Neck Muscles and Anatomy: A Comprehensive Guide
Neck Muscles
Lateral Neck
Platysma
Source: Wide, thin muscle situated on the side of the neck, below the superficial fascia.
Insertion: Below the subcutaneous tissue of the subclavicular region, up to the bottom edge of the maxilla. Intersects at the midline, and muscle fibers blend into the facial skin.
Action: Draws down the skin of the chin and lower lip (sad expression).
Sternocleidomastoid
Source: Thick muscle extending obliquely from the upper chest to the mastoid process.
Insertion: Formed by two parts: the sternal and clavicular bundles. The sternal fascicle emerges from the front of the manubrium via a strong tendon, widening and directing upwards and backwards to the outer surface of the mastoid process and the superior nuchal line. The clavicular bundle inserts into the inner surface of the clavicle (posterior edge), extending almost vertically upwards to insert into the anterior border of the mastoid process and the superior nuchal line. The two bundles merge distally.
Nerve: Spinal accessory nerve and cervical plexus.
Action: Flexes the head towards the chest and rotates it to the opposite side.
Scalenes
Source: Triangular muscles located deep on each side of the neck. There are three: anterior, middle, and posterior scalene.
Insertion: Anterior scalene: anterior tubercles of the third to sixth cervical vertebrae to the tubercle of Lisfranc on the first rib. Middle scalene: anterior tubercles of the last six cervical vertebrae to the first two ribs. Posterior scalene: posterior tubercles of the third to sixth cervical vertebrae to the second rib.
Innervation: Anterior rami of the third, fourth, and fifth cervical nerves to the anterior scalene. Anterior rami of the third and fourth cervical nerves to the middle and posterior scalenes.
Action: Elevate the ribs or flex the cervical spine.
Rectus Capitis Lateralis
Source: Fleshy, cylindrical muscle situated on either side of the atlas and axis.
Insertion: Transverse process of the atlas and the jugular process of the occipital bone.
Innervation: Anterior ramus of the first cervical nerve.
Action: Tilts the head laterally or stabilizes the cervical spine.
Region of the Hyoid Bone
Suprahyoid Muscles
Digastric
Source: Arcs from the base of the skull to the upper jaw.
Insertion: Consists of two bellies: the posterior belly inserts into the mastoid process (digastric groove) and extends upwards and forwards to the digastric fossa. The anterior belly inserts into the mandible.
Innervation: Posterior belly: facial nerve. Anterior belly: mandibular branch of the trigeminal nerve.
Action: Depresses the mandible or elevates the hyoid bone.
Stylohyoid
Source: Thin, elongated muscle.
Insertion: Styloid process to the body of the hyoid bone.
Innervation: Facial nerve.
Action: Elevates the hyoid bone.
Mylohyoid
Source: Thin, flat, quadrilateral muscle forming the floor of the mouth.
Insertion: Mylohyoid line of the mandible to the hyoid bone and the median raphe.
Innervation: Mandibular branch of the trigeminal nerve.
Action: Elevates the hyoid bone and tongue.
Geniohyoid
Source: Cylindrical muscle located above the mylohyoid.
Insertion: Inferior mental spine of the mandible to the hyoid bone.
Innervation: Hypoglossal nerve.
Action: Depresses the mandible or elevates the hyoid bone.
Infrahyoid Muscles
Sternohyoid
Source: Ribbon-shaped muscle extending from the hyoid bone to the chest.
Insertion: Medial end of the clavicle and manubrium to the inferior border of the hyoid bone.
Innervation: Ansa cervicalis.
Action: Depresses the hyoid bone.
Omohyoid
Source: Digastric muscle extending from the hyoid bone to the scapula.
Insertion: Superior border of the scapula to the lateral aspect of the hyoid bone.
Innervation: Ansa cervicalis.
Action: Depresses and retracts the hyoid bone.
Sternothyroid
Source: Wide, strap-like muscle beneath the sternocleidomastoid.
Insertion: Posterior surface of the manubrium and first costal cartilage to the oblique line of the thyroid cartilage.
Innervation: Ansa cervicalis.
Action: Depresses the larynx and hyoid bone.
Thyrohyoid
Source: Short muscle below the sternohyoid.
Insertion: Oblique line of the thyroid cartilage to the inferior border of the hyoid bone.
Innervation: Ansa cervicalis.
Action: Depresses the hyoid bone or elevates the larynx.
Prevertebral Region
Longus Colli
Source: Long, thin muscle extending from the atlas to the third thoracic vertebra.
Insertion: Anterior tubercle of the atlas to the bodies of the second and third thoracic vertebrae and the anterior tubercles of the fourth and fifth cervical vertebrae.
Innervation: First four cervical nerves.
Action: Flexes the cervical spine.
Rectus Capitis Anterior
Source: Flattened, triangular muscle extending from the occipital bone to the cervical vertebrae.
Insertion: Inferior surface of the basilar part of the occipital bone to the anterior tubercles of the third to sixth cervical vertebrae.
Innervation: Deep cervical plexus.
Action: Flexes the head or rotates it to the same side.
Rectus Capitis Minor
Source: Quadrilateral muscle located behind the rectus capitis anterior.
Insertion: Basilar part of the occipital bone to the lateral mass of the atlas.
Innervation: Suboccipital nerve.
Action: Flexes the head.
Internal Organs of the Neck
- Spinal cord
- Cervical spine
Neck Regions
- Lateral: Platysma, sternocleidomastoid, scalenes, rectus capitis lateralis
- Suprahyoid: Digastric, stylohyoid, mylohyoid, geniohyoid
- Infrahyoid: Sternohyoid, omohyoid, sternothyroid, thyrohyoid
- Prevertebral: Longus colli, rectus capitis anterior, rectus capitis minor
Other Structures
- Arteries and veins
- Lymph nodes
- Pharynx
- Larynx
- Trachea
- Thyroid
Fasciae of the Neck
- Superficial cervical fascia: Surrounds the neck superficially, enclosing the sternocleidomastoid, trapezius, and superficial jugular vein.
- Middle cervical fascia: Surrounds the strap muscles, carotid sheath, and viscera (trachea, esophagus, thyroid).
- Deep cervical fascia: Surrounds the prevertebral and paravertebral muscles and scalene muscles.
The neck is located between the lower jaw and the clavicles.