Shoulder and Brachial Plexus - LO 2

2. Describe the blood supply to the shoulder region, and give an example of collateral blood supply.

The blood supply to the shoulder is comprised of several anastomosing arteries. High mobility joints typically have an extensive collateral supply. The arteries that supply the shoulder come from the subclavian a. and its continuation, the axillary a.

The axillary a. begins as a continuation of the subclavian a. at the distal end of the first rib. The axillary a. consists of three parts, defined by their relationship to the pectoralis minor m. The 1st part is medial to pectoralis minor, the 2nd part is posterior (deep) to pectoralis minor, and the 3rd part is lateral to pectoralis minor.

The axillary a., its parts, and their branches are as follows:

- Axillary a.
  - 1st part
    - Superior thoracic a.
  - 2nd part
    - Thoraco-acromial a. (supplies pectoralis major & minor mm., deltoid m., shoulder joint)
    - Lateral thoracic a. (supplies serratus anterior m.)
  - 3rd part
    - Subscapular a. (supplies infraspinatus m., teres minor & major mm., subscapularis m.)
      - Thoracodorsal a. (supplies latissimus dorsi m.)
      - Circumflex scapular a. (supplies infraspinatus m., teres minor & major mm.)
    - Anterior circumflex humeral a. (supplies deltoid m. & proximal portions of arm mm.)
      - Near surgical neck of humerus
    - Posterior circumflex humeral a. (supplies deltoid m. & proximal portions of arm mm.)
      - Near surgical neck of humerus

There are several arterial anastomoses in the shoulder region, two that are of particular importance at the shoulder:

- Anastomosis between the dorsal scapular a., the suprascapular a., and the circumflex scapular a. on the posterior scapula.
- Anastomosis between the anterior & posterior circumflex humeral aa. and often acromial branches from the thoracoacromial a.

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