Region 1: Anterior Triangle of the Neck and Submandibular Region



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Region 1: Anterior Triangle of the Neck and Submandibular Region

Infrahyoid Muscles (strap muscles): sternohyoid, sternothyroid, thyrohyoid, omohyoid



Sternohyoid

O

posterior manubrium (sterno)

I

Hyoid bone, medial to omohyoid (hyoid)

Inn.

Ansa cervicalis (C1, C2, C3)

Sternothyroid

O

Posterior manubrium below sternohyoid (sterno)

I

Thyroid cartilage (thyroid)

Inn.

Ansa cervicalis (C1, C2, C3)

Thyrohyoid

O

Thyroid cartilage (thyro)

I

Hyoid bone

Inn.

Branches C1, C2 via hypoglossal nerve

Omohyoid

O

Superior border of scapula (near SUPRASCAPULAR NOTCH)

I

Hyoid bone lateral to sternohyoid

Inn.

Ansa cervicalis (C1, C2, C3)

Not.

Composed of INFERIOR and SUPERIOR BELLIES

Suprahyoid Muscles: digastric, stylohyoid, myohyoid, geniohyoid

Digastric

O

Posterior Belly: mastoid bone

I

Anterior Belly: internal surface of mandible

Inn.

Posterior Belly: facial nerve (CN VII)

Anterior Belly: nerve to mylohyoid (off of inferior alveolar nerve  branch of trigeminal nerve)



Stylohyoid

O

Styloid process (stylo)

I

Body of hyoid bone

Inn.

Facial nerve (CN VII)

Mylohyoid

O

Mylohyoid line of mandible

I

Body of hyoid bone

Inn.

Nerve to the mylohyoid (CN V)

Not.

Form the floor of the mouth

Geniohyoid

O

Inferior mental spine (on inner surface of symphysis menti)

I

Hyoid bone

Inn.

Branch of C1 via hypoglossal nerve

Anterior Triangle

--Boundaries: base  lower margin of mandible

anterior  midline of neck

posterior  SCM muscle

--Subdivisions: 4 smaller triangles

*Digastric/submandibular triangle

a. Boundaries: two bellies of digastric (anterior and posterior)

lower border mandible

*Carotid triangle

a. Boundaries: posterior belly of digastric

superior belly of omohyoid

anterior margin of SCM muscle

*Muscular triangle

*Submental triangle

Submandibular Triangle

--Floor: mylohyoid and hyoglossus muscles

--Contents:

a. submandibular gland: major salivary gland

*lays below and in front of angle of the mandible

*Divided into large superficial part and smaller deep part

--superficial part: lays on inferior surface of mylohyoid muscle

--deep part: lays b/w mylohyoid and hyoglossus mm.

*submandibular duct (Wharton’s duct): opens under the tongue through an opening of a small papilla (SUBLINGUAL CARUNCLE)

b. submandibular lymph nodes

c. facial artery: branch of external carotid artery

*arises in carotid triangle  winds under border of mandible at ANTERIOR edge of masseter muscle  enters face

*terminal branch: submental artery

d. facial vein

*accompanies and runs posterior to facial artery

*To: internal jugular vein

e. mylohyoid nerve: sending branches to mylohyoid and anterior belly of digastric

f. intermediate tendon of the digastric muscle

g. hypoglossal nerve (CN XII): passes b/w mylohyoid and hyoglossus mm.

h. lingual nerve (from CN V): passes b/w mylohyoid and hyoglossus mm.

i. lingual artery (from external carotid artery): passes deep to hyoglossus m.

Blood Supply: Arterial

--Common Carotid Artery

*In carotid sheath with internal jugular vein and vagus nerve (CN X)

*at level of upper border of thyroid cartilage divides into internal and external carotid arteries

--at bifurcation: carotid body (chemoreceptors for O2 levels in blood)

carotid sinus (sense blood pressure)

--Internal Carotid Artery: no branches in the neck

--External Carotid Artery: branches in the neck

*superior thyroid artery: 4 branches

--superior laryngeal artery (accompanies internal branch of superior laryngeal nerve through thyrohyoid membrane)

*ascending pharyngeal artery: 1st artery to come off posterior surface of external carotid artery

* lingual artery: passes deep to hyoglossus muscle to supply tongue

*facial artery: passes to/throught submandibular gland to supply face

*occipital artery: comes off oppositie of facial artery, grooves medial surface of the mastoid process

--terminates in posterior scalp lateral to greater occipital nerve (C2)

*Posterior auricular artery

Blood Supply: Venous

--Venous Drainage of Superficial Structures of Head and Neck

*posterior auricular vein

*retromandibular vein

*facial vein

*external jugular vein

--From: posterior auricular vein and retromandibular vein

--Venous Drainage of Deep Structures of the Neck

*internal jugular vein

--Lies in carotid sheath with carotid artery and vagus nerve

--Descends from jugular foramen  moves from posterior to lateral in relation to carotid artery

Lymphatic Drainage of Head and Neck

--Facial nodes

--At junction of Head and Neck: submental, submandibular, occipital nodes

Nervous Supply

--Cranial Nerves in Anterior Triangle of Neck

*Trigeminal Nerve (CN V)

a. n. to mylohyoid: supplies mylohyoid and anterior belly of digastric

*Facial Nerve (CN VII)

a. cervical branch: supplies platysma

b. main trunk: supplies stylohyoid and posterior belly of digastric

*Glossopharyngeal Nerve (CN IX)

a. Supplies carotid sinus

*Vagus Nerve (CN X): passes inside carotid sheath  Lat to Med VNA

a. superior laryngeal nerve

--external branch: supplies cricothyroid m.

--internal branch: passes through thyrohyoid membrane and is sensory to laryngeal mucosa above true vocal folds

b. pharyngeal branch: forms pharyngeal plexus that contains motor fibers to pharyngeal muscles (except tensor veli palatine  CN V) and sensory to pharyngeal mucous membrane

c. recurrent (inferior) laryngeal branch: supplies vocal muscles and mucous membrane below true vocal folds

*Accessory Nerve (CN XI)

a. spinal part: enters deep surface of SCM to supply trapezius m.

*Hypoglossal Nerve (CN XII): carries brances from C1, C2 to ansa cervicalis in cervical plexus

--Ansa Cervicalis

*Innervates: infrahyoid muscles (strap muscles)

*forms a loop on anterior surface of internal jugular vein by connecting branches of hypoglossal and cervical nerves

~descendens hypoglossi/superior root: fibers from C1, C2 run with hypoglossal nerve

~descendens cervicalis/inferior root: fibers from C2, C3

--Cervical Portion of Sympathetic System

*superior cervical ganglion: branches to internal and external carotid aa.

*Middle cervical ganglions

*Inferior cervical ganglion: may fuse with 1st thoracic ganglion to form stellate ganglion

Thyroid Gland

--Shaped like the later H, endocrine gland

*2 lateral lobes: extending form oblique line of thyroid cartilage down to level of 5th or 6th tracheal ring

*Isthmus: connects lower thirds of lateral lobes, covers the 2nd and 3rd tracheal rings

--Blood Supply

*superior thyroid artery

*inferior thyroid artery

--Parathyroid Glands



*two superior and inferior on dorsal side of thyroid gland




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