Triangles of the Neck

Fascial layers and compartments

Superficial Cervical Fascia (subcutaneous connective tissue) – cutaneous nerves and vessels; platysma muscle

Deep Cervical Fascia

Investing layer – encircles the neck and "invests" the trapezius and sternocleidomastoid muscles

Prevertebral layer – surrounds vertebrae and vertebral muscles

Visceral layer (pretracheal superiorly, buccopharyngeal inferiorly) – encloses "viscera" (esophagus, larynx, etc.)

Carotid sheath – one on each side, contains common and internal carotid arteries, internal jugular vein, and vagus nerve

The retropharyngeal space (between prevertebral and pretracheal) is the "Danger space" in infections

Surface Anatomy and Landmarks

Thyroid cartilage with lamina – at C4-C5

Cricoid cartilage – at C6, the transition from larynx to trachea

Hyoid bone – has greater and lesser horn, Digastric muscle connects styloid process with the lesser horn.

Triangles of the Neck

(1) Posterior Triangle – posterior to sternocleidomastoid, anterior to trapezius, subdivided by inferior belly of omohyoid

Supraclavicular triangle – below inferior belly of the posterior omohyoid

Occipital triangle – superior to the inferior belly of the posterior omohyoid

contents of posterior triangle

External jugular vein (medial), spinal accessory nerve (lateral),
Floor of posterior triangle – "she likes my penis alot" = splenius capitus, levator scapuli, medial scalene, posterior scalene, anterior scalene.

Cervical Plexus – (C1-C4), sensory nerves, pass under the sternocleidomastoid "let’s get things started"

Lesser occipital nerve – runs to occiput

Great auricular nerve – runs up to ear

Transverse cervical nerve – goes across neck

Supraclavicular nerve – runs inferiorly to the clavicle

Deep posterior triangle – branches of the thyrocervical trunk: "I tried teaching crazy sex" = inferior thyroid, transverse cervical, suprascapular arteries

Superior thyroid artery comes off external carotid, inferior thyroid artery comes off thyrocervical trunk(from subclavian)

(2) Anterior Triangle – anterior to the sternoceidomastoid, lateral to the midline of neck

Muscular triangle – inferior to superior omohyoid, laryngeal prominence in center and strap muscles on sides

"strap muscles" attach to hyoid bone,

infrahyoid bodies inferior to hyoid, sternohyoid, sternothyroid, thyrohyoid, and omohyoid all innervated by ansa cervicalis (C1, C2, and C3) except thyrohyoid which gets C1

suprahyoid bodies superior to hyoid

digastric (2 bellies, anterior (ABD) and posterior (PBD)) innervated by CN VII (PBD) and CN V (ABD)

stylohyoid – travels with posterior digastric, innervated by CN VII (pierces through the posterior digastric)

mylohyoid – forms the floor of the oral cavity, innervated by CN V

geniohyoid – lies deep to mylohyoid, innervated by a direct branch of C1

genioglossus and hypoglossus – both insert into tongue, innervated by CN XII

Carotid triangle – contains Carotid Sheath, a tubular structure containing the internal jugular vein, vagus nerve (CN X), and either the common carotid or internal carotid artery. The internal carotid provides no branches to the neck. Sympathetic trunk lies deep to carotid sheath.

Submandibular triangle – between the anterior Digastric and the mandible. Contains submandibular gland.

Submandibular gland – a paired, U shaped salivary gland, wrapped around the myohyoid muscle.

Submental triangle – unpaired; bounded inferiorly by hyoid bone and laterally by right and left anterior bellies of the Digastric muscles. Contains lymph nodes and little veins that join to form the Anterior Jugular vein

Nerves

other than the Vagus, nerves of the anterior triangle are derived from ventral primary rami of cervical spine, cranial nerves, or cervical levels of the sympathetic trunk

CN V (V₃, mandibular branch of Trigeminal) has a branch for the ABD and mylohyoid..

CN VII facial – innervates the stylohyoid and PBD as it leaves the skull, innervates Platysma a little later.

CN X Vagus – gives rise to superior laryngeal nerve and recurrent laryngeal nerves while in the sheath.

CN XI spinal accessory – innervates the trapezius and Sternocleidomastoid.

CN XII hypoglossal – motor to intrinsic musculature of the tongue and all extrinsic tongue muscles except the palatoglossus. The Ansa Cervicalis of the cervical plexus appears to "hang from" CN XII.

Phrenic nerve – "C3, 4, and 5, keeps the diaphragm alive", travel down on the anterior scalene muscle

Cervical sympathetic trunk – lies deep to the carotid sheath, on the anterior surface of the prevertebral fascia.

Consists mainly of ascending preganglionic sympathetic axons which originate from T1-T4.