Placentation, Gestation, and Parturition (3) Flashcards
What are the three final prepartum steps of repro?
formation of placenta, aquisition of endocrine function of placenta, and initiation of parturition
define gestation
period of time female is pregnant
what are euthrerian mammals?
mammals with placenta
define implantation
attachment of placental membrane to endometrium
what species is true implantation?
humans
define placenta
organ of metabolic exchange between conceptus and dam
what is the placenta responsible for?
maintain pregnancy and induction of parturition
define parturition
giving birth
what inititiates parturition?
the fetus
what are the four events that occur during parturition?
myometrial contractions, dilation of cervix, expulsion of fetus, expulsion of extraembryonic membranes
define conceptus
embryo and extraembryonic membranes
define chorion villus
functional unit of fetal placenta
what are the four types of placentas?
diffuse, zonary, discoid, cotyledonary
what animal has a diffuse placenta?
pigs
describe a diffuse placenta
velvet like surface with many closely spaced chorionic villi
initial attachment of the diffuse placenta
day 12
when is the diffuse placenta well established
day 18-20
what animals have a zonary placenta?
dogs and cats
describe a zonary placenta
pigmented ring on either end, important for iron transport
transport zone equals…
poor vascularity
what animals have a cotylledonary placenta?
ruminants
describe a cotyledonary placenta
discrete button like structures called cotyledons
how many cotyledons do sheep and cows have?
sheep have 90-100, cows have 70-100
define placentome
point of interface between fetal cotyledon and maternal cotyledon that originates from the caruncles
what placenta is essentially diffuse before attachment?
cotyledonary
when does intial attachment occur for a cotyledonary placenta?
cow day 25, sheep day 16
when is the cotyledonary placenta well established?
cow day 40, sheep day 30
what are placentas classified by?
number of placental layers that separate fetal blood from the maternal blood
how many layers is an epitheliochorial placenta?
6
how many layers is an endotheliochorial placenta?
5
how many layers is a hemochorial placenta?
3
what do the hormones secreted by the placenta do?
stimulate ovarian function, amintain pregnancy, influence fetal growth, stimulate mammary function, and assist in parturiton
how many stages are there to parturition?
3
what are the three stages of parturition?
initation of conceptus, expulsion of fetus, and expulsion of fetal membranes
what is secreted by the fetus during stress?
fetal cortisol
what does fetal cortisol do?
causes enzymes to be made to convert progesterone to estradiol and causes placenta to produce prostaglandin
when does the CL start to regress?
stage one during contractions
what happens in stage two of parturition?
fetus is in the cervical canal
what is relaxin?
glycoprotein produced by CL or placenta
what does relaxin do?
stimulated by prostaglandin, softens cervix and relaxes pelvic ligaments
what initiates secretions?
estradiol
what does mucous do?
lubricates birth canal
define dystocia
difficult birth
when does dystocia typically occur?
during stage 2
three causes of dystocia
large fetus, failure to fetal rotation, multiple birth in monotoccus species
