L5.5.2: Neck Muscles

• NECK MUSCLES

  • Platysma

  [a] Sternocleidomastoid

  [b] Splenius Capitis

  [c] Levator Scapula

  [d] Scalenus Medius

  [e] Scalenus Anterior

  [f] Trapezius

  [g] Inferior Hyoideus

  [h] Sternohyoideus

  
• Platysma (not seen on the image)

  ○ Structure: Single, sheetlike muscle that covers the anterolateral neck

  ○ Insertion: area around the mouth

  ○ Pull the corners of the mouth inferiorly to produce a downward sag of the mouth; Hence, producing the “sad clown face”

  ○ The “shaving muscle”

  ○ Movement: tenses skin of the neck during shaving
• Sternocleidomastoid

  ○ Structure: Two-headed muscles found on each side of the neck

  ○ One head arises from the sternum and the other from the clavicle

  ○ The “prayer muscle”

  ○ Movement: flexing the neck (bowing of the head)

  ○ If only one muscle contracts, the face is rotated toward the shoulder on the opposite side and tilts the head to its own side
• Splenius Capitis

  ○ Deep muscle of the neck

  ○ Origin: the lower half of the nuchal ligament and the spinous processes of the 7th cervical vertebra and the superior 3 thoracic vertebra

  ○ Insertion: the mastoid process of the temporal bone

  ○ Movement: laterally flex and rotate the neck
• Levator Scapula

  ○ Posterior axio-appendicular muscle

  ○ Connects the upper limb to the vertebral column and lies in the posterior triangle of the neck

  ○ Superior aspect is covered by sternocleidomastoid, and its inferior part by trapezius
• Scalenus Medius

  ○ Located between levator scapula

  ○ Largest and longest muscle in the scalene group of lateral neck muscles

  ○ Often penetrated by the dorsal scapular and long thoracic nerves

  ○ Deeply placed, lying behind sternocleidomastoid
• Scalenus Anterior

  ○ Anteriorly located, belongs to the scalene group

  ○ Deeply placed, lying behind the sternocleidomastoid

  ○ Located between the subclavian vein and the subclavian artery
• Trapezius

  ○ Pair of large triangular muscles extending over the back of the neck and shoulders

  ○ Stabilize and move the scapula

  ○ Movements:

  ■ Its upper fibers can elevate and upwardly rotate the scapula and extend the neck

  ■ Its middle fibers adduct / retract the scapula
• Inferior Hyoideus

  ○ Attached to the hyoid bone
• Sternohyoideus

  ○ Attached to the sternum and the hyoid bone
• TORTICOLLIS or WRYNECK - an injury where the neck remains rotated toward one side. It is caused by a difficult birth where one of the sternocleidomastoid muscles is injured and developed spasms.