Axilla

The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superiorly by the imaginary plane between the superior borders of the first rib, clavicle and scapula (above which are considered part of the neck), medially by the serratus anterior muscle and thoracolumbar fascia, anteriorly by the pectoral muscles and posteriorly by the subscapularis, teres major and latissimus dorsi muscle. The soft skin covering the lateral axilla contains many hair and sweat glands. In humans, the formation of body odor happens mostly in the axilla. These odorant substances have been suggested by some to serve as pheromones, which play a role related to mate selection, although this is a controversial topic within the scientific community. The underarms seem more important than the pubic area for emitting body odor, which may be related to human bipedalism. Anatomically, the boundaries of the axilla are: The lower posterior boundary is called the posterior axillary fold and this is a compound structure consisting of the latissimus dorsi and teres major muscles. It can descend after weight loss. The anterior boundary is called the anterior axillary fold and this is rounded in shape and formed by the lower border of the pectoralis major. Some sources also include the pectoralis minor. It can elongate after weight loss. The contents of the axilla include the axillary vein and artery, as well as the brachial plexus, lymph nodes and fat. The axilla is the space between the side of the thorax and the upper arm. Axillary artery and its branches Axillary vein and its tributaries Infraclavicular part of the brachial plexus Long thoracic and intercostobrachial nerves Five groups of axillary lymph nodes and the associated lymphatics Axillary fat and areolar tissue in which the other contents are embedded The term "underarm" typically refers to the outer surface of the axilla.