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Flashcards in Exam III: Neck II Deck (39):

Neck: Nerves

1. Cervical
Cervical plexus: anterior rami of C1 – C4
Posterior rami: C2 – C5; innervate deep muscles of neck and back along with the skin that covers them

2. Cranial nerves
CN V – Trigeminal innervates anterior belly of digastric and mylohyoid muscles
CN VII – Facial innervates facial muscles, platysma, stylohyoid, posterior digastric muscles
CN IX – Glossopharyngeal innervates carotid body and sinus
CN X – Vagus
CN XII - Hypoglossal

3. Sympathetic chain


Spinal Nerve Cuts

1. If you cut anterior roots, you won’t get motor function for skeletal muscles and length of muscle spindles; complain of weakness; carry GSE and GVE
2. If you cut posterior roots, you lose sensory function from the skin/dermatome/numbness; posterior carry GSA and GVA
Posterior Ramus: muscles are paralyzed/weakness along with skin on top of it/in that dermatome
Anterior Ramus: sensory and motor; numbness, loss of sensation; anterior rami all carry GSE/innervate muscle
Rami have GVE, GVA, GSA, and GSE (mixed)


Cervical Plexus

Loops: interconnections between C1 and C2, C2 and C3, etc.; have axons from C1 come down and mix with C2 aka many nerves at various spinal cord levels

Sensory Nerves: innervate skin; 4 cutaneous nerves, proprioception, the subtrapezial plexus joins the CN XI to go down to trapezius

Motor nerves: innervate skeletal muscle; most are derived from ansa cervicalis (loops that connect C1 to C3/thyrohyoid); innervate strap muscles; phrenic nerve (closest to anterior scalene muscle)

Hitchhiking: CN XII comes down and the cervicalis joins and travel together as one nerve and then split off again later

Gray rami: unmyelinated on all 31 levels; postganglionic sympathetic leave the sympathetic chain and go to the spinal nerve


Nerve Point

All of the cutaneous nerves (C1 – C4 anterior rami) that come from cervical plexus come from nerve point:
Greater auricular
Transverse Cervical
Lesser occipital: goes through the platysma and innervates the skin over top of it
Supraclavicular: skin over trapezius and clavicle

Nerve Point: located on the posterior border of the SCM; at this point where all cutaneous nerves emerge and then distribute; goes through the platysma


Ansa Cervicalis, Superior Root, Hypoglossal Nerve Functions

Ansa Cervicalis; if cut, it will no longer innervate the strap muscles within the anterior triangle (digastric muscles, stylohyoid, thyrohyoid, sternohyoid, omohyoid, sternothyroid, mylohyoid, and geniohyoid)

Cutting the superior root: no motor to innervated infrahyoid muscles; instability in swallowing and weakness in infrahyoid muscles

CN XII/Hypoglossal: if cut, it will no longer innervate the posterior belly of the digastric muscle, stylohyoid, hyoglossus, mylohyoid, and tongue; trouble moving the tongue, and difficulty swallowing; also realize there are hitchhiking with other nerves so can affect those as well


Scalene Triangle and Brachial Plexus

Runs underneath the clavicle: suprascapular
Transverse cervical artery runs front to back; nerve is back to front
Accessory phrenic nerve
Between anterior and middle scalene: brachial plexus and subclavian artery goes through the triangle


Innervation of Trapezius and SCM

Cut accessory nerve (CN XI) before SCM: SCM and trapezius affected causing weakness when shrugging shoulder, abduction above 90 degrees of humerus, and hard to turn head to opposite side
Cut accessory nerve after SCM: trapezius only because innervated by accessory nerve XI


Vagus Nerve: CN X

Skeletal muscle is inside viscera
GVE – glands, parasympathetic fibers that control the secretions
SVA – taste (special visceral afferent)
GVA – damage to vagus nerve

Off the vagus nerve above digastric muscles there is a superior laryngeal nerve, which divides into an external branch and internal branch (one goes outside and on goes inside the larynx)

CN X, the pre ganglionic in brain stem and post is in the wall of the organ in this case larynx; very short post ganglionic for parasympathetic

Vagus nerve innervates 2/3 of the organs within the body; vagus means wonderer because it goes around the body within the carotid sheath (when in the neck)


Distribution of CN X in the Neck

Pharyngeal branches
Superior laryngeal nerve: internal laryngeal and external laryngeal nerves
Recurrent/Inferior laryngeal nerve

External laryngeal nerve innervates only 1 muscle
Recurrent nerve on the right goes underneath subclavian; on the left goes underneath the aorta

Goes under subclavian and go back up towards the larynx


Neurovascular Pairs Involving the Larynx

1. Internal laryngeal nerve runs w/ superior laryngeal artery
2. External laryngeal nerve runs w/ superior thyroid artery
3. Recurrent laryngeal nerve runs w/ inferior thyroid artery
Need to ligate these vessels during a thyroidectomy causing injury and damage


Lesions of Vagus Nerve: Etiologies

Vagus nerve damaged due to:
1. Carotid Surgery
2. Thyroid Surgery
3. Aortic Aneurysm
4. Bronchial Carcinoma


Cervical Sympathetic Chain

The cervical sympathetic ganglia are fused:
Superior Cervical (C1 - 4)
Middle Cervical (C5 - 6)
Inferior Cervical (C7 - 8)

Inferior cervical (C7-8) and T1 fuse= form stellate ganglion
Information in the whole chain ganglion originate from T1 T4
The C number reference= spinal NERVE levels (not spinal cord levels)


Branches from the Cervical Sympathetic Chain

1. Gray rami: are how we distribute from the sympathetic chain back into spinal nerves
2. Sympathetic cardiac: develops in the neck and carried down
3. Internal and external carotid nerves associated with the internal and external carotid arteries
4. Cervical sympathetic cardiac: remnant of development from when your heart moved from in front of your head to your chest
5. Laryngopharyngeal Branches:


Cervicothoracic Ganglion Block & Lesion of the Cervical Sympathetic Trunk

Sympathetic chain affects upper extremities
Raynaud's: lack of blood supply due to vasospasm of sympathetic in fingers

If you have a tumor and invades the sympathetic chain, what happens? Skin can’t sweat so becomes dry, sebaceous glands aren’t working, vasodilation and loss of vasculature tone so face and neck become flushed, lesions of the sympathetic chain give rise to Horner’s syndrome


Axon Types in Lesser Occipital and Ansa Cervicalis

What axon types are present in the:
1. Lesser Occipital Nerve: innervate skin (GSA), GVE, GSE, and GVA; cell bodies are dorsal root ganglia for GSA; GVE pre is in IML and post is in sympathetic chain

2. Ansa cervicalis
GSE – cell body in anterior horn
GSA – posterior root ganglion
GVE – T1-T4 of IML and cell bodies in sympathetic chain
GVA - posterior root ganglion T1-T4

Every nerve will have autonomics


Neck Viscera

Pharynx: nasopharynx, oropharynx, laryngopharynx
Glands: thyroid and parathyroids


Cervical Portion of the Esophagus

The muscular arrangement of the esophagus varies by region:
Upper 1/3 is skeletal muscle
Middle 1/3 is mixed
Lower 1/3 is smooth muscle

All muscles in the esophagus is innervated by the vagus nerve


Laryngeal Cartilages

1. Arytenoid cartilage – shaped liked a pyramid, and sits on top an articulate with cricoid, attached to vocal chords, can change the tension of vocal cords, and open up larynx

2. Thyroid cartilage is c shaped, and has a synovial joint, but doesn’t go along the back completely; angle on front is Adam’s apple (laryngeal prominence) formed by laminae projections; articulates with cricoid cartilage

3. Cricoid cartilage: thin in the front and tall in the back; most inferior of the cartilages, but completely encircles the airway

Tracheal “rings” but C shaped because incomplete


Laryngeal Cartilage Joints

Synovial joints are formed with each other
Thyroid articulates with facet on cricoid so it can move back and forth
Arytenoid articulates with posterior facets on cricoid so it can swivel


Laryngeal Membranes

Thyrohyoid membrane: tough fibro-elastic ligament that spans between the superior margin of the thyroid cartilage below and the hyoid bone above; there is a small opening/aperture which transmits the superior laryngeal artery and internal laryngeal nerve

Quadrangular membrane – ends inferiorly as the vestibular ligament, which gives support


Laryngopharynx: Posterior View of Larynx

Laryngeal inlet + aryepiglottic fold
Piriform recess

Food goes into the piriform then into the epiglottis- common space for food to get stuck

Girl in ER has a laryngeal foreign body and is constantly coughing; the foreign object is eliciting a cough reflex; the afferent part of the reflex is telling the brain that there is something there = vagus
The efferent part of the reflex causing the cough= other than muscles in the thorax, is the phrenic nerve causing the laryngeal muscles to contract


Laryngeal Spaces and Folds

Vestibule/ Introitus
Vocal Fold/Vestibular Fold
Rima Vestibule, Ventricle, and Rima Glottis
Rima glottis is between the right and left vocal folds
You close the vocal cords during Valsalva maneuver
When you talk or take a deep breath you open the rima glottis so air can enter


Laryngeal Ligaments

Cricothyroid ligament – ends superiorly as vocal ligament/ vocal cord

Hyo-epiglottic ligament: extends from the midline of the epiglottis, anterosuperiorly to the body of the hyoid bone

Cricotracheal ligament: runs from the lower border of the cricoid cartilage to the adjacent upper border of the first tracheal cartilage

Thyrohyoid ligaments: posterior border of the thyrohyoid membrane are thickened to form the lateral thyrohyoid ligament, and thickened anteriorly in the midline to form the median thyrohyoid ligament


The Laryngeal Saccule/Ventricle and Laryngocoele

Infection in ventricle can come up through the ventricular fold and go between the pretracheal and buccopharyngeal fascia


Larynx Attachments

Stylohyoid and digastric; stylohyoid ligament
Geniohyoid and mylohyoid
Infrahyoid muscles


Laryngeal Musculature: Cricothyroid and Thyroartenoid

Cricothyroid sits on outside of larynx and goes up to hyoid cartilage
Innervation: only laryngeal muscle innervated by external laryngeal nerve (rest of laryngeal muscles are innervated by recurrent laryngeal branches of the vagus nerve (CN X))
Action of the muscle: when contracts the thyroid cartilage is moved forward making the vocal cords tighter/stretches to tense up the vocal ligament/cords (high pitched voice)

Thyroarytenoid pulls the thyroid cartilage back and makes the vocal chords/ligaments have less tension (deep voice)


Laryngeal Musculature: Posterior and Lateral Cricoarytenoid

These 2 muscles change the size of rima glottis- both antagonistic
When posterior cricoarytenoid contracts it increases the size of rima glottis
When lateral cricoarytenoid contracts it decreases the size of rima glottis
Recurrent laryngeal nerve innervates them


Laryngeal Musculature: Transverse and Oblique Arytenoid & Ary-epiglottis

Transverse Arytenoid: closes the rima glottis

Oblique Arytenoid: closes the rima glottis, but also closes the epiglottis; the two muscles form an "X" over the transverse arytenoid muscles; continues upwards as the ary-epiglotticus, which runs on each side of the larynx and acts to support the aryepiglottic folds and contraction of both muscles facilitates closure of the additus between the folds

Both the transverse and oblique arytenoid contract, pulling the arytenoid cartilage together

All are innervated by the recurrent laryngeal branch of the vagus nerve (X) except cricothyroid


Innervation of the Larynx

Superior laryngeal nerve
1. Internal
2. External- innervation of cricothyroid

Recurrent laryngeal nerve: innervates all the muscles and mucosa except cricothyroid

Cough reflex involves motor and sensory
Vagus and phrenic nerve elicits cough reflex
Vocal cords are the dividing line: all the mucosa above is internal innervation; recurrent is the bottom of the line


Vasculature of Larynx: Blood Supply

The major blood supply to the larynx is by the superior and inferior laryngeal arteries

Superior Laryngeal Artery: originates near the upper thyroid cartilage from the superior thyroid branch of the external carotid artery, and accompanies the internal branch of the superior laryngeal nerve through the thyrohyoid membrane

Inferior Laryngeal Artery: originates from the inferior thyroid branch of the thyrocervical trunk of the subclavian artery with the recurrent laryngeal nerve


Vasculature of Larynx: Veins

veins draining the larynx accompany the arteries

Superior Laryngeal Veins: drain into superior thyroid veins, which in turn drain into the internal jugular veins

Inferior Laryngeal Veins: drain into inferior thyroid veins, which drain into the left brachiocephalic vein


Lymphatic Drainage of the Larynx

Supraglottic – upper deep cervical nodes
Infraglottic – pretracheal, lower deep cervical
Above the rima glottis/vocal cords = supra glottic
Below the vocal fold/cords = infraglottic

Neoplasm/laryngeal tumor: coming from cord and below it is infraglottic


Cervical Portion of the Trachea

Cricoid is the complete ring and then below is C shaped tracheal rings
Why no cartilage in esophagus but in airway only? You don’t want your airway closed and the esophagus needs to be able to accommodate different sizes of food boluses


Thyroid + Parathyroid: Location and Fascial Relations

Go through skin, investing fascia, infrahyoid fascia, pretracheal space, and then pretracheal fascia to get to the thyroid gland

The thyroid gland doesn’t completely surround the larynx/trachea- has a narrow band in the front and then has lateral lobes
10% of people= pyramidal lobe of thyroid
Innervated by the recurrent laryngeal branch of the vagus nerve (X)
Very rich and dense blood supply because gland
Parathyroid gland: found on backside of the lateral lobes- may have variations in number of parathyroid glands ranging from 2-7… average is 4


Parathyroid Gland

There are typically 4 parathyroid glands, but may range from 2 – 7 in number. Their location is highly variable.

Metastasis of neoplasms arising from the parathyroids: If outside of the gland they can spread by local spread/fascial spaces in the neck, lymph, and vasculature


Vasculature of Thyroid and Parathyroid

Superior and inferior thyroid arteries on each side
Superior consists of anterior and posterior glandular branch, which both anastomose with the isthmus or inferior thyroid artery, respectively
Inferior thyroid artery is a branch of the thyrocervical trunk

Thyroid ima artery: may come off brachiocephalic or common carotid; coming from thorax crossing superior aperture making its way to the gland

If doing a thyroidectomy, 10% of people have the thyroid ima artery coming from common carotid, and if cut bleeds a lot because comes off the aorta


Lymphatic Support of the Thyroid

Pretracheal/Prelaryngeal nodes
Paratracheal nodes
Superior Deep Cervical [jugulodigastric] nodes
Inferior Deep Cervical [jugulo-omohyoid] nodes

Key point: any metastases will get into deep cervical nodes eventually
Innervation of the thyroid gland: mostly towards the blood vessels; controlled by hypothalamic hormones


Drainage of the Thyroid

5-6 vessels draining the thyroid and parathyroid glands
Three veins that drain the thyroid gland:
1. superior thyroid vein drains the area supplied by the superior thyroid artery
2 & 3. Middle and Inferior thyroid veins drain the rest of the thyroid gland

The middle and superior veins drain into the internal jugular vein and the inferior thyroid veins drain into the right and left brachiocephalic veins

The parathyroid vessels follow the same patterns


Surgical Removal of the Thyroid

Inferior laryngeal artery runs with recurrent laryngeal nerve
If damage of recurrent laryngeal nerve then you get paralysis of one side of neck
Hitchhiking: for thyroid tumor, two vessels – superior thyroid artery runs with external laryngeal nerve; inferior thyroid artery can damage recurrent largyneal nerve if cut
If recurrent damaged, then one of the vocal cords is paralyzed, cricothyroid muscle will be unaffected (high pitch one innervated by superior external laryngeal nerve)