LIFESCI 4X03 Lecture Notes - Lecture 2: Bulb Of Vestibule, Labia Minora, Granulosa Cell
9 Nov 2016
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The breasts (or mammary glands) are considered secondary sexual characteristics, meaning that they are not components of the genitals, but do differ between the sexes. The breast tissue lies between the skin and the muscles of the chest wall; some breast tissue extends up into the armpits. Each breast consists of about 15 to 20 lobes that are separated from one another by fibrous and fatty tissue. The lobes are further subdivided into lobules and (in women who are producing milk) each lobule comprises numerous small cavities called alveoli. Each alveolus is lined by glandular cells that secrete milk into its central cavity. A layer of muscle cells surrounds each alveolus: when these muscles contract, milk is squeezed out of the alveolus into a system of ducts that connect all the alveoli to the nipple - a process called milk letdown. The milk then collects in a bundle of lactiferous sinuses near and within the nipple.
