Physiology of lactation

PHYSIOLOGY OF LACTATION

1. DR NILESH KATE
MBBS,MD
PROFESSOR
DEPT. OF PHYSIOLOGY
PHYSIOLOGY
OF LACTATION.

2. OBJECTIVES.
Development & functional anatomy of breast
Physiology of lactation.

3. INTRODUCTION.
Breastfeeding characteristics of all mammals
including humans
Method of nourishing newborn.
Friday, June 19, 2020

4. Development of Breast.
Present in both the sexes but rudimentary in
males & well developed in females.
Friday, June 19, 2020

5. Phases of development of
breast.
In intrauterine life
At birth
At puberty
In pregnancy
During lactation
Friday, June 19, 2020

6. Breast in intrauterine life
(Embryogenesis)
Mammary bud –at 18-19
weeks of gestation
thickened mass of
epithelium develop.
16-20 solid outgrowths
arises & project into dermis
Then this thickened mass &
outgrowth canalized –form
Rudimentaryduct system.
Friday, June 19, 2020

7. Breast in intrauterine life
(Embryogenesis)
Terminal part of outgrowth
proliferate into secretory
elements, Occurs at puberty.
Proximal end of each duct
opens into common pit by
cavitation of thickened
mass
Growth of mesodermal
tissue pushes wall of the pit
outwards as Nipple.
Friday, June 19, 2020

8. Breast at birth
At birth rudimentary as tiny nipples & few
ducts radiating from it.
Friday, June 19, 2020

9. Breast at puberty
Upto puberty remain quiescent then
changes occurs
Thelarche–(9-11 yrs of age) at the time of
puberty before menses.
Breast gets enlarged & only duct system proliferate
& shows branching.
Friday, June 19, 2020

10. Breast at puberty
At Menarche –after menses cyclical growth
correspond with menstrual cycle.
In proliferative phase–duct cells proliferate.
In luteal phase –progesterone stimulate
proliferation of terminal ductules –glandular
tissue forms.
Friday, June 19, 2020

11. Breast at puberty
At Menstruation –as both oestrogen &
progesterone levels no prolifearation of
duct cells & glandular tissue.
With further cycles progressive growth
occurs with fat deposition in adipose tissue.
Friday, June 19, 2020

12. Breast in pregnancy
Growth of both –Glandular & Ductal tissue
occurs.
Only during first pregnancy glandular tissue
develops fully.
Friday, June 19, 2020

13. Breast in pregnancy
In first half –Duct system proliferate &
shows sprouting & branching along with
growth of stroma & deposition of fat.
In second half –growth of glandular tissue
occurs.
Friday, June 19, 2020

14. Breast during lactation
After child birth alveolar cells get enlarged &
distended & starts forming milk
(Lactogenesis)
Involution–after normal period of lactation
(7-9 months) alveolar epithelium undergoes
apoptosis & glands revert back to non-
pregnant state.
Friday, June 19, 2020

15. Functional anatomy of breast.
Gross anatomy –
round elevated
structure present over
pectoral region, with
central dark
pigmented area -
areola& projected
above surface -
Nipple.
Friday, June 19, 2020

16. Histological structure.
The fascia covering mammary gland is
connected by suspensory ligaments to
overlying skin & underlying muscle.
Consists of 15-20 lobes & each lobe has
number of lobules.
Glandular tissue –consists of alveoli having
secretary cells
Friday, June 19, 2020

17. Histological structure.
Secretion–Apocrine in nature by exocytosis
into ducts.
About 15-20 ducts opens at summit of nipple
Just before opening lactiferous ducts shows
dilatation called –Lactiferous sinus.
Friday, June 19, 2020

18. Histological structure.
Smaller ductules lined by single columnar
epithelial cells & near opening at nipple lined
by squmous cells.
Around alveoli ductules & lobules are
present in myoepithelial cells –so squeeze &
pour content into ductules.
Friday, June 19, 2020

19. Electron microscopically.
Secretorycells contains rough & smooth
endoplasmic reticulum, numerous
mitochondria, Golgi apparatus & Lysosomes.
Protein as membrane bound vesicles & fat as
large globule.
Friday, June 19, 2020

20. Control of breast development
and growth
Oestrogen–mainly for ductal growth & fat deposition,
also causes thickening of nipple.
Progesterone–for Glandular tissue development.
Other hormones –Growth hormone, thyroxine, cortisol &
insulin cause growth & development.
Corpus luteal & placental hormones –during pregnancy
Prolactin.
Friday, June 19, 2020

21. Friday, June 19, 2020

22. HUMAN PROLACTIN
Structure &
secretion
Single peptide chain
secreted by
acidophilic cells of
anterior pituitary
gland.
Friday, June 19, 2020

23. Placental concentration
Pulsatile
Shows diurnal variations
During pregnancy –start at 8
th
week & peak
(200-400 ng/ml) at term
Sources–placenta, amniotic fluid & maternal
anterior pituitary gland.
During pregnancy & lactation –affected by
oestrogen.
Friday, June 19, 2020

24. Control of prolactinsecretion
Hypothalamic
control –Prolactin
inhibitory factor from
Arcuate nucleus of
hypothalamus acts on
anterior pituitary
gland.
Friday, June 19, 2020

25. Factors enhancing release of
Prolactin.
TRH
Stress
Psychological, Physiological
& Pathological.
Oxytocin
Other
Dopamine antagonists,
adrenergic blockers,
serotonin agonists.
Prolactin.
Friday, June 19, 2020

26. PHYSIOLOGICAL EFFECTS OF
PROLACTIN
Prolactin
Breast
growth
Lactogenic
effect.
Suppression of
ovarian cycle in
nursing mothers
Friday, June 19, 2020

27. Applied aspects.
Chiari-Frommel syndrome. –
Persistence of lactation (Galactorrhoea)
Amennorrhoea
Genital atrophy ( Due to suppression of FSH & LH)
Chromophobe cell tumour of pituitary
gland.
Galactorrhoea & high level prolactin in non-
pregnant womens.
Friday, June 19, 2020

28. PHYSIOLOGY OF LACTATION.
Phases of lactation
Mammogenesis
Lactogenesis
Galactokinesis
Galactopoiesis.
Friday, June 19, 2020

29. Mammogenesis
Breast develops fully
& prepared for milk
secretion after
delivery.
Hyperplasia of ductal
& alveolar tissue
Areola–Pigmented.
Sebaceous glands
becomes prominent in
areola
Nipples become larger
& pigmented.
Friday, June 19, 2020

30. Lactogenesis
Stage I
First colostrumsecreted, rate 1/100
th
,
Composition same as human milk except fats absent.
Cause –high Prolactin & HCS
No free flow of milk –due to suppresiveeffects of
oestrogen & progesterone.
STAGE II
Initiation of lactation.
Rate –500-750 ml/day
Due to sudden loss of Oestrogen &
progesterone.
Friday, June 19, 2020

31. Human milk
Types
Colostrum–Deep yellow colour fluid during
postpartum
Contains –high protein, immunoglobulins & lactoferrins
Granular bodies –colostrum corpuscle (alveolar cells,
Leucocytes with fats)
Transition milk or intermediate milk –6-15
th
day.
Mature milk –after 15
th
day.
Friday, June 19, 2020

32. Composition of human milk.
Friday, June 19, 2020

33. Formation of milk.
Mammary gland –metabolically active
Amino acids , FA, glucose & Ca derived from
plasma into alveolar cells
Process involved are
Fat synthesis & secretion
Ion & water secretion
Transcytosis of immunoglobulins
Exocytosis.
Friday, June 19, 2020

34. Galactokinesis
expulsion of milk
Milk ejection
Milk expulsion
Milk let down
Suckling effect.
(Psychological
component)
Cry, sight, sound.
Friday, June 19, 2020

35. Inhibition of milk ejection
Pain
Alcohol
Psychol
ogical
stress
Friday, June 19, 2020

36. Galactopoiesis
Maintenance of milk secretion.
Depend on surge in prolactin secretion.
In nursing mothers reflex causes 10-20 fold
rise in prolactin secretion for 1 hr & it occurs
at every feeding.
It depend on infants demand.
Friday, June 19, 2020

37. Importance of lactation.
Advantages of breastfeeding to the baby
Advantages of breastfeeding to the
mother.
Friday, June 19, 2020

38. Advantages of breastfeeding to
the baby
Balanced diet –contains proteins, minerals, fats,
carbohydrates & vitamins
Protection against infection –high lymphocytes,
neutrophils, macrophages, lysozymes &
immunoglobulins.
Easily digestible
Growth factors –epidermal growth factors, insulin
& somatostatin C
Other–sterile, convenient, inexpensive, no allergy.
Friday, June 19, 2020

39. Advantages of breastfeeding to
the mother.
Lactational ammenorrhoea (natural
contraception)
Involution of uterus.
Protection against breast engorgement.
Protection against obesity –body fat used for
milk synthesis.
Emotional bonding.
Protection against cancer.
Friday, June 19, 2020

40. Friday, June 19, 2020
THANK YOU