DR NILESH KATE

MBBS,MDASSOCIATE 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

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