OINAs

Question 1

Name the origin, insertion, innervation, and action of the sternocleidomastoid (SCM) muscle.

Answer 1

Origins:

• -Sternal head: Manubrium of the sternum
• -Clavicular head: Medial 1/3 of the clavicle

Insertion: Lateral surface of the mastoid process, and lateral 1/2 of the superior nuchal line of the occipital bone

Innervations:

• -Spinal accessory nerve (CN XI)
• -Anterior primary rami of the C1 and C2 spinal nerve roots

Actions:

• -Unilaterally: Cervical rotation to the opposite side, and lateral cervical flexion to same side
• -Bilaterally: Flexion of the lower cervical spine (C3 - C7) with anterior translation of the cervical vertebrae and no sagittal rotation; extension of the upper cervical spine (occiput, atlas, axis) (i.e., capital extension, or head-on-neck extension)

References:

• -Anatomy OINA Packet
• -C. Anatomy app

Question 2

Name the origin, insertion, innervation, and action of the flexor carpi radialis muscle.

Answer 2

Origins:

• -Deep antebrachial fascia
• -Medial epicondyle of the humerus via the common flexor tendon. (Note: The common flexor tendon is the combined tendon for the five superficial muscles in the anterior compartment of the forearm, which include the pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis.)

Insertions:
–Palmar aspects of the bases of the second and the third metacarpal bones. (Note: The long tendon of the flexor carpi radialis muscle attaches primarily to the base of the second metacarpal bone with a slip or short offshoot of the tendon inserting into the base of the third metacarpal bone.)

Innervation:
–Median nerve communicating primarily from the C6, C7, and C8 spinal nerve roots

Actions:

• -Radial deviation of the wrist
• -Flexion of the wrist

References:

• -Anatomy OINA Packet
• -C. Anatomy app