physiology of lactation varsha hirani

1. PRESENTER: DR VARSHA V. HIRANI
FACILITATOR: PROF. MUSOKE

2. OBJECTIVES:
Understand the structure of the breast
Describe the stages of lactation
Composition of breast milk
 Factors affecting lactation
Medications that affect lactation
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3. Definition of lactation
Lactation describes the production of breast
milk and its secretion from the mammary
gland after delivery
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4. Structure of the breast
 Parenchyma consists of 10-15 ducts extending from
the nipple to terminate in grape-like clusters known as
alveoli (basic unit) via ductules from lobules
 There are 15-20 pyramid shaped lobes separated by
cooper ligament and each contains lobules which are
further separated by fat and connective
tissue(stroma)
 Nipple surrounded by area of hyperpigmented skin –
areola
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6. Physiology of Lactation.
Lactation can be divided into 5 stages:
1. Mammogenesis-Development of breasts to
a functional state
2. Lactogenesis-Synthesis and secretion of milk
from the breast alveoli
3. Galactokinesis-Ejection of milk outside the
breast
4. Galactopoiesis-Maintenance of lactation
5. Involution-regression and atrophy post
lactation
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8. 1.Mammogenesis
 Growth of ducts and lobuloalveolar systems
 This starts from birth to puberty and continues in
pregnancy
 Ductal sprouting predominates in 1st trimester and
lobular sprouting occurs more in 2nd trimester
hence the breast will contain more glandular
epithelial cells than stroma
 Just before and during parturition there is a new
wave of mitotic activity causing growth growth and
maturation
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9. Hormonal influence during
mammogenesis
Prepubertal growth-
 depends on estrogen and progesterone.
 Secretion of prolactin and somatotropin by the
pituatory gland results in mammary growth.
 Adrenocorticotrophic hormone(ACTH) and thyroid
stimulating hormone(TSH) acting on the adrenal
gland and thyroid gland also play a minor role in
growth of the mammary gland
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Hormonal influence during
mammogenesis…
Pubertal growth-
 When the hypophyseal-ovarian –uterine cycle is
established, there is extensive branching of the duct
system and parenchymal proliferation and canalization
of the lobuloalveolar units controlled by estrogen and
progesterone

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During pregnancy
 In early pregnancy a marked increase in ductular
sprouting, branching and lobular formation is evoked
by luteal and placental hormones.
Progesterone:causes increased growth of alveoli size
and lobes,
Estrogen:Stimulates milk duct system to grow and
differentiate, deposition of fat.
Prolactin:contributes to increased growth and
differentiation of the alveoli and ductal structures

12. Types of lobules
 Type 1- (virginal lobule) when an average of 11 alveolar
buds/ductules cluster around a terminal duct, this is
apparent within 1 to 2 years after onset ofmenses
 Type 2 - changing levels of estrogen and progesteron
during menstrual cycle stimulates type 1 lobules to
sprout new alveolar buds and evolve to mature
structures, type 2-47 lobules
 Type 3- in pregnancy, 80 lobules
 Type 4-attained in late pregnancy with breast milk
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14. 2. LACTOGENESIS(stage 1)
Stage 1: occurs in mid pregnancy
 There is initiation of milk synthesis,
 alveoli differentiates into secretory cells and prolactin
stimulates mammary secretory cells to produce milk.
 insulin and serum growth factor induced cell
division of stem cells of the gland and presence of
cortisol for formation of alveoli is required for
induction of milk synthesis .
 Further differentiation is inhibited by high levels of
progesterone from the placenta and loss of
progesterone receptors in the lactating breast
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15. Prolactin:
 exerts its effects through receptors for initiation of milk
secretion located on the alveolar surfaces.
 stabilizes and promotes transcription of mRNA and
stimulates synthesis of lactoalbumin, which is a
regulatory protein of the lactose synthetase enzyme system
 Increases lipoprotein activity in the mammary gland
 In conjunction with estrogen and progetserone it attracts
and retain Ig-A immunoblasts
 estrogen enhances prolactin production by 10-20 fold. This
is regulated by human placental lactogen which has an
inhibitory effect
 Its inhibited by prolactin inhibiting factor under control
of catecholamines in the hypothalamus.
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16. LACTOGENESIS-stage 2
 Stage 2: from late pregnancy to day 8.
 This is triggered by rapid drop in progesterone
levels after placental delivery
 requires the presence of elevated levels of prolactin
and cortisol , insulin, growth hormone and
parathyroid hormone to facilitate mobilization of
nutrients and minerals
 there is a switch from endocrine to autocrine
control
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17. 2. Lactogenesis. Pathways for milk secretion
by the mammary epithelial cell
I - Exocytosis : milk protein and lactose are
transported in Golgi-derived secretory
vesicles, with water and electrolytes in to the
alveolar lumen
II – Reverse Pinocytosis: lipid formed in
smooth ER forms droplets and covered by
phospholipid membrane transported as milk-fat
globule
III – Apical transport: Direct movement of
monovalent ions, water, and glucose across
the apical membrane of the cell.
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18. Lactogenesis……
IV – Transcytosis. sodium, potassium,
chlorides, some monosaccharides, and
water
V - The paracellular pathway for some
interstitial fluid components and
leukocytes to pass by diapedesis through
the tight junctions.
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19. Pathways for milk secretion by the
mammary epithelial cell
I. Exocytosis
II. Reverse
pinocytosis
III.Apical transport
IV.Transcytosis
V. Paracellular
pathways
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21. galactokinesis
• Depends on the suckling mechanism of the
baby and the contractile action which will
express milk from the alveoli into the ducts.
• This contraction is brought about by the
action of Oxytocin
• Milk let down reflex/milk ejection reflex
• Inhibited by psychic condition /pain /breast
engorgement
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22. oxytocin:
 Released from posterior lobe of the pituatory gland
during nipple stimulation or sensory stimulation(
visual, tactile , olfactory or auditary)
 Causes ejection of milk from the alveoli gland by
contraction of the myoepithelial cells into ductules
and ducts
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23. 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
The baby. This occurs between 30sec. to 60sec.
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25. Galactopoiesis.
 Prolactin is the hormone for maintenance of
lactation
 And suckling is essential for maintenance of
milk secretion
 Periodic breast feeding relieves pressure in
the ducts and promotes more secretion
Controlled by autocrine system(supply-demand)
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26. 5. Involution
Apoptotic cell death and tissue remodelling
post lactation
Requires a combination of lactogenic
hormone deprivation and local signals to
undergo regression and atrophy
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27. Variations in composition :
Colostrum(1-5 days) – is reacher in proteins ,minerals,
immunoglobulins , anti inflammatory factors(PGE1 and
PGE2, cytokines), phagocytes and lymphocytes.
Mature milk(>30 days)-larger quantity than colostrum,
Foremilk –thin, proteins, lactose, water and other
nutrients.
Hindmilk –more fat therefore whiter, provides much of
the energy of a feed.
 Other components include human growth factors, cortisol,
insulin, thyroxine and prolactin
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29. FACTORS AFFECTING LACTATION
Maternal problems:
 stress(post c/s,stressful vaginal delivery or other psychosocial
stresses) opiates and beta-endorphins are released that block
the stimulus-secretion coupling thus reducing oxytocin release
 polycystic ovarian syndrome,
 theca lutein cysts,
 obesity,
 labour analgesia,
 dm type 1,
 placental retention-increased circulating progesterone
 Alcohol dependence
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30. FACTORS AFFECTING LACTATION..
 Infrequent suckling/failure to empty breast
causes Elevated intrammary pressure also disrupts
connections between cells and their attachment to
the basement membrane disrupting synthesis and
secretion of milk components.
 Premature infants-prolactin may not be
sufficient
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31. MEDICATIONS AND LACTATION
Medications that increase lactation-
 metoclopramide
 domperidone
 phenothiazine neuroleptics -chlorpromazine
 risperine
 Hypoglycemics
 H2 antagonists-cimetidine
 Antihypertensives-methyl dopa, b blockers
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32. MEDICATIONS AND LACTATION
Medications that reduce lactation-
 Bromocryptine(dopamine agonist)
 Progesterone,estrogen-OCP
 Clomiphene citrate
 ergotamine
 pseudoephedrine(in cough syrups)
 Pyridoxine
 Prostaglandins- PGE/F2alpha
 Levodopa/carbidopa
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33. Advise to the mother to improve
lactation
 Good health;
 Early and sufficient
treatment of illnesses;
 Proper balance between
rest and exercise;
 Freedom from worry
 Care of the breast
/nipples during
pregnancy
 Post natally frequent
breast feeding
 Avoid breast
engorgement
 Plenty of fluids
 Adequate nutrition.
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34. Thank you!

35. ANY QUESTIONS?
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36. References
 E-medicine – Human milk and lactation.
 Breastfeeding and human lactation-Jones and Bartlett
Series.
 Breast feeding, guide for medical proffesion by Ruth
Lawrence.