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

39. Lactation • Lactation ensures that the newborn does not have to obtain food on its own. • Everything that the mother eats is broken down into the nutrients that the offspring receives. • The newborn receives all these nutrients in the form of milk. • The newborn must receive milk, colostrum, right after birth or it will die. • Colostrum contains antibodies and growth hormones

40. Colostrum vs. milk

41. The Mammary Gland • Exocrine gland; common to all mammals; Mammary glands are sophisticated sweat glands • Function: nourish the neonate - Food source: fat, protein, sugar (CHO), vitamins, minerals, water - Protection:immunoglobulins

42. Growth of the mammary glands • Between birth and puberty • The mammary gland experiences isometric growth • Between puberty and pregnancy • Grows allometrically (faster than the body) • 4 hormones responsible for growth • Progesterone, estrogen, prolactin, growth hormone • During pregnancy • Alveoli begin to develop into lobules • Placental lactogen is responsible for secreting milk

43. Anatomy

44. Anatomical differences- Inguinal • 2 Canals per teat • Camel and cow

45. Anatomical Differences- Inguinal • 1 Canal per teat • Sheep, goat

46. Anatomical Differences- Inguinal • 2-3 ducts per teat • Pig, horse

47. Anatomical Differences- Inguinal • 5-6 ducts per teat • Dog, cat, rodents, rabbits

48. Anatomical Differences - thoracic • 8-10 ducts per teat • Primates, elephants

49. Milk ejection • Transfers the milk from the alveoli to the ducts • Milk ejection is a neuroendocrine reflex requiring • Sensory activation (stimulation, auditory) • http://www.youtube.com/watch?v=tQ-TuWgw3B4 • Neural activation of hypothalamus • Oxytocin release • Contraction of myoepithelial cells • Transfer of milk into ducts

50. Cool facts • Kangaroos can nurse from two different teats; one joey can be 6 months of age another can be just born. The mother can produce two different kinds of milk. • The alpine black salamander is pregnant for 3 years. • In sea horses ,the male is responsible for giving birth. The female lays her eggs into his pouch to grow. • “Caesarian” came from Julius Caesar who was said to be born by an incision in the abdomen and uterine wall of his mother.