The axilla, commonly known as the armpit, is a pyramidal space situated between the upper arm and the side of the chest. It serves as a passageway for nerves, blood vessels, and lymphatics that supply the upper limb. Here's an overview of its anatomy, including the axillary artery, its branches, parts, and relation to the pectoralis minor muscle, as well as the anastomoses around the elbow joint:

### Axillary Artery

The axillary artery is a continuation of the subclavian artery and becomes the brachial artery as it passes beyond the inferior border of the teres major muscle. It can be divided into three parts based on its relationship to the pectoralis minor muscle:

1. **First Part**: Located proximal to the pectoralis minor muscle.

2. **Second Part**: Located posterior (behind) the pectoralis minor muscle.

3. **Third Part**: Located distal to the pectoralis minor muscle.

### Branches of the Axillary Artery

1. **First Part**:

   - **Superior Thoracic Artery**: Supplies the first and second intercostal spaces and the superior part of the serratus anterior muscle.

2. **Second Part**:

   - **Thoracoacromial Artery**: Divides into four branches: pectoral, deltoid, acromial, and clavicular.

   - **Lateral Thoracic Artery**: Supplies the serratus anterior muscle and mammary gland.

3. **Third Part**:

   - **Subscapular Artery**: Gives rise to the circumflex scapular artery and thoracodorsal artery.

   - **Anterior Circumflex Humeral Artery**: Supplies the head of the humerus and shoulder joint.

   - **Posterior Circumflex Humeral Artery**: Travels with the axillary nerve through the quadrangular space to supply the deltoid muscle and shoulder joint.

### Relation to Pectoralis Minor Muscle

The pectoralis minor muscle serves as an important anatomical landmark for the axillary artery. This muscle originates from the third to fifth ribs and inserts on the coracoid process of the scapula. The second part of the axillary artery lies directly posterior to the pectoralis minor, which helps in identifying and locating the branches of the artery during surgical procedures.

### Anastomoses Around the Elbow Joint

Anastomoses are connections between blood vessels that provide alternative pathways for blood flow. Around the elbow joint, there are several important anastomoses involving branches from the brachial, ulnar, and radial arteries:

- **Superior Ulnar Collateral Artery** (from the brachial artery) anastomoses with the **Posterior Ulnar Recurrent Artery** (from the ulnar artery).

- **Inferior Ulnar Collateral Artery** (from the brachial artery) anastomoses with the **Anterior Ulnar Recurrent Artery** (from the ulnar artery).

- **Radial Collateral Artery** (from the profunda brachii artery) anastomoses with the **Radial Recurrent Artery** (from the radial artery).

- **Middle Collateral Artery** (from the profunda brachii artery) anastomoses with the **Interosseous Recurrent Artery** (from the common interosseous artery).

These anastomoses ensure a continuous blood supply to the forearm and hand, even if one of the major arteries becomes obstructed.