Reproduction Lecture

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Major Reproductive Patterns in Mammals. Spontaneous OvulationOvulation

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Reproduction Lecture

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1. Reproduction Lecture

2. Major Reproductive Patterns in Mammals Spontaneous Ovulation Ovulation – Copulation - Fertilization – Implantation – Development – Birth – Lactation Induced Ovulation Delayed Fertilization Delayed Development Delayed Implantation/Embryonic Diapause

3. Induced Ovulation Ovulation occurs within a few hours after copulation In felids and some rodents the follicles develop but ovulation does not occur until after copulation In Lagomorphs, final growth of the follicles and ovulation are induced by copulation

4. Delayed Fertilization There is a delay in ovulation and fertilization until long after copulation has taken place Found in many temperate zone bats of Family Vespertilionidae Copulation occurs in fall of year, sperm is stored over the winter in female uterus and vagina Ovulation occurs after hibernation season, then fertilization takes place (in spring of year)

5. Delayed Development Fertilization occurs, blastocyst implants in uterine lining but development is very slow Found in both Mega and Microchiroptera bats

6. Delayed Implantation Normal fertilization and early cell cleavage to blastocyst stage (before implantation) Blastocyst goes into dormant stage May occur in some animals at every fertilization Seals, Badgers, Weasels, Bears, some deer, armadillos

7. Delayed Implantation May occur after only some fertilizations some rodents, insectivores Some species have a “post-partum estrous” where female mates soon after birth of litter (a few hrs after) Implantation may not occur until after lactation ends

8. Embryonic Diapause Characteristic of some marsupials Like Delayed Implantation except time between birth of young and next mating is typically longer, and embryo does not develop to blastocyst before diapause Sucking of first young puts 70 – 100 cell stage embryo into diapause Diapause may last 235 days

9. Placenta Structure Placentas found in Marsupial mammals Most marsupials have a Choriovitelline Placenta Some marsupials (bandicoots) have a Chorioallantoic Placenta Placenta found in Eutherian mammals All Eutherian mammals have a Chorioallantoic Placenta

10. Choriovitelline Placenta Yolk sac is greatly enlarged Yolk sac provides majority of nutritional needs of developing embryo Embryo gains a limited amount of nutrition from mother Connection between blastocyst and uterine wall is weak

11. Choriovitelline Placenta

12. Chorioallantoic Placenta Blastocyst adheres to endometrium of uterus and sink deeply into endometrium A strong adhesion is enhanced by rapid development of chorionic villi (in eutherians) Complex extensive network of villi provides mechanical strength and increased surface area for exchange of material

13. Chorioallantoic Placenta

14. Types of Placentas in Eutherian Mammals Classification is based upon arrangement of villi that attach to endometrial lining of uterus Diffuse, villi are scattered evenly throughout uterus Cotylendonary, villi are found in evenly spaced patches throughout the uterus

15. Types (Continued) Zonary, a continuous band of villi within the uterus Discoidal, villi occupy one or two disc shaped areas within uterus

16. Types (Continued)

17. Types (Another View)

18. Another Classification of Placenta Types Based upon layers that separate maternal and fetal blood Fetal capillary walls, connective tissue, epithelial cells of fetal extra-embryonic membrane, uterine epithelial cells, uterine connective tissue, uterine capillary walls (maximum of 6 layers of tissue)

19. Various Systems Epitheliochorial System has six tissue layers Villi rest in pockets in the endometrium Found in pigs, lemurs, horses, and whales Syndesmochorial Epithelium of uterus erodes at site of attachment leaving 5 layers of separation Found in ruminating artiodactyls like cows, sheep and goats

20. Systems (Continued) Endotheliochorial Chorion of the fetus is in direct contact with capillary walls of maternal blood supply (4 layers of separation) Found in carnivores Hemochorial Chorionic villi are in direct contact with maternal blood (3 layers of separation) Found in advanced primates including humans, insectivores, bats and some rodents

21. Systems (Continued) Endothelioendothelial Maternal and fetal capillaries are next to each other with no connective tissue between them (2 layers of separation) Hemoendothelial Fetal capillaries are in direct contact with maternal blood (1 layer of separation) Found in some rodents and lagomorphs

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