Armpit

Armpit, technically called the axilla, is the term applied to a space or hollow situated between the inner aspect of the arm and the upper part of the chest-wall. In shape it is pyramidal, the apex being directed upwards and inwards towards the root of the neck, while the base is directed downwards and outwards. The skin covering the base is characterised by its dark colour and the presence of hairs and sweat-glands of large size. The extent or depth of the space varies according to the position of the arm, being greatest when the arm hangs by the side, but gradually diminishes as the arm is elevated. In the latter position, the fore and hind boundaries become prominent borders, and are called the axillary folds. The large vessels and nerves for the supply of the upper limb pass through the space from apex to base, lying in close relation to the outer wall, and thus they are well protected from injury. Lodged in the space there are numerous lymphatic glands. These are apt to become inflamed, and lead to the formation of abscesses which, from the large size of the space and the resistant character of the tissues forming its base, may attain considerable proportions.