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Breasts are bilateral glandular structures
Extends from 2nd to 6th rib in the mid-clavicular line.
It lies in the subcutaneous tissue over the fascia
covering the pectoralis major or even beyond that to
lie over the serratus anterior and external oblique.
Structures (non lactating breast):
The areola is placed about the center of the breast and
is pigmented. It is about 2.5 cm in diameter.
There are numerous sebaceous glands over it.
It contains few involuntary muscles.
The nipple is a muscular projection covered by
pigmented skin. It is vascular and surrounded by
unstriped muscles which make it erectile.
It accommodates about 15-20 lactiferous ducts and
Each breast is divided into 15-20 lobes by fibrous septa
which radiate from the center.
Each lobe consists mainly of fibro fatty tissue. The
glandular tissue consists mainly of duct system in non
One lactiferous duct drains a lobe.
The lobes are divided into lobules, each lobule
containing a certain number of alveoli and ducts (10-
The alveoli contain acini cells (columnar epithelium),
which produce milk and are surrounded by
These ducts connect, with larger ones called
There is a dense network of capillaries surrounding the
Contraction of myoepithelial cells squeezes the alveoli
and ejects the milk into the larger duct.
One large duct leaves each lobe and widens to form a
lactiferous sinus or ampulla.
A lactiferous tubule from each sinus opens on the
surface of the nipple.
Increase in breast size in early weeks of gestation. This
is due to hypertrophy and proliferation of ducts and
alveoli which are shown in the peripheral lobules
(effects of oestrogen and progesterone).
Vascularity is increased which results in appearance of
bluish veins running under the skin.
The axillary tail is enlarged and painful.
Presence of striae from stretching.
Nipples and areola: The nipples become larger, erectile
and deeply pigmented.
Secretion: Secretion can be squeezed from out of the
breast (sticky) at about 12th week.
By 16th week, it becomes thick and yellowish. The
demonstration of secretion from a breast of the
women who has never lactated is an important sign of
pregnancy. In latter months, colostrum may be
expressed from the nipples.
The physiological basis of lactation is divided into four
1. Preparation of breasts (mammogenesis).
2. Synthesis and secretion from the breast alveoli
3. Ejection of milk (galactokinesis).
4. Maintenance of lactation (galactopoiesis).
Pregnancy is associated with a remarkable growth of
both the ductal and lobuloalveolar systems.
Milk secretion actually starts on 3rd or 4th postpartum
Around this time, the breasts become engorged, tense,
tender and feel warmth.
When the progesterone and estrogen are withdrawn
following delivery, prolactin begins its milk secretory
The secretory activity is enhanced directly or indirectly
by growth hormone, thyroxine, glucocorticoids and
Prolactin stimulates mammary glandular ductal
growth and epithelial cell proliferation and induces
milk protein synthesis.
Occurs by mid pregnancy.
Mammary gland becomes competent to secrete milk.
Lactose, total protein, and immunoglobulin
concentrations increase within the secreted glandular
fluid, whereas sodium and chloride concentrations
High circulating levels of progesterone and estrogen
hold the secretion of milk in check.
Stage 2 (day 2 or 3 to day 8 after birth):
Occurs around the time of delivery.
Onset of copious milk secretion.
Blood flow, oxygen, and glucose uptake increase, and
citrate concentration increases sharply.
Progesterone plays a key role.
Removal of the placenta is necessary for the initiation
of milk secretion; however, the placenta does not
inhibit established lactation control.
Discharge of milk from the mammary glands depends
not only on the suction exerted by the baby during
suckling but also on the contractile mechanism which
expresses the milk from the alveoli into the ducts.
Presence of the infant or the infant's cry can induce
letdown without suckling.
A sensation of rise of pressure in the breasts by milk
experienced by the mother at the beginning of the
sucking is called "draught".
The milk ejection reflex is inhibited by factors such as
pain, breast engorgement or adverse psychic
Prolactin appears to be the single most important
Continuous suckling is essential for removal of milk
from glands, also release prolactin.
Secretion is the continuous process unless suppressed
by congestion or emotional disturbances.
A healthy mother will produce about 500-800 ml of
milk/day with about 500 Kcal /day.
This requires 600 Kcal/day for the mother which must
be made up from the mother's diet or from her body
Inadequate milk production/ lactation failure may be
due to infrequent suckling or due to endogenous
suppression of prolactin (pyridoxin, diuretics or
retained placental bits).
Fraser DM, Cooper MA.Myles textbook for
midwives.15th edition. Philadelphia:churchill
Dutta DC.Textbook of obstetrics. 6th
edition.Calcutta:New central book agency;2004
Human milk and lactation. [Updated on
December 14, 2010, Cited on 5th June 2012].
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