Pregnancy & Lactation

1. Pregnancy & Lactation

2. Fertilization • After breeding, the sperm and egg unite to form a zygote. • After the nuclei have fused the zygote becomes an embryo. • Embryos do not have any anatomical form.

3. Fertilization • Fetus is the potential offspring still within the uterus. • Conceptus is the product of conception which includes: • Embryo • Membranes • placenta

4. Development of zygote • After fusion of nuclei, the zygote undergoes a series of mitotic division. • The first division creates a two celled embryo. • These cells are called blastomeres. • Each blastomere undergoes divisions yielding 4, 8, and 16 daughter cells. • Twins are derived from blastomeres of a 2-celled embryo that divide independently.

6. Development • When a solid ball of cells is formed and blastomeres can’t be counted, the embryo is called a morula. • During this stage, fluid fills the cell and creates a cavity called a blastocoele. • When a distinct cavity is recognized, the embryo is called a blastocyst. • After growing, the blastocyst starts to crack the membrane and now becomes a free-floating embryo in the uterus.

8. Development • http://www.youtube.com/watch?v=cO6vFYH7QJA

10. Development • As the hatched blastocyst continues to grow, it forms three different layers known as the endoderm, ectoderm, and mesoderm. • Ectoderm • CNS • Sense organs • Mammary glands • Sweat glands • Skin • Hair • Mesoderm • Circulatory • Skeletal • Muscle • Reproductive tracts • Kidneys • Urinary ducts • Endoderm • Digestive • Liver • Lungs • Pancreas • Thyroid gland • Other glands

11. Break time • http://www.youtube.com/watch?v=WpK9XNAQfH4

12. Placentas

13. Placenta • The placenta is a transient organ of metabolic interchange between mother and offspring. • Also produces a variety of hormones. • Placentas have 4 different membranes: • Allantois • Yolk sac • Amnion • Chorion

14. Placental Membranes • Yolk Sack • In birds to nourish embryo • In mammal a source of blood cells and primordial germ cells • Amnion • Non-vascular, fluid filled • Fluid produced by fetus • Protective cushion • Ruptures at birth

15. Placental Membranes • Allantois • Blood vessels • Fuses with chorion • Brings blood vessels to chorion • Chorion • Outermost membrane • Attachment to mother

16. Amniotic Cavity Chorion Amnion Allantois Cavity Yolk Sack Allantochorion (Chorioallantois) Cotyledon

17. Placenta • The functional unit of the placenta is the chorionic villus. • Placentas are classified according to their chorionic villi. • The four classifications are: • Diffuse • Zonary • Discoid • Cotyledonary

18. Placenta • Diffuse: • Pig & horse • Characterized by having uniform distribution of the villi covering the surface. • Microcotyledons are the functional interface between mother and offspring

20. Placenta • Zonary: • Dogs & cats • A prominent region of exchange that forms a zone around the middle of the conceptus.

21. Placenta • Discoid: • Rodents & primates • Characterized by having one or two distinct adjacent discs. • These discs interface with the endometrium and provide nutrient and metabolic waste exchange.

23. Art

24. Placenta • Cotyledonary • Ruminants (cows, sheep, goats, deer, etc.) • Characterized by having numerous, button-like structures called cotyledons. • Cotyledons are the placental unit for blood vessels and connective tissue. • A placentome consists of a fetal cotyledon and a maternal cotyledon.

26. Re-cap

27. Break • http://www.youtube.com/watch?v=Yk9n48ZB8XQ • Stand up and shake off your hands

28. Parturition

29. Parturition • A complex cascade of events • Triggered by the fetus • Separated into three stages: • 1. Initiation of contractions • 2. expulsion of fetus • 3. expulsion of membranes

30. Stage 1 • “Labor” • Initiated by fetus • Fetus becomes stressed due to lack of • Nutrients • Oxygen • Space • This stress leads to a series of hormone secretions initiating contractions and dialation.

31. Stage 1 comparison • Cow – 2 to 6 hours • Dog 6 to 12 hours • Horse – 1 to 4 hours • Alpaca – 2 to 6 hours • Human – 8+ hours

32. Stage 2 • Expulsion of the fetus • As the hormones increase so do the contractions • As the contractions increase, the feet and head of the fetus put pressure on the membranes causing them to rupture. • As the fetus enters the birth canal, they become hypoxic causing stronger contractions. • Positive feedback loop

33. Stage 2 comparison • Cow – 30 to 60 min • Dog – 6 hours • Horse – 12 to 30 min • Alpaca – 5 to 90 min • Human – 2 hours

34. Stage 3 • Membrane expulsion • In most species, stage three quickly follows stage 2. • Easy process • Retained placenta • Can cause disease, need to be removed manually

35. Stage 3 comparison • Cow – 6 to 12 hours • Dog – 15 minutes • Horse – 1 hour • Alpaca – 45 to 180 min • Human – 1 hour or less

36. Dystocia • Difficult birth • Difficulties usually occur in the second stage due to the fetus not positioned correctly. • Other causes • Size of fetus • Improper rotation (head comes first) • multiple births

37. Puerperium • The period after birth in which the reproductive tract returns to non-pregnant conditions. • 4 events of puerperium • Myometrial contractions • Endometrial repair • Resumption of ovarian function • Elimination of bacteria

38. Lactation