THE TRIANGLES OF THE NECK

BONY LANDMARKS OF NECK:

1.HYOID BONE: Suspended in space by the hyoid muscles. Right below the floor of the mouth.

2.THYROID CARTILAGE: It forms the Laryngeal Prominence, or Adam's Apple, overlying the Thyroid Gland and Larynx.

3.CRICOID CARTILAGE: Cartilaginous ring right below the Thyroid Cartilage.

FASCIAL LAYERS OF THE NECK:

1.Investing Fascia: Outermost layer below skin. Encloses the Sternocleidomastoid and Trapezius muscles.

2.Pretracheal Fascia: Anterior to the spine, completely enclosed within investing fascia. Contents:

1.Thyroid Gland

2.Trachea

3.Esophagus

3.Prevertebral Fascia: Enclosing the musculature surrounding the spine.

4.Carotid Sheath: Completely enclosed within investing fascia, on either side of the pretracheal fascia. Contents:

1.Common Carotid Artery

2.Internal Jugular Vein

3.Vagus Nerve

5.Retropharyngeal Space: Potential space between the pretracheal fascia and prevertebral fascia.

POSTERIOR TRIANGLE OF THE NECK: That region posterior to the Sternocleidomastoid muscle, and anterior to the Trapezius.

1.DANGER ZONE: That part of the posterior triangle inferior to the Spinal Accessory Nerve. It contains:

1.The Spinal Accessory Nerve (XI)

2.Brachial Plexus

2.VEINS OF POSTERIOR TRIANGLE: EXTERNAL JUGULAR VEIN = The union of the Retromandibular and Posterior Auricular Veins

1.Eventually pierces investing fascia but not prevertebral fascia.

2.It can fill and become visible from holding breath, or from congestive heart failure.

3.Most of the facial veins drain into the external jugular.

4.Transverse Cervical (from back of danger zone) and Suprascapular veins drain into External Jugular.

CERVICAL PLEXUS. Formed from ventral primary rami of cervical vertebral levels. All of below come off of Cervical Plexus and penetrate investing fascia of

the posterior triangle, but not superficial fascia.

1.A set of cutaneous nerves from this plexus penetrate the investing fascia in this region, to innervate the posterior triangle.

2.Lesser Occipital Nerve:

1.The Greater Occipital Nerve is not from the Cervical Plexus, as it is from the Dorsal Primary Ramus of C1.

2.It runs along the posterior of the Sternocleidomastoid muscle.

3.Great Auricular Nerve -- runs along the External Jugular.

4.Transverse Cervical Nerve

5.Supraclavicular Nerve

6.Phrenic Nerve: Runs on top of (adhered to) the anterior scalene muscle

7.ANSA CERVICALES: Originates from C1-C3. Supplies motor innervation to the strap muscles.

1.It surrounds the Carotid Sheath.

2.Superior Root: Some branches of the Hypoglossal Nerve (XII) get mixed up with Ansa Cervicales C1 fibers ------> innervate the Geniohyoid

muscle.

1.As a result, parts of the superior root tag along the Hypoglossal to get to the strap muscles.

2.These muscles tag along as the nerve enters back through the Hypoglossal Canal.

3.Inferior Root, containing lower cervical levels.

BRACHIAL PLEXUS: Travels between the Anterior and Middle Scalene muscles to reach the axilla.

1.CERVICAL RIB: The presence of a "cervical rib" coming out above T1 at C7 can impinge on the Brachial Plexus and/or the Subclavian Artery, causing

problems.

ANTERIOR TRIANGLE OF THE NECK: The anterior region of the neck, between the two heads of the Sternocleidomastoid.

1.SUBMANDIBULAR TRIANGLE

1.Borders:

1.Posterior belly of Digastric: Lateral border

2.Anterior belly of Digastric: Medial border

3.Mandible: Superior border

2.Contents:

1.Facial Artery

2.Hypoglossal Nerve (XII)

3.Submandibular Salivary Glands

4.Muscles: Digastric, Mylohyoid, Hyoglossus

2.CAROTID TRIANGLE

1.Borders:

1.Superior Belly of the Omohyoid: Medial Border

2.Posterior Belly of the Digastric: Superior Border

3.Sternocleidomastoid: Lateral Border

2.Contents: This triangle overlies the Bifurcation of the Carotid. It contains the Carotid Sheath, as well as the external jugular vein outside of the carotid

sheath.

3.Layers: As you cut through the Carotid Triangle, you find the following in order from superficial to deep:

1.External Jugular Vein, outside of investing fascia

2.Investing Fascia

3.Carotid Sheath:

1.Internal Jugular Vein is superficial and lateral to the common carotid.

2.Common Carotid Artery

3.SUBMENTAL TRIANGLE

4.MUSCULAR TRIANGLE:

1.Borders:

1.Superior Bellies of the Omohyoid Lateral borders

2.Midline of the neck: Medial borders

2.Contents: The Strap Muscles --

ARTERIES OF THE NECK:

1.BRANCHES OF THE EXTERNAL CAROTID: Following is a complete list of principle branches off the External Carotid.

1.3 anterior branches

1.Superior Thyroid Artery -- Thyroid gland and part of anterior neck

2.Lingual Artery -- to tongue

3.Facial Artery

2.1 medial branch

1.Ascending Pharyngeal Artery -- to pharynx

3.2 posterior branches

1.Occipital Artery -- back of neck and behind ear

2.Posterior Auricular Artery -- behind and around ear

4.2 terminal branches -- External Carotid ends as these two terminal branches

1.Maxillary Artery -- goes onto palate, nose, infraorbital region

2.Superficial Temporal Artery -- blood supply to temporal scalp

1.THE THYROCERVICAL TRUNK: Comes directly off the Subclavian.

1.Inferior Thyroid Artery -- not the Superior Thyroid!

2.Transverse Cervical Artery

3.Ascending Cervical

2.COSTOCERVICAL TRUNK -- Comes off Subclavian and gives off a Deep Cervical Artery which goes to anastomose with the Occipital Artery.