Page 49 - 84 human physiolofy part-1

The Integumentary System

Mammary Glands

Mammary glands are the organs that, in the female
mammal, produce milk for the sustenance of the young.
These exocrine glands are enlarged and modified sweat
glands and are the characteristic of mammals which gave
the class its name.

Structure

The basic components of the mammary gland are the
alveoli (hollow cavities, a few millimetres large) lined with
milk-secreting epithelial cells and surrounded by
myoepithelial cells. These alveoli join up to form groups
known as lobules, and each lobule has a lactiferous duct
that drains into openings in the nipple. The myoepithelial
cells can contract, similar to muscle cells, and thereby push
the milk from the alveoli through the lactiferous ducts
towards the nipple, where it collects in widenings (sinuses)
of the ducts. A suckling baby essentially squeezes the milk Cross section of the breast of a human female.
out of these sinuses.

One distinguishes between a simple mammary gland, which consists of all the milk-secreting
tissue leading to a single lactiferous duct, and a complex mammary gland, which consists of all the
simple mammary glands serving one nipple.

Humans normally have two complex mammary glands, one in each breast, and each complex
mammary gland consists of 10-20 simple glands. (The presence of more than two nipples is known as
polythelia and the presence of more than two complex mammary glands as polymastia.)

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