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After implantation a portion of the
endometrium becomes modified known as
The decidua basalis – Portion of endometium
between chorion and stratum basalis –
The decidua capsularis – portion of the
endometrium covers the embryo located
between embryo and uterine cavity.
The decidua parietalis – Non involved area of
It is formed by the union of
maternal decidua and foetal
chorionic villi and is
connected to the foetus by the
Formed during the 6th
weeks of pregnancy
The fully developed placenta is
disc-shaped with a diameter of
15 to 20cm and thickness of 2-
5cm and weighs about 500gm.
There are numerous foetal
chorionic villi lined by trophoblast
They contain foetal blood.
In the intervillous spaces are the
maternal blood sinuses containing
In the placenta, maternal and foetal
blood come in contact, but do not
mix as they are separated by the
The placenta is essential
A) Vital foetal functions
B) for maintaining
Functions of Placenta
Glucose, iron, calcium, phosphorus, aminoacids, water,NaCl , vitamins and
Excretory Function: Waste
products like urea, uric acid diffuse form foetal to maternal blood
Immunological function: The
foetus is antigenically a foreign body, the placenta protects the
embryoand foetus from rejection. The MHC class I and II are not present
on the placental trophoblast.
Barrier Function: Though
large molecular weight substances cannot cross the placenta
Respiratory Function: Exchange
of oxygen and CO2 between fetuse and mother. It is facilitated by three
factors: HbF, Large quantity of Hb, Double Bohr effect
Placenta is the temporary endocrine organ of
pregnancy and synthesizes many hormones.
Oestrogens are synthesized in the
Greatly increases blood flow to the
uterus, placenta and foetus.
Stimulates the development of
ducts of breast gland.
Increases the sensitivity to
Development and growth of
uterus,accessory sex organs.
its concentration greatly increases
towards the end of pregnancy.
Progesterone Is synthesized in the
syncitiotrophoblast from maternal
Its concentration greatly increases
and reaches a peak towards the
end of pregnancy (up to 19
It is the hormone of pregnancy
It suppresses ovulation and
inhibits uterine motility
Increase the development of the
alveolar system of the mammary
It maintains the corpus
luteum of pregnancy to
secrete estrogen and
stimulates foetal androgen
Stimulates the growth of
Helps for pregnancy
Also human placental lactogen
(HPL) or chorionic growth hormone
It has lactogenic and growth
begins about the 6th
gestation peak by 36th
It promotes lipolysis, inhibits
gluconeogenesis and glucose
Favours retention of nitrogen,
calcium and phosphorous.
It also has anti insulin effects.
FETO PLACENTAL UNIT
The interaction between fetus and mother during synthesis of
steroid hormones called Feto- Placental Unit.
Urinary oestriol level is clinically used as an index of the health of the fetus
Parturition is a
process by which the
and placenta are
expelled from the
It is also called
INITIATION OF LABOUR
At the end of about 40 weeks
of gestation, uterine
contractions begin. Initially
they are weak and painless
Then the intermittent
contractions become painful
and increase in frequency,
duration and force, and the
I - Stage of Labour
From the beginning of
painful contractions of
the uterus to the full
dilatation of the cervix is
the first stage of labour.
At this time the
membranes rupture and
amniotic fluid is
It last for about 16
II – Stage of Labor
This stage begins with
complete dilatation of the
The foetus gradually passes
down the dilated canal by
merging of uterus, cervix and
vagina as a single broad
Finally the foetus is delivered.
Voluntary contraction of the
abdominal muscles and
diaphragm, and straining
assists in delivery.
III – Stage of Labor
The expulsion of the
placenta which follows
a few minutes after the
delivery of foetus.
Followed by delivery
there is beginning of
Following parturition, there is involution of the
uterus and pelvic organs.
The postpartum period of six weeks is called
However, it takes 3 months for the maternal
system to return to the pregravid state, and is
sometimes referred to as “fourth trimester”
Mechanism of Parturition
At the end of pregnancy the uterus is greatly distended but the cervix
As labour begins, cervix dilates, afferent impulses travel up to the
hypothalamus, and increase oxytocin release.
More glucocoritcoids with less andrgens –fall in progesterone
Oxytocin acts directly on the uterine smooth muscles, and also by
increasing prostaglandin PGE2 formation
Reduces formation of progesterone and increases oestrogens
(E/P) leads to increased production of prostaglandins.
STAGES OF BREAST DEVELOPMENT
Up to Puberty: - Rudimentry
After Puberty : - Each menstrual cycle proliferation of lobulo – alveolar
↑in duct system - Enlargement of Gland
Surface Epithelium invaginate
Invaginated column of cells become hollow
Hollow Solid columns of cells form duct & alveoli
month of pregnancy there is small amount of
Oestrogen & Progesterone suppress the ↑ activity of
At the time of parturition the oestrogen & progestrone
level ↓ & prolactin ↑.
↑ Secretion of breast milk.
GALACTOKINESIS (LET –DOWN
- Neuro – Endocrine Reflex:
Suckling of baby
Impulses to hypothalamus
Relayed to neuro hypophysis
Release of oxytocin
Oxytocin to breast gland
Contraction of myoepithelial cells
Maintenance depends on
Prolactin - Helps in continuous secretion.
GH - Lactogenic Effect
Thyroxine - Metabolism in breast gland.
Cortisol - Permissive action.
2. Continuous Expulsion:
- Feeding & expulsion.
- ↑ quality of milk
Endocrine Control Of Breast Development
Action of Progesterone:
↑ the size & number.
Action of Prolactin:
↑ Alveoli growth by GH, Cortisol and
Growth Hormone: Growth of breast gland
Thyroid Hormone: Maintains Metabolic
activity maintains Normal growth.
HCG & HPL : Stimulate growth of breast
Insulin: Provides glucose for energy.
Hyper secretion of Milk:
- Physiological – in Newborns
- Drugs: (Galactogogues)
- Metoclopramide - Prolactin↑
- Sulpuride – Dopamine antagonist
Chiari – Frommel Syndrome:
Persistance of lactation and amenorrhea in women who do not
nurse after delivery
This condition is called CHIARI – FROMMEL SYNDROME
Persistent prolactin secretion without the secretion of FSH and LH
necessary to produce maturation of new follicles and ovulation