Structures in Triangles of the Neck

Arteries

Transverse cervical – branch of thyrocervical trunk, runs laterally across the posterior triangle, supplies the scapula

Suprascapular – branch of thyrocervical trunk, runs posterior to the clavicle to supply the muscles of the scapula

Subclavian – left from arch of aorta, right from brachiocephalic trunk; branches are (1) vertebral, (2) internal thoracic, (3) thyrocervical trunk, (4) costocervical trunk, and (5) dorsal scapular. It continues to the arm as the Axillary.

Axillary – continuation of the subclavian after it crosses lateral to the 1^st rib. "She likes to suck a penis" (supreme thoracic, lateral thoracic, thoracoacromial trunk (CAPD), subscapular, anterior and posterior circumflex humorals)

Common carotid – left common carotid originates from the aortic arch, the right common carotid arises from the bifurcation of the brachiocephalic trunk. Both ascend posterior to the sternoclavicular joint within a carotid sheath.

Internal carotid – from common carotid, originates at the level of the superior border of thyroid cartilage. The internal carotid artery has no branches in the neck, it supplies structures within the skull. It passes into the skull via the carotid canal (in the petrous portion of the temporal bone) and enters the middle cranial fossa beside dorsum sellae.

Vertebral – arises from the subclavian and ascends through the transverse foramina of the cervical vertebrae (not C7) and enters the skull through the foramen magnum. With the internal carotids, the vertebral arteries are the 4 main blood suppliers to the brain.

Thryrocervical trunk – arises from the 1^st part of the subclavian, just medial to the scalenus anterior. Gives rise to the inferior thyroid artery, the suprascapular artery, and the transverse cervical artery

Bones

Clavicle – most frequently broken bone in the body, attaches upper limbs to the thorax.

Membranes

Cricothyroid – connects the arch of the cricoid cartilage with the thyroid cartilage. The median cricothyroid ligament produces a soft spot inferior to the thyroid cartilage where the airway is closest to the skin and most accessible.

Miscellaneous

Posterior triangle – between sternoclediomastoid muscle anteriorly, trapezius muscle posteriorly, and clavicle inferiorly.

contains: external jugular vein, 3^rd portion of subclavian artery, transverse cervical artery, suprascapular artery, and occipital artery; accessory nerve (CN XI), lesser occipital nerve, and ventral rami of the brachial plexus.

Occipital triangle – superior to inferior belly of omohyoid muscle; CN XI crosses; occipital artery at apex

Supraclavicular triangle – smaller; below omohyoid; external jugular vein and suprascapular artery cross superficially; the subclavian artery lies deep in here; a.k.a. the "subclavian triangle"

Anterior triangle – bounded medially by the midline of neck, superiorly by the inferior border of the mandible, and laterally by the sternocleidomastoid; 3 paired subdivisions, 1 unpaired (submental)

Muscular triangle – below the omohyoid; contains the infrahyoid muscles, and the neck viscera

Carotid triangle – bounded superiorly by the Digastric, inferiorly by the Superior Omohyoid, posteriorly by the Sternocleido-mastoid. Contains: carotid sinus (senses BP), the carotid body (senses Ý pCO₂ or ß pO₂), Carotid Sheath, which contains the common carotid artery, the internal jugular vein, CN X, and ansa cervicalis.

Submandibular triangle – lies inferior to mandible, superior to digastric muscle, contains: submandibular gland, CN XII, the nerve to the mylohyoid muscle, parts of the facial artery and vein, and the submental artery

Submental triangle – UNPAIRED, under the mandible, contains submental lymph nodes and the anterior jugular vein.

Pharynx – common route for food and air, located posterior to the nasal and oral cavities, ~15cm long

3 parts:

(1) nasopharynx posterior to the nose and superior to soft palate,
(2) oropharynx posterior to mouth,
(3) laryngeaopharynx posterior to the larynx.

Esophagus – thick, distensible, muscular tube that extends from the pharynx to the stomach (~25cm), posterior to trachea

Larynx – between the pharynx and trachea, used for sound production, epiglottis keeps food from entering trachea

Laryngeal prominence (Adam’s apple) – anterior neck, produced by thyroid cartilage, more noticeable on men

Cricoid cartilage – part of the laryngeal skeleton, inferior to thyroid cartilage, lies at C6, where the larynx and trachea join

Trachea – "windpipe", fibrocartilaginous tube supported by tracheal rings, extends from larynx to roots of lungs (~12cm)

Thyroid isthmus – usually lies anterior to the 2^nd and 3^rd tracheal rings, connects the lobes of the thyroid

Muscles

NOTE: for muscles without specified origins and insertions, origins are the inferior attachments and insertions are the superior attachments.

Sternocleidomastoid – divides the neck into anterior and posterior triangles

Origin:

Sternal head from manubrium lateral to the jugular notch
Clavicular head from the superior surface of the medial 1/3^rd of the clavical

Insertion: lateral surface of the mastoid process and lateral ½ of superior nuchal line

Innervation: CN XI, C2, and C3

Action: acting alone tilts the head to ipsilateral side, together flexes the neck

Trapezius – defines the posterior border of the posterior triangle; Innervation: CN XI

Platysma

Origin: fascia over pectorals and deltoid

Insertion: inferior border of mandible and skin of the lower face

Innervation: cervical branch of CN VII

Action: tenses the skin of the neck

Subclavius – under clavicle, Innervation: subclavian nerve (a branch off the superior trunk of the Brachial Plexus)

Omohyoid – Divides the anterior and posterior triangles into subdivisions

Origin: suprascapular notch

Insertion: inferior border of hyoid

Innervation: C1, C2, and C3 via ansa cervicalis

Action: depresses, retracts, and steadies the hyoid bone

Spenius capitis

Origin: inferior ½ of ligamentum nuchae and spinous processes of T1-6

Insertion: lateral aspect of mastoid process and lateral 1/3^rd of superior nuchal line.

Innervation: dorsal rami of middle cervical spinal nerve.

Action: laterally flexes and rotates head and neck to the ipsilateral side. Bilaterally, extends the head and neck.

Levator scapulae

Origin: posterior tubercles of transverse processes of C1-4

Insertion: superior part of medial border of scapula.

Innervation: dorsal scapular nerve (C5) and cervical spinal nerves (C3 and C4)

Action: elevates scapula and tilts its glenoid cavity inferiorly.

Scalenus – consists of anterior, medius, and posterior; brachial plexus lies between anterior and medius

Anterior

Medius

Origin: posterior tubercles of transverse processes C2-C7

Insertion: superior surface of 1^st rib

Innervation: ventral rami of cervical spinal nerves (C3 and C8)

Action: flexes neck laterally, elevates 1^st rib during forced inspiration

Posterior

Origin: posterior tubercles of transverse processes C4-6

Insertion: 2^nd rib

Innervation: ventral rami of cervical spinal nerves (C7 and C8) Action: flexes neck lat., lifts 2^nd rib during forced inspir.

Infrahyoid (strap)

Omohyoid – see above

Sternohyoid

Origin: manubrium and medial clavical

Insertion: body of hyoid

Innervation: C1-3 (ansa cervicalis)

Action: depresses hyoid after swallowing

Sternothyroid – deep to sternohyoid

Origin: posterior manubrium

Insertion: oblique line of thyroid cartilage

Innervation: C2, C3 via ansa cervicalis

Action: depresses hyoid and larynx

Thyrohyoid

Origin: oblique line of thyroid cartilage

Insertion: inferior border of body and greater horn of hyoid

Innervation: C1 (via CN XII)

Action: depresses hyoid bone and elevates larynx

Nerves

Supraclavicular (C3-4) – arise as a single trunk; divides into medial (supplies sternoclavicular joint), intermediate, and lateral (supplies the AC joint) branches. Also sends small branches to the skin of the neck, shoulder, and chest.

Accessory (CN XI) – MOTOR, cranial root arises from mucleus ambiguus, spinal root from spinal nucleus (C6-C1); axons enter cranium via foramen magnum and exit via jugular foramen; innervates trapezius and sternocleidomastoid

Lesser Occipital (vent. Ramus C2) – ascends a short distance along the posterior border of the sternocleidomastoid before dividing into several branches that supply the skin of the neck and scalp posterior to the auricle

Great Auricular (C2-3) – a superficial ascending branch of the cervical plexus, passes external to the parotid, doesn’t enter, splits into anterior and posterior branches.

Transverse cervical (C2-3) – curves around the posterior border of the sternocleidomastoid near its middle and then passes transversely across it. Its branches supply the skin over the anterior triangle of the neck.

Brachial plexus – "Randy Travis Drinks Cold Beer"

Phrenic (C3-5) – ~30cm long, sole motor nerve to the thoracic diaphragm. Chiefly C4, formed at the superior part of the lateral border of scalenus anterior at the level of the thyroid cartilage.

Vagus (CN X) – ("wandering" in Latin) leaves the skull via the jugular foramen, travels down the carotid sheath, main parasympathetic nerve to the organs of thorax and abdomen, recurrent laryngeal nerve a branch of CN X, loops around the subclavian on the right and the aorta on the left. Cardiac branches originate in the neck and thorax.

Ansa cervicalis (C1-3) – a loop in the cervical plexus that supplies both bellies of omohyoid, sternohoyoid, and thryohyoid.

Veins

External Jugular – drains scalp and face, begins just under the auricle, empties into the subclavian 2cm above clavicle.

Suprascapular

Subclavian–continuation of axillary vein from 1^st rib to scalenus anterior where it joins the internal jugular to form brachiocephalic vein

Internal jugular – enclosed within the carotid sheath for its entire course, largest vein of neck, from the jugular foramen (inferior to the external auditory meatus) to join the subclavian as the brachiocephalic vein (behind medial clavicle)

Retromandibular – formed by the union of the superficial temporal and maxillary veins, posterior to the mandible; descends within the parotid gland; divides into a posterior (joins posterior auricular vein) and anterior branch (joins facial vein)

Anterior jugular – smallest jugular, arises near hyoid from the submental venous plexus; has communicating branch