4. Preattachment development of the embryo Senger, pg 286 8-cell embryo morula early blastocyst hatched blastocyst

9. Extraembryonic Membranes Senger, pg 290

10. Function of Fetal Membranes and Fluids Yolk Sac – Originates from fetal midgut. Nutrient supply for early embryo. Absorbs uterine sectretions from endometrium to stimulate early embryonic development. Amnion – Innermost membrane directly surrounding the fetus. Protects from injury and provides lubrication for parturition. Prevents lung collapse and opens digestive tract. Allantois – Originates from the gut and forms the umbilicus. Supports blood vessels. Reservoir of nutrients and wastes. Chorioallantois: product of fusion between the allantoic and chorionic membranes Chorion – Outermost membrane in direct contact with uterine tissue. Becomes vascularized by allantoic vessels. Site of hormone production, nutrient and gas exchange.

13. Diffuse Placenta Uterine Endometrium Fetal Chorion Senger, pg 308

14. Cotyledonary Placenta Senger, pg 310

15. Cotyledonary Placenta Fetus Umbilicus Placentomes

16. Types of Placentas Maternal Blood Maternal endothelium Maternal connective tissue Maternal epithelium Fetal epithelium Fetal connective tissue Fetal endothelium Fetal Blood Type = degree of invasiveness, based on layers separating maternal blood from the fetal epithelium Least Invasive epitheliochorial synepitheliochorial endotheliochorial Most Invasive hemochorial

20. Relative Development Cleavage Differentiation Growth More than 50% of the total weight of the fetus at parturition is gained during the last two months of gestation fertilization ZP Disintegration parturition placentation Shift from classification as embryo to fetus

21. Days 45-147 Days 11-45 Days 0-10 Sheep Days 68-336 Days 15-68 Days 0-14 Mare Days 28-113 Days 7-28 Days 0-6 Sow Days 45-283 Days 13-45 Days 0-12 Cow Growth Differentiation Cleavage Species

22. Parturition The process by which the uterus expels the products of conception

36. Senger, pg 321

37. synepitheliochorial Cotyledonary IFNtau 147 days Sheep epitheliochorial Diffuse Migration-estrogen/protein 336 days Mare epitheliochorial Diffuse Estrogen 113 days Sow epitheliochorial Cotyledonary IFNtau 283 days Cow Placental Type Placental Shape Pregnancy recognition signal Gestation Length Species

38. Lactation

40. Mammary Gland Anatomy Tissue of Mammary Gland: Secretory cells Alveoli Myoepithelial cells Ducts Blood Vessels

41. Mammary Gland Anatomy

42. Initiation of Lactation: (lactogenesis) 1. Increased formation and development of duct system 2. Increased formation and development of secretory cells 3. Development of capacity for milk synthesis

43. Hormones Required for Lactation 1. Estrogen : stimulates duct growth 2. Progesterone : stimulates alveolar development 3. Growth Hormone (somatotropin): stimulates milk production 4. Thyroid Hormones: enhance development and function of mammary tissue 5. Corticoids: enhance synthesis of enzymes necessary for milk biosynthesis 6. Prolactin: initiation of lactogenesis 7. Oxytocin: stimulate myometrial contractions to release milk from alveoli to ducts 8. Insulin: maintain function and survival of secretory cells 9. Placental Lactogen: general mammary tissue growth Adrenalin: prevents milk ejection; blocks secretion of oxytocin, causes vasoconstriction in mammary gland Administration of bST to dairy cattle increases milk production 15-40%. Suggested that bST stimulates insulin-like growth factor-1 (IGF-1) which stimulates the secretory cells.