E - Intro to Neck

Platysma Muscle

"grimace muscle"

Roots of the Brachial Plexus in Posterior Triangle

(C5-T1): exit between anterior and middle scalene muscles and descend between the 1st rib, clavicle, and superior scapula to enter the axilla. The roots will form trunks (upper, middle, and lower). *Branches* - Suprascapular nerve (off upper trunk): supraspinatus and infraspinatus muscles - Dorsal scapular nerve (off C4-5 roots): levator scapulae, rhomboid major, and rhomboid minor muscles - Long Thoracic nerve (off C5-7 roots): serratus anterior muscle

Carotid Sinus

(baroreceptor): at bifurcation; innervated by CN IX (carotid sinus nerve) ("sinus pressure" carotid sinus detect pressure changes)

Carotid Body

(chemoreceptor): medial side of the bifurcation; innervated mainly by the carotid sinus nerve (and by X)

Occipital Arteries

(off external carotid artery) - Crosses the apex of the posterior triangle to serve the posterior ½ of the SCALP

Transverse/Superficial Cervical Arteries

(off the thyrocervical trunk of subclavian artery) - Across the anterior scalene muscle and phrenic nerve ~2cm superior to the clavicle - Dorsal scapular branch accompanies the dorsal scapular nerve; it may arise independently from the subclavian artery

Anterior Jugular Veins

(usually a left and a right) Begin below the chin in the superficial fascia and pass inferiorly just lateral to the midline. They duck under the SCM and pass laterally to enter the EJVs. - Communicate through the anterior jugular arch that passes across the midline of the neck just above the manubrium. If present, it could cause bleeding problems during a tracheotomy procedure

Suprascapular Arteries

(usually off thyrocervical trunk, or off subclavian artery) - Passes inferolaterally across the anterior scalene and phrenic nerve, then posterior to the clavicle to serve the scapula and associated muscles

Cervical Plexus in Posterior Triangle

(ventral rami C1-4) *Phrenic nerve (C3, 4, 5)*: originates from the C3-5 cervical plexus roots and crosses the anterior surface of the anterior scalene muscle (it is also in the anterior triangle) - Motor, sensory, and sympathetic fibers; forms at the superior border of the thyroid cartilage (~C4), and lies deep to the prevertebral fascia *Accessory phrenic nerve (contribution from C5)*: if present, it lies lateral to the main nerve and descends posterior to the subclavian vein - Sensory (Erb's point) & motor (ansa cervicalis )

Thyrohyoid (Innervation)

*C1* by hitching a ride on XII - Runs superiorly from the oblique line of the thyroid cartilage to the hyoid

Trapezius muscle

*Innervation: CN XI* Attachments: superior nuchal line, external occipital protuberance, nuchal ligament, and spinous processes C7-T12 - Elevates, retracts, and rotates the scapula superiorly. *Posterior boundary of the posterior triangle*

Deep cervical/Prevertebral muscles

*Scalenes: anterior, middle, & posterior; longus capitis, and longus colli* Flex the head and neck anteriorly and laterally Attach to the upper ribs, where some act as accessory inspiratory muscles by elevating the ribs. Location: just anterior and lateral to the vertebral column, posterior to the viscera of the neck.

Submandibular Sub-Triangle Contents

- *Submandibular salivary gland* (fills most of the triangle) - *Submandibular lymph nodes*: receive lymph from anterior tongue and the oral cavity - *XII*: passes between mylohyoid and hyoglossus muscles; occipital artery twists around it - *Nerve to mylohyoid (V3)*: from ITF to innervate digastric anterior belly and mylohyoid - *Lingual artery*: is passing through - *Submandibular duct*: on the lateral surface of the hyoglossus muscle and is crossed by the lingual nerve (as heads toward the tongue) - *Parts of facial artery and vein; submental artery* (branch of facial artery)

Superficial Cutaneous sensory branches of the cervical plexus: C1-4

1.) *Lesser occipital (C2)*: neck and SCALP posterosuperior to the auricle 2.) *Great auricular (C2,3)*: ascends vertically across SCM, usually posterior to the EJV, to serve the skin of the parotid gland, posterior auricle, and angle of the mandible to the mastoid process 3.) *Transverse cervical (C2,3)*: anterior triangle (passes anterior to SCM, but deep to the EJV and platysma) 4.) *Supraclaviculars (C3,4)*: neck and shoulder (emerge as a common trunk under the SCM)

Posterior Triangle Nerves

Accessory Nerve Roots of Brachial Plexus Cervical Plexus - Phrenic Nerve

Carotid Sheath

All three previous layers of deep fascia fuse to form the carotid sheath - Surrounds the major neurovascular bundle of the neck, so it is a potential space that is continuous from cranial cavity to mediastinum where infections and extravasated blood can spread *Contents*: CCA, ICA, IJV, X, deep cervical lymph nodes, sympathetic periarterial plexuses, and nerve branches to the carotid body & sinus

Omohyoid (Innervation)

Ansa cervicalis (motor part of cervical plexus): C1-3 - Two bellies (superior and inferior) with the tendon attached to the clavicle

Sternothyroid (Innervation)

Ansa cervicalis (motor part of cervical plexus): C2,3 - Lies deep to the sternohyoid and attaches to the oblique line of the thyroid cartilage

Digastric Muscle

Anterior and posterior bellies joined by a tendon that glides in a fibrous sling at the greater horn of the hyoid - Anterior belly: nerve to mylohyoid (from V3) - Posterior belly: VII

Submandibular Sub-Triangle Borders

Anterior and posterior bellies of the digastric and the mandible Floor is formed by the mylohyoid, hyoglossus and middle pharyngeal constrictor muscles

Neck Boundaries

Anterior neck ("neck proper" or cervix): extends from the inferior border of the mandible to the clavicles and sternum Posterior neck (nucha or "nape"): extends from the occipital bone and mastoid processes, to C7, then to the trapezius muscles. - The posterior bony skeleton is C1-7, bounded inferiorly by the clavicle and manubrium

Subclavian Veins

Anterior to the anterior scalene and phrenic nerve and drains the upper extremity - Joins IJV to form brachiocephalic vein

Infrahyoid muscles

Attach hyoid bone and larynx to sternum and scapula. Antagonists of suprahyoid muscles; depress the hyoid and larynx after having been elevated during swallowing. Infrahyoid and suprahyoid muscles work together to stabilize hyoid so it can form a solid base for the muscles that move tongue. (all ansa cervicalis except Thyrohyoid = C1) - Sternohyoid - Sternothyroid - Thyrohyoid - Omohyoid

Suprahyoid muscles

Attach the hyoid bone to the mandible and temporal bones. They constitute the floor of the mouth, are involved in elevating the hyoid bone during the first stages of swallowing, and they assist in opening the mouth. - Geniohyoid - Mylohyoid - Digastric - Stylohyoid "Genny, My (hair) Dye Stylist is SUPER!"

Potential Spaces of the Neck

Between the layers of deep fascia in the neck, around the pharynx, and in the floor of the mouth. Infections may spread through these spaces and can sometimes spread into the thorax - Retropharyngeal Space - Pretracheal Space - Lateral Pharyngeal Spaces, Parapharyngeal Space - Submandibular Space

Submental Sub-Triangle

Borders: hyoid, mandible, and the right and left digastric anterior bellies. The floor is the 2 mylohyoid muscles, which form the median fibrous raphe Contents: submental lymph nodes and small veins that unite to form anterior jugular vein

Muscular Sub-Triangle

Borders: neck midline, superior belly of the omohyoid, and anterior border of the SCM. Its floor is formed by the sternohyoid and sternothyroid muscles Contents: pretracheal fascia covers infrahyoid muscles and neck viscera The floor muscles are often reflected for surgical access to the thyroid gland, larynx, and trachea

Geniohyoid (Innervation)

C1 by hitching a ride on XII

Carotid Sub-Triangle Contents

CCA and branches (*Some Anatomists Like Freaking Out* Poor Medical Students) Superior root of ansa cervicalis Thyroid gland Larynx Deep cervical lymph nodes Inferior Jugular Vein CN X Branches of the cervical plexus - This triangle is important for surgical access to the ICA for angiography or endarterectomy External Carotied Artery Branches: Some Anatomists Like Freaking Out Poor Medical Students (Superior Thyroid, Ascending Pharyngeal, Lingual, Facial, Occipital, Posterior Auricular, Maxillay, Superficial Temporal) - All of these are in the Carotid Triangles except for the "Poor Medical Students" who get left out

Sternocleidomastoid muscle (SCM) Innervation

CN XI (some branches of the cervical plexus may be afferent in function)

Prevertebral fascia

Covers the prevertebral muscles both anteriorly and posteriorly - Attaches to the base of the cranium and to spinous processes and bodies of cervical vertebrae - Covers many of the deep nerves and vessels of the neck - Passes into the posterior mediastinum inferiorly - Cervical spinal nerves (ventral rami) pass laterally through the prevertebral layer between the scalene muscles

Superior deep/jugulodigastric and Inferior deep/jugulo-omohyoid

Deep cervical lymph nodes grouped according to the muscle to which they are associated - Submental and submandibular lymph nodes drain the lips, chin, and tongue - Lymph nodes along the IJV drain the nuchal region and laryngo-tracheo-thyroid region

Carotid Sub-Triangle Borders

Digastric posterior belly, omohyoid superior belly, and anterior border of SCM. Its floor consists of the thyrohyoid, hyoglossus, and all three pharyngeal constrictor muscles

Internal Jugular Vein (IJV)

Drains brain, anterior face, cervical viscera, and deep muscles of the neck - Begins at the jugular foramen and runs in the carotid sheath with the ICA, CCA, and CN X. It leaves the anterior triangle when it passes deep to the SCM. - Unites with the subclavian vein to form the brachiocephalic vein, posterior to the sternal end of the clavicle. Its inferior end has a dilation (the inferior bulb), and has a valve

Posterior Triangle Veins

External Jugular Vein Subclavian Vein

Carotid Triangle Clinical Relevancy

Important for many reasons: taking a carotid pulse; and any surgical procedure to access the common carotid or its branches, IJV, the Vagus or hypoglossal nerves. Atherosclerotic plaques are common and the access point to remove the plaque is through the carotid triangle.

Internal Jugular Vein (IJV) Tributaries

Inferior petrosal sinus, facial, lingual, pharyngeal, and superior thyroid veins

Pretracheal Fascia

Limited to anterior neck - Attaches to the hyoid and laryngeal cartilages superiorly and *blends with the fibrous pericardium in the thorax inferiorly* 2 parts: 1.) Muscular: thin and surrounds the infrahyoid muscles 2.) Visceral: surrounds the thyroid gland, trachea, and esophagus - Attaches to the thyroid cartilage superiorly, and extends down into the anterior mediastinum

Cutaneous sensory branches of the cervical plexus: C1-4

Location: deep to the SCM; nerve loops that lie anteromedial on the levator scapula and middle scalene Superficial branches: are cutaneous (C1-4) that pass into the skin just posterior to the midpoint (Erb's Point) of the SCM - Blockage of these nerves with an anesthetic agent at this location will deaden sensation in a wide area of the neck

Ansa cervicalis

Loop of motor nerve fibers from cervical plexus that serves almost all infrahyoid muscles (except Thyrohyoid) - Superior root: C1 fibers ride and loop down from CN XII - Inferior root: C2, 3 (C1 fibers that hitch a ride on CN XII to innervate the thyrohyoid and geniohyoid muscles are NOT part of the ansa cervicalis)

Supraclavicular Lymph Nodes

Lymph nodes: part of inferior deep nodes, drain superficial cervical nodes - Left side: *receive drainage from the internal organs via the thoracic duct* These are one of the first visible locations where advanced metastasis occurs from internal organs (called "sentinel" LNs by some clinicians). However, enlarged supraclavicular nodes could also result from breast cancer, esophageal cancer, lymphoma, or even an infection in the arm

Anterior Triangle Boundaries

Medial: anterior midline of neck Posterior: SCM Superior: inferior border of the mandible Apex: jugular notch Roof: subcutaneous tissue with the platysma Floor: pharynx, larynx, and thyroid gland - Recall the hyoid lies in the anterior triangle opposite C3. The anterior triangle above and below the hyoid bone are often called suprahyoid and infrahyoid regions, respectively Vessels: External carotid artery (ECA) system & IJV: see "Carotid Triangle"

External Carotid Artery

Most branches originate in the carotid or submandibular triangles *Middle branch*: ascending pharyngeal ascends on the pharynx, supplies it, the prevertebral muscles, middle ear, and cranial meninges 3 Anterior branches: - Superior Thyroid a - Lingual a - Facial a 2 Posterior branches: - Occipital a - Posterior Auricular a

Internal Carotied Artery

NO Branches in the Neck

Posterior Triangle Subdivisions

Occipital Omoclavicular

Superficial Cervical Fascia/Subcutaneous tissue of the Neck Contents

Platysma muscle Superficial Veins *External jugular vein (EJV) Anterior jugular veins* Cutaneous sensory branches of the cervical plexus: C1-4

Posterior Triangle Boundaries

Posterior: anterior border of trapezius Anterior: posterior border of SCM Inferior: middle third of the clavicle Apex: where the SCM and trapezius meet on the superior nuchal line Roof: investing layer of deep cervical fascia Floor: prevertebral fascia on the splenius capitis, levator scapulae, middle and posterior scalene muscles

Sternocleidomastoid muscle (SCM)

Sternal head: round tendon attaches to the manubrium Clavicular head: attaches to the medial 1/3 of the clavicle - Lesser supraclavicular fossa: space between the heads; supraclavicular lymph nodes Proximal attachment: mastoid process and superior nuchal line *Separates the anterior triangle from the posterior triangle* Unilateral contraction: lateral neck flexion and rotates the head so the face is turned superiorly toward the opposite side Bilateral contraction: flexes the neck to bring the chin to the thorax

Muscles of the Triangles

Sternocleidomastoid muscle (SCM) Trapezius muscle Suprahyoid muscles Infrahyoid muscles Deep cervical/Prevertebral muscles

Anterior Triangle Sub-Triangles

Submental Sub-Triangle Submandibular Sub-Triangle Muscular Sub-Triangle Carotid Sub-Triangle

Lymphatic Drainage of the Neck

Superficial Anterior and Lateral Lymph Nodes lie along the External Jugular Vein in the superficial fascia --> drain into the *Deep Cervical Lymph Nodes*, which lie deep to the SCM, along the Internal Jugular Vein - Superior deep/jugulodigastric and Inferior deep/jugulo-omohyoid - Supraclavicular Lymph Nodes

Anterior Triangle Nerves

Superior Laryngeal Nerve Ansa Cervicalis Transverse Cervical CN X, XI, XII Vagus Nerve Branches - Pharyngeal Branches - Carotid Branches - Superior Laryngeal Branches - Recurrent Laryngeal Nerves

Occipital Posterior Triangle

Superior to omohyoid inferior belly Major contents: External Jugular Vein, occipital artery, posterior branches of the cervical plexus, CN XI, trunks of the brachial plexus, superior deep cervical nodes

Subclavian (3rd part) Arteries

Supplies upper extremity Starts about a finger's breadth superior to the clavicle opposite the anterior scalene. It lies posterior to the subclavian vein in the omoclavicular triangle. You can feel it in this triangle, and can *control bleeding in the upper extremity*.

Deep Fascia of the Neck (Purpose)

Supports the viscera, muscles, vessels, and deep lymph nodes - Allows neck structures to move and glide past one another without difficulty (e.g. pass bolus down the pharynx, or when turning your head) - Boundaries of compartments and barriers to prevent the spread of infection or abscesses. A specific compartment may be opened by incision and drained - Fascial layers may be separated by pus or fluid accumulation, creating a connection where an infection may spread to another body region (e.g. to the mediastinum) - Natural cleavage planes used as guides during dissection and exposing surgical fields

Posterior Triangle Arteries

Suprascapular Occipital Transverse/Superficial Cervical Subclavian (3rd part) ""SOTS - Super Odd Transvestite Substitutes"

Investing Fascia

Surrounds the entire neck just deep to the superficial fascia; forms a roof over the neck triangles - Splits to enclose the SCM and trapezius Stays divided: attaches to the anterior and posterior sides of the manubrium, forming a suprasternal space that encloses the inferior parts of the anterior jugular veins, the jugular venous arch, and some lymph nodes - Attachments: superior nuchal line, mastoid process, and spines of cervical vertebrae - Splits to enclose the submandibular glands and the parotid glands' fibrous capsules - Inferiorly attaches to the clavicle, manubrium, and scapula. Binds the inferior belly of the omohyoid to the clavicle

Deep Cervical Nodes and Carotid Sheath

The deep cervical lymph nodes lie on the carotid sheath and often need to be removed when they become involved in cancer of head and neck structures. Because these nodes are intimately related to the internal jugular vein, it is often necessary to remove it as well.

Mylohyoid (Innervation)

V3: nerve to mylohyoid

Stylohyoid (Innervation)

VII attaches to the hyoid bone at the greater horn

Lateral Pharyngeal Spaces

adjacent to the lateral surfaces of the pharynx between the pharynx and the muscles of the infratemporal fossa *Boundaries*: skull superiorly and investing fascia on the hyoid inferiorly - Continuous with the retropharyngeal space posteriorly and the submandibular space superiorly

Sternohyoid (Innervation)

ansa cervicalis (motor part of cervical plexus): C1-3

Facial Artery

arises either in common with the lingual artery or just superior to it. It passes deep to the digastric anterior belly and angle of the mandible. It loops to groove and supply the submandibular gland; then hooks around the middle of the inferior border of the mandible to enter the face

Common Carotid Artery (CCA)

ascends and bifurcates at ~C4 (superior border of the thyroid cartilage) into the Internal Carotid Artery and External Carotid Artery

Posterior Auricular Artery

ascends between the external acoustic meatus and mastoid process. It supplies the adjacent muscles, parotid gland, facial nerve, and structures in the temporal bone, auricle, and SCALP - 2 terminal branches: maxillary & superficial temporal

Omoclavicular Posterior Triangle

between omohyoid inferior belly and clavicle Major contents: Subclavian artery, part of the Subclavian vein, Suprascapular artery, Supraclavicular lymph nodes - Supraclavicular fossa is seen in surface anatomy

Pretracheal Space

between the infrahyoid muscles and the trachea. It can extend into the anterior mediastinum, where the pretracheal fascia blends with the pericardium

Retropharyngeal Space

between visceral prevertebral and visceral pretracheal fasciae - Movement of the pharynx, esophagus, trachea, and larynx during swallowing

Recurrent Laryngeal Nerve in Anterior Triangle

both the left and right nerves pass through the neck, but only the right recurrent laryngeal originates from the vagus in the neck

CN XII in Anterior Triangle

enters submandibular triangle deep to the posterior belly of the digastric

Superior Laryngeal Nerve in Anterior Triangle

external & internal branches (the internal pierces the thyrohyoid membrane with the superior laryngeal artery to enter the larynx)

Hyoid Bone

floating "U shaped" bone located at *C3* Landmark for neck structures, and several cartilages of the larynx. - Body, 2 greater horns, 2 lesser horns, - Suspended from the styloid processes by the Stylohyoid ligaments. - Attaches anterior neck muscles (suprahyoid and infrahyoid), and muscles of the larynx and pharynx

External Jugular Vein (EJV)

formed just below the angle of the mandible just inferior to the auricle by the union of the retromandibular vein (posterior division) & posterior auricular vein - Crosses the outer surface of the SCM in the superficial fascia, just deep to the platysma - Pierces the investing layer of deep fascia at the posterior border of the SCM, then descends to the inferior posterior triangle to join the subclavian vein - Receives the transverse cervical, suprascapular, and anterior jugular veins - Approximate it by drawing a vertical line from the angle of the mandible to the midpoint of the clavicle

Submandibular Space

located below the tongue in the floor of the mouth 2 interconnected parts: one above the mylohyoid muscle (deep part) and one below it (superficial part). Infections may originate in this space from the teeth, salivary glands, or oral cavity and could spread into the thorax. - Communicates with the lateral pharyngeal spaces inferiorly

Cervical Cardiac Branches in Anterior Triangle

nerves to the heart arising in the neck

CN IX in Anterior Triangle

passes b/n the stylopharyngeus and middle constrictor muscles to gain access to the oropharynx and oral cavity

Lingual Artery

passes deep to CN XII and the posterior belly of the digastric to enter the oral cavity deep to the hyoglossus muscle

Occipital Artery

passes posteriorly, immediately medial and parallel to the posterior belly of the digastric twisting around CN XII

Pharyngeal Branches in Anterior Triangle

pharyngeal constrictor and soft palate muscles

Superior Thyroid Artery

runs deep to the infrahyoid muscles and ends at the thyroid gland. It gives rise to the *superior laryngeal artery* (supplies the larynx).

Accessory Nerve

serves the SCM before it emerges 1/3 down its border - Passes postero-inferiorly through the triangle within or deep to the investing fascia, on the prevertebral fascia of the levator scapula muscle - Vulnerable in the roof of the posterior triangle Lesions of CN XI may be caused by penetrating trauma, surgical error, or compression of the nerve leaving the cranial cavity. Hallmark sign of trapezius damage: "drooped shoulder"

Buccopharyngeal fascia

the posterior and superior-most part of the visceral layer of the Pretracheal Fascia surrounding the superior pharynx and esophagus

Alar Fascia

thin delicate fascia that crosses the retropharyngeal space. It attaches to the buccopharyngeal fascia from the skull to C7, extending laterally to blend with the carotid sheath

Carotid Branches in Anterior Triangle

tiny; form plexus with branches of IX. They are afferent nerves supplying the carotid sinus and carotid body, carrying chemical and pressure information

Parapharyngeal Space

two lateral pharyngeal spaces + retropharyngeal space