Anatomy: The Neck, Anatomy, Superficial Structures of the Neck

Sternocleidomastoid Muscle. 

It also acts as an accessory muscle of inspiration, along with the scalene muscles of the neck

Sternocleidomastoid
The triangles of the neck. (Anterior triangles to the left; posterior triangles to the right.)
Muscles of the neck. Lateral view.
Latin	musculus sternocleidomastoideus
Gray's	subject #111 390
Origin	manubrium sterni, medial portion of the clavicle
Insertion	mastoid process of the temporal bone, superior nuchal line of the occipital bone
Artery	occipital artery and the superior thyroid artery
Nerve	motor: accessory nerve sensory: cervical plexus (ventral ramus of the second cranial nerve)
Actions	Acting alone, tilts head to its own side and rotates it so the face is turned towards the opposite side. Acting together, flexes the neck, raises the sternum and assists in forced inspiration.

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The Sternocleidomastoid is crossed by the platysma and the External Jugular Vein. The Sternocleidomastoid covers the great vessels of the neck and the cervical plexus of the nerves. 

Congenital torticollis: The Sternocleidomastoid may be injured at birth resulting in congenital torticollis. There is fixed rotation and tilting of the head owing to contracture of the sternocleidomastoid muscle. Birth injury, tearing fibers of the muscle during NVD vaginal delivery - bleeding - swelling and then fibrosis of the sternocleidomastoid. This shortening of the muscle is evident at age 3 to 4 when the neck elongates. Managed by physiotherapy that promotes daily stretching and tilting the head. 

Spasmodic torticollis may develop in adults - Stiff neck. 

 

Posterior Triangle of the Neck. 

The Sternocleidomastoid, the Trapezius and Clavicle form the posterior triangle of the neck. The trapezius and the Sternocleidomastoid meet at the superior nuchal line - where the Occipital Artery passes through the apex of the posterior triangle, before it ascends over the posterior aspect of the head.

The roof of the Posterior triangle of the Neck -  Covered by deep fascia and superficial to this fascia is the Platysma veins, nerves and skin.

The muscular FLOOR of the posterior triangle is formed by splenius capitus, levator scapulae, scalenus medius and scaleneus posterior muscles. The four mascles are covered by a carpet of Deep Cervical Fascia. The Spenius capitus muscle arises from the the ligamentum nuchae and the spinous process of the superior thoracic vertebrae. The Spenius Capitus runs superolaterally and inserts into the mastoid process.
Levator scapulae muscle lifts the scapula, arises from the first 4 cervical vertebrae and inserts into the medial boarder of the scapulae.
Scalenus Posterior Muscle arises from the lower two to three cervical vertebrae (4th, 5th, 6th cervical vertebrae) and inserts into the 2nd rib.
Scalenus Medius Muscle arises from the posterior tubercles of  ALL the cervical vertebrae. Inserts on the posterior part of the 1st rib. The Scalenus medius lies posterior to the roots of the brachial plexus.

Levator scapulae muscle
Muscles connecting the upper extremity to thevertebral column. (Levator scapula visible at upper right, at the neck.)
Latin	musculus levator scapulae
Gray's	subject #121 435
Origin	Posterior tubercles oftransverse processes of C1 - C4 vertebrae
Insertion	Superior part of medial border of scapula
Artery	dorsal scapular artery
Nerve	cervical nerve (C3, C4) anddorsal scapular nerve (C5)
Actions	Elevates scapula and tilts itsglenoid cavity inferiorly by rotating scapula

Contents of the Posterior Triangle:  Vessels and nerves of the Neck and Upper Limb'


The External Jugular Vein begins near the angle of the mandible, inferior to the lobule of the auricle, by union of the posterior division of the retromandibular vein and the posterior auricular vein. The external jugular vein crosses the sternocleidomastoid muscle in the superficial fascia and then pierces the fascia roof of the posterior triangle at he posterior boarder of the sternocleidomastoid muscle. It then passes obliquely through the inferior part of the posterior triangle to empty in the subclavian vein 2cm superior to the clavicle. 


A raised JVP in heart failure may be seen throughout the course of the external jugular Vein. A JVP is raised in increased thoracic pressure, obstructed by a tumour, and enlarged supraclavicular lymph nodes. Opera singers have bilateral enlargement of their external jugular veins due to prolonged periods of increased intrathoracic pressure. IV Fluid overload may have a engorged JVP. Laceration of the external jugular about 5cm superior to the clavicle, may result in air embolism as the External Jugular can not retract when it pierces the deep fascia of the posterior triangle - the patient may present with dyspnea and cyanosis.

Vein: External jugular vein
Veins of the head and neck. (External jugular visible at center.)
Veins
Latin	vena jugularis externa
Gray's	subject #168 646
Drains from	cranium, face
Source	posterior facial vein,posterior auricular vein,anterior jugular vein
Drains to	subclavian vein
MeSH	Jugular+Veins

Anatomy: The Neck, anatomy, Posterior Triangle of the Neck

Arteries of the Posterior Triangle of the Neck

The third part of the subclavian artery. The subclavian artery has 3 parts - separated by the scalenus anterior in thirds - the last third is the part between the scalenus anterior and the clavicle. It is a fingerbreath superior to the clavicle.

The transverse cervical artery arises from the thyrocervical trunk - a branch of the subclavian artery. The transverse cervical artery runs superficially and laterally across the posterior triangle, 2 to 3 cm superior to the clavicle.

The Suprascapular artery from the branch of the thyrocervical trunk - runs posterior to the clavical to the muscles around the scapula.

Artery: Transverse cervical artery
Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries. Transverse cervical artery is labeled, branching from the thyrocervical_trunk.
Superficial and deep branches from the transverse cervical artery.
Latin	arteria transversa cervicis, arteria transversa colli
Gray's	subject #148 82
Supplies	Trapezius Sternocleidomastoid
Source	Thyrocervical trunk
Branches	Superficial branch Deep branch
Vein	Transverse cervical veins

Occipital artery is a branch of the external carotid artery enters the apex of the posterior triangle before ascending to the occipital area. 

Nerves in the posterior triangle. The Accessory nerve (CN XI) that divides the posterior triangle into a superior and inferior parts. The Accessory nerve is a motor nerve consisting of spinal (C1 to C5) and cranial roots. The spinal roots travel superiorly and enter the posterior cranial fossa through the foramen magnum. Here they join the cranial roots of the accessory nerve from the Medulla. Both combined roots leave the skull through the jugular foramen.

The Spinal roots separates immediately and supplies the Sternocleidomastoid muscle and the trapezius muscle.

Lesions to the Accessory Muscle are rare. The Accessory Nerve may be damaged by Traumatic injury, tumours to the base of the skull, fractures involving the jugular foramen, and neck lacerations. Presents with weakness in turning the head to the OPPOSITE site against resistance. Unilateral paralysis of the trapezius muscle is evident by the patients inability to elevate and retract the shoulder, and is unable to lift the arm above the horizontal level. Drooping of the shoulder is obvious.


The Accessory Nerve function can also be functionally impaired by inflamed lymph nodes in the neck. During surgical dissection of the neck lymph nodes care should be taken to isolate and preserve the  Accessory Nerve. 

Nerve: Accessory nerve
Plan of upper portions of glossopharyngeal, vagus, and accessory nerves.
Inferior view of the human brain, with the cranial nerves labelled.
Latin	nervus accessorius
Gray's	subject #206 913
Innervates	sternocleidomastoid muscle, trapezius muscle
MeSH	Accessory+Nerve

The Cervical Plexus


, Anterior triangle, Arteries, Carotid Artery, Carotid Body, , Hyoid Muscles, Muscles, Neck, Nerves, , Posterior triangle, raised JVP, , XI

Anatomy Neck. Superficial Structures of the Neck. Accessory Nerve, Anterior triangle, Arteries, Carotid Artery, Carotid Body, Cervical Plexus, Hyoid Muscles, Muscles, Neck, Nerves, Platysma, Posterior triangle of the Neck, raised JVP, Sternocleidomastoid, XI

Platysma Muscle is a wide, thin, subcutaneous sheet of striated muscle that is located in the superficial fascia of the neck. The platysma covers the superior part of the anterior triangle and the anteroinferior part of the posterior triangle of the neck. Its fibers blend with the facial muscles.  The Platysma is the muscle of facial expression.

Platysma muscle
Platysma is visible at bottom, in neck
Gray's	subject #110 387
Origin	subcutaneous tissue of infraclavicular and supraclavicular regions - Fascia and Skin over Pectoralis major and deltoid muscles
Insertion	base of mandible; skin of cheek and lower lip; angle of mouth; orbicularis oris
Artery	branches of the Submental artery and Suprascapular artery
Nerve	cervical branch of the facial nerve (CN VII)
Actions	Draws the corners of themouth inferiorly and widens it (as in expressions of sadness and fright). Also draws the skinof the neck superiorly whenteeth are clenched

 

An Raised JVP can be seen under the platysma Muscle.


Cervical branch of the facial nerve supplies the platysma - and may be damaged by malignant parotid or submandibular cancer (Ca). The cervical branch of the facial nerve may also be damaged by surgical procedures like the removal of a branchial cyst. Injury to the mandibular branch produces a noticeable facial deformity and damaged to the cervical branch of the facial nerve produces unsightly drooping neck. A gaping of the skin incision may be present after the removal of a thyroid - if the platysma edges were not sutured.

Nerve: Cervical branch of the facial nerve
Plan of the facial and intermediate nerves and their communication with other nerves. (Labeled at center bottom, as "Cervical".)
The nerves of the scalp, face, and side of neck. (Cervical labeled at center, in dark region under jaw.)
Latin	ramus colli nervi facialis
Gray's	subject #202 905
From	facial nerve