extra embryonic membranes : amnion chorion allantois and yolk sac ....types of placenta ..diffused cotyledonary zonary and others

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extraembryonic membranes and placenta types

1. S.Y.B.Sc ZOOLOGY COURSE 10 UNIT 1 COMPARATIVE EMBRYOLOGY SUB TOPIC: EXTRA-EMBRYONIC MEMBRANES Date : 21-01-2022

2. Somatopleure : Amnion & Chorion Splanchnopleure : Yolk Sac & Allantois

3. ENDOGENOUS YOLK SAC IN TELEOST FISHES ENDOGENOUS YOLK SAC IN TELEOST FROG

4. EXOGENOUS YOLK SAC IN SHARK

5. AMNION Formed from Somatopleure Definition: Protective membrane that surrounds embryo forming a sac of fluid Formed from : somatic mesoderm and ectoderm Cavity is called amniotic cavity & filled with amniotic fluid Amniotic fluid is viscous : Provides Free flotation of embryo for its even growth Efficient shock absorber (to protect from mechanical injury) Protects embryo from dessication Amnion is connected to embryo at ventral hollow stalk called somatic umbillicus

6. CHORION The outermost layer of extra-embryonic membrane Involved in respiration in birds The wall of the chorion is made of two layers: Outer Ectoderm & Inner somatic mesoderm

7. ALLANTOIS

8. Placenta Characteristic feature of viviparous vertebrates Not seen in egg laying animals (Yolk reserve) Foeto -maternal Association (To accomplish Nourishment) Placenta in mammals Egg laying mammals: Lactate (but no placenta) Marsupials /Therians (Kangaroo) : Morphological & histological basis Intimacy of foeto -maternal association Extra embryonic membrane comes in contact with reproductive tract of mother and forms close association Why placenta is form?/Functions Carbon dioxide, oxygen , hormones, toxicants are exchanged at placenta through network of capillaries

9. Chorio -Vitelline Placenta Marsupial Mammals Rudimentary , short lived placenta Milk (from Pouch) Nourishment : Nourishment from placenta negligible Allantois small Yolk sac + Chorion = Yolk Sac placenta / chorio vitelline placenta Blood supply though vitelline blood vessels Chorion does not form Villi

10. Yolk sac placenta

11. Chrio-allantoic or allantochorionic placenta Yolk sac rudimentary Chorion + Allantois fuse together Chorion developes villi to get more closely associated with maternal mucosa Seen in Marsupials & Eutherians

12. TYPES OF PLACENTA

13. Chorionic Placenta When allantois and chorion association is insignificant or absent Based on type of embryo implantation in uterine wall and attachment with embryo Central/Superficial Implantation Eccentric Implantation Interstitial Implantation

14. Central/Superficial Implantation Embryo remains In centre of uterine lumen & extra-embryonic membrane make superficialcontact with Uterine mucosa Eg . Lower mammals : marsupials , eutherians (Dogs, sheep, cat , cow, rabbit) Eccentric implantation : Embryo lies on one side of endometrial wall Embryo is not entirely covered entirely by uterine epithellium Eg . Mouse & rat Interstitial implantation Embryo is completely buried inside the uterine mucosa Embryo is completely covered by endometrial tissue Eg . Human , chimpanzee , guinea pig

15. TYPE OF PLACENTAE Based on implantation Central/Superficial Implantation Eccentric Implantation Interstitial Implantation Based On Morphological characteristic features Diffused Cotyledonary Zonary Disocoidal Intermediate Based on intimacy of foeto -maternal tissue Non-deciduous placenta Deciduous placenta Contra-deciduous placenta Based on Histological characteristics Epithelio-chorial placenta Syndesmo-chorial placenta Endothelio-chorial placenta Hemo-chorial placenta Haemo — endothellial placneta

16. Based On Morphological characteristic features Diffused Cotyledonary Zonary Disocoidal Intermediate

17. DIFFUSED PLACENTA Villi are distributed uniformly on the surface of the chorion except terminal ends It is seen in: Mare, pig etc COTYLEDONARY PLACENTA Villi are developed in patches on chorionic surface while remaining part of chorion is smooth These patches are called as cotyledons Sheep, goat, cattle Based On Morphological characteristic features

18. INTERMEDIATE PLACENTA Combination of diffused & cotyledonary placenta. There are some isolated villi present between cotyledonary patches Eg . Camel &Giraffe ZONARY PLACENTA Villi are developed along a equatorial belt on blastocyst. This belt is usually elliptical in shape Eg . Carnivores like dog, fox, lion, tiger, mongoose DISCOIDAL PLACENTA Villi are confined in a disc like area, eccentrically on blastocyst. Eg . Rat , Bat, Rabbit , Bare, monkeys

19. THANK YOU COMPARATIVE EMNBRYOLOGY ENDS HERE