Lactation is the biological term used for the production of breast milk. When a baby suckles at the breast, nerve stimuli are sent from the special receptor cells located in the breast to the hypothalamus which is located in the brain. The hypothalamus is then stimulated to activate the pituitary gland ninto producing two different hormones.
These hormones are called oxytocin and prolactin. The hormone called oxytocin is stored in the pituitary gland and acts on muscle cells. These muscles surround the milk glands where milk is produced. Oxytocin causes the muscles cells to contract in turn squeezing milk out of the glands into the ducts.
Prolactin is the second hormone which is involved in the lactation process. Prolactin is also produced by the pituitary gland and is released into the blood stream each and every time the baby suckles at the breast. When prolactin is released into the blood stream, it travels to the milk glands in the breast and stimulates the glands to produce milk. The level of prolactin increases in the mother during pregnancy, but milk production is suppressed by another hormone, progesterone, until its level drops off after birth.
Oxytocin causes what is known and referred to as the "letting down" of milk from the glands. This causes different sensations in different mothers. Some will report shooting pains, others report a tingling feeling and sensation. Some report no sensation at all. All are normal. After this process, the milk is then transferred from the breast to the baby by a combination of two processes:
* Active milk expulsion by the mother due to the let down reflex
* Active removal by the baby who works on the breast tissue with tongue and jaw to receive milk.
The more a baby feeds at the breast the more milk will be produced. The mother needs to bring the baby to the breast often so that her milk supply can keep up with the demands of her growing baby.
Source: MNT Training OCN Maternity Practitioner Award Course Handbook.