Fertilization, Pregnancy, & Parturition Flashcards by Ashley Ackert

Maternal Recognition of Pregnancy in Bitches

No signal need

CL maintained for duration of normal gestation regardless of pregnancy status

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Yolk Sac

Early nutrient supply for early embryo

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Microcotelydons

Present on fetal side in horse pregnancy

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Allantois

Fuses w/ chorion

Carries blood vessels of placenta

Reservoir for nutrients & waste

Site of umbilical cord attachment

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Amnion

Protects fetus from injury

Lubrication for parturition

Waste reservoir

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Labyrinthine Placental Interdigitation

Fetal vasculature forms sponge-like configuration with maternal side

Ex. dog

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Epitheliochorial

5-6 layers separating maternal & fetal circulation

Ex. horses, pigs, ruminants

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Hemochorial

3 layers separating maternal & fetal circulation

Ex. primates, rodents

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Anencephaly in Parturition

Fetuses without functional brain have delayed timing of parturition (no functional control of pituitary)

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Lamellar/Microcodyledonary Placental Interdigitation

Elaborate folding of endometrium onto which trophoblast is draped

Ex. horse

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Maternal Recognition of Pregnancy in Queens

Fetoplacental relaxin may stimulate prolactin

Prolactin is luteotropic

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Puerperium

Time from fetal delivery until complete uterine involution

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Maternal Recognition of Pregnancy in Mares

Conceptus migration

Secretion of PGE2 by conceptus promotes oviductal transport

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Villous Placental Interdigitation

Extensive tree-like branches of fetal vasculature

Ex. cow

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Zonary Placenta

Most intimate contact found in belt-like area encircling conceptus

Single (dog, cat)

Double (ferret, raccoon)

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Chorion

Attaches to uterus

Absorbs nutrients from uterus

Maternal/fetal gas exchange

Hormone production

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Zona Block

Prevents multiple sperm from fertilizing oocyte (polyspermy)

Cortical granules exocytosis

Hardening of zona pellucida (ZP2, ZP3)

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Placenta (roles)

Nutrient exchange

Gas exchange

Stores waste

Protective

Endocrine functions

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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