1. Pectoral region
In the male, the contour of pectoral region is formed by the large pectoralis major muscle, while in females by the breast.
It is covered by superficial and deep fascia (pectoral fascia).
superficial fascia: of the pectoral region tends to be thickest in male in the region deep to the nipple and areola. In female it forms large masses between and around the breast glandular tissue of the breast. It contains the superficial vessels and nerves and continuous with the superficial fascia of lateral thoracic wall, the abdomen, the arm, and the neck.

2. Pectoral region
Pectoral fascia: The deep pectoral fascia is a thin lamina, covering the surface of the pectoralis major, and sending numerous prolongations between its fasciculi. It is attached to the front of the sternum, to the clavicle superiorly. Laterally and below it is continuous with the fascia of the shoulder, axilla, and thorax. Posteriorly, it is attached to the spinous processes of the thoracic vertebræ

3. Pectoral region
Muscle of the pectoral region
1. Pectoralis major muscle: it is enclosed by the pectoral fascia, it is large fan-shaped muscle arises from clavicle, sternum, and upper six costal cartilages. It is inserted into the lateral lip of bicipital groove of humerus. Nerve supply: Medial and lateral pectoral nerves from brachial plexus ( nerve roots:C5, 6, 7, 8; T1). Function: Adducts arm and rotates it medially; clavicular fibers also flex arm.

4. Pectoral region
1. Pectoralis major muscle

5. Pectoral region
Muscle of the pectoral region
2. Pectoralis Minor muscle: it is a thin triangular muscle that lies beneath the pectoralis major. It arises from the 3rd, 4th, and 5th ribs and runs upward and laterally to be inserted by its apex into the coracoid process of the scapula. Nerve supply: Medial pectoral nerve from brachial plexus (roots:C6, 7, 8).
Function: Depresses point of shoulder; if the scapula is fixed, it elevates the ribs of origin.

6. Pectoral region
Muscle of the pectoral region
3.Subclavius muscle: it is small rounded muscle, it arises from the 1st costal cartilage and it is inserted in the clavicle. Nerve supply: Nerve to subclavius from upper trunk of brachial plexus (roots:C5,6).
Function: Depresses the clavicle and steadies this bone during movements of the shoulder girdle.

7. Pectoral region
Nerves:
Are mainly the nerves to the pectoral muscles: the medial and lateral pectoral nerves (anterior thoracic nerves), they are arise from medial and lateral cords of the brachial plexus.

8. Pectoral region
Blood vessels:
The two chief arteries of the pectoral region are the thoracoacromial artery and lateral thoracic artery: branches of axillary artery. The thoracoacromial artery pierces the clavipectoral fascia and give rise to four branches: clavicular, pectoral, deltoid, and acromial.
The lateral thoracic artery runs downward along the anterolateral aspect of the chest wall.
The arteries are all accompanied by veins.

9. The Axilla

10. The Axilla
The axilla, or armpit, is a pyramid-shaped space between the upper part of the arm and the side of the chest.
It forms an important passage for nerves, blood, and lymph vessels as they travel from the root of the neck to the upper limb.

11. The Axilla
The upper end of the axilla, or apex, is directed into the root of the neck and is bounded in front by the clavicle, behind by the upper border of the scapula, and medially by the outer border of the first rib.

12. The Axilla
The lower end, or base, is bounded in front by the anterior axillary fold (formed by the lower border of the pectoralis major muscle), behind by the posterior axillary fold (formed by the tendon of latissimus dorsi and the teres major muscle), and medially by the chest wall.

13. The Axilla
Walls of the Axilla

14. ■ Anterior wall: By the pectoralis major, subclavius, and
The Axilla
Walls of the Axilla:
■ Anterior wall: By the pectoralis major, subclavius, and
pectoralis minor muscles.

15. The Axilla
Walls of the Axilla:
■ Posterior wall: By the subscapularis, latissimus dorsi, and teres major muscles from above down.

16. The Axilla
Walls of the Axilla:
■ Medial wall: By the upper four or five ribs and the intercostal spaces covered by the serratus anterior muscle.

17. The Axilla
Walls of the Axilla:
■ Lateral wall: By the coracobrachialis and biceps muscles in the bicipital groove of the humerus.

18. The Axilla
Walls of the Axilla:
The base is formed by the skin stretching between the anterior and posterior walls.

19. Key Muscle in the Axilla (Pectoralis Minor):
It crosses the axillary artery and the brachial plexus of nerves. It is used when describing the axillary artery to divide it into three parts.

20. The Axilla
Clavipectoral Fascia
It is a strong sheet of connective that is attached above to the clavicle. Below, it splits to enclose the pectoralis minor muscle and then continues downward as the suspensory ligament of the axilla and joins the fascial floor of the armpit.

21. The Axilla
Contents of the Axilla
The axilla contains the principal vessels and nerves to the upper limb and many lymph nodes. These structures are embedded in fat.

22. Contents of the Axilla:
The axillary artery and its branches, which supply blood to the upper limb.
The axillary vein and its tributaries, which drain blood from the upper limb.
The lymph vessels and lymph nodes, which drain lymph from the upper limb and the breast and from the skin of the trunk, down as far as the level of the umbilicus.
The brachial plexus, is an important nerve plexus, which innervates the upper limb.

23. Axillary Artery
It begins at the lateral border of the 1st rib as a continuation of the subclavian artery and ends at the lower border of the teres major muscle, where it continues as the brachial artery. The pectoralis minor muscle crosses in front of the axillary artery and divides it into three parts (first, second, and third part).

24. Axillary Artery
Throughout its course, it is closely related to the cords of the brachial plexus and their branches and is enclosed with them in a connective tissue sheath called the axillary sheath. If this sheath is traced upward into the root of the neck, it is seen to be continuous with the prevertebral fascia.

25. Second Part: it lies behind the pectoralis minor muscle.
Axillary Artery
First Part: it extends from the lateral border of the 1st rib to the upper border of the pectoralis minor.
Second Part: it lies behind the pectoralis minor muscle.
Third Part: This extends from the lower border of the pectoralis minor to the lower border of the teres major muscle.

26. Branches of the Axillary Artery:
From the first part:
The highest thoracic artery is small and runs along the upper border of the pectoralis minor.

27. Branches of the Axillary Artery:
From the second part:
The thoracoacromial artery immediately divides into terminal branches.
The lateral thoracic artery runs along the lower border of the pectoralis minor.

28. Branches of the Axillary Artery:
From the third part:
The subscapular artery runs along the lower border of the subscapularis muscle.
The anterior and posterior circumflex humeral arteries wind around the front and the back of the surgical neck of the humerus, respectively.

29. Axillary Vein
It is formed at the lower border of the teres major muscle by the union of the venae comitantes of the brachial artery and the basilic vein. It runs upward on the medial side of the axillary artery and ends at the lateral border of the 1st rib by becoming the subclavian vein. The vein receives tributaries, which correspond to the branches of the axillary artery, and the cephalic vein.

30. Axillary vessels