Pregnancy

Question 1

capacitation

Answer 1

• sperm must undergo capacitation in the female tract before they become fertile
• head of sperm is stripped of surface molecules and seminal plasma proteins

Question 2

fertilization penetration

Answer 2

• 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)

Question 3

morula

Answer 3

• cleavage divisions ( 2 cell, 4 cell, cytoplasm keeps being divided between cells)
• ball of cells within ZP

Question 4

blastocyte

Answer 4

• 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

Question 5

embryonic membranes

Answer 5

amnion - cushion
allantois - waste collection
chorion - fetal placenta, chorioallantois

Question 6

maternal recognition of pregnancy

Answer 6

• 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

Question 7

pregnancy diagnosis

Answer 7

• transrectal palpation - detectable by 5-6 weeks post breeding( operator fatigues/injuries)
• transrectal ultrasound
• blood or milk - progesterone

Question 8

elongation of attachement

Answer 8

• in ruminants, rapid growth of trophectoderm
• grows into both uterine horns
• attached to endometrium

Question 9

placenta

Answer 9

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 )

Question 10

types of placenta

Answer 10

• 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)

Question 11

cotyledonary placenta

Answer 11

• placentome ( cotyledon - fetal, caruncle - maternal)
• cattle 70-120 placentomes, up to 5-6cm at term

Question 12

freemartin

Answer 12

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

Question 13

epitheliochorial

Answer 13

• 6 layers (ruminants, pigs and horses)
• greatest separation
• no trasnfer of antibodies - needs colostrum for passive immunity

Question 14

endotheliochorial

Answer 14

• 5 layers (dogs and cats)
• degration of endometrial basement membrane

Question 15

hemochorial

Answer 15

• 3 layers (humans and rodents)
• maternal blood directly contacts chorionic epithelium
• transfer of passive immunity ( antibodies )

Question 16

parturition

Answer 16

3 phases
- dilation of cervix
- rythmic contractions of the myometrium to expel of the fetus
- expulsion of the placenta

Question 17

cervical softening

Answer 17

• 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

Question 18

preparation - uterus

Answer 18

• 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)

Question 19

initiation of labour

Answer 19

• 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)

Question 20

fetal lungs

Answer 20

• produce pulmonary surfactant (for alveolar inflation)
• surfactant secreted into amniotic fluid
• inflammation in uterus
• nuclear factor kB
  prostaglandin production
  oxytocin receptors

Question 21

oxytocin

Answer 21

• 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

Question 22

positive feedback cycle

Answer 22

• uterus contraction
• cervical stretch
• oxytocin (uterus contraction)
• PGF 2a (increases sensitivity to oxytocin, uterus contraction)

Question 23

delivery of fetus and placenta

Answer 23

• 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