What is lactation? Lactation results when the mammary glands in the breasts of a mother provide milk for her infant.
The first stage of lactation is called Mammogenesis, which occurs when the breasts are formed, right from birth, through to puberty and, then, the process is completed during pregnancy.
This stage of lactation begins in a woman when she is still in her own mother’s womb, as a tiny embryo. At 12 weeks gestation, the breasts have grown nipples, areolae, alveoli (milk-producing cells), and mammary buds. Sex hormones will then further develop the breasts until she is born.
During puberty, Estrogen and pituitary growth factors will prompt the breasts to grow. More and more breast tissue is stored with every monthly ovulation cycle, up until the age of 35.
A woman’s breasts are only prepared to produce milk once she has become pregnant; this is when the final changes in the breasts transpire to enable her to provide milk. The hormones accountable for these changes during pregnancy include Prolactin, Placental lactogen, Estrogen, Progesterone, and the Adrenocorticotropic hormone.
So What Changes Occur During Pregnancy?
A network of milk ducts spread and multiply within the breast. The areolae and Montgomery's tubercles become larger. The nipples become more extended.
Stage 2 and 3 Lactogenesis
Each breast contains about 20 lobes of glandular tissue (they look like miniature trees) The “leaves" of these trees are made up of alveoli, which are the milk-producing cells. The milk moves from the alveoli to the ductules and then into the ducts, and then eventually out the nipple through duct openings.
The breast also carries many blood and nerve vessels as well as lymph vessels.
The second stage of lactation is called Lactogenesis: (making of milk) (stages 1 and 2) This is when a mother starts to adequately produce milk. Stage 1 is between mid-pregnancy and two days postpartum (after the birth). Stage 2 is between day 3 and day 8 postpartum.
Lactogenesis stages 1 and 2 are controlled by hormones.
In stage 1, the mother's breasts may feel enlarged; this is because of the alveoli that have begun to create colostrum.
In stage 2 the alveoli cells become restricted and tightly spaced. This improves the production of lactose, glucose, and milk lipids and lessens the production of protein, sodium, chloride, nitrogen, and magnesium.
During this stage, the breasts may feel warm and become engorged if they are not emptied frequently enough. If the mother does not breastfeed, her breasts will stop producing mature milk and start providing colostrum once again. Eventually, they will stop producing milk altogether. The breasts will begin to produce colostrum after three days of no milk extraction from them.
Lactogenesis stage 3: Also called galactopoiesis. This is the creation and sustaining stage of mature milk from day 9 postpartum until the mother and/or baby decides to wean.
Lactogenesis stage 3 is controlled by the autocrine system, but hormones do still play a part.
The more milk that is expelled from the breasts, the more milk will be produced. Milk production relies on the supply and demand system. Also, each breast works alone; if the mother breastfeeds more from one breast, that breast will produce more milk than the other, which is why a mom can breastfeed from just one breast.
Why Does The Breast Produce Less When It Is Full?
Prolactin cannot bind to the receptors that trigger the release of more prolactin. A whey protein in the milk called (FIL) feedback inhibitor of lactation hinders the production of milk when the alveoli are full. Once the alveoli are empty, there will be less FIL, and therefore, more milk can be created.
Involution: This is when the breasts cease to produce milk after weaning.