Fertilization Flashcards
Which species deposit sperm into the anterior vagina?
Cow
Ewe
Doe
Bitch
What are the post-capacitation events leading to fertilization?
- hyperactive motility
- binding to zona pellucida
- acrosomal reaction
- penetration of zona pellucida
- sperm-oocyte membrane fusion
- sperm engulfed
- decondensation of sperm nucleus
- formation of male pronucleus
Describe the acrosome reaction
- enzymes are released
- penetration of sperm through zona pellucida
- sperm enter perivitelline space
- membranes fuse
- cortical reaction induced
Describe the cortical reaction
- sperm head attaches to oocyte plasma membrane and initiate blockage of polyspermy
- ZP hardens and vitelline membrane changes
Where does fertilization take place in the cow?
apulla-isthmus junction of the oviduct
What is syngamy?
fusion of male and female pronuclei
What are the barriers to fertilization?
- cumulus cells (surround ovulated oocyte)
- zona pellucida
- oocyte membrane
What must occur before the embyro can attach to the uterus?
- develop within the zona pellucida
- subsequent hatch from ZP
- maternal recognition of pregnancy
- formation of extra-embryonic membranes
What is totipotency?
the ability of a single blastomere to develop into a fully formed individual
What is the most totipotent cell?
zygote
Describe what occurs in development of a free martin
- AMH from bull block mullerian ducts, resulting in posterior vagina with no anterior vagina
- testosterone from bull causes clitoral enlargement and brain changes
- ovaries do not grow, but are chimeric (ovotestis)
What happens if there is no maternal recognition of the embryo?
PGF2a is produced, lysis of the CL, and the animal goes back to estrus
- the bitch will not return to cycle
Describe maternal recognition in ruminants
- interferon tau is produced by trophoblastic cells
- inhibits oxytocin receptor synthesis, therefore no PGF2a release
Describe maternal recognition in the sow
- blastocyst produces estradiol
- re-routes PGF2a release into the uterine lumen where it is destroyed
- need at least 2 conceptus in each horn
Describe maternal recognition in the mare
- PGE2 is produced by the embryo
- blastocyst trans-uterine migration
- reduced synthesis of PGF2a
What is the functional unit of the placenta?
chorionic villi
What are the layers in an epitheliochorial fetal/maternal relationship?
- endometrial endothelium
- endometrial interstitium
- endometrial epithelium
- chorionic epithelium
- chorionic interstitium
- chorionic endothelium
What are the layers in an endotheliochorial fetal/maternal relationship?
- endometrial endothelium
- endometrial interstitium
- chorionic epithelium
- chorionic interstitium
- chorionic endothelium
What are the laters in a hemochorial fetal/maternal relationship?
- chorionic epithelium
- chorionic interstitium
- chorionic endothelium
- direct contact with maternal blood pool
Which species have epitheliochorial fetal/maternal relationship?
sow, mare, camelid, cow, ewe, doe
Which species have endotheliochorial fetal/maternal relationship?
bitch and queen
In a cotyledonary placenta, which is the maternal portion, and which is the fetal portion?
maternal - caruncles
fetal - cotyledons
What is a placentome?
caruncle/cotyledon complex
Which species have diffuse placenta?
mare, sow, camelid
Which species have cotyledonary placenta?
cow, ewe, doe, deer
Which species have zonary placenta?
bitch, queen, ferret
What are the functions of the placenta?
- stimulate ovarian function (eCG)
- stimulate mammary function (lactogen)
- induction of parturition (convert P4 to estrogens)
- assist in parturition (relaxin and estrogen)
- maintain pregnancy (P4)
What are endometrial cups?
- unique to the mare
- produces equine chorionic gonadotropin
- helps with luteinization of secondary CL
