3 - fertilisation, luteolysis and early embryo

Question 1

oestrus cycle of the bitch

Answer 1

moneoestrus
spontaneous ovulators
pro-oestrus and oestrus last 6-10 days
LH surge = late pro-oestrus/early oestrus
ovulation occurs over a couple of days 48-72 hours after LH surge
corpus luteum lasts 60-70 days - no luteolytic mechanism

Question 2

ovulation of bitch

Answer 2

takes 2-3days and progesterone increases before ovulation

Question 3

12 month cycle in bitch

Answer 3

anestrus - 5 months
proestrus - 9 days = follicular phase
estrus - 9 days = follicular phase
diestrus - 2 months = luteal phase

Question 4

fertilisation of bitch eggs

Answer 4

viable for 5 days so fertilisation period is 2-5 days after ovulation

Question 5

where does fertilisation occur in the bitch

Answer 5

oviduct - ampulla = wider part of oviduct near to ovary

Question 6

where semen is deposited

Answer 6

vagina - cows, sheep, dog and cats
cervix - pigs
cervical lumen - horses

Question 7

how is semen aided in transport within female tract

Answer 7

smooth muscle contractions of female tract
sperm motility

Question 8

what must sperm do for successful fertilisation

Answer 8

transverse the cervix
transport through uterus to the oviduct
bind to the zona pellucida - capacitation reveals specific receptor on sperm for zona protein zp3
undergo acrosome reaction - release enzymes to digest ZP
penetrate the zona pellucida and fuse with the oocyte membrane - results in zona block - biochemical changes in zona pellucida and or oocyte membrane to prevent polyspermy

Question 9

what is capacitation

Answer 9

within female tract spermatozoa undergo changes that allow them to become fertile

Question 10

stages of capacitation

Answer 10

epididymis - surface molecules of sperm coated in seminal plasma proteins that mask membrane molecules
female tract - seminal plasma coating and some surface molecules removed revealing molecules that can bind to zona pellucida of oocyte

Question 11

the isthmus

Answer 11

main site of sperm storage until ovulation

Question 12

acrosmal reaction

Answer 12

very quick - 15 mins
acrosome swells , membrane fuses with over-laying plasma membrane, vesicles form followed by exocytosis of proteolytic enzymes
acrosome - reacted sperm then work their way though the ZP - 5-20mins