Anatomy of the Neck

• Study notes on the neck and back muscles

Topography of the Neck

• The anterior cervical region contains the submandibular (digastric), submental, muscular, and carotid triangles.
• The anterior cervical region includes the lower pharynx, esophagus, larynx, trachea, and thyroid.
• The sternal and clavicular heads of the SCM muscle define the small lesser supraclavicular fossa.
• The SCM region contains parts of the major vascular structures of the neck.
• The lateral cervical region contains the omoclavicular and occipital triangles.
• In the lateral cervical region are scalene muscles, and both cervical and brachial plexuses.
• The posterior cervical region includes the trapezius and suboccipital muscles, plus the vertebral artery and posterior branches of the cervical plexus.

Deep Cervical Fascia

• The deep cervical fascia is divided into four layers that enclose the structures of the neck including:
• Investing (superficial) layer: this muscular layer envelops the entire neck and splits to enclose the sternocleidomastoid and trapezius muscles
• Pretracheal layer: a visceral layer, surrounds the thyroid gland, larynx, trachea, pharynx, and esophagus
• Prevertebral layer: a muscular layer that surrounds the cervical vertebral column and associated neck muscles
• Carotid sheath: this neurovascular layer encloses the common carotid artery, internal jugular vein, and vagus nerve

Superficial Muscles of the Neck

• These include the platysma and sternocleidomastoid muscles.

Platysma

• This is a broad, superficial muscle that runs subcutaneously from the upper chest area to the mandible.
• Its functions include reinforcing the skin of the neck, pulling the lips to the sides and down, and opening jaw.

Sternocleidomastoid Muscle (SCM)

• This is a prominent muscle on the sides of the neck
• The origin is the sternum and clavicle.
• The insertion is the mastoid process.
• Unilateral contraction of the SCM flexes the head laterally on the ipsilateral side and rotates the head to the contralateral side.
• Bilateral contraction of the SCM flexes the neck dorsally.
• The SCM is also an accessory respiratory muscle.
• Congenital torticollis (wryneck) is a condition in which one of the sternocleidomastoid muscles (SCM) is abnormally short
• The shortening is thought to be the result of trauma at birth (tears or stretching of the SCM) causing bleeding and swelling within the muscle and subsequent scar tissue

Suprahyoid Muscles

• These include the digastric, stylohyoid, mylohyoid, and geniohyoid muscles.
• The mylohyoid muscle creates the diaphragm of the mouth

Infrahyoid Muscles

• These include the sternohyoid, omohyoid, thyrohyoid, and sternothyroid muscles.
• Suprahyoid Muscles function to form the floor of the mouth, elevate the hyoid bone during swallowing and support the opening of the jaw
• Infrahyoid Muscles function to depress the larynx and hyoid bone after swallowing

Deep Muscles of the Neck

• These include the scalene muscles, and the longus colli and splenius cervicis muscles.

Scalene Muscles

• The three scalene muscles are the anterior, middle, and posterior scalene.
• The transverse processes of cervical vertebrae (C2-C7) serve as the origin for the scalene muscles.
• The insertion point for the scalene muscles: the first or second rib
• Accessory muscles of respiration.

Splenius Cervicis Muscle

• This muscle originates from the spinous processes T3-T6
• It inserts on the posterior tubercles C1-C3.
• Unilateral contraction results in ipsilateral flexion and rotation of the head and cervical spine
• Bilateral contraction causes dorsal extension of the head and cervical spine.

Longus Colli Muscle

• This muscle originates from the transverse processes of C5-T3
• It inserts on the atlas anterior arch.
• Unilateral contraction results in ipsilateral flexion of the head
• Bilateral contraction stabilizes and rotates of the head

Superficial Muscles of the Back

• These include the trapezius, latissimus dorsi, major and minor rhomboid, serratus posterior (superior and inferior), and levator scapulae muscles.

Trapezius Muscle

• Consists of descending, transverse, and ascending parts.
• The descending part originates from the occipital bone and spinous process of C1-C7, inserting on the lateral one third of the clavicle;
• Its function is to draw the scapula obliquely upward, rotate the glenoid cavity superiorly, and tilt the head to the same side while rotating it to the opposite side.
• The transverse portion originates from the aponeurosis at T1-T4 spinous processes, inserting on the acromion, used to draw scapula medially;
• The ascending part originates from the spinous process of T5-T12, inserting on the scapular spine, used to draw the scapula medially downward and to steady the scapula on the thorax.

Musculus Latissimus Dorsi

• Parts include the vertebral, scapular, costal, and iliac parts.
• The vertebral part originates from the spinous process of T7-T12 vertebrae and thoracolumbar fascia.
• The scapular part originates from the scapula (inferior angle). -The costal component originates from the 9th to 12th ribs.
• The iliac part originates from the iliac crest (posterior one third).
• All parts insert on the crest of lesser tubercle of the humerus (anterior angle).
• Its function is internal rotation, adduction, extension, and respiration ("cough muscle").

Rhomboid Major

• This originates from the spinous processes of T2-T5 and inserts on the inferior part of the medial border of the scapula;
• Used for scapula elevation and retraction.

Rhomboid Minor

• This originates from the spinous processes of C7-T1, and inserts on the superior part of the medial border of the scapula
• It's used for scapula elevation and retraction.

Serratus Posterior Superior Muscle

• Originates from spinous processes C7-T3 and inserts on ribs 2-5
• It functions for unilateral lateral flexion and the bilateral actions of dorsal extension and inspiration

Serratus Posterior Inferior Muscle

• Originates from spinous processes T11-L2 and inserts on ribs 9-12.
• It functions to provide unilateral for lateral flexion and bilaterally for inspiration and forced expiration

Levator Scapulae Muscle

• Originates from the transverse processes of C1-4, and inserts on the superior medial angle of the scapula;
• Functions to provide scapula elevation (shrugging), and returns the elevated arm to its neutral position

Deep Muscles of the Back

• These include the erector spinae and transversospinalis muscles.
• The erector spinae muscle is made up of iliocostalis, longissimus and spinalis mm.
• The transversospinalis group includes semispinalis, multifidus
• Musculi intertransversarii et interspinalii

Explore anatomical structures within the anterior and lateral cervical regions and landmarks. Learn about the impact of injuries, like whiplash, on neck muscles and nerve function, particularly concerning the spinal accessory nerve.