 |
|
|
|
|
 |
|
| |
LACTOGENESIS LACTATION HUMAN MILK
Category: Child Health
Abstract : Lactogenesis is the process by which the mammary gland develops the capacity to
secrete milk. It includes all processes necessary to transform the mammary gland
from its undifferentiated state in early pregnancy to its fully differentiated
state sometime after pregnancy. It is this fully differentiated state that
allows full lactation. The 2 stages of lactogenesis are discussed
below. BR
Lactogenesis is the process by which the mammary gland develops the capacity to
secrete milk. It includes all processes necessary to transform the mammary gland
from its undifferentiated state in early pregnancy to its fully differentiated
state sometime after pregnancy. It is this fully differentiated state that
allows full lactation. The 2 stages of lactogenesis are discussed
below.
Lactogenesis has been divided into 2 stages.
Stage 1 occurs by mid
pregnancy. It is the process whereby the mammary gland becomes competent to
secrete milk. During stage 1, lactose, total protein, and immunoglobulin
concentrations increase within the secreted glandular fluid, sodium and chloride
concentrations decrease. The gland is now sufficiently differentiated to secrete
milk, as evidenced by the fact that women often describe drops of colostrum on
their nipples in the second or third trimester. The secretion of milk, however,
is held in check by high circulating levels of progesterone and
estrogen.
Stage 2 of lactogenesis occurs around the time of delivery. It
is defined as the onset of copious milk secretion. In stage 2, blood flow,
oxygen, and glucose uptake increase, and the citrate concentration increases
sharply. This increase of citrate is considered a reliable marker for
lactogenesis stage 2. Progesterone plays a key role in this stage. Removal of
the placenta (ie, the source of progesterone during pregnancy) is necessary for
the initiation of milk secretion; however, the placenta does not inhibit
established lactation. Work by Haslam and Shyamala reveals that this
noninhibition occurs because progesterone receptors are lost in lactating
mammary tissues. In addition, maternal secretion of insulin, growth hormone
(GH), cortisol, and parathyroid hormone (PTH) facilitates the mobilization of
nutrients and minerals that are required for lactation.
The stages of
lactation can be summarized as follows (adapted from Riordan and Auerbach,
1998):
• Mammogenesis: Mammary (breast) growth occurs. The size and weight of
the breast increase.
• Lactogenesis
o Stage 1 (late pregnancy):
Alveolar cells are differentiated from secretory cells.
o Stage 2 (day 2 or 3
to day 8 after birth): The tight junction in the alveolar cell closes. Copious
milk secretion begins. Breasts are full and warm. Endocrine control switches to
autocrine (supply-demand) control.
• Galactopoiesis (later than day 9
after birth to beginning of involution): Established secretion is maintained.
Autocrine system control continues.
• Involution (average 40 days after
last breastfeeding): Regular supplementation is added. Milk secretion decreases
from the buildup of inhibiting peptides.
Hit: 321 times
Related Articles in Child Health :
|
| |
|
|
|
|
|
Advertise with Health Information Encyclopedia