The document discusses the physiology of lactation, including: 1. The anatomy of the breast and changes during pregnancy like increased size and vascularity. 2. The components of colostrum, which is higher in protein and vitamins than milk. 3. The four phases of lactation - preparation of breasts during pregnancy, milk synthesis after delivery stimulated by hormones like prolactin, ejection of milk, and maintenance of lactation.

1. PHYSIOLOGY OF LACTATION
Presentation by:
Prativa Dhakal
M.Sc. Nursing
Batch 2011

2. Objectives
 Explain the anatomy of breast.
 State the physiological changes of breast during
pregnancy.
 List the components of colostrum
 Explain the stages of physiology of lactation.
 References
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3. Anatomy of breast
 Breasts are bilateral glandular structures
 In female constitute accessory reproductive
organs.
 The shape of breast varies among the women and
also in different periods of life. But the size of
base of the breast is fairly constant.
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4. Anatomy of breast contd…
 Development: The parenchyma of the breasts
is developed from the ectoderm. The
connective tissue stroma is from the
mesoderm
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5. Anatomy of breast contd…
 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.
 An axillary prolongation (axillary tail), if present, lies in the
axillary fossa, sometimes deep to the deep fascia.
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7. Anatomy of Breast
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11. Anatomy of breast contd…
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.
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12. Anatomy of breast contd…
 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 their openings.
 The whole breast is embedded in subcutaneous fat
(absent beneath the nipple and areola).
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13. Anatomy of breast contd…
 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 lactating breast.
 One lactiferous duct drains a lobe.
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14. Anatomy of breast contd…
 The lining epithelium of the duct is cubical, become
stratified squamous near the openings.
 The lobes are divided into lobules, each lobule
containing a certain number of alveoli and ducts (10-
100).
 The alveoli contain acini cells (columnar epithelium),
which produce milk and are surrounded by
myoepithelial cells.
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15. Anatomy of breast contd…
 These ducts connect, with larger ones called
lactiferous ducts.
 There is a dense network of capillaries surrounding
the alveoli.
 These are situated between the basement membrane
and epithelial lining.
 Contraction of myoepithelial cells squeezes the alveoli
and ejects the milk into the larger duct.
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16. Anatomy of breast contd…
 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.
 At places, the fibrofatty connective tissue extends from
the skin down to the deep fascia in between the lobes.
These bands are called suspensory ligaments of
Cooper.
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17. Anatomy of breast contd…
Blood supply:
Arterial supply: Lateral thoracic-branches of the axillary artery
Internal mammary
Inter costal arteries
Veins: The veins follow the courses of arteries.
Lymphatics: a. lateral hemisphere- anterior axillary nodes
b. Upper convexity- infra clavicular group
c. Medial convexity- mediastinal glands
d. Inferior convexity- mediastinal glands
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18. Anatomy of breast contd…
Nerve supply: The nerve supply is from fourth, fifth
and sixth intercostal nerves.
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20. Physiological changes of breast during
pregnancy
 Changes are best evident in primigravida.
 In multigravida, the changes are not clearly evident.
 Size: Increased size of the breasts becomes evident
even in early weeks. This is due to marked
hypertrophy and proliferation of ducts (oestrogen) and
the alveoli (oestrogen and progesterone) which are
marked in the peripheral lobules.
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21. Physiological changes of breast during
pregnancy contd…
 There is also hypertrophy of the connective tissue stroma.
Myoepithelial cells become prominent.
 Vascularity is increased which results in appearance of
bluish veins running under the skin.
 Quite often the "axillary tail" (prolongation of the breast
tissue under cover of the pectoralis major) becomes
enlarged and painful.
 There may be evidence of striation due to stretching of the
cutis.
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22. Contd…
Nipples and areola: The nipples become larger,
erectile and deeply pigmented.
 Variable number of sebaceous glands (5-15),
become hypertrophied and are called
Montgomery's tubercles. Those are placed
surrounding the nipples. Their secretion keeps the
nipple and the areola moist and healthy.
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23. Contd…
 Appearance of secondary areola.
 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.
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24. Comparison of non-pregnant and pregnant breast
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25. Lactation
 For the first two days following delivery, no further
anatomic changes in the breasts occur.
 The secretion from the breast called colostrum
which starts during pregnancy becomes more
abundant during the period.
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26. Lactation
Properties and Components of breastmilk
 Human milk varies in its composition
 With the time of day
 With the stage of lactation
 In response to maternal nutrition
 Because of individual variations.
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27. Components of the colostrum
 It is deep yellow serous fluid, alkaline in reaction.
 It has got a higher specific gravity; high protein,
vitamin A, sodium and chloride content but has got
lower carbohydrate, fat and potassium than the
breast milk.
 It contains antibody (IgA) produced locally.
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28. Components of the colostrum contd…
 Microscopically: fat globules, colostrum corpuscles and
acinar epithelial cells.
 The colostrum corpuscles are larger polynuclear
leucocytes, oval or round in shape containing
numerous fat globules.
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29. Advantages of colostrum
 The antibodies (IgA, IgG, IgM) and humoral
factors (lactoferrin) provides immunological
defence to the new born.
 It has laxative action on the baby because of large
fat globules.
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30. Physiology of lactation
The physiological basis of lactation is divided into
four phases:
1. Preparation of breasts (mammogenesis).
2. Synthesis and secretion from the breast alveoli
(lactogenesis).
3. Ejection of milk (galactokinesis).
4. Maintenance of lactation (galactopoiesis).
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31. Physiology of lactation contd…
Mammogenesis
 Pregnancy is associated with a remarkable growth
of both the ductal and lobuloalveolar systems.
 An intact nerve supply is not essential for growth
of the mammary glands during pregnancy.
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32. Physiology of lactation contd…
Lactogenesis
 Milk secretion actually starts on 3rd or 4th postpartum
day.
 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
activity.
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33. Contd…
 The secretory activity is enhanced directly or indirectly
by growth hormone, thyroxine, glucocorticoids and
insulin.
 Prolactin stimulates mammary glandular ductal growth
and epithelial cell proliferation and induces milk protein
synthesis.
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34. There are 2 stages of lactogenesis :
Stage 1:
 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
decrease.
 High circulating levels of progesterone and estrogen
hold the secretion of milk in check.
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35. Stages of lactogenesis contd…
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 lactationcontrol.
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36. Stages of lactogenesis contd…
 Work by Haslam and Shyamala reveals that
progesterone receptors are lost in lactating
mammary tissues, thus decreasing the inhibitory
effect of circulating progesterone.
 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.
 Endocrine control switches to autocrine (supply-
demand)
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37. Physiology of lactation contd…
Galactokinesis
 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.
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38. During suckling, a conditioned reflex is set up:
Ascending impulses from the nipple and areola
thoracic sensory (4, 5 and 6) afferent neural arc
paraventricular and supra optic nuclei of the hypothalamus
Oxytocin from the posterior pituitary produces contraction of
the myoepithelial cells of the alveoli and the ducts containing
milk. ("milk ejection" or "milk let down" reflex)
Milk is forced down into the ampulla of lactiferous ducts,
wherefrom it can be expressed by the mother or sucked by
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39. Neural reflex arc
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41. Lactation contd…
 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
condition. AM
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42. Physiology of lactation contd…
Galactopoiesis
 Prolactin appears to be the single most important
galactopoietic hormone.
 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.
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44. Milk production
 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 store.
 For this purpose a store of about 5 kg of fat during
pregnancy is essential to make up any nutritional
deficit during lactation.
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45. Stimulation of lactation
Following delivery important steps are:
i. To put baby to the breast at 2-3 hours interval
from the first day.
ii. Plenty of fluids to drink
iii. To avoid breast engorgement.
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46. Inadequate milk
production/lactation failure
 It may be due to infrequent suckling or due to
endogenous suppression of prolactin (ergot
preparation, pyridoxin, diuretics or retained
placental bits).
 Unrestricted feeding at short interval (2-3hrs.) is
helpful.
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47. Drugs to improve milk
production/galactogogues
 Metoclopramide (10 mg thrice daily) increases milk
volume (60-100%) by increasing prolactin levels.
 Sulpuride (dopamine antagonist) has also been
found effective.
 Intranasal oxytocin contracts myoepithelial cells and
causes milk let down reflex.
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48. Lactation suppression
 Bromocriptine (dopamine agonist that inhibits
prolactin) 2.5 mg, 1 tab daily for 10-14 days.
 Side effects are: hypotension, rebound breast
engorgement, secretion, myocardial infarction and
puerperal stroke.
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49. Lactation suppression contd…
 Suppression of lactation is necessary if the baby is
born dead or dies in the neonatal period or if breast
feeding is contradicted.
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50. References:
 Jacob A.A comprehensive textbook of midwifery and
gynecological nursing.3rd edition.New Delhi:Jaypee;2012.
 Fraser DM, Cooper MA.Myles textbook for midwives.15th
edition. Philadelphia:churchill livingstone elsevier;2009
 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]. Available from :
http://emedicine.medscape.com/article/1835675-overview
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