Figure 2235

Photomicrographs and diagram of a lactating mammary gland.

a. Low-magnification micrograph of a fast green-osmium-stained section of a lactating mammary gland. Portions of several large lobules and an excretory duct are seen. Many of the alveoli exhibit a prominent lumen, even at this magnification. x60. b. A higher magnification of an area in a shows lipid droplets (black circular profiles) within the secretory cells of the alveoli as well as in the alveolar lumina. The arrows indicate plasma cells within the interstitial spaces. X480. c. Diagram of a lactating mammary gland epithelial cell. (Redrawn after Bloom W, Fawcett DW. A Textbook of Histology. 10th ed. Philadelphia: WB Saunders, 1975.)

sequent to this initial development, slight changes in the morphology of the glandular tissue occur during each ovarian cycle. During pregnancy, the corpus luteum and placenta continuously produce estrogens and progesterone. Estrogen present in the circulation stimulates proliferation of the lactiferous duct components, and progesterone stimulates growth of alveoli. It is now believed that the growth of the mammary glands also depends on the presence of prolactin, produced by the adenohypoph-ysis; hCS, produced by the placenta; and adrenal glucocorticoids.

Lactation is under the neurohormonal control of the adenohypophysis and hypothalamus

Although estrogen and progesterone are essential for the physical development of the breast during pregnancy, both of these hormones also suppress the effects of prolactin and hCS, the levels of which increase as pregnancy pro gresses. Immediately after birth, however, the sudden loss of estrogen and progesterone secretion from the placenta and corpus luteum allows the prolactin to assume its lactogenic role. Production of milk also requires adequate secretion of growth hormone, adrenal glucocorticoids, and parathyroid hormones.

The act of suckling during breast-feeding initiates sensory impulses from receptors in the nipple to the hypothalamus. The impulses inhibit the release of prolactin-inhibiting factor, and prolactin is then released from the adenohypophysis. The sensory impulses also cause the release of oxytocin in the neurohypophysis. Oxytocin stimulates the myoepithelial cells that surround the base of the alveolar secretory cells and the base of the cells in the larger ducts, causing them to contract and eject the milk from the alveoli and the ducts. In the absence of suckling, secretion of milk ceases, and the mammary glands begin to regress. The glandular tissue then returns to an inactive condition.

Golgi apparatus granular endoplasmic reticulum protein process of myoepithelial cell

Golgi apparatus granular endoplasmic reticulum protein process of myoepithelial cell

New Mothers Guide to Breast Feeding

New Mothers Guide to Breast Feeding

For many years, scientists have been playing out the ingredients that make breast milk the perfect food for babies. They've discovered to day over 200 close compounds to fight infection, help the immune system mature, aid in digestion, and support brain growth - nature made properties that science simply cannot copy. The important long term benefits of breast feeding include reduced risk of asthma, allergies, obesity, and some forms of childhood cancer. The more that scientists continue to learn, the better breast milk looks.

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