Structure/Morphology
The nipple is usually a cylindrical, highly pigmented tissue that projects anteriorly from the center of the breast. Although its shape and size greatly vary, it is usually 10–12 mm wide and 9–10 mm high (Zucca-Matthes, Urban and Vallejo, 2016).
The nipple is surrounded by the areola and both structures are referred to as the nipple-areolar complex (NAC). The skin covering the NAC is convoluted and shares similar structures, however, the nipple does not contain sebaceous glands. The nipple does, however, hold the openings for 15–20 lactiferous ducts are arranged cylindrically around the nipple.
The skin of the NAC has no subcutaneous fat. The skin of the nipple sits on areolar smooth muscle fibers that are arranged both radially (Meyerholz muscle) and circularly (Sappey muscle). This areolar muscle is continuous with the smooth muscle surrounding the lactiferous ducts in the nipple. Contraction of the muscle allows for secretion of the milk produced by the lactiferous glands (Zucca-Matthes, Urban and Vallejo, 2016).
Related parts of the anatomy
Key Features/Anatomical Relations
The nipple is located at the level of the fourth intercostal space at the mid-clavicular line. However, this varies greatly, depending on the sex and age of the individual.
Function
Milk produced by the lactiferous glands of the breast leaves through the nipple to deliver milk to an infant.
List of Clinical Correlates
- Polythelia (supernumerary nipple)
References
Zucca-Matthes, G., Urban, C. and Vallejo, A. (2016) 'Anatomy of the nipple and breast ducts', Gland Surgery, 5(1), pp. 32-36.
