(18) Neck: Posterior Triangle & Anterior Triangle 1

the neck contains

major cardiovascular structures, major nerves, & the proximal ends of the GI system (pharynx & esophagus), respiratory system (larynx & trachea), endocrine system (thyroid & parathyroid), & CNS (spinal cord)

bones of the neck

hyoid, clavicle, scapula, cervical vertebrae, mastoid process, styloid process

superior border of the neck

styloid process & mastoid process

posterior border of the neck

the 7 cervical vertebrae

inferior border of the neck

clavicle & acromion of scapula

anterior border of neck

hyoid bone & cartilage of trachea

hyoid bone

bone of the neck that does not articulate with any other bones & is instead suspended by ligaments and muscles

characteristics of cervical vertebrae

-Transverse foramen in transverse processes (for passage of vertebral artery)

-Bifid spinous process

-Small vertebral bodies with ridged uncinate processes that extend up between vertebra

-Triangular vertebral foramen that is large relative to vertebral body

Atlas (C1)

First cervical vertebrae that has no vertebral body (anterior tubercle instead) & a superior articular surface on each side that articulates with the occipital condyles of the skull to support the head

Axis (C2)

Second cervical vertebrae that has a characteristic odontoid process/dens (the vertebral body of C1 that moved down during development) that articulates with the anterior arch of the atlas to allow for movement

vertebral prominens

spinous process of C7, which is the longest cervical spinous process

Posterior triangle of the neck/Lateral cervical region

composed of the posterior border of the sternocleidomastoid, the superior border of the trapezius, & the middle 3rd of the clavicle

Trapezius

muscle that runs from the superior nuchal line/external occipital protuberance/ligamentum nuchae to the lateral 1/3 of the clavicle/spine & acromion of the scapula.

-Unilateral contraction laterally flexes head on neck to same side

-Bilateral contraction extends & hyperextends the head

-Innervated by the spinal accessory nerve (somatic motor) & cervical ventral rami (proprioception)

Sternocleidomastoid (SCM)

Muscle that runs from the mastoid process to the manubrium/medial 1/3 of clavical.

-Unilateral contraction laterally flexes head on neck to same side, & rotates head to the contralateral side to turn the face superiorly

-Bilateral contraction weakly flexes the neck

-Innervated by the spinal accessory nerve (somatic motor) & cervical ventral rami (proprioception)

superficial fascia of the neck

outer layer of the neck that contains fat, platysma, external jugular vein, & cutaneous branches of the cervical plexus

deep (cervical) fascia of the neck

Inner layer of the neck consisting of 4 fascial layers: Investing layer, Prevertebral fascia, Pretracheal fascia, & Carotid sheath. Whiplash injuries can cause pain here.

investing layer/external cervical fascia

most superficial layer of the neck's deep fascia that runs from the skull base to the thorax, creating a space that extends into the posterior mediastinum. Surrounds the Sternocelidomastoid, Trapezius, Parotid gland, & Submandibular gland.

prevertebral fascia

layer of the neck's deep fascia that surrounds the prevertebral & scalene muscles. Also contains the phrenic nerve & sympathetic trunk. Relatively posterior.

prevertebral muscles

longus capitis & longus colli

Longus Capitis

muscle surrounded by prevertebral fascia that runs from anterior surfaces of cervical vertebrae to the skull

Longus Colli

muscle surrounded by prevertebral fascia that runs from anterior surfaces of cervical vertebrae but don't cross the skull

Scalene muscles (anterior, middle, posterior)

3 muscles surrounded by prevertebral fascia on the lateral side of the neck that form the floor of the posterior triangle

pretracheal fascia

layer of the neck's deep fascia that surrounds the larynx, esophagus, pharynx, thyroid and parathyroid (the "organ column" of the neck). relatively anterior.

carotid sheath

layer of the neck's deep fascia found bilaterally that surrounds the vagus nerve, common carotid arteries, internal carotid arteries, & internal jugular vein

Retropharyngeal space

space between the deep fascial layers of the neck that extends from the skull base to the posterior mediastinum that provides space for movement from head/neck. Contains "danger space" because infections can spread along a wide area.

"roof" meaning for a neck triangle

lateral or superficial direction; more external

"floor" meaning for a neck triangle

medial or deep direction; more internal

roof (superficial boundary) of posterior triangle

investing layer of deep fascia

floor (deep boundary) of posterior triangle

prevertebral layer of deep fascia

location of the external jugular vein in the posterior triangle

lies deep (but very close) to the platysma & rests on the SCM

location of the brachial plexus in the posterior triangle

between anterior and medius scalene muscles, & partly under the inferior belly of the omohyoid muscle

location of the accessory nerve in the posterior triangle

deep to the investing layer of deep cervical fascia, on the deep surfaces of the trapezius and sternocleidomastoid

cervical plexus

Plexus formed by ventral rami branches of some cervical spinal nerves after they exit their intervertebral foramina. Consists of both a cutaneous part to skin & a somatic motor part to skeletal muscles.

cutaneous nerves of the cervical plexus

Great Auricular nerve

Lesser occipital nerve

Accessory Nerve

Supraclavicular

Transverse cervical nerve

great auricular

Branch of the cervical plexus consisting of C2-C3 ventral rami running anterior to the ear. Provides somatic sensation to the ear & the skin over the mastoid & parotid areas. Travels with the external jugular vein deep to platysma.

lesser occipital nerve

Branch of the cervical plexus consisting of C2 ventral rami running behind the ear. Provides somatic sensation to the scalp.

accessory nerve

CN XI branch of the cervical plexus deep to investing layer of deep fascia

supraclavicular nerve

Branch of the cervical plexus consisting of C3-C4 ventral rami running toward the clavicle. Provides somatic sensation to the skin of the shoulder, & proprioceptive innervation to the trapezius.

transverse cervical nerve

Branch of the cervical plexus consisting of C2-C3 ventral rami running toward the anterior neck & piercing platysma. Provides somatic sensation to the skin over the anterior triangle of the neck.

Nerve point of the neck

Location halfway along the posterior border of the sternocleidomastoid muscle from which all cutaneous branches of the cervical plexus converge and become superficial.

pain is referred back to the neck from organ of the trunk via the

phrenic nerve & the supraclavicular nerve

Anterior triangle of the neck/Anterior cervical region

composed of the anterior border of the sternocleidomastoid, the inferior border of the mandible, & the midline of the neck. Contains the thyroid & parathyroid glands, infrahyoid (strap) muscles, hyoid bone, & cartilage

roof of the anterior triangle

investing layer of deep cervical fascia

floor of the anterior triangle

pharynx & larynx

superficial structures of the anterior triangle are covered by the

platysma, the bilateral parts of which do NOT meet in the midline & may spread ever farther apart with age

4 subtriangles of the anterior triangle

muscular triangle, submandibular triangle, carotid trianle, submental triangle

muscular triangle

subtriangle of the anterior triangle that contains the Hyoid, Thyrohyoid membrane, Laryngeal prominence, Cricothyroid ligament, Cricoid cartilage, Isthmus of thyroid gland, & trachea.

thyrohyoid membrane

connects thyroid cartilage to hyoid bone

laryngeal prominence (Adam's apple)

cartilaginous protrusion that is larger in males

median cricothyroid ligament

connects cricoid cartilage to thyroid cartilage

cricoid cartilage

A ring of cartilage that forms the lower part of the larynx.

isthmus of thyroid gland

middle of thyroid gland that joins the 2 lobes

superior thyroid notch

notch in middle of the superior border of thyroid cartilage

parts of thyroid gland

Right lobe, left lobe, pyramidal lobe (in some people), isthmus

infrahyoid (strap) muscles

sternohyoid, omohyoid, sternothyroid, thyrohyoid. Function during swallowing & speaking. Have their own fascia, which lies between investing layer of deep fascia and pretracheal fascia. None are directly in the midline of the neck.

Sternohyoid

longest strap muscle that runs from the sternum to the hyoid ---Depresses hyoid bone.

-Innervated by ansa cervicalis.

Omohyoid

Double-bellied strap muscle that runs from the scapula, through the posterior triangle, & up to the hyoid. Middle tendon wraps around clavicle.

-Depresses & retracts hyoid bone

-Innervated by ansa cervicalis.

Sternothyroid

Strap muscle posterior to the sternohyoid that runs from the sternum to thyroid cartilage, inserting on the oblique line of thyroid cartilage.

-Depresses larynx.

-Innervated by ansa cervicalis.

Thyrohyoid

Strap muscle that runs from the oblique line of thyroid cartilage to the hyoid.

-Depresses hyoid bone & elevates larynx.

-Innervated by nerve to thyrohyoid

ansa cervicalis

Structure made of ventral rami of cervical spinal nerves that provides motor innervation to 3 of the 4 strap muscles.

a tracheotomy is usually performed by cutting through

thyroid cartilage

superficial temporal vein

runs anterior to ear & joins maxillary vein to form retromandibular vein

maxillary vein

drains blood from the maxillary region & joins superficial temporal vein to form retromandibular vein

retromandibular vein

Formed by superficial temporal and maxillary veins. Splits into an anterior & posterior division.

anterior division of retromandibular vein

joins facial vein to form common facial vein

common facial vein

Union of the facial and anterior retromandibular veins that drains into both the internal jugular vein & communicating vein.

posterior division of retromandibular vein

Joins posterior auricular vein to form external jugular vein

posterior auricular vein

drains the lateral scalp posterior to the ear. Joins posterior division of retromandibular vein to form external jugular vein.

communicating vein

drain some of the common facial vein. Joins with anterior jugular vein to drain into the external jugular vein.

anterior jugular vein

A vein that begins below the chin & descends near the midline to drain into the external jugular vein with the communicating vein.

external jugular vein

drains most superficial veins of the neck. Pieces the investing layer of deep fasica to drain into the subclavian vein, for which it is the only tributary.