Infrahyoid Muscles Flashcards

Study the four infrahyoid muscles, including their attachments, anatomical layers, innervation, actions, and relationships to the larynx.

Card 1 of 28Question

What are the infrahyoid muscles?

Four paired muscles in the anterior neck that primarily depress or stabilize the hyoid bone and larynx.

In This Section

1. What are the infrahyoid muscles?

Four paired muscles in the anterior neck that primarily depress or stabilize the hyoid bone and larynx.

2. Which four muscles form the infrahyoid muscle group?

The sternohyoid, sternothyroid, omohyoid, and thyrohyoid muscles.

3. Why are the infrahyoid muscles commonly called strap muscles?

Their elongated, relatively flat shape resembles straps extending across the anterior neck.

4. Which infrahyoid muscles form the superficial muscular layer?

The sternohyoid and omohyoid muscles.

5. Which infrahyoid muscles form the deeper muscular layer?

The sternothyroid and thyrohyoid muscles.

6. Where does the sternohyoid muscle originate?

From the posterior surface of the manubrium, medial end of the clavicle, and adjacent sternoclavicular ligament.

7. Where does the sternohyoid muscle insert?

On the inferior border of the body of the hyoid bone.

8. What is the primary action of the sternohyoid muscle?

Depression of the hyoid bone after swallowing or elevation.

9. Where does the sternothyroid muscle originate?

From the posterior surface of the manubrium and adjacent first costal cartilage.

10. Where does the sternothyroid muscle insert?

On the oblique line of the thyroid cartilage.

11. What is the primary action of the sternothyroid muscle?

Depression of the thyroid cartilage and larynx.

12. How many bellies does the omohyoid muscle have?

Two, a superior belly and an inferior belly connected by an intermediate tendon.

13. Where does the inferior belly of the omohyoid originate?

From the superior border of the scapula near the suprascapular notch.

14. Where does the superior belly of the omohyoid insert?

On the inferior border of the body of the hyoid bone, lateral to the sternohyoid attachment.

15. What stabilizes the intermediate tendon of the omohyoid muscle?

A fascial sling attaching it to the clavicle and surrounding deep cervical fascia.

16. What is the main action of the omohyoid muscle?

Depression, retraction, and stabilization of the hyoid bone.

17. Which part of the omohyoid muscle divides the posterior cervical triangle?

The inferior belly, separating the occipital and omoclavicular triangles.

18. Where does the thyrohyoid muscle originate?

From the oblique line of the thyroid cartilage.

19. Where does the thyrohyoid muscle insert?

On the inferior border of the body and greater horn of the hyoid bone.

20. What are the actions of the thyrohyoid muscle?

Depression of the hyoid bone or elevation of the larynx when the hyoid is fixed.

21. Which nerve supplies most infrahyoid muscles?

The ansa cervicalis, a motor loop associated with the cervical plexus.

22. Which infrahyoid muscle is not supplied by the ansa cervicalis?

The thyrohyoid muscle.

23. What is the motor nerve supply of the thyrohyoid muscle?

C1 spinal nerve fibers traveling temporarily with the hypoglossal nerve, then branching as the nerve to thyrohyoid.

24. Which spinal nerve roots contribute to the ansa cervicalis?

C1 to C3, with C1 fibers forming the superior root and C2 to C3 fibers forming the inferior root.

25. Which fascial layer encloses the infrahyoid muscles?

The muscular portion of the pretracheal layer of deep cervical fascia.

26. How do the infrahyoid muscles contribute to swallowing?

They stabilize and reposition the hyoid bone and larynx during the coordinated swallowing sequence.

27. What is the relationship of the sternothyroid muscle to the thyroid gland?

It lies anterior to the thyroid gland and covers much of its anterolateral surface.

28. Why are the infrahyoid muscles important during thyroid surgery?

They overlie the thyroid gland and may require separation or retraction to expose the gland.