Scalene Muscles Flashcards

Study the scalene muscles, including their cervical attachments, rib insertions, innervation, actions, neurovascular relationships, and clinical anatomy.

Card 1 of 28Question

What are the three principal scalene muscles?

The anterior scalene, middle scalene, and posterior scalene muscles.

In This Section

1. What are the three principal scalene muscles?

The anterior scalene, middle scalene, and posterior scalene muscles.

2. Where are the scalene muscles located?

In the lateral neck, extending from the cervical vertebrae to the first and second ribs.

3. Where does the anterior scalene muscle originate?

From the anterior tubercles of the transverse processes of C3 to C6.

4. Where does the anterior scalene muscle insert?

On the scalene tubercle and adjacent superior surface of the first rib.

5. Where does the middle scalene muscle originate?

From the posterior tubercles of the transverse processes of C2 to C7.

6. Where does the middle scalene muscle insert?

On the superior surface of the first rib, posterior to the groove for the subclavian artery.

7. Where does the posterior scalene muscle originate?

From the posterior tubercles of the transverse processes of C4 to C6.

8. Where does the posterior scalene muscle insert?

On the external surface of the second rib.

9. What is the primary innervation of the anterior scalene muscle?

Muscular branches from the anterior rami of cervical spinal nerves C4 to C6.

10. Which spinal nerve roots commonly supply the middle scalene muscle?

Anterior rami of cervical spinal nerves C3 to C8.

11. Which spinal nerve roots commonly supply the posterior scalene muscle?

Anterior rami of cervical spinal nerves C6 to C8.

12. What is the main action of unilateral scalene contraction when the ribs are fixed?

Ipsilateral lateral flexion of the cervical spine.

13. How do the scalene muscles assist respiration?

They help elevate and stabilize the first and second ribs during inspiration.

14. Which scalene muscles primarily act on the first rib?

The anterior and middle scalene muscles.

15. Which scalene muscle primarily acts on the second rib?

The posterior scalene muscle.

16. What is the interscalene triangle?

An anatomical space bounded by the anterior scalene, middle scalene, and first rib.

17. Which major neurovascular structures pass through the interscalene triangle?

The roots and trunks of the brachial plexus and the subclavian artery.

18. What is the relationship of the subclavian vein to the anterior scalene muscle?

The subclavian vein passes anterior to the anterior scalene muscle.

19. What is the relationship of the subclavian artery to the anterior scalene muscle?

The subclavian artery passes posterior to the anterior scalene muscle, between the anterior and middle scalenes.

20. Which nerve descends along the anterior surface of the anterior scalene muscle?

The phrenic nerve.

21. Which cervical spinal nerve roots form the phrenic nerve?

C3, C4, and C5, with C4 usually providing the largest contribution.

22. What is the relationship of the brachial plexus to the middle scalene muscle?

The brachial plexus roots emerge between the anterior and middle scalenes, anterior to the middle scalene.

23. Which fascial layer covers the scalene muscles?

The prevertebral layer of deep cervical fascia.

24. What is the scalenus minimus muscle?

An accessory scalene muscle that may extend from the lower cervical region to the first rib or suprapleural membrane.

25. What is the anatomical basis of neurogenic thoracic outlet syndrome associated with the scalene muscles?

Compression or irritation of the brachial plexus within the interscalene region.

26. How can scalene muscle abnormalities contribute to arterial thoracic outlet compression?

Muscular hypertrophy, fibrous bands, or anatomical variations can narrow the passage containing the subclavian artery.

27. Why is the anterior scalene muscle an important landmark during an interscalene brachial plexus block?

The brachial plexus roots and trunks lie in the groove between the anterior and middle scalene muscles.

28. Which nerve may be affected by local anesthetic spread during an interscalene brachial plexus block?

The phrenic nerve, potentially causing temporary ipsilateral hemidiaphragmatic weakness.