Physiology of lactation

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

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

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

Development of Breast.
 Present in both the sexes but rudimentary in
males & well developed in females.

Phases of development of
breast.
 In intrauterine life
 At birth
 At puberty
 In pregnancy
 During lactation

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
Rudimentary duct system.

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.

Breast at birth
 At birth rudimentary as tiny nipples & few
ducts radiating from it.

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.

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.

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.

Breast in pregnancy
 Growth of both – Glandular & Ductal tissue
occurs.
 Only during first pregnancy glandular tissue
develops fully.

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.

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.

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

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

 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.

 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.

Electron microscopically.
 Secretory cells contains rough & smooth
endoplasmic reticulum, numerous
mitochondria, Golgi apparatus & Lysosomes.
 Protein as membrane bound vesicles & fat as
large globule.

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.

HUMAN PROLACTIN
 Structure &
secretion
 Single peptide chain
secreted by
acidophilic cells of
anterior pituitary
gland.

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

Control of prolactin secretion
 Hypothalamic
control – Prolactin
inhibitory factor from
Arcuate nucleus of
hypothalamus acts on
anterior pituitary
gland.

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

PHYSIOLOGICAL EFFECTS OF
PROLACTIN
Prolactin
Breast
growth
Lactogenic
effect.
Suppression of
ovarian cycle in
nursing mothers

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.

PHYSIOLOGY OF LACTATION.
 Phases of lactation
 Mammogenesis
 Lactogenesis
 Galactokinesis
 Galactopoiesis.

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.

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

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 – 6-15th
day.
 Mature milk – after 15th day.

Composition of human milk.

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.

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

Inhibition of milk ejection
Pain
Alcohol
Psychol
ogical
stress

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.

Importance of lactation.
 Advantages of breastfeeding to the baby
 Advantages of breastfeeding to the
mother.

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.

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.

THANK YOU

Physiology of lactation

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