Pregnancy Flashcards
capacitation
- sperm must undergo capacitation in the female tract before they become fertile
- head of sperm is stripped of surface molecules and seminal plasma proteins
fertilization penetration
- sperm penetrates the cumulus cells
- binds to the zona pellucida
- triggers acrosomal reaction
- acrosomal enzymes weaken ZP
- sperm penetrates ZP
- fuses with plasma membrane of ovum
- triggers reaction to block binding of other sperm
- fertilin (on sperm_ binds with ZP3 receptors (on ZP)
- acrosome reaction (releases hydrolytic enzymes)
- sperm binds with ovum plasma membrane
- triggers release of cortical granules (prevents other sperm from fusing with membrane, inactive ZP3 receptors, prevents entry of additional sperm)
morula
- cleavage divisions ( 2 cell, 4 cell, cytoplasm keeps being divided between cells)
- ball of cells within ZP
blastocyte
- trophoblast (outer layer of cells, will become placenta and membranes)
- inner cell mass ( will become embryo/fetus)
- blastocele (fluid filled pocket )
- hatching ( must hatch out of zona pellucida
embryonic membranes
amnion - cushion
allantois - waste collection
chorion - fetal placenta, chorioallantois
maternal recognition of pregnancy
- CL will regress unless dam recognizes pregnancy
- ruminants - interferon tau ( secreted by blastocysts day 13-21, blocks oxytocin receptor synthesis in endometrium (blocks production of PGF2a
- humans - human chorionic gonadotropin
- sows - estrodiol 0 secretes blastocysts
pregnancy diagnosis
- transrectal palpation - detectable by 5-6 weeks post breeding( operator fatigues/injuries)
- transrectal ultrasound
- blood or milk - progesterone
elongation of attachement
- in ruminants, rapid growth of trophectoderm
- grows into both uterine horns
- attached to endometrium
placenta
temporary organ = only during pregnancy
maternal- fetal interface = exchange of nutrients and waste
endocrine organ = secretion into maternal and fetal circulation, progesterone, estrogens, chorionic gonadotropin
- relaxin - relaxin of connection tissue
- placental lactogen (development of mammary gland )
types of placenta
- classified based on distrubution of chrionic villi
- diffuse - even distribution (pigs and horses)
- cotyledonary - buttons (ruminants )
- zonary - band (cats and dogs)
- discoid - disc ( humans and rodents)
cotyledonary placenta
- placentome ( cotyledon - fetal, caruncle - maternal)
- cattle 70-120 placentomes, up to 5-6cm at term
freemartin
heifer bron twin to a bull calf
- >90% infertile
- male/female twin
- fusion of chronic villi between twins (anastomoses) shared blood flow (chimera)
- exposure to anti-mullerian hormone and testerone from the male
- masculinization underdeveloped tract
epitheliochorial
- 6 layers (ruminants, pigs and horses)
- greatest separation
- no trasnfer of antibodies - needs colostrum for passive immunity
endotheliochorial
- 5 layers (dogs and cats)
- degration of endometrial basement membrane
hemochorial
- 3 layers (humans and rodents)
- maternal blood directly contacts chorionic epithelium
- transfer of passive immunity ( antibodies )
parturition
3 phases
- dilation of cervix
- rythmic contractions of the myometrium to expel of the fetus
- expulsion of the placenta
cervical softening
- cervix remains tightly closed during pregnancy
- relaxin = hormone produced by CL and placenta
- relaxes connective tissue (collagen of the cervix, increases elasticity of pelvic ligaments)
- PGF 2a
- stimulated by high estrogen
- local production of enzymes that break down collagen
preparation - uterus
- creation of connexons
- gap junctions between myometrial cells allows uterus to contract as a unit
- stimulated by high estrogen at the ens of gestation
- synthesis of oxytocin receptors in myometrium (stimulated by high estrogen, critical for initiation)
initiation of labour
- corticotropin releasing hormone (CRH)
- produced by fetal placenta
- placental clock - sets timing of parturition
- stimulates fetal ACTH (cortisol= lung maturation (surfactant is produced), DHEA - estrogen production by placenta, precursor to estrogen)
- removal of progesterone block (converted to estrogen)
fetal lungs
- produce pulmonary surfactant (for alveolar inflation)
- surfactant secreted into amniotic fluid
- inflammation in uterus
- nuclear factor kB
prostaglandin production
oxytocin receptors
oxytocin
- hormones produced by hypothalamus, released from posterior pituitary
- powerful muscle stimulant
- labour initiates due to increase in number of receptors (ability to repsond to oxytocin, not increase in secretion)
- secretion stimulation by pressure of fetus on cervix (positive feedback loop)
pitocin = synthetic oxytocin used to induce labour and contractions
positive feedback cycle
- uterus contraction
- cervical stretch
- oxytocin (uterus contraction)
- PGF 2a (increases sensitivity to oxytocin, uterus contraction)
delivery of fetus and placenta
- coordinated contractions of uterus and abdominal muscles
- normal presentation - head first with feet extended (dystocia - diffisult birth)
- second wave of contractions to deliver placenta
- placentophagy - eating the placenta
