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 fetomaternal organ.
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:- villi are simple
projections, they lie in loose contact with uterus.
 Deciduate type placenta

11. CONT…….
 On the basis of histology:-
Five types:-
 Epitheliochorial placenta(e.g; pig, horse):-fetal chorion is in
contact with epithelium of uterus.
 Syndeumose chorial placenta(e.g; sheep, cow):- The allanto-
chorionic with will pierce into the uterus of the mother.
 Endothelio chorial placenta(e.g ;dog, carnivores):- the
chorion of fetus will come in contact with endothelium of mother’s
uterus.
 Hemochorial placenta (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:-
 Diffused type placenta:-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.
 Zonary placenta:- The villi are in the form of transverse
zones. e.g; carnivores (dog, cat)
 Discoidal placenta:- 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…..
 Barrier function:- acts as the protective barrier for
the fetus against in maternal blood.
 Larger molecular size drugs like insulin, heparin are
transferred minimally.
 Only IgG antibodies 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