Anatomy of the Neck: Muscles, Glands, and Arteries

Sternocleidomastoid

Origin:

• Sternal head: Manubrium of sternum
• Clavicular head: Medial 1/3 of clavicle

Insertion: Outer surface of mastoid process, lateral 1/3 of superior nuchal line
Nerve Supply:

• Motor: Accessory nerve
• Sensory: C2, C3

Action:

• Both muscles contract: Flexes neck forward
• One muscle contracts: Bends neck to the opposite side and rotates to the same side

Relations:

• Superficial: Skin
• Deep: Carotid sheath

Digastric Muscle

Origin:

• Anterior belly: Lower border of mandible
• Posterior belly: Digastric notch of mastoid process

Intermediate tendon: Connected to hyoid bone
Nerve Supply:

• Anterior belly: Mylohyoid nerve
• Posterior belly: Facial nerve

Function:

• Anterior belly: Depresses mandible, elevates hyoid bone
• Posterior belly: Elevates hyoid bone, retracts mandible

Relations:

• Superficial: Skin, fascia, submandibular salivary gland
• Deep: Carotid sheath

Mylohyoid Muscle

Origin: Mylohyoid line of mandible
Insertion: Hyoid bone
Nerve Supply: Mylohyoid nerve
Function: Supports floor of mouth, elevates hyoid bone and tongue

Geniohyoid

Origin: Inferior genial tubercle of mandible
Insertion: Body of hyoid bone
Nerve Supply: C1 via hypoglossal nerve
Function: Depresses mandible, elevates hyoid bone

Scalene Muscles

Origin: Transverse processes of cervical vertebrae
Insertion: First and second ribs
Nerve Supply: Cervical spinal nerves
Function: Flex and laterally bend the neck, elevate ribs during inspiration

Trapezius

Origin: External occipital protuberance, superior nuchal line, ligamentum nuchae, spinous processes of C7-T12
Insertion: Lateral third of clavicle, acromion, and spine of scapula
Nerve Supply: Accessory nerve (CN XI), C3-C4 spinal nerves
Function: Elevates, depresses, retracts, and rotates scapula

Submandibular Salivary Gland

Extensions:

• Anteriorly: Mental foramen
• Posteriorly: Angle of mandible
• Above: Mylohyoid line
• Below: Digastric muscle

Superficial part:

• Lateral: Submandibular fossa
• Medial: Mylohyoid, hyoglossus
• Inferior: Skin, fascia

Deep part:

• Lingual nerve above
• Hypoglossal nerve below

Submandibular Duct

Arterial Supply: Facial, lingual arteries
Nerve Supply:

• Lingual nerve (sensory)
• Sympathetic: Plexus around facial artery
• Parasympathetic: Superior salivary nucleus → facial nerve → chorda tympani nerve → lingual nerve → submandibular ganglion

Thyroid Gland

Shape: Butterfly shaped
Location: Lower neck

• Isthmus: Anterior to 2nd, 3rd, and 4th tracheal rings
• Lateral lobes: Extend superiorly to the oblique line of the thyroid cartilage and inferiorly to the 6th or 7th tracheal ring

Relations:

• Isthmus: Anteriorly - skin, fascia, infrahyoid muscles; Posteriorly - 2nd, 3rd, and 4th tracheal rings
• Lateral lobes: Posteriorly - parathyroid glands; Medially - above: larynx and pharynx, below: trachea and esophagus

Arterial Supply:

• Superior thyroid artery: From external carotid artery
• Inferior thyroid artery: From thyrocervical trunk of subclavian artery
• Thyroid ima artery (occasional): From arch of aorta

Common Carotid Artery

Origin: Thorax (brachiocephalic trunk on the right, arch of aorta on the left)
Course: Ascends in the neck within the carotid sheath, medial to the internal jugular vein, and deep to the sternocleidomastoid muscle
Branches in the neck: None

Internal Carotid Artery

Origin: Bifurcation of the common carotid artery at the upper border of the thyroid cartilage
Course: Ascends in the neck within the carotid sheath, enters the carotid canal in the temporal bone, traverses the cavernous sinus
Termination: Leaves the cavernous sinus and divides into the anterior and middle cerebral arteries
Branches:

• Neck: No branches
• Cranial cavity: Ophthalmic artery, anterior cerebral artery, middle cerebral artery, posterior communicating artery

External Carotid Artery

Origin: Bifurcation of the common carotid artery at the upper border of the thyroid cartilage (C3-C4 level)
Course: Ascends in the neck external to the carotid sheath, enters the parotid gland
Branches:

• Anterior: Superior thyroid artery, lingual artery, facial artery
• Posterior: Posterior auricular artery, occipital artery
• Medial: Ascending pharyngeal artery