T4: parturition Flashcards
what is a freemartin calf
-heifer: sterile
-Bull: normal/ fertile
-chorion fusion: share the fetal blood supply (day 39)
-female is exposed to more amounts of testosterone/ AM hormone
-hormones pass through the placenta, could have male features
what are the fetal adrenal changes with age
-change in adrenal size is a response to stress
- lack of space, gas exchange, nutrients
-placenta hits a max size
what is under control from the mother
fetus starts parturition, adrenal glands specifically
-not under the control from the mother
what is the organ that is responsible for initiating parturition
kidney, specifically the adrenal gland
-cortisol is released, creating adrenalin, which results in parturition and lung maturation
describe the pathway of parturition
- fetal nutritional demands/ placental insufficiency directs to the hypothalamus
- Corticotrophes Releasing hormone released through the hypothala. portal system which acts on the anterior pituitary
- the anterior pituitary is acted on, corticotropes release ACTH into circulation which act on the adrenal cortex
- this acts on fetal corticosteroids releasing cortisol
-making lung (surfactant: allows gas exchange), liver (glycogen), Thyroid (metabolism)
5.cortisol acts on the placentome
-decreases progesterone, increases estrogen and PGF2a - estrogen acts on
-uterine myometrium (gap junctions) = uterine contractions
-uterine endometrium/ oxytocin receptors = PGF2a aids in uterine contractions
-cervical ripening
-estrogen in the cow/sow triggers regression
-estrogen acts on ovary to create relaxin and aid in cervical ripening - increase in PGF2a aids in sow/cow CL regression and acts on CL in the ovary
what are the hormones that peak with fetal cortisol
estrogen, PGF2a, progesterone drops
what is an example of positive feedback
how oxytocin is released form the anterior pituitary and acts on the fetus/ placenta
-this sends nerve signals to the spinal cord, to the PVN in the brain, back to the anterior pituitary
-more oxytocin released creates stronger contractions
describe the orientation of the fetus
-fetus must reorient prior to parturition
-initially on back
-reorient so feet and head will exit first
-abnormal orientation results in dystocia
the orientation is not important in what species
the pig
what is breach
the rear of the fetus comes first
describe the distribution of prenatal loses
-fertilization=100% (under optimal conditions)
—2/3 loss is during embryonic development, due to
-imprinting
-compaction
-blastocyst hatching and formation
-failure to prevent CL regression
-maternal recognition of pregnancy
—1/3 loss during fetal stage
-crowding, placental insufficiencies, not the fetus directly
describe the stages of labor
- preparative (2-12 hours)
-myometrial contractions
-uterine pressure
-abdominal discomfort
-cervical dilation - Expulsion of fetus (30-180 mins)
-strong uterine contractions
-rupture of the allantochorion
-appearance of the amnion
-maternal recumbence and straining
-not only uterine but abdominal contractions as well
-rupture of the amnion and delivery
what is the last stage of labor
- expulsion of the placenta (1-12 hours)
-uterine contractions
-chorionic villi loosen
-expulsion of the placenta
-delayed in ruminants due to presence of cotelydons separating independently
-suckling induces oxytocin release which triggers further uterine contractions
what is dystocia and what are the complications
-difficult birth
-excessive fetal size (90% for cattle)
-abnormal presentations (5% for cattle)
-multiple births (twins)
-uterus become fatigued
what is a retained placenta
-if not expelled withing 24 hr it may be retained for 5-6 days
-most common in cattle (5-15%)
-not seen in sows/ewes
-sometimes seen in mares (retained= >4 hours)
-never want to pull out the placenta because it could damage the uterus
