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CHAPTER 38: PREGNANCY & PARTURITION (Pregnancy (Life span extension of…
CHAPTER 38: PREGNANCY & PARTURITION
Pregnancy
Embryo: Fusion of oocyte & spermatozoon in oviduct
Spermatozoa
oxidative (aerobic) to glycolytic (anaerobic)
coalesce in special reservoir in female tract
release a few sperm on a continuous basis
changes
capacitation
removal of glycoprotein coat
acrosome reaction
release of:
hyaluronidase → breakdown of HA in intercellular matrix surrounding oocyte
acrosin → digest acellular coating around oocyte
change surface of sperm to allow fusion w oocyte
removal of acrosomal cap
result in tail movement: flagellar beat
Oocyte
undergoes 1st meiotic division before fertilization *depending on species
Embryo
develop to morulla (4-5 days)
allow
uterus → finish inflammatory response
endometrial gland → secrete nutrients under progesterone influence from developing CL
Life span extension of CL: important in LDA & cats
DA luteal activity controlled by uterus, PGF2α important for establishment of pregnancy
Embryo
synthesize estrogen
produce substances that modify uterine production of PGF2α
movement
result in suppression of PGF2α synthesis (cow)
modification of secretion mode: pulsatile → continuous (sheep)
14 days before pregnancy/postovulation → trophoblastin
Cat CL last for 35-40 days after ovulation regarless of the presence of pregnancy
early modification of luteal activity not important for preganancy establishment
Luteal phase in nonpregnant animals is often slightly longer than pregnant animals
Luteotropin *depend on species
Synergism of relaxin + progesterone
LH
Prolactin
Chorionic gonadotropin (CG) (by trophoblastic cell of embryo) [primates, equine]
Implantation
Interstitial (primate)
Eccentric (dog, cat)
Caruncle (ruminant)
Villus (horse, pig)
Placenta as endocrine organ
Production of progesterone
Primates
early in gestation
maintain pregnancy within 2-3w after implantation
unable to produce progesterone from estrogen
Domestic animal
later in pregnancy
sheep day 50-150, horse day 70-340, cat day 45-65
never produce enough progesterone for preg. → cattle, pigs
Produce relaxin (cat, dog, horse; early pregncy.)
Produce placental lactogen
primate, goat, sheep, cattle
somatotropic & lactogenic effect
prolactin-like properties
Parturition
Increased estrogen and PGF2α → fetal cortisol initiate delivery
Estrogen increased in latter part of pregncy.
stimulate production of contractile protein & gap junction
increase contractile potential
facilitate contractile process
Fetal
adrenal cortex
hypothalamus
adenohypophysis
Fetus cortisol secretion
increase estrogene & thus increase synthesis & release of uterine PGF2α
PGF2α effect
release of intracellular Ca ion
cervix relaxation & dilation
regression of CL & progesterone withdrawal (cat, dog, cattle, goat)
overcome suppressive effect of progesterone (horse, primate)
Estrogen
induce oxytocin receptor formation
Oxytocin
synergistic with PGF2α
Relaxin
separation of pubic symphysis
relaxation of pubic muscle
CL: cow pig
placenta: cat, dog, horse