Areolar glands or Glands of Montgomery are sebaceous glands in the areola surrounding the nipple. The glands make oily secretions (lipoid fluid) to keep the areola and the nipple lubricated and protected. Volatile compounds in these secretions may also serve as an olfactory stimulus for newborn appetite.
The portions of the gland on skin's surface are called "Montgomery tubercles". The round bumps are found in the areola, and on the nipple itself. They can become exposed and raised when the nipple is stimulated. The skin over the surface opening is lubricated and tends to be smoother than the rest of the areola. The tubercles become more pronounced during pregnancy.
The number of glands can vary greatly, usually averaging from 4 to 28 per nipple.