Muscles of the Neck

Question 1

Sternocleidomastoid

Answer 1

• Origin: Anterior surface of manubrium (sternal head); Superior surface of medial 1/3 of clavicle (Cleido/Clavicular head)
• Insertion: Mastoid process and lateral 1/3 of superior nuchal line
• Action: Laterally flex neck and rotate face superiorly in opposite direction (unilateral); Extend neck at atlanto-occipital joint, flex head, extend superior and flex inferior cervical vertebra so chin thrust forward while head still level (bilateral); Elevate manubrium and clavicle in deep respiration (pump handle movement)

Question 2

Omohyoid (and middle tendon)

Answer 2

• Origin: Superior border of scapula (inferior belly); Middle tendon (superior belly)
• Insertion: Middle/intermediate tendon (inferior belly); Body of hyoid (superior belly)
• Middle tendon attaches to 1st costal cartilage and clavicle
• Action: Depress larynx, hyoid, and floor of mouth and resist elevation of these structures

Question 3

Sternohyoid

Answer 3

• Origin: Posterior surface of manubrium
• Insertion: Body of hyoid
• Action: Depress larynx, hyoid, and floor of mouth and resist elevation of these structures

Question 4

Infrahyoid Muscles (Superficial and Deep)

Answer 4

Superficial (side by side)
1. Omohyoid
2. Sternohyoid
Deep (superior/inferior)
1. Sternothyroid
2. Thyrohyoid

Question 5

Sternothyroid

Answer 5

• Origin: Posterior surface of manubrium
• Insertion: Lamina of thyroid cartilage
• Action: Depress larynx, hyoid, and floor of mouth and resist elevation of these structures

Question 6

Thyrohyoid

Answer 6

• Origin: Lamina of thyroid cartilage
• Insertion: greater horn/cornu of hyoid
• Action: Depress Larynx, hyoid, and floor of mouth and resist elevation of these structures

Question 7

Innervation of all Infrahyoid Muscles

Answer 7

All from branches of the Cervical Plexus (Ansa Cervicalis)