This document discusses placentation and endocrinology of gestation. It covers several key points: - Placentation involves the attachment of placental membranes to the endometrium, with true implantation occurring in rodents and humans where the conceptus buries itself beneath the endometrial surface. - The placenta is a transient organ that facilitates metabolic exchange between the conceptus and dam. It has both fetal and maternal components and serves major functions like maintaining pregnancy and promoting fetal growth. - Placentas are classified based on how chorionic villi are distributed and how separated the fetal and maternal blood supplies are. Major hormones produced by the placenta that support pregnancy include h

1. Placentation and
Endocrinology of
Gestation
Prof. Dr. Nasim Ahmad
THER 608
Chap. 14 1

2. 2

3. 3

4. 4

5. 5

6. Placentation
• Implantation = attachment of
placental membranes with the
endometrium eg., Eutherian
Mammals
• True implantation = only in rodents
& human where conceptus burries
itself into endometrium and
temporarily disappears beneath the
surface 6

7. • Placenta = transient organ of
metabolic interchange between
conceptus and the dam (Transient
endocrine organ)
• Two components = (Fetal &
Maternal)
Fetal – derived from chorion
Maternal – derived from
endometrium
Placenta
7

8. Placenta: a transitional
endocrine gland
Major Functions
• Maintenance of pregnancy
• Stimulation of the mammary
gland
• Promotion of fetal growth
8

9. FUNCTIONS OF THE PLACENTA
9

10. THE DIFFUSED
PLACENTA OF MARE
CONSISTS OF MANY
MICROCOTYLEDONS
OVER THE ENTIRE
SURFACE OF
CHORION
10

11. Classifications of Placenta
I. Classification according to the distribution of
chorionic villi (CV)
Diffuse = uniform distribution (e.g.., sow &
mare)
Zonary = band like zone (e.g.., dogs & cats)
Discoid = form a regionalized disc (rodents &
primates)
Cotyledonary = numerous discrete button-like
structures called cotyledons (Cow, buffalo,
sheep & Goat)
Placentomes = Maternal caruncles + fetal
cotyledons 11

12. ZONARY PLACENTA
12

13. COTYLEDONRYPLACENTA
INRUMINANTS
13

14. DISCOID PLACENTA
14

15. II. Classification based on separation of the
fetal and maternal blood
• Epitheliochorial (Sow & Mare)
Epithelium of endometrium & CV are
intact.
• Syndesmochorial (Ruminants)
1. Epith of Endometrium transiently erodes
and then regorws causing intermittant
exposure of maternal capillaries to the
chorionic epith.
2. Binucleate giant cells (BNGC) originating
from the trophoblastic cells are formed
continuously; 20 % placenta 15

16. 3. BNGC secrete placental Lactogen and
Pregnancy Specific Protein B (PSPB) and
steroids (Progesterone/ estrogens)
• Endotheliochorial (Dogs & Cats)
Complete erosion of endomet epith and
underlying interstitium. So maternal capill
are directly exposed to epith cells of
chorion.
• Haemochorial (Primates & Rodents)
Chorionic epith is in direct apposition to
maternal pools of blood.
16

17. Sow & Mare
Ruminants
Dogs & Cats
Primates &
Rodents
17

18. MIGRATION OF THE GIANT CELLS:
Ruminants
18

19. Regulation of Exchange Between
Fetus and Dam
1. Simple diffusion
Gases and water pass from ↑ to ↓ conc.
2. Facilitated diffusion
Glucose & other metabolically important
material, i.e., amino acids are
transported by facilitated diffusion
through specific carrier molecules.
3. Active transport (AT)
Placenta contains AT pumps for Na, K &
Ca
19

20. THE SUBSTANCES WHICH CAN OR
CANNOT PASS THROUGH PLACENTA
• Glucose pass easily
• Proteins don't cross placental barrier.
• Lipid don’t cross placenta. Large
peptide hormones (TSH, ACTH and
GH) Insulin and glucagon don’t cross
placenta.
• Hormones with smaller mol wt.
(steroids, thyroid hormones) and the
catecholamines (epinephrine and
norepinephrine) cross the placenta
with relative ease 20

21. • Vitamins/ minerals are transferred at
variable rates. Fat soluble vitamins don’t
cross placenta with relative ease, while
water soluble vitamins (B&K) can cross.
• Toxic/pathogenic materials (Ethyl
alcohol, lead, mercury & Phosphorus)
cross placenta easily. Opiate drugs and
barbiturates and antibiotics can cross
placenta
• Viruses (measles, Herpes and HIV) can
be transmitted from pregnant mother to
fetus.
• Bacteria (syphilis) can also be transmitted
to fetus. 21

22. human Chorionic Gonadotropin
(hCG) (LH like)
• Secreted by trophoblastic cells of
chorion as early as blastocyst hatches
• Can be detected in urine & blood of
pregnant woman as early as day 8-10 of
gestation
• Luteotropic stimulus for ovulatory CL
• Luteal LH receptors bind to hCG →
sustained progesterone production
• hCG inj. to non-primate → LH-like action
(ovulation)
22

23. 23

24. Progesterone
• Inhibition of myometrial contractions
• In ewe, mare, & woman, CL is not needed for
the entire length of pregnancy because placenta
take over production of progesterone
• Progesterone from Placenta is not involved in
pregnancy maintenance in bitch, camel, goat,
queen, rabbit and sow
• Placental P4 begin for pregnancy maintenance:
Cow 6-8 mo Mare 70 days
Ewe 50 days Woman 60-70 days
24

25. 25

26. 26

27. Estrogen
• It is an important product of placenta
particularly during last part of
gestation
• Peak of estrogen in most spp. signals
early preparturient period
27

28. Placental Lactogen
(Somatomammotropin)
• Polypeptide in ewe, goat, cow & human
• Secreted by BNGC
• Similar to GH, so promote growth of fetus
• Lactogenic activity
• In cow and goat, both the properties are
equivalent.
• In ewe and woman, lactogenic activity is
very much pronounced than the
somatotropic activity
28

29. Relaxin
• Secreted in human, mare, cat, dog,
pig, rabbit, monkey
• In rabbit, entirely by placenta and not
at all by ovary.
• During parturition, other than rabbit, it
is secreted by both placenta and
ovary.
• Not produced by bovine placenta at
any stage of gestation? 29

30. equine chorionic gonadotropin
(eCG) or PMSG (like FSH)
• Secreted by endometrial cups of the
placenta at time of attachment of
conceptus to endometrium
• Luteotropin (production of P4)
• Control formation of accessory CL
formed by ovulation at day 40-70 of
pregnancy
• Lutenization of antral follicles that don’t
ovulate
• Used for superovulation in other spp.
30

31. Production of eCG is
related to weight of
endometrial cups in
Mare
31

32. 32

33. 33

34. Thank You
34

35. 35
Gravid Horn
Non-Gravid Horn

36. 36
Right sided
uterine
torsion,
Buffalo

37. 37
Cotyledon
Fetal side
Maternal side
caruncle
placentome

38. 38
Cotyledons
chorio allantois
Uterus

39. 39
Caruncle 10 cm

40. 40
Crypts of caruncle
clearly visible

41. 41
Uterine layer
Chorio Allantois after detaching
the cotyledons

42. 42

43. 43
Amniotic membrane

44. 44
Blood supply
contributing to
umblical cord

45. 45
Fetus attached to placenta