Fertilization, Pregnancy, & Parturition Flashcards
Maternal Recognition of Pregnancy in Bitches
No signal need
CL maintained for duration of normal gestation regardless of pregnancy status
Yolk Sac
Early nutrient supply for early embryo
Microcotelydons
Present on fetal side in horse pregnancy
Allantois
Fuses w/ chorion
Carries blood vessels of placenta
Reservoir for nutrients & waste
Site of umbilical cord attachment
Amnion
Protects fetus from injury
Lubrication for parturition
Waste reservoir
Labyrinthine Placental Interdigitation
Fetal vasculature forms sponge-like configuration with maternal side
Ex. dog
Epitheliochorial
5-6 layers separating maternal & fetal circulation
Ex. horses, pigs, ruminants
Hemochorial
3 layers separating maternal & fetal circulation
Ex. primates, rodents
Anencephaly in Parturition
Fetuses without functional brain have delayed timing of parturition (no functional control of pituitary)
Lamellar/Microcodyledonary Placental Interdigitation
Elaborate folding of endometrium onto which trophoblast is draped
Ex. horse
Maternal Recognition of Pregnancy in Queens
Fetoplacental relaxin may stimulate prolactin
Prolactin is luteotropic
Puerperium
Time from fetal delivery until complete uterine involution
Maternal Recognition of Pregnancy in Mares
Conceptus migration
Secretion of PGE2 by conceptus promotes oviductal transport
Villous Placental Interdigitation
Extensive tree-like branches of fetal vasculature
Ex. cow
Zonary Placenta
Most intimate contact found in belt-like area encircling conceptus
Single (dog, cat)
Double (ferret, raccoon)
Chorion
Attaches to uterus
Absorbs nutrients from uterus
Maternal/fetal gas exchange
Hormone production
Zona Block
Prevents multiple sperm from fertilizing oocyte (polyspermy)
Cortical granules exocytosis
Hardening of zona pellucida (ZP2, ZP3)
Placenta (roles)
Nutrient exchange
Gas exchange
Stores waste
Protective
Endocrine functions
Horse Twins
Foal death
Not enough room in mare uterus for both placentas to have full contact w/ maternal membranes
Maternal Recognition of Pregnancy in Sows
Conceptus produces estradiol
Rerouting of endometrial PGF2alpha from circulation into lumen of uterus
Discoid Placenta
Interaction found in 1 or 2 round areas
Ex. primates, rodents
Canine - Maternal Side
Marginal hematomas (possible iron storage)
Stagnant maternal blood
Hemoglobin converted to green uteroverdin at parturition
Non-deciduate/Adeciduate
Complete separation of maternal & fetal tissues
Ex. sow, mare, some ruminants
Syngamy
Merging haploid sets of xsomes on mitotic spindle
Sperm/Oocyte Interaction
Ovulation → sperm capacitation & acrosome rxn → penetration of cumulus and ZP → Zona block & Membrane block → meiotic resumption → 2nd polar body extruded → pronuclear formation → DNA synthesis → metabolic exchange → syngamy → cleavage
Membrane/Vitelline Block
Prevents multiple sperm from fertilizing oocyte (polyspermy)
Changes in vitelline membrane polarization
Folded Placental Interdigitation
Undulations in endometrium onto which trophoblast is draped
Ex. pig
Cotyledonary Placenta
Specialized endometrium (caruncles) are in contact w/ vascularized portion of chorion (cotyledon)
Ex. ruminants
“Tau” “cow”
Maternal Recognition of Pregnancy in Ruminants
Trophoblast cells of conceptus product INF-tau
INF-tau blocks endometrial synthesis of estrogen receptors & oxytocin receptors
(no stimulation of PGF2alpha)
Fertilization
Male & female gametes unite to form single-celled zygote
Prototherian
Egg-laying mammals
Ex. Platypus, echidnas
Removal of Progesterone Block
Fetal cortisol induces placental conversion of P4 → estrogen
Endotheliochorial
4-5 layers separating maternal & fetal circulation
Ex. carnivores
Deciduate
Loss of maternal tissue (endometrium) at parturition
Ex. carnivores, humans, rodents
Placenta (definition)
Vascular organ formed in uterus during pregnancy
Maternal & embryonic/fetal tissues
Eutherian
Chorioallantoic placenta
Most mammals
Metatherian
Choriovitelline (“yolk sac”) placenta
Ex. marsupials
Trabecular Placental Interdigitation
Branching structures
Ex. human
Placentome
Caruncle (maternal) + cotyledon (fetal)
Connected by villi
Gets larger as pregnancy progresses
Diffuse Placenta
Maternal & fetal intimate contact found throughout placenta
Ex. horse, pig
Uteroverdin
Hemoglobin on maternal side of the placenta turns green during parturition
Ex. canines
Green puppies!
Stage II of Parturition
Fetal Expulsion:
Allantoic fluid followed by amniotic fluid
Active abdominal contractions
Fetus enters birth canal & is born
Ferguson Reflex
Uterine contraction → cervical stretch → afferent impulses from cervical stretch receptors → reflex oxytocin secretion → more uterine contraction
Positive feedback loop
Fetal HPA Axis
Incr. in fetal ACTH → incr. fetal cortisol → dec. P4, incr. estrogen → (PGF2alpha → luteolysis) → PGF2alpha & oxytocin → uterine contractions → Ferguson reflex → parturition
Stage III of Parturition
Fetal membrane (placental) expulsion
Oocyte Cumulus Complex (OCC)
- Cumulus layer
- Zona pellucida (ZP1, ZP2, ZP3)
- Perivitelline space (contains 1st polar body)
- Viteline membrane
Stage I of Parturition
Preparation:
Isolation from herd
Udder (colostrum, edema)
Tissue softening
Uterus begins to make small contractions
