Sternocleidomastoid Muscle

Sternocleidomastoid Muscle

Sternocleidomastoid Muscle

The sternocleidomastoid muscle, AKA sternomastoid or SCM muscle take its  name from their connection to three bony structures.

  1. The sternum or breastbone
  2. The clavicle or collarbone
  3. Mastoid process of the occipital bone of the skull

Origin: The clavicular division originates at superior medial third of clavicle and the sternal division originates at superior manubrium of sternum. Insertion: Both divisions of sternocleidomastoid muscle insert into  mastoid process of the skull. Action:

  1. Rotate the head to the opposite side
  2. Oblique rotation and lifting the head
  3. Neck Flexion
  4. Assist scalene in inspiration
  5. Cervical plexus nerve of sternocleidomastoid provides proprioception, spacial body orientation in static posture and during movement. 1

Upper Trapezius

upper Trapezius

Upper Trapezius

Origin of upper trapezius: External occipital protuberance, medial third of the superior nuchal line,, ligamentum nuchae, spinous processes of 7th cervical vertebrae.

Insertion: lateral third of the clavicle, medial side of the acromion process.

Actions: Elevates the scapula,  rotates the scapula upward, retracts scapula when contracting with other sections of trapezius muscle.