Arteries of the Shoulder Girdle

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What is Collateral Circulation?

The clinical importance of collateral circulation in the arm is only apparent when the main arterial pathway to the arm is interrupted. For example, if the axillary artery is obstructed between the thyrocervical trunk and subscapular artery, the direction of blood flow in the subscapular artery is reversed, enabling blood to reach the distal part of the axillary artery. Slow occlusion of an artery will often allow sufficient collateral circulation to develop. Sudden occlusion of an artery does not permit this development of the collateral circulation to prevent ischemia.

Suprascapular Artery:

Comes off the thyrocervical trunk (first branch of subclavian artery). May also originate at the 3rd part of the subclavian instead. Travels anteriorly to the scalenus anterior muscle and the root of the brachial plexus then above to the transverse ligament to enter and supply the infraspinatus and supraspinatus fossa containing muscles.

Transcervical Artery:

Comes off the thyrocervical trunk (first branch of the subclavian artery). Follows the posterior belly of omohyoid muscle and supplies the trapezius and levator scapulae muscles. Eventually becomes the dorsal scapular artery.

Dorsal Scapular Artery:

70% off 2nd or 3rd part of subclavian artery and 30% off transverse cervical. Descends deep to the rhomboid muscle. Supplies the rhomboid, levator scapulae and serratus anterior muscle. The dorsal scapular artery is a continuation of the transverse cervical artery distal to the levator scapulae.

Subscapular Artery:

Comes off the 3rd part of the axillary artery to the subscapularis muscle.

Circumflex Scapular Artery:

Comes off the subscapular artery. Feeds the lateral border of the scapula.

Intercostal Arteries:

Form anastomoses with the dorsal scapular artery.

Anastomoses around Scapula:

The anastomoses around the scapula play a major surgical role during ligation of an injured axillary or subclavian artery (the axillary artery is a continuation of the subclavian artery into the upper limb). So the axillary artery can be ligated between the thyrocervical and the subscapular artery which result in directing blood flow from the anastomoses sites to the axillary artery distal to the ligation (i.e. the subscapular artery will receive blood via the suprascapular, transverse cervical, dorsal scapular and intercostal arteries), but unfortunately, axillary artery ligation distal to the subscapular artery will result in severe reduction in blood flow to the arm.

Subclavian Steal Syndrome:

This is a rare condition caused by a narrowing of the left subclavian artery near its origin. In order to compensate for the reduction in blood flow to the arm, blood will flow from the right vertebral artery into the left vertebral artery and then into the left subclavian artery. This results in reduction of blood flow to the brain, causing giddiness, fainting attacks and problems with ischemia of the left arm.

Chapters on Shoulder Anatomy:

1. Arteries of the Axilla
2. Arteries of the Shoulder Girdle
3. Axillary Artery Aneurysm
4. Axillary Fat and Fascia
5. Axillary Nerve Block
6. Bones and Fractures of the Upper Limb
7. Boundaries of the Axilla
8. Breast Cancer and Axillary Lymph Nodes
9. Erb-Duchenne Palsy
10. Joints of the Shoulder Girdle
11. Klumpke's Paralysis
12. Lymph Nodes of the Axilla
13. Muscles of the Axilla
14. Muscles of the Shoulder Girdle
15. Notes on Shoulder Bursae
16. Roots and Trunks of the Brachial Plexus
17. Winged Scapula in Computer Programmer
18. Transient Axillary Paralysis
19. Variation of Brachial Plexus Structure
20. Veins of the Axilla

Additional Reading:

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4. Lymphoid Tissue
5. Integument
6. Respiratory System
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8. Renal/Urinary System
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10. Female Reproductive System

Gross Anatomy

1. Back and Nervous System
2. Thorax
3. Abdomen, Pelvis, and Perineum
4. Upper Limb
5. Lower Limb
6. Head and Neck
7. Chest Wall
8. Shoulder

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