Pregnancy, placentation, gestation Flashcards
Define syngamy
fusion of male & female pronuclei
Define embryo
organism early stages of dev. -> no anatomical form not recognisable as a species
Define conceptus
product of conception
Define morula
early embryo - has ball of cells called blastomeres
Define blastocyst…
develops from morula. has inner cell mass & cavity called blastocoele
Fetus
potential offspring recognisable as a given species
Define attachement
attachment of conceptus to endometrial wall
Steps required before attachment…
- dev. within zona pelucida (cleavage)
- hatching of embryo
- maternal recognition of pregnancy
- formation of extra embryonic membranes
Redraw early embryonic development
Without looking!
Extra embryonic membrane formation…
- pre-attachment period is long
- rapid embryonic growth mainly due to extra embryonic membrane formation
- formation of EM essential for embryo to attach to uterus
After hatched blastocyst is formed, what does it require for survival?
- adequate luteal function
- adequate progesterone synthesis
- progesterone responsive uterus
Extra embryonic membranes originate from…?
mesoderm
endoderm
trophoblast
Amnion is formed from…? how? Characteristics…
via invagination of mesodermal & trophectodermal layers
- encloses fetus in fluid-filled cavity
- hydraulic protection
- anti-adhesion material
ICM turns into …?
embryo
What forms the yolk sac? Characteristics…
expansion of mesoderm cavity & primitive endoderm
- transient (regresses in size as conceptus develops)
-
What forms the allantois? Properties…
Primitive gut from the embryo
- liquid waste from embryo
- forms fusion with chorion -> allantochorion
- contains vessels that connect fetus with placental circulation
What is the chorion?
Outer layer of the embryonic membranes
What is the allantochorion?
foetal contribution to the placenta
provides surface for attachment
Amnionic fluid…
secretions from resp. tract & mouth
protective…
Allantoic fluid…
foetal urine
secretions from allantoic membrane
allantochorion next to endometrium, stores foetal waste not transferable to mother, helps maintain osmotic pressure of foetal plasma
Maternal recognition of pregnancy involves…?
- Luteal phase must be maintained (prog. levels must be high -> embryogenesis & attachment)
- embryo signals presence to the dam
Failure of maternal recognition = ?
luteolysis, low prog. + termination of pregnancy
Describe maternal recognition of pregnancy in the bovine & ovine
INT-t (interferon tau) day gestation (d15-16 bov., d13-14 ovi.) produced by embryo -> blocks oxytocin receptors -> block PGF2alpha
Describe maternal recognition of pregnancy in swine
E2 control -> modifies excretion of PGF2alpha (exocrine PGF2a secretion)
gestation d11-12
endocrine PGF2a -> luteolysis
Describe maternal recognition of pregnancy in equine
presence & migration of conceptus
gestation d14
Placentation…
- Attachment of embryo to endometrial surface
- formation of placenta (fetal - chorion, maternal - uterine endometrium)
- metabolic exchange bwn mum & fetus
- aquisition of endo. function of placenta
Placental dev. classification based on…?
number of layers
distribution of chorionic villi
terminology…
prefix - maternal side
suffix - foetal side
eg. epitheliochorial
Epitheliochorial found in …? chorionic villi
mare - diffuse
sow - diffuse
ruminants - cotyledonary
Endotheliochorial found in …?
dog & cats - zonary
Hemochorial found in …?
humans & primates - discoid
Classification of chorionic villi? spp?
diffuse (mare & sow)
zonary (dogs & cats)
discoid (rodents & primates)
cotyledonary (ruminants)
Placentomes are..?
cotyledon (fetal) + caruncle (maternal)
Placental functions…
stimulate ovarian function
maintain pregnancy
stimulate mammary function
assist in parturition
Placenta as an endocrine organ…
relaxin & placental lactogen
Binucleate giant cells
Endometrial cups
