Muscles - Infrahyoids

Question 1

Where are the infrahyoids located?

Answer 1

Inferior to the hyoid - they can be split into superficial plane and deep plane muscles.

Question 2

What is the arterial supply and venous drainage of these muscles?

Answer 2

Superior and inferior thyroid arteries, first branch of the external carotid artery.

Venous drainage via the corresponsing arteries.

Question 3

What are the muscles of the superficial plane?

Answer 3

1) Omohyoid
2) Sternohyoid

Question 4

Omohyoid

Answer 4

Comprised of two muscle bellies that are connected by a muscular tendon.

Origin (inferior belly) - arises from the scapula - runs supermedially underneath the sternocleidomastoid muscle.

Origin (superior belly) - inferior belly is attached to the superior belly by an intermediate tendon, which is anchored to the clavicle by the deep cervical fascia.

Insertion - hyoid bone

Action - depresses the hyoid bone

Innervation - anterior rami of C1-C3, carried by a branch of the ansa cervicalis.

Question 5

Sternohyoid

Answer 5

Origin - sternum and sternoclavicular joint

Insertion - hyoid bone

Action - depresses the hyoid bone

Innervation - anterior rami of C1-C3, carried by a branch of the ansa cervicalis

Question 6

What are muscles of the deep plane?

Answer 6

1) Sternothyroid
2) Thyrohyoid

Question 7

Sternothyroid

Answer 7

The sternothyroid is much wider and deeper than the sternohyoid muscle. It is located with the deep plane.

Origin - manubrium of the sternum

Insertion - thyroid cartilage

Actions - depresses the thyroid cartilage

Innervation - anterior rami of C1-C3, a branch of the ansa cervicalis

Question 8

Thryohyoid

Answer 8

Short band of muscle - a continuation of the sternothyroid.

Origin - arises from the thyroid cartilage of the larynx

Insertion - attaches to the hyoid bone

Action - depresses the hyoid. If the hyoid is fixed it can elevate the larynx.

Innervation - anterior ramus of C1 - carried with the hypoglossal nerve.