Placenta structure and functions

Tyes of placenta structure and functions

1. TOPIC–PLACENTA:-FINE STRUCTURE
AND TYPES
Dr. Ramkumar Lodhi
Conservation Biology Lab
School of studies in ZOOLOGY

2. SYNOPSIS
INTRODUCTION
STRUCTURE OF PLACENTA
TYPES OF PLACENTA
FUNCTIONS
HORMONES
CONCLUSION
REFERENCES

3. INTRODUCTION
Placenta is derived from the Greek word, plakuos, meaning
flat cake and this reflects its typical appearance.
Placenta is a fetal organ of pregnancy, which is responsible
for providing nutrition and oxygen to the fetus as well as
excretory function.
In Eutherian mammals, the embryo develops in the uterus
of mother. Placenta is not common to all mammals.
In prototherian, mammals are egg laying. Hence placenta is
not formed in uterus.

4. ANATOMY
Placenta is fleshy
weight –500gm
Diameter –15-20cm
Thickness –2.5cm
Spongy to feel
Occupies 30% of the uterine wall

5. PLACENTA
This is a fetomaternalorgan.
It has two components:-
Fetal part:-develops from the chorionic sac
Maternal part:-derived from the
endometrium
The placenta and the umbilical cord are the
transport system for substances between the
mother and the fetus.

6. STRUCTURE OF PLACENTA
Placenta is limited by the amniotic membrane on the fetal
side and by the basal plate on the maternal.
Amniotic membrane:-single layer of cuboidal
epithelium loosely attached to adjacent chorionic plate
and does not take part in placental formation.
Chorionic plate:-forms the roof of the placenta from
outside.
From inwards consists of
Syncytotrophoblast
Cytotrophoblast
Extraembryonic mesoderm with branches of umbilical
vessels

7. CONT…….
Basal plate:-forms the floor from outside and inward it
consist of
Compact and spongy layer of decidua basalis
Layer of Nitabuch
Cytotrophoblastic shell
syncytiotrophoblast

9. TYPES OF PLACENTA
Placenta is classified in three ways:-
On the nature of contact
On the distribution of villi
On the basis of histology
On the nature of contact:-
Two types:-
Indeciduate type placenta:-villiare simple
projections, they lie in loose contact with uterus.
Deciduate type placenta

11. CONT…….
On the basis of histology:-
Five types:-
Epitheliochorialplacenta(e.g;pig,horse):-fetal chorion is in
contact with epithelium of uterus.
Syndeumosechorialplacenta(e.g;sheep,cow):-The allanto-
chorionic with will pierce into the uterus of the mother.
Endotheliochorial placenta(e.g;dog,carnivores):-the
chorion of fetus will come in contact with endothelium of mother’s
uterus.
Hemochorialplacenta(e.g; bat, man, primates,
insectivores):-The chorion of fetus will float in the blood pools of
mother’s uterus.
Hemo endothelial placenta (e.g; rat, rabbit):-maternal blood
appears to be separated from the fetal blood only by the
endothelium of the chorionic capillaries.

13. CONT……..
On the distribution of villi:-
Five types:-
Diffusedtypeplacenta:-The villi are uniformly
distributed on the surface of blastocyst. e.g: horses, pigs
Cotyledonary placenta:-Villi are arranged in groups.
e.g; cattle, sheep, goat
Intermediate type placenta:-rare type, shows free villi
on cotyledons.
Zonaryplacenta:-The villi are in the form of transverse
zones. e.g; carnivores (dog, cat)
Discoidalplacenta:-villi are arranged in a circular plate
as in human and rodent placentae.

15. FUNCTIONS
It help in respiratory function
Excretory function
Nutritional
It produces or metabolizes the hormones and
enzymes necessary to maintain the pregnancy.
Immunological function :-It transfer the
immunoglobulin(IgG)to the fetus and filters out the
potentially toxic harmful antibodies.
Endocrine functions

16. CONT…..
Barrierfunction:-acts as the protective barrier for
the fetus against in maternal blood.
Larger molecular size drugs like insulin, heparin are
transferred minimally.
Only IgGantibodies and antigens can pass placental
barrier in both directions.

17. PLACENTAL HORMONES
Human chorionic gonadotrophin : -it is a
glycoprotein with high content of sialic acid and
other carbohydratic residues. Its molecular weight
is about 30,000.
Chorionic growth hormone prolactin or
HPL :-it is secreted in increasing quantities by the
syncytotrophoblast cells from the first weeks of
pregnancy.
Its molecular wt. is about 18,500.

18. CONT…….
Estrogen
Progesterone
Chorionic thyrotrophin
Relaxin
Corticotrophic releasing hormone

19. CONCLUSION
Placenta act as protective barrier for the fetus against
in maternal blood.
it help in respiratory functions.
It is responsible for providing nutrition and oxygen
to the fetus.
It produces or metabolize the hormones and
enzymes.

20. REFERENCES
Female reproduction:-
Roy. O. Greep
Comparative endocrinology by D.B.Tembhare
Google search