The armpit (or axilla) is the area on the human body directly under the area where the arm connects to the shoulder. Hair usually grows in the armpits of both males and females beginning in adolescence, though it is the norm in Western society for females to remove it. Also, armpits develop BO or body odor; for this, there is a wide variety of commercial deodorant and antiperspirant products.
Anatomically, the axilla is bounded anteriorly by the pectoralis major and minor muscles, posteriorly by subscapularis and the scapula, medially by the ribcage and by serratus anterior, and laterally by coracobrachialis and the short head of biceps brachii.
The axilla is a pyramidal space, situated between the upper lateral part of the chest and the medial side of the arm.
The axillary artery and vein, with the brachial plexus of nerves, extend obliquely along the lateral boundary of the axilla, from its apex to its base, and are placed much nearer to the anterior than to the posterior wall, the vein lying to the thoracic side of the artery and partially concealing it.
At the forepart of the axilla, in contact with the Pectorales, are the thoracic branches of the axillary artery, and along the lower margin of the Pectoralis minor the lateral thoracic artery extends to the side of the chest.
The apex of the axilla is the interval between the posterior border of the clavicle, the superior border of the scapula, and the external border of the first rib.
The axilla is bounded medially by the upper ribs and their intercostal muscles and by the serratus anterior; it is limited laterally by the intertubercular groove of the humerus.
The chief contents of the axilla are the axillary artery and vein, a part of the brachial plexus and its branches, and the axillary lymph nodes.