AXILLARY REGION
- This region is suited btw. the thoracic cage, the shoulder girdle, & the free upper limb.
- Its inner space called called Axillary fossa has square pyramid shape with:
1. Apex :
- It is called the axillary inlet.
- Major vessels and nerves pass between the neck and axilla through this inlet (cervico-axillary canal).
- It is triangular in shape and bounded by (3 bones): clavicle anteriorly, upper border of scapula posteriorly, and outer border of 1ˢᵗ rib medially.
2. Base :
- It is formed of (3 layers): skin, superficial fascia, and deep (axillary) fascia stretching between the inferior margins of walls of the axilla.
- N.B: lower part of clavipectoral fascia fuses with the axillary fascia causing retraction of the skin of the base of the axilla inward when the arm is abducted.
3. Four Walls :
3.1 Anterior wall
- It is formed of (3 muscles): pectoralis major, pectoralis minor, and subclavius with clavipectoral fascia.
3.2 Medial Wall
- It is the upper part of the thoracic wall.
- It is formed of (3 structures): upper 4-5 ribs, upper 4-5 intercostal muscles, and upper part of serratus anterior muscle.
3.3 Lateral wall :
- It is the narrowest wall.
- It is formed of (3 structures): intertubercular groove of the humerus, coracobrachialis muscle, and short head of biceps brachii muscle.
3.4 Posterior wall
- It is formed of (3 muscles): subscapularis, teres major, and latissimus dorsi.
- The tendon of latissimus dorsi winds around the lower border of teres major and form together the posterior axillary fold (it can be grasped between the fingers).
→ There are 2 foramena in the post. wall :
- 1. Lateral Axillary foramen (Quadrangular space)
- 2.Medial n n (Triangular space)
Triangular space