PLACENTA, PARTURITION AND LACTATION
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Transcript of PLACENTA, PARTURITION AND LACTATION
DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
PLACENTA, PARTURITION &
LACTATION
OBJECTIVIES Placenta –structure Functions of placenta Hormones of placenta Fetoplacental unit Parturition Stages of parturition Mechanism of
parturition. Lactation Stages of lactation
FERTILIZATION
The genetic material
from a sperm cell
and secondary
Oocyte merges into a
single nucleus is
called fertilization.
IMPLANTATION
About six days after
fertilization the
blastocyst attaches
to the endometrium
a process called
implantation
FERTILIZATION
PLACENTA After implantation a portion of the
endometrium becomes modified known as decidua.
The decidua basalis – Portion of endometium between chorion and stratum basalis – Maternal placenta
The decidua capsularis – portion of the endometrium covers the embryo located between embryo and uterine cavity.
The decidua parietalis – Non involved area of endometrium
PLACENTA – MACROSCOPIC VIEW
PLACENTA It is formed by the union of
maternal decidua and foetal chorionic villi and is connected to the foetus by the umbilical cord.
Formed during the 6th to 12th 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.
PLACENTA There are numerous foetal chorionic
villi lined by trophoblast cells.
They contain foetal blood.
In the intervillous spaces are the
maternal blood sinuses containing
maternal blood.
In the placenta, maternal and foetal
blood come in contact, but do not
mix as they are separated by the
placental barrier.
WHY PLACENTA?
The placenta is essential for
A) Vital foetal functions and
B) for maintaining pregnancy
Functions of PlacentaNutritive function:
Glucose, iron, calcium, phosphorus, aminoacids, water,NaCl , vitamins and fatty acids
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 - FunctionsMOTHER
NUTRITION
OXYGEN
ANTIBODIES
HORMONES
PLACENTA FOETUS
CARBON
DIOXIDE
METABOLITES
STORAGE
PLACENTAL
HORMONES
BLOOD
ENDOCRINE FUNCTION
Endocrine Function: Placenta is the temporary endocrine organ of pregnancy and synthesizes many hormones.
1. Oestrogen
2. Progesteron
3. HCG
4. HCS
5. Relaxin
OESTROGEN Oestrogens are synthesized in the
syncitiotrophoblast.
Greatly increases blood flow to the uterus, placenta and foetus.
Stimulates the development of ducts of breast gland.
Increases the sensitivity to oxytocin.
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 cholesterol.
Its concentration greatly increases and reaches a peak towards the end of pregnancy (up to 19 μg/100 ml)
It is the hormone of pregnancy It suppresses ovulation and
menstruation inhibits uterine motility maintains pregnancy Increase the development of the
alveolar system of the mammary gland
Human Chronic Gonadotrophin (HCG)
Synthesized by syncitiotrophoblast
It maintains the corpus luteum of pregnancy to secrete estrogen and progesterone
stimulates foetal androgen secretion.
Stimulates the growth of breast gland
Helps for pregnancy diagnosis tests.
HUMAN CHORIONIC SOMATOMAMMOTROPHIN (HCS)
Also human placental lactogen (HPL) or chorionic growth hormone – prolactin.
It has lactogenic and growth stimulating effects.
begins about the 6th week of gestation peak by 36th week (about 15 mg/ml).
It promotes lipolysis, inhibits gluconeogenesis and glucose utilization.
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 Parturition is a
process by which the fetus, membranes and placenta are expelled from the uterus
It is also called labour
INITIATION OF LABOUR At the end of about 40 weeks
of gestation, uterine
contractions begin. Initially
they are weak and painless
(Braxton –Hicks).
Then the intermittent
contractions become painful
and increase in frequency,
duration and force, and the
cervix dilates
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
expelled.
It last for about 16 hours.
II – Stage of Labor This stage begins with
complete dilatation of the cervix.
The foetus gradually passes down the dilated canal by merging of uterus, cervix and vagina as a single broad channel.
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
uterine contraction.
PLACENTA – AFTER EXPULSION
POST CHANGES Following parturition, there is involution of the
uterus and pelvic organs.
The postpartum period of six weeks is called puerperium.
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
is soft.
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.
Regulation of Parturition
LACTATIONDefinition
Process by which milk secretion is Initiated, maintained and ejected Secreted by mammary glands Natural food of newborns .
COMPOSITION Colostrum
Fat – small globules
Carbohydrate – Lactose
Protein – Lactalbumin
- Lactoglobulin
- Lactoferrin, Lysozyme, Leukocytes
- Long chain W-3 Fatty acid
- IgA
STAGES OF LACTATION Mammogenesis Lactogenesis Galactokinesis Galactopoiesis
STAGES OF BREAST DEVELOPMENT(Mammogenesis)
Up to Puberty: - RudimentryAfter Puberty : - Each menstrual cycle proliferation of lobulo – alveolar system. ↑in duct system - Enlargement of Gland
Mammogenesis
Surface Epithelium invaginate
Invaginated column of cells become hollow
Hollow Solid columns of cells form duct & alveoli
LACTOGENESIS
From 5th month of pregnancy there is small amount of prolactin secretion.
Oestrogen & Progesterone suppress the activity of prolactin.
At the time of parturition the oestrogen & progestrone level & prolactin .
Secretion of breast milk.
GALACTOKINESIS (LET –DOWN REFLEX)
- Neuro – Endocrine Reflex:
Suckling of baby
Impulses to hypothalamus
Relayed to neuro hypophysis
Release of oxytocin
Oxytocin to breast gland
Contraction of myoepithelial cells
- Milk in ejected.
SUCKLING REFLEX OR
MYOEPITHELIAL REFLX
GALACTOPOIESISMaintenance depends on
1.Hormones: Prolactin - Helps in continuous secretion. GH - Lactogenic Effect Thyroxine - Metabolism in breast gland. Cortisol - Permissive action.
2. Continuous Expulsion: - Feeding & expulsion. 3. Nutrition - quality of milk
Endocrine Control Of Breast Development
Action of Progesterone:
↑ the size & number. Action of Prolactin:
↑ Alveoli growth by GH, Cortisol and thyroxin.
Growth Hormone: Growth of breast gland Thyroid Hormone: Maintains Metabolic activity maintains Normal growth.
HCG & HPL : Stimulate growth of breast gland.
Insulin: Provides glucose for energy.
GALACTORREA 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
Cause: Persistent prolactin secretion without the secretion of FSH and LH
necessary to produce maturation of new follicles and ovulation
STAGES OF LACTATION
Thank You