Page 50 - 84 human physiolofy part-1

Chapter 3

Dissection of a lactating breast. 1 - Fat; 2 - Lactiferous duct/lobule; 3 - Lobule; 4 - Connective
tissue; 5 - Sinus of lactiferous duct; 6 - Lactiferous duct
Also, "click" this;"Breast tissue", to this a movie visiual of the breast.

Development and hormonal control

The development of mammary glands is controlled by hormones. The mammary glands exist in
both sexes, but they are rudimentary until puberty when in response to ovarian hormones, they begin to
develop in the female. Click this [1]to see what breast tissue does in a female during menustration.
Estrogen promotes formation, while testosterone inhibits it.

At the time of birth, the baby has lactiferous ducts but no alveoli. Little branching occurs before
puberty when ovarian estrogens stimulate branching differentiation of the ducts into spherical masses
of cells that will become alveoli. True secretory alveoli only develop in pregnancy, where rising levels
of estrogen and progesterone cause further branching and differentiation of the duct cells, together with
an increase in adipose tissue and a richer blood flow.

Colostrum is secreted in late pregnancy and for the first few days after giving birth. True milk
secretion (lactation) begins a few days later due to a reduction in circulating progesterone and the
presence of the hormone prolactin. The suckling of the baby causes the release of the hormone
oxytocin which stimulates contraction of the myoepithelial cells.

Breast cancer

As described above, the cells of mammary glands can easily be induced to grow and multiply by

50 | Human Physiology