Term
| Describe & elaborate on the steps of sperm transport |
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Definition
1. Immediate transport from vagina to cervix
-some retrograde loss, phagocytosis
2. Cervix
-folds help to remove non-motile sperm & some abnormal sperm
3. Uterus
-neutrophils remove dead sperm but also some functional ones as well
-capacitation begins
4. Oviduct
-capacitation completed, gained hypermotility
5. Fertilization
-acrosome reaction
-penetration of oocyte
-male & female pronuclei form |
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Term
| Describe the structure of the oviduct as it relates to oocyte transport |
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Definition
-well developed internal mucosa in the infundibulum & ampulla
-ciliated epithelium is under control of E2, beats to move fluid towards the uterus
-secretory cells provide nutrients for oocyte & antimicrobial compounds
-smooth muscle layers can contract to assist oocyte transport |
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Term
| What is the first 'trap' in sperm transport? |
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Definition
cervical folds
-acidic mucus produced kills microorganisms & create a mucus plug |
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Term
| What role does E2 play in facilitating sperm passage through the cervix? |
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Definition
-makes mucus less acidic, thinner, more elastic
-forms strands/privilege pathways for sperm to get through |
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Term
| Describe process of AI in cows & reasons for failure to become pregnant |
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Definition
Semen dose deposited at body of uterus (first AI) or anterior cervix (repeat AI)
-cow not in heat
-poor AI technique, deposited at wrong side of uterus
-early embryonic death (poor/no attachment) |
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Term
| What are the primary sources of sperm loss in AI with cows? |
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Definition
retrograde flow
wrong horn |
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Term
| Describe the steps involved to initiate contractions of the female reproductive tract to achieve effective sperm transport (4) |
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Definition
1. Mating/ cervical manipulation
2. Nervous stimulation sends signal to posterior pituitary
3. Oxytocin is secreted
4. Estradiol:P4 ratio is increased, muscular contractions of uterus & oviducts help move sperm upwards |
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Term
| What is capacitation? Where does it take place? |
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Definition
loss of surface proteins on sperm, triggering reorganization of plasma lipid mmb composition
-initiated in uterus, will be completed by the time sperm reach oviduct |
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Term
| What 3 important steps are required for fertilization to take place |
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Definition
-penetration of corona radiata
-perforation of zona pellucida (acrosome reaction)
-transfer of nucleus |
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Term
| How is the corona radiata penetrated? |
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Definition
| -first sperms to reach the oocyte release enzymes which dissociates the granulosa cells |
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Term
| What is the acrosomal reaction? What is required for the zona pellucida to be penetrated? |
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Definition
-membrane proteins on cell surface bind to glycoproteins of zona pellucida
-acrosin + hyaluronidase is released in close proximity to oocyte
-inner & outer acrosomal membranes fuse |
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Term
| Where does fertilization occur? |
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Definition
| at the ampulla-isthmic junction |
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Term
| Describe the steps of fertilization |
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Definition
1. Oocyte arrives at junction, cumulus is lost
2. Hyperactivated spermatozoa pass though remaining cumulus, bind to zona pellucida
3. Acrosome reaction occurs, vitelline membrane of zona pellucida is penetrated
4. Cortical granules are lost, 2nd polar body is extruded
5. Syngamy (gametes unite) |
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Term
| Describe the cell divisions that take place during fertilizatoin |
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Definition
-oocyte complete meiosis as sperm enters
-male & female haploid pronuclei fuse to form a zygote (diploid) ... 1 large cell
-zygote divides every 24hrs, forming smaller cells (but not growing in size)
-unattached embryo converts to blastocyst when the morula enters the uterus |
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