Superficial and Lateral Cervical Muscles-pp3

Question 1

What is the origin, insertion, function, and innervation for the STERNOCLEIDOMASTOID muscle?

Answer 1

Ori:
-Sternal Head: Manubrium of the sternum
-Clavicular head: Clavicle
Ins:
-Sternal Head: Superior nuchal line
-Clavicular head: Mastoid process
Fun:
1. UNILATERAL contraction causes ipsilateral lateral flexion (ear to same shoulder) BUT contralateral rotation of head.
2. BILATERAL contraction of posterior fibers extends head backwards while contraction of anterior fibers flexes head and cervical spine forward.
3. If the cervical spine is FIXED SCM contraction raises the pectoral girdle and thorax (used in deep inspiration)
Inn: Spinal branch of Accessory nerve, CN XI, and some fibers from C2 ventral ramus.

Question 2

What is the origin, insertion, function, and innervation for the TRAPEZIUS muscle?

Answer 2

Ori: Spinous processes of T1-12, external occipital protuberance, and superior nuchal line.
Ins: Scapula AND Clavicle
Fun: Responsible for moving the pectoral girdle and, in turn, the upper extremities. Also, bends head and neck postero-laterally (back and to the side).
Inn: Spinal branch of accessory, CN XI and C3 & C4 ventral rami

Question 3

Specifically, how does each part of the trapezius, upper, middle and lower, play a role in scapular rotation?

Answer 3

Upper Trap: Elevates scapula
Middle Trap: Retracts scapula
Lower Trap: Depresses scapula