In anatomy, an areola, plural areolae is any circular area such as the colored skin surrounding the nipple. Careful inspection of a mature human female nipple will reveal several small openings arranged radially around the tip of the nipple lactiferous ducts from which milk is released during lactation.
Other small openings in the areola are sebaceous glands, known as Montgomery’s glands or glands of Montgomery, which provide lubrication to protect the area around the nipple and assist with suckling and pumping of the lactation. These can be quite obvious and raised above the surface of the areola, giving the appearance of goose-flesh. This tissue, in addition to supporting the flow of milk, also bears the brunt of physical stress that the suckling involves.
Another reason for its color comes from an abundance of two polymers: eumelanin the brown pigment and pheomelanin the red pigment. The genetically-directed amount of these pigments determines the color of the areola.
They can range from pale yellow to nearly black, but generally tend to be paler among people with lighter skin tones and darker among people with darker skin tones. Additionally, it has been claimed that a reason for the differing color is to make the nipple area more visible to the infant. An individual’s areolae may also change color over time in response to hormonal changes caused by menstruation, certain medications, and aging.
Most notably, the areolae may darken substantially during pregnancy—some regression to the original color may occur after the baby is born, but again, this varies from individual to individual. Human areolae are mostly circular in shape but many women and some men have areolae that are noticeably elliptical. The average diameter of male areolae is around 25 mm 1 in. Sexually mature women have an average of 30 mm 1.2 in, but sizes range up to 100 mm 4 in or greater. Lactating women, or women with particularly large breasts, may have even larger areolae.