Neck Anatomy, Moore's Ch. 8

supraclavicular nerves

(C3 and C4), which emerge as a common trunk under cover of the SCM and send small branches to the skin of the neck and cross the clavicle to supply the skin over the shoulder (Fig. 8.4C). Deep motor branches include branches arising from the anterior rami of cervical nerves supplying the rhomboids

Great auricular nerve

(C2 and C3), ascending vertically across the SCM onto the parotid gland, where it divides and supplies skin over the gland, posterior aspect of the auricle, and the area of skin extending from the angle of the mandible to the mastoid process.

Transverse cervical nerve

(C2 and C3), supplying the skin covering the anterior cervical region; the nerve curves around the middle of the posterior border of the SCM and passes anteriorly and horizontally across it deep to the EJV and platysma.

Lesser occipital nerve

(C2), supplying the skin of the neck and scalp posterosuperior to the auricle.

pretracheal layer of deep cervical fascia

Surrounds structures in the anterior neck only. Attached superiorly to the hyoid. Muscular part invests the infrahyoid muscles. *visceral part invests the thyroid gland*, trachea, and esophagus and continues superiorly as the buccopharyngeal fascia. Is continuous with the fibrous pericardium.

prevertebral layer

layer of deep cervical fascia forms a tubular sheath for the *vertebral column and the muscles associated with it*, such as the longus colli and longus capitis anteriorly, the scalenes laterally, and the deep cervical muscles posteriorly. The prevertebral layer extends laterally as the axillary sheath, which surrounds the axillary vessels and brachial plexus.

investing layer

most superficial deep fascial layer, surrounds the entire neck deep to the skin and subcutaneous tissue. At the "four corners" of the neck, the investing layer splits into superficial and deep layers of fascia to enclose (invest) the sternocleidomastoid (SCM) and trapezius muscles.

sternocleidomastoid muscle (SCM)

visibly divides each side of the neck into anterior and lateral cervical triangles. The sternocleidomastoid is innervated by the ipsilateral accessory nerve CN II. It supplies only motor fibres. The cervical plexus supplies sensation, including proprioception, via the ventral primary rami of C2 and C3.

small omoclavicular (subclavian) triangle

the superior surface of the neck by the supraclavicular fossa. The inferior part of the external jugular vein (EJV) crosses this triangle superficially; the subclavian artery lies deep in the (subclavian) triangle.

pharynx

( Greek: "throat") cone-shaped passageway leading from the oral and nasal cavities in the head to the esophagus and larynx. The pharynx chamber serves both respiratory and digestive functions.

Superficial Cervical fascia

*subcutaneous tissue of the neck*. Contains fat tissue and fibrous connective tissue. Not considered a layer of skin. Contains fat tissue and fibrous connective tissue.

infrahyoid muscles (strap muscles)

the sternohyoid, sternothyroid, thyrohyoid and omohyoid muscles.

brachial plexus

Anterior rami of C5-C8 and T1 are the roots of the brachial plexus. They appear between the anterior and the middle scalene muscles. Five rami unite to form the three trunks (superior, middle, and inferior), which descend inferolaterally through the lateral cervical region. The plexus then passes between the first rib, clavicle, and superior border of the scapula (the cervicoaxillary canal) to enter the axilla, providing innervation for most of the upper limbs.

sternocleidomastoid region

the region between these triangular regions, corresponding to the area of this broad, strap-like muscle

platysma

Broad muscle extending from the chest and shoulder muscles to the side of the chin; responsible for depressing the lower jaw and lip. Arises in *Superficial Cervical fascia* (subcutaneous tissue)

Platysma

Innervation: Cervical branch of facial nerve (CN VII) Superior Attachment: border of mandible, skin, and subcutaneous tissues of lower face Inferior Attachment: Fascia covering superior parts of pectoralis major and deltoid muscles Main Action(s): Draws corners of mouth inferiorly and widens it as in expressions of sadness and fright; draws skin of neck superiorly when teeth are clenched indicating tension

Sternocleidomastoid

Innervation: Spinal accessory nerve (CN XI; motor); C2 and C3 nerves (pain and proprioception) Superior Attachment: Sternocleidomastoid (B-E) Lateral surface of mastoid process of temporal bone and lateral half of superior nuchal line Inferior Attachment: Sternal head: anterior surface of manubrium of sternum. Clavicular head: superior surface of medial third of clavicle Main Action(s): Unilateral contraction: tilts head to same side (i.e., laterally flexes neck) and rotates it so face is turned superiorly toward opposite side Bilateral contraction: (1) extends neck at atlanto-occipital joints, (2) flexes cervical vertebrae so that chin approaches manubrium, or (3) extends superior cervical vertebrae while flexing inferior vertebrae so chin is thrust forward with head kept level With cervical vertebrae fixed, may elevate manubrium and medial end of clavicles, assisting pump-handle action of deep respiration

The trapezius

Innervation: Spinal accessory nerve (CN XI; motor); C3 and C4 nerves (pain and proprioception) Superior Attachment: Medial third of superior nuchal line, external occipital protuberance, nuchal ligament, spinous processes of C7- T12 vertebrae Inferior Attachment: Lateral third of clavicle, acromion and spine of scapula Main Action(s): Elevates, retracts, and rotates scapula Descending (superior) part: elevate pectoral girdle, maintain level of shoulders against gravity or resistance Middle part: retract scapula Ascending (inferior) part: depress shoulders Descending and ascending parts: rotate scapula upward With shoulders fixed, bilateral contraction extends neck; unilateral contraction produces lateral flexion to same side

spread of infection

The investing layer of deep cervical fascia helps prevent the spread of abscesses. If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection usually does not spread beyond the superior edge of the manubrium. If, however, the infection occurs between the investing fascia and the visceral part of the pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium.

Motor branches

The deep branches passing anteromedially are motor branches, including the roots of the phrenic nerve and the ansa cervicalis

MUSCLES IN LATERAL CERVICAL REGION

The floor of the lateral cervical region is usually formed by the prevertebral fascia overlying four muscles (Fig. 8.4): splenius capitis, levator scapulae, middle scalene (L. scalenus medius), and posterior scalene (L. scalenus posterior). Sometimes part of the inferior part of the anterior scalene (L. scalenus anterior) appears in the inferomedial angle of the lateral cervical region.

Retropharyngeal space

The largest interfacial space in the neck which permits movement of the pharynx, esophagus, larynx, tracheal during swallowing The largest and most clinically important interfascial space in the neck because it is the major pathway for the spread of infection (Fig. 8.2A). It is a potential space that consists of loose connective tissue between the visceral part of the prevertebral layer of deep cervical fascia and the buccopharyngeal fascia. Inferiorly, the buccopharyngeal fascia is continuous with the pretracheal layer of deep cervical fascia. The alar fascia crosses the retropharyngeal space. This thin layer is attached along the midline of the buccopharyngeal fascia from the cranium to the level of the C7 vertebra and extends laterally to blend with the carotid sheath. The retropharyngeal space is closed superiorly by the base of the cranium and on each side by the carotid sheath. This space permits movement of the pharynx, esophagus, larynx, and trachea relative to the vertebral column during swallowing.,

Lateral Cervical Region

The lateral cervical region (posterior triangle of the neck) is bounded: Anteriorly by the posterior border of the SCM. Posteriorly by the anterior border of the trapezius. Inferiorly by the middle third of the clavicle between the trapezius and the SCM. By an apex, where the SCM and trapezius meet on the superior nuchal line of the occipital bone. By a roof, formed by the investing layer of deep cervical fascia. By a floor, formed by muscles covered by the prevertebral layer of deep cervical fascia.

CERVICAL REGIONS (triangles of neck)

The neck is divided into regions. The four major regions are the (1) sternocleidomastoid region (2) posterior cervical region (3) lateral cervical region (4) anterior cervical region

Posterior Cervical Region

The region posterior to the anterior border of the trapezius is the posterior cervical region. The suboccipital region is deep to the superior part of this region. Trapezius

NERVES OF LATERAL CERVICAL REGION

The spinal accessory nerve passes deep to the SCM

carotid sheath

Three major fascial layers in the neck contribute to the carotid sheath: the investing fascia, the pretracheal fascia, and the prevertebral fascia. The carotid sheath contains: The common and internal carotid arteries. The internal jugular vein (IJV). The vagus nerve (CN X). also: Deep cervical lymph nodes. The carotid sinus nerve. Sympathetic nerve fibers (carotid periarterial plexuses).

Congenital Torticollis

Torticollis is a contraction of the cervical muscles that produces twisting of the neck and slanting of the head (Fig. B8.1). The most common type of congenital torticollis (wry neck) results from a fibrous tissue tumor (L. fibromatosis colli) that develops in the SCM before or shortly after birth. Occasionally, the SCM is injured when an infant's head is pulled excessively during a difficult birth, tearing its fibers (muscular torticollis). This tearing may result in a hematoma that may develop into a fibrous mass entrapping a branch of the spinal accessory nerve (CN XI), thus denervating part of the SCM. Surgical release of a partially fibrotic SCM from its distal attachments to the manubrium and clavicle may be necessary to enable the child to tilt and rotate the head normally.

lateral cervical region

a *larger occipital triangle superiorly* and divided into a smaller *sublcavian triangle* inferiorly (omoclavicular triangle) by the inferior belly of the omohyoid (Fig. 8.3).

superior laryngeal nerve

a branch of the vagus nerve. It controls the sensory supply to the superior laryngeal mucosa and stops foreign objects from entering the larynx; divides into two terminal branches, internal and external laryngeal nerves

cervical plexus

anterior rami of C1-C4 make up the roots of the cervical plexus The plexus lies anteromedial to the levator scapulae and middle scalene muscle and deep to the SCM. The superficial branches of the plexus that initially pass posteriorly are cutaneous branches (Fig. 8.4B, C). The deep branches passing anteromedially are motor branches, including the roots of the phrenic nerve and the ansa cervicalis http://www.showme.com/search/?q=cervical%20plexus%20nerves

cutaneous nerves

are responsible for providing sensory innervation to the skin

suprascapular nerve

arises from the superior trunk of the brachial plexus, runs across the lateral cervical region to supply the supraspinatus and infraspinatus muscles on the posterior aspect of the scapula. It also sends articular branches to the glenohumeral joint

suprascapular nerve

arises from the superior trunk of the brachial plexus, runs across the lateral cervical region to supply the supraspinatus and infraspinatus muscles on the posterior aspect of the scapula. It also sends articular branches to the glenohumeral joint.

deep cervical fascia

consists of three fascial layers: investing, pretracheal, and prevertebral. These layers support the viscera (ie. thyroid gland), muscles, vessels, and deep lymph nodes. Fascial layers form natural cleavage planes, allowing separation of tissues during surgery. condenses around the common carotid arteries; IJV; and Vagus to form the carotid sheath

Cutaneous branches of the cervical plexus

emerge around the middle of the posterior border of the SCM, often called the nerve point of the neck, and supply the skin of the neck, superolateral thoracic wall, and the scalp between the auricle and the external occipital protuberance. Close to their origin, the roots of the cervical plexus receive communicating branches (L. rami communicantes), most of which descend from the superior cervical ganglion in the superior part of the neck.

phrenic nerves

originate chiefly from the fourth cervical nerve (C4) but receive contributions from the C3 and C5 nerves. The phrenic nerves contain motor, sensory, and sympathetic nerve fibers. These nerves provide the sole motor supply to the diaphragm as well as sensation to its central part. In the thorax, the nerves supply the mediastinal pleura and the pericardium

pus may perforate the prevertebral layer of deep cervical fascia and enter the retropharyngeal space,

producing a bulge in the pharynx (retropharyngeal abscess). This swelling may cause difficulty in swallowing (dysphagia) and speaking (dysarthria). Similarly, air from a ruptured trachea, bronchus, or esophagus (pneumomediastinum) can pass superiorly in the neck.

SCM has two heads

the rounded tendon of the sternal head attaches to the manubrium, and the thick fleshy clavicular head attaches to the superior surface of the medial third of the clavicle.

lesser supraclavicular fossa

space where the two heads are separated inferiorly. The heads join superiorly as they pass obliquely upward to attach to the mastoid process of the temporal bone

The important nerve crossing the occipital triangle is the _______________

spinal accessory nerve (CN XI).

Cervical dystonia (abnormal tonicity of the cervical muscles) / spasmodic torticollis,

usually begins in adulthood. It may involve any bilateral combination of lateral neck muscles, especially the SCM and trapezius.