum of the humerus the circumference of the head is smooth it is broad medially where it articulates with the radial notch of the ulna narrow in the rest of its extent which is embraced by the annular ligament the head is supported on a round smooth and constricted portion called the neck on the back of which is a slight ridge for the insertion of part of the supinator beneath the neck on the medial side is an eminence the radial tuberosity its surface is divided into a posterior rough portion for the insertion of the tendon of the biceps brachii and an anterior smooth portion on which a bursa is interposed between the tendon and the bone the body or shaft corpus radii the body is prismoid in form narrower above than below and slightly curved so as to be convex lateral it presents three borders and three surfaces borders the volar border margot volaris anterior border extends from the lower part of the tuberosity above to the anterior part of the base of the staloid process below and separates the volar from the lateral surface its upper third is prominent and from its oblique direction has received the name of the oblique line of the radius it gives origin to the flexor digitorum sublimus and flexor polisus longus the surface above the line gives insertion to part of the supinator the middle third of the volar border is indistinct and rounded the lower fourth is prominent and gives insertion to the pronator quadratus and attachment to the dorsal carpal ligament it ends in a small tubercle into which the tendon of the brachioradialis is inserted the dorsal border margot dorsalis posterior border begins above at the back of the neck and ends below at the posterior part of the base of the staloid process it separates the posterior from the lateral surface it is indistinct above and below but well marked in the middle third of the bone the interosseous crest crista interossea internal or interosseous border begins above at the back part of the tuberosity and its upper part is rounded and indistinct it becomes sharp and prominent as it descends and at its lower part divides the two ridges which are continued to the anterior and posterior margins of the ulnar notch to the posterior of the two ridges the lower part of the interosseous membrane is attached while the triangular surface between the ridges gives insertion to part of the pronator quadratus this crest separates the volar from the dorsal surface and gives attachment to the interosseous membrane surface the volar surface faciase volaris anterior surface is concave in its upper three fourths and gives origin to the flexor polysis longus it is broad and flat in its lower fourth and affords insertion to the pronator quadratus a prominent ridge limits the insertion of the pronator quadratus below and between this and the inferior border is a triangular rough surface for the attachment of the volar radiocarpal ligament at the junction of the upper and middle thirds of the volar surface is the nutrient foramen which is directed obliquely upward the dorsal surface faciase dorsalis posterior surface is convex and smooth in the upper third of its extent and covered by the supinator its middle third is broad slightly concave and gives origin to the abductor polysis longus above and the extensor polysis brevis below its lower third is broad convex and covered by the tendons of the muscles which subsequently run in the grooves on the lower end of the bone the lateral surface faciase lateralis external surface is convex throughout its entire extent its upper third gives insertion to the supinator about its center is a rough ridge for the insertion of the pronator terrace its lower part is narrow and covered by the tendons of the abductor polysis longus and extensor polysis brevis the lower extremity the lower extremity is large of quadrilateral form and provided with two articular surfaces one below for the carpus and another at the medial side for the ulna the carpal articular surface is triangular concave smooth and divided by a slight antero posterior ridge into two parts of these the lateral triangular articulates with the navicular bone the medial quadrilateral with the lunate bone the articular surface for the ulna is called the ulnar notch sigmoid cavity of the radius it is narrow concave smooth and articulates with the head of the ulna these two articular surfaces are separated by a prominent ridge to which the base of the triangular articular disc is attached this disc separates the wrist joint from the distal radio ulnar articulation this end of the bone has three nonarticular surfaces volar dorsal and lateral the volar surface rough and irregular affords attachment to the volar radiocarpal ligament the dorsal surface is convex affords attachment to the dorsal radiocarpal ligament and is marked by three grooves enumerated from the lateral side the first groove is broad but shallow and subdivided into two by a slight ridge the lateral of these two transmits the tendon of the extensor karpi radialis longus the medial the tendon of the extensor karpi radialis brevis the second is deep but narrow and bounded laterally by a sharply defined ridge it is directed obliquely from above downward and lateral word and transmits the tendon of the extensor polysis longus the third is broad for the passage of the tendons of the extensor indices proprio and extensor digitorum communus the lateral surface is prolonged obliquely downward into a strong conical projection the styloid process which gives attachment by its base to the tendon of the brachio radialis and by its apex to the radial collateral ligament of the wrist joint the lateral surface of this process is marked by a flat groove for the tendons of the abductor polysis longus and extensor polysis brevis structure the long narrow medullary cavity is enclosed in a strong wall of compact tissue which is thickest along the interosseous border and thinnest at the extremities except over the cup shaped articular surface fovea of the head where it is thickened the trabeculae of the spongy tissue are somewhat arched at the upper end and pass upward from the compact layer of the shaft to the fovea capituli they are crossed by others parallel to the surface of the fovea the arrangement at the lower end is somewhat similar ossification the radius is ossified from three centers one for the body and one for either extremity that for the body makes its appearance near the center of the bone during the eighth week of fetal life about the end of the second year ossification commences in the lower end and at the fifth year in the upper end the upper epithesis fuses with the body at the age of 17 or 18 years the lower about the age of 20 an additional center sometimes found in the radial tuberosity appears about the 14th or 15th year end of section 39 section 40 of gray's anatomy part one this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Leanne Howlett anatomy of the human body part one by Henry Gray 6b the hand part one the carpus the skeleton of the hand is subdivided into three segments the carpus or wrist bones the metacarpus or bones of the palm and the phalanges or bones of the digits the carpus asa carpi the carpal bones aid in number are arranged in two rows those of the proximal row from the radial to the ulnar side are named the navicular lunate triangular and pisiform those of the distal row in the same order are named the greater multangular lesser multangular capitate and hamate common characteristics of the carpal bones each bone accepting the pisiform presents six surfaces of these the volar or anterior and the dorsal or posterior surfaces are rough for ligamentous attachment the dorsal surfaces being the broader except in the navicular and lunate the superior or proximal and inferior or distal surfaces are articular the superior generally convex the inferior concave the medial and lateral surfaces are also articular where they are in contact with the contiguous bones otherwise they are rough and tuberculated the structure and all is similar these cancellous tissue enclosed in a layer of compact bone bones of the proximal row upper row the navicular bone os navicular manas scaffold bone the navicular bone is the largest bone of the proximal row and has received its name from its fancied resemblance to a boat it is situated at the radial side of the carpus its long axis being from above downward lateral word and forward the superior surface is convex smooth of triangular shape and articulates with the lower end of the radius the inferior surface directed downward lateral word and backward is also smooth convex and triangular and is divided by a slight ridge into two parts the lateral articulating with the greater multangular the medial with the lesser multangular on the dorsal surface is a narrow rough groove which runs the entire length of the bone and serves for the attachment of ligaments the volar surface is concave above and elevated at its lower and lateral part and to a rounded projection the tubercle which is directed forward and gives attachment to the transverse carpal ligament and sometimes origin to a few fibers of the abductor polysis brevis the lateral surface is rough and narrow and gives attachment to the radial collateral ligament of the wrist the medial surface presents two articular facets of these the superior or smaller is flattened of semilunar form and articulates with the lunate bone the inferior or larger is concave forming with the lunate a concavity for the head of the capitate bone articulations the navicular articulates with five bones the radius proximally greater and lesser multangulars distally and capitate and lunate medially the lunate bone os lunatum semilunar bone the lunate bone may be distinguished by its deep concavity and crescentic outline it is situated in the center of the proximal row of the carpus between the navicular and triangular the superior surface convex and smooth articulates with the radius the inferior surface is deeply concave and have greater extent from before backward than transversely it articulates with the head of the capitate and by a long narrow facet separated by a ridge from the general surface with the hay mate the dorsal and volver surfaces are rough for the attachment of ligaments the former being the broader and of a somewhat rounded form the lateral surface presents a narrow flattened semilunar facet for articulation with the navicular the medial surface is marked by a smooth quadrilateral facet for articulation with the triangular articulations the lunate articulates with five bones the radius proximally capitate and hay mate distally navicular laterally and triangular medially the triangular bone os trichotum cuneiform bone the triangular bone may be distinguished by its pyramidal shape and by an oval isolated facet for articulation with the pisiform bone it is situated at the upper and ulnar side of the carpus the superior surface presents a medial rough non-articular portion and a lateral convex articular portion which articulates with the triangular articular disc of the wrist the inferior surface directed lateral word is concave sinuously curved and smooth for articulation with the hay mate the dorsal surface is rough for the attachment of ligaments the volver surface presents on its medial part an oval facet for articulation with the pisiform its lateral part is rough for ligamentous attachment the lateral surface the base of the pyramid is marked by a flat quadrilateral facet for articulation with the lunate the medial surface the summit of the pyramid is pointed and roughened for the attachment of the ulnar collateral ligament of the wrist articulations the triangular articulates with three bones the lunate laterally the pisiform in front the hay mate distally and with the triangular articular disc which separates it from the lower end of the ulna the pisiform bone os pisiform the pisiform bone may be known by its small size and by its presenting a single articular facet it is situated on a plane anterior to the other carpal bones and is spheroidal in form its dorsal surface presents a smooth oval facet for articulation with the triangular this facet approaches the superior but not the inferior border of the bone the volar surface is rounded and rough and gives attachment to the transverse carpal ligament and to the flexor carpi ulnarus and abductor digitai quintai the lateral and medial surfaces are also rough the former being concave the latter usually convex articulation the pisiform articulates with form articulates with one bone the triangular bones of the distal row lower row the greater multangular bone os multangulum magis trapezium the greater multangular bone may be distinguished by a deep groove on its volar surface it is situated at the radial side of the carpus between the navicular and the first metacarpal bone the superior surface is directed upward and medial word medially it is smooth and articulates with a navicular laterally it is rough and continuous with the lateral surface the inferior surface is oval concave from side to side convex from before backward so as to form a saddle shaped surface for articulation with the base of the first metacarpal bone the dorsal surface is rough the volar surface is narrow and rough at its upper part is a deep groove running from above obliquely downward and medial word it transmits the tendon of the flexor carpi radialis and is bounded laterally by an oblique ridge this surface gives origin to the oponens polisus and to the abductor and flexor polisus brevis that also affords attachment to the transverse carpal ligament the lateral surface is broad and rough for the attachment of ligaments the medial surface presents two facets the upper large and concave articulates with the lesser multangular the lower small and oval with the base of the second metacarpal articulations the greater multangular articulates with four bones the navicular proximally the first metacarpal distally and the lesser multangular and second metacarpal medially the lesser multangular bone os multangulum minus trapezoid bone the lesser multangular is the smallest bone in the distal row it may be known by its wedge shaped form the broad end of the wedge constituting the dorsal the narrow end the volar surface and by its having four articular facets touching each other and separated by sharp edges the superior surface quadrilateral smooth and slightly concave articulates with the navicular the inferior surface articulates with the proximal end of the second metacarpal bone it is convex from side to side concave from before backward and subdivided by an elevated ridge into two unequal facets the dorsal and volar surfaces are rough for the attachment of ligaments the former being the larger of the two the lateral surface convex and smooth articulates with the greater multangular the medial surface is concave and smooth in front for articulation with the capitate rough behind for the attachment of an interosseous ligament articulations the lesser multangular articulates with four bones the navicular proximally second metacarpal distally greater multangular laterally and capitate medially the capitate bone oscapitatum osmagnum the capitate bone is the largest of the carpal bones and occupies the center of the wrist it presents above a rounded portion or head which is received into the concavity formed by the navicular and lunate a constricted portion or neck and below this the body the superior surface is round smooth and articulates with the lunate the inferior surface is divided by two ridges into three facets for articulation with the second third and fourth metacarpal bones that for the third being the largest the dorsal surface is broad and rough the volar surface is narrow rounded and rough for the attachment of ligaments and a part of the adductor policies obliquus the lateral surface articulates with the lesser multangular by a small facet at its anterior inferior angle behind which is a rough depression for the attachment of an interosseous ligament above this is a deep rough groove forming part of the neck and serving for the attachment of ligaments it is bounded superiorly by a smooth convex surface for articulation with the navicular the medial surface articulates with the haymate by a smooth concave oblong facet which occupies its posterior and superior parts it is rough in front for the attachment of an interosseous ligament articulations the capitate articulates with seven bones the navicular and lunate proximally the second third and fourth metacarpals distally the lesser multangular on the radial side and the haymate on the ulnar side the haymate bone os hematom un-siform bone the haymate bone may be readily distinguished by its wedge-shaped form and the hook-like process which projects from its volar surface it is situated at the medial and lower angle of the carpus with its base downward resting on the fourth and fifth metacarpal bones and its apex directed upward and lateral word the superior surface the apex of the wedge is narrow convex smooth and articulates with the lunate the inferior surface articulates with the fourth and fifth metacarpal bones by concave facets which are separated by a ridge the dorsal surface is triangular and rough for ligamentous attachment the volar surface presents at its lower and ulnar side a curved hook-like process the hamulus directed forward and lateral word this process gives attachment by its apex to the transverse carpal ligament and the flexor carpi ulnarus by its medial surface to the flexor brevis and oponens digitai quintai its lateral side is grooved for the passage of the flexor tendons and to the palm of the hand it is one of the four immanences on the front of the carpus to which the transverse carpal ligament of the wrist is attached the others being the pisiform medially the oblique ridge of the greater multangular and the tubercle of the navicular laterally the medial surface articulates with the triangular bone by an oblong facet cut obliquely from above downward and medial word the lateral surface articulates with the capitate by its upper and posterior part the remaining portion being rough for the attachment of ligaments articulations the hamate articulates with five bones the lunate proximally the fourth and fifth metacarpals distally the triangular medially the capitate laterally end of section 40 recording by lianne howlett section 41 of graze anatomy part one this is a libra vox recording all libra vox recordings are in the public domain for more information or to volunteer please visit libra vox.org recording by lianne howlett anatomy of the human body part one by henry gray six b part two the metacarpus the metacarpus consists of five cylindrical bones which are numbered from the lateral side asa metacarpalia one through five each consists of a body and two extremities common characteristics of the metacarpal bones the body corpus shaft the body is prismoid in form and curved so as to be convex in the longitudinal direction behind concave in front it presents three surfaces medial lateral and dorsal the medial and lateral surfaces are concave for the attachment of the enteroscii and separated from one another by a prominent anterior ridge the dorsal surface presents in its distal two-thirds a smooth triangular flattened area which is covered in the fresh state by the tendons of the extensor muscles this surface is bounded by two lines which commence in small tubercles situated on either side of the digital extremity and passing upward converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity this ridge separates two sloping surfaces for the attachment of the enteroscii dorsalis to the tubercles on the digital extremities are attached the collateral ligaments of the metacarpal phalangeal joints the base or carpal extremity bases is of a cuboidal form and broader behind than in front it articulates with the carpus and with the adjoining metacarpal bones its dorsal and volar surfaces are rough for the attachment of ligaments the head or digital extremity capitulum presents an oblong surface markedly convex from before backward less so transversely and flattened from side to side it articulates with the proximal phalanx it is broader and extends farther upward on the volar than on the dorsal aspect and is longer in the antero posterior than in the transverse diameter on either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpal phalangeal joint the dorsal surface broad and flat supports the extensor tendons the volar surface is grooved in the middle line for the passage of the flexor tendons and marked on either side by an articular eminence continuous with the terminal articular surface characteristics of the individual metacarpal bones the first metacarpal bone os metacarpale one metacarpal bone of the thumb is shorter and stouter than the others diverges to a greater degree from the carpus and its volar surface is directed toward the palm the body is flattened and broad on its dorsal surface and does not present the ridge which is found on the other metacarpal bones its volar surface is concave from above downward on its radial border is inserted the oponent polisus its ulnar border gives origin to the lateral head of the first enterosceus dorsalis the base presents a concave convex surface for articulation with the greater multangular it has no facets on its sides but on its radial side is the tubercle for the insertion of the abductor polisus longus the head is less convex than those of the other metacarpal bones and is broader from side to side than from before backward on its volar surface are two articular iminences of which the lateral is the larger for the two sesamoid bones in the tendons of the flexor polisus brevis the second metacarpal bone os metacarpale two metacarpal bone of the index finger is the longest and its base the largest of the four remaining bones its base is prolonged upward and medial word forming a prominent ridge it presents four articular facets three on the upper surface and one on the ulnar side of the facets on the upper surface the intermediate is the largest and is concave from side to side convex from before backward for articulation with the lesser multangular the lateral is small flat and oval for articulation with the greater multangular the medial on the summit of the ridge is long and narrow for articulation with the capitate the facet on the ulnar side articulates with a third metacarpal the extensor carpai radialus longus is inserted on the dorsal surface and the flexor carpai radialus on the volar surface of the base the third metacarpal bone os metacarpal three metacarpal bone of the middle finger is a little smaller than the second the dorsal aspect of its base presents on its radial side a pyramidal eminence the styloid process which extends upward behind the capitate immediately distal to this as a rough surface for the attachment of the extensor carpai radialus brevis the carpal articular facet is concave behind flat in front and articulates with the capitate on the radial side is a smooth concave facet for articulation with the second metacarpal and on the ulnar side two small oval facets for the fourth metacarpal the fourth metacarpal bone os metacarpal four metacarpal bone of the ring finger is shorter and smaller than the third the base is small and quadrilateral its superior surface presents two facets a large one medially for articulation with the hamate and a small one laterally for the capitate on the radial side are two oval facets for articulation with the third metacarpal and on the ulnar side a single concave facet for the fifth metacarpal the fifth metacarpal bone os metacarpal five metacarpal bone of the little finger presents on its base one facet on its superior surface which is concave convex and articulates with the hamate and one on its radial side which articulates with the fourth metacarpal on its ulnar side is a prominent tubercle for the insertion of the tendon of the extensor carpy ulnarus the dorsal surface of the body is divided by an oblique ridge which extends from near the ulnar side of the base to the radial side of the head the lateral part of this surface serves for the attachment of the fourth enterocis dorsalis the medial part is smooth triangular and covered by the extensor tendons of the little finger articulations besides their phalangeal articulations the metacarpal bones articulate as follows the first with the greater multangular the second with the greater multangular lesser multangular capitate and third metacarpal the third with the capitate and second and fourth metacarpals the fourth with the capitate hamate and third and fifth metacarpals and the fifth with the hamate and fourth metacarpal end of section 41 recording by leanne howlett section 42 of gray's anatomy part one this is a livervox recording all livervox recordings are in the public domain for more information or to volunteer please visit the livervox.org recording by david laurance anatomy of the human body part one by henry gray the phalanges of the hand phalanges digitorum minus the phalanges are fourteen in number three for each finger and two for the thumb each consists of a body in two extremities the body tapers from above downward is convex posteriorly concave in front from above downward flat from side to side its sides are marked by rough which give attachment to the fibrous sheaths of the flexor tendons the proximal extremities of the bones of the first row present oval concave articular surfaces broader from side to side than from before backward the proximal extremity of each of the bones of the second and third rows present a double concavity separated by a median ridge the distal extremities are smaller than the proximal and each ends in two condyles separated by a shallow groove the articular surface extends farther on the volar than on the dorsal surface a condition best marked in the bones of the first row the ungual phalanges are convex on their dorsal and flat on their volar surfaces they are recognized by their small size and by a roughened elevated surface of a horseshoe form on the volar surface of the distal extremity of each which serves to support the sensitive pulp of the finger articulations in the four fingers the phalanges of the first row articulate with those of the second row and with the metacarpals the phalanges of the second row with those of the first and third rows and the ungual phalanges with those of the second row in the thumb which has only two phalanges the first phalanx articulates by its proximal extremity with the metacarpal bone and by its distal with the ungual phalanx ossification of the bones of the hand the carpal bones are each ossified from a single center and ossification proceeds in the following order in the capitate and hamate during the first year the former proceeding the latter in the triangular during the third year in the lunate and greater multangular during the fifth year the former proceeding the latter in the navicular during the sixth year in the lesser multangular during the eighth year and in the pysiform about the twelfth year occasionally an additional bone the oscentral is found on the back of the carpus lying between the navicular less multangular and capitate during the second month of fetal life it is represented by a small cartilaginous nodule which usually fuses with the cartilaginous navicular sometimes the siloed process of the third metacarpal is detached and forms an additional ossicle the metacarpal bones are each ossified from two centers one for the body and one for the distal extremity of each of the second third fourth and fifth bones one for the body and one for the base of the first metacarpal bone the first metacarpal bone is therefore ossified in the same manner as the phalanges and this has led some anatomists to regard the thumb as being made up of three phalanges and not have a metacarpal bone and two phalanges ossification commences in the middle of the body about the eighth or ninth week of fetal life the centers for the second and third metacarpals being the first and that for the first metacarpal the last to appear about the third year the distal extremities of the metacarpals of the fingers and the base of the metacarpal of the thumb begins to ossify they unite with the bodies about the 20th year the phalanges are each ossified from two centers one for the body and one for the proximal extremity ossification begins in the body about the eighth week of fetal life ossification of the proximal extremity commences in the bones of the first row between the third and fourth years and a year later in those of the second and third rows the two centers become united in each row between the 18th and 20th years in the ungual phalanges the centers of the body appear in the distal extremities of the phalanges instead of the middle of the bodies as in the other phalanges moreover of all the bones in the hand the ungual phalanges are the first to ossify footnote alan thompson demonstrated the fact that the first metacarpal bone is often developed from three centers that is to say there is a separate nucleus for the distal end forming a distinct epiphysis visible at the age of seven or eight years he also stated that there are traces of a proximal epiphysis in the second metacarpal bone in footnote end of section 42 recording by david laurence brampton ontario september 2008


Now let me ask you this because in a way you're I mean you're calling it the freedom dividend so that gives individuals hypothetically more freedom but here's what I worry about and I'm not saying that this is something that you're proposing but this is what I'm worried about post-Yang presidency we pass UBI you served two terms you know you've been president now but we have a republican administration and what they tend to do is they pitch the idea of freedom but oftentimes it's a Trojan horse to privatize social safety net programs so let me give you an example so republicans often talk about a voucher they like to do that they talk about voucher voucher programs for healthcare for education now what is this in actuality it's a ploy to privatize it because if you devalue the utility of these types of social safety net programs what happens you open the door to privatization because that undermines public support and so here's what I worry about if we get UBI and that kind of becomes the standard it replaces food stamps for the most part how can we how can we protect what exists for you know the social safety net alongside UBI if people still opt for welfare instead of UBI simply because it benefits them more like for example my dad it just benefits him to get you know the 1300 from social security so how can we protect social security if it's devalued because of UBI you know that this is a very legitimate and important consideration and one of the things that I said to to folks is that on the bright side because people you know very understandably it's like look conservatives love to try and like you know chop away at these programs and like might having the freedom dividend make it easier for them to do so and then there is a contrary point of view that that this freedom dividend could itself become sort of like a tree trunk where you can't chop it because everyone's getting it and then you're like okay like well it's sort of hard to to attack it and the Alaska example is instructive where you know they've had it for almost 40 years and like it's so popular like you can't touch it and so there is like a trade off first as you I think can tell I would be the last person who wants to take away social programs for anyone and certainly like you're right that it's possible that the president after me is then like ooh like let me see if I can you know right because I mean you can't be president forever so that's what I'm worried about is future administrations yeah it's a legitimate concern you know that the thing that I'd suggest it to people is that you have to take a look at our current situation which is that I'm not sure how hatchet proof our existing programs are right now like the the conservatives are already successfully pulled back benefits in various in various states in various environments that's true and so it's not like right now in the absence of the freedom dividend dividend these programs are bulletproof a lot of people are actually very concerned about these programs future and and the the fear I have if you look into you know what I think is coming with this wave of automation is that the thing that's driving the hatcheting away of various welfare programs is this mindset of scarcity that is predominant and unfortunately it's getting higher and stronger as financial insecurity sweeps the country more or less where then if you have people who are struggling themselves economically it's easier for conservative leaders to look at them and say hey guys what's that yeah we don't have enough money to go around you know we have to do we have to get rid of these welfare programs for the people and then the people who are curious they are like yeah that's right that's why like things aren't good is because we're wasting money on these like other people and and that mindset is getting stronger and deeper and nastier all the time because we're pushing more and more americans and communities into economic distress right so in the freedom dividend world where people don't feel like they're very future and their their kids futures are like in question and then you know you get the economic boot off of people's throat and they have a greater sense of abundance and future orientation and maybe even like you know lower stress levels then it's going to be harder to gin them up to attack and hatchet welfare programs because if you go and say hey these people are getting this stuff then they'll be like who cares you know like my life is fine my kids are fine i'm getting stuff they're getting some more stuff like maybe that's fine too maybe they need it maybe you know their circumstances are different than mine so if you have yeah because this is what i this is what concerns me the most and i'm supportive of ubi to be clear so if you are also kind of concerned with the same thing of future administrations getting in and you know using ubi to pitch cutting other social safety net programs why not redesign your current ubi proposal to make it supplement existing social safety net programs because i think that that would make everything uh all of these problems that i'm i'm bringing up kind of go away because if it truly is universal everybody gets it nobody's gonna want to get rid of in congress is gonna want to get rid of ubi if it's so popular and additionally if it supplements our existing social safety net programs then they can no longer use ubi republicans can no longer say well you have ubi so you don't need food need food stamps let's cut that so why not supplement what already exists why make it either or you know i i think part of it is that the way that the freedom dividend is positioned is that we're saying the right of citizenship now as an american is that you should be getting a floor of a thousand dollars a month um and that principle then um i believe can make it very very popular uh very quickly um and so if that's the principle then you go to someone and say hey you know you may already be receiving benefits of a certain kind we're guaranteeing you a floor of a thousand dollars a month doesn't matter what your situation is um and so like in an ideal world like if you gave me again a choice it's like hey pass ubi on top of the existing social safety nets like you know i would i would take that um but i believe that it's going to be more uh achievable uh and again we'd be talking about the alleviation of gross poverty uh in our time if we have it as like a blanket floor across the board so but it's but you you know like the question is a really interesting one like though the way that i've uh the way that i understood even the original basic income proposals it was around this universal floor for everyone and that's the the approach that we've chosen