Cervical Plexus Anatomy

The cutaneous branches of the cervical plexus pierce the investing fascia at the anterior border of the sternocleidomastoid muscle.

The inferior belly of the omohyoid muscle is kept in place by its suprascapular nerve.

The third part of the subclavian artery's pulsation can be felt by pressing downwards behind the clavicle at the medial border of sternocleidomastoid.

The subclavian vein slips into the posterior corner of the triangle on its way to the external jugular vein.

The transverse cervical artery divides at the posterior border, with the ascending branch running up to the muscle.

The cervical plexus is formed by simple loops between the anterior rami of the upper five cervical nerves.

Muscular branches from C2 and 3 innervate the trapezius, while branches from C3 and 4 innervate the sternocleidomastoid.

The inferior root of the ansa cervicalis is formed by union of a branch each from C1 and C2.

The phrenic nerve is formed mainly from C4 with unimportant contributions from C3 and C6.

The lesser occipital nerve (C2) is a slender branch that hooks around the accessory nerve and runs up along the anterior border of sternocleidomastoid.

The sternocleidomastoid muscle divides each side of the neck into anterior and posterior triangles, running perpendicular to the midline.

The anterior triangle of the neck is delineated by the posterior border of the sternocleidomastoid, the inferior border of the mandible, and the midline of the neck.

The submental, digastric, carotid, and muscular triangles are subdivisions of the posterior triangle of the neck, providing a structured approach to understanding its complex anatomy.

The sternocleidomastoid muscle originates from three distinct heads: the manubrium, the clavicle, and the sternal angle, each contributing uniquely to its overall function.

The triangular interval located above the sternoclavicular joint, between the two heads of the sternocleidomastoid, provides a superficial access point for the external jugular vein.

The manubrial tendon of the sternocleidomastoid attaches to the posterior aspect of the manubrium, specifically to enhance leverage for neck flexion.

The most superficial portion of the clavicular head of the sternocleidomastoid inserts onto the inferior nuchal line, lateral to the insertion of the sterno-occipitalis fibers.

The accessory nerve penetrates the sternocleidomastoid muscle superficially, coursing along its external surface before entering the posterior triangle.

The deep cervical fascia splits into three layers to enclose the sternocleidomastoid, with each layer contributing to the muscle's structural integrity and function.

The sternocleidomastoid muscle's attachment to the hyoid bone directly facilitates swallowing by modulating laryngeal elevation and depression.

The transverse cervical nerve, originating from C2 and C3, innervates the skin along the posterior aspect of the neck, extending from the chin to the sternum.

Interruption of the main trunk of the transverse cervical nerve results in a circumscribed area of anesthesia, typically limited to a small circular region in the anterior neck.

The sternocleidomastoid muscle is primarily innervated by the spinal part of the accessory nerve, specifically through branches originating distal to the point of entry into the muscle.

The transverse cervical nerve is anatomically positioned superior to the transverse cervical artery in the cervical region.

Contraction of the right sternocleidomastoid muscle results in the head turning to the right side with the chin rotating towards the left.

The supraclavicular nerve, primarily derived from C4, emerges independently at the anterior border of the sternocleidomastoid muscle.

When the head is in a normal position, simultaneous contraction of both sternocleidomastoid muscles primarily extends the cervical spine and flexes the atlanto-occipital joints.

The intermediate group of branches of the supraclavicular nerve consistently pass posterior to the clavicle to innervate the skin extending down to the anterior axillary line.

The floor of the posterior triangle is formed by the investing layer of deep cervical fascia.

The lateral group of supraclavicular nerve branches exclusively innervates the skin over the acromion and the upper half of the deltoid muscle.

The greater occipital and third occipital nerves, originating from the anterior rami of C2 and C3 respectively, provide sensory innervation to the posterior skin of the neck.

The anterior fibers of the sternocleidomastoid muscle, which lie just in front of the lateral atlanto-occipital joints, primarily extend the skull on the atlas.

The blood supply to the sternocleidomastoid muscle is derived from branches of the subclavian and inferior thyroid arteries.

The first cervical nerve (C1) provides cutaneous innervation to a small region of skin located directly behind the ear.

The C2 dermatome primarily covers the anterior part of the neck, extending inferiorly to the clavicle and superiorly to the mandibular region.

In operations within the posterior triangle, the subclavian vein and the vagus nerve, located deep to the prevertebral fascia, are at high risk of injury.

The supraclavicular nodes, located within the posterior triangle, are directly associated with the upper group of deep cervical nodes.

The dermatomal map of the neck exhibits sharp, distinct boundaries with minimal overlap between adjacent cervical nerve segments.

The accessory nerve traverses the posterior triangle, lying superficial to the investing layer of deep cervical fascia, which makes it relatively protected from surgical injury.

Cerebral cortex innervation of the segments innervating the anterior horn cells of the sternocleidomastoid originate from the contralateral side.

Triangles of the Neck

Posterior Triangle

Anterior Triangle

Submental, Digastric, Carotid, and Muscular Triangles

Sternocleidomastoid (SCM)

SCM Heads of Origin

Triangular Interval (SCM)

SCM Insertion

Investing Layer of Deep Cervical Fascia

SCM Function

Transverse Cervical Nerve

Supraclavicular Nerve

Medial Group of Supraclavicular Nerve

Intermediate Group Supraclavicular Nerve

Lateral Group Supraclavicular Nerve

Greater Occipital Nerve

Third Occipital Nerve

First Cervical Nerve (C1)

C2 Dermatome

C3 Dermatome

Sternocleidomastoid: Deep Structures

Sternocleidomastoid: Blood Supply

Sternocleidomastoid: Nerve Supply

Sternocleidomastoid: Action Alone

Sternocleidomastoid: Action Together

Sternocleidomastoid: Test

Posterior Triangle: Definition

Posterior Triangle: Roof

Posterior Triangle: Floor

Posterior Triangle: Contents

Surface Marking of Accessory Nerve

Cervical Plexus Formation

Muscular Branches of Cervical Plexus

Phrenic Nerve Origin

Phrenic Nerve Course

Phrenic Nerve Function

Lesser Occipital Nerve Distribution

Great Auricular Nerve Distribution

Great Auricular Nerve Course

Ansa Cervicalis Function