ANS 3319C Reproductive Physiology and Endocrinology
Fertilization
Sperm Transport, Capacitation, & Fertilization 1) Site of semen deposition natural mating
♦ Cranial vagina: cow, sheep, rabbit, primates, dog, cat, rodents
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Rodents: gel plug produced for vagina, prevents retrograde sperm loss
♦ Cervix: Pig
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Gel fraction: ê retrograde sperm loss
♦ Cervical lumen into uterus: horse
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Gel fraction: ê retrograde sperm loss
2) Site of semen deposition artificial insemination (Fig 12-11 & 12-12)
♦ ____________________________: mare, cow, sheep (Fig 12-6)
♦ ____________________________: sow (Fig 12-7)
♦ ____________________________: dogs & cats (Fig. 12-7)
3) Sequence of events post copulation (Fig 12-1)
Fig. 12-1
5
Fertilization
• acrosome reaction
• spermatozoon penetrates
oocyte
• male and female pronuclei form
4
Immediate Transport
• retrograde loss
• phagocytosis
• entrance into
cervix/uterus
2
Oviduct
Cervix
• capacitation completed
• hyperactive motility
3
Uterus
• capacitation initiated
• phagocytosis
1
• “privileged”
pathways
• removal of
non-motile
sperm
• removal of
some
abnormalities
117 ANS 3319C Reproductive Physiology and Endocrinology
Fertilization
4) Sperm loss from tract
♦ Retrograde transport
♦ Phagocytosis by neutrophils (WBC): vagina & uterus (Fig 12-2)
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Digest some sperm (foreign to female)
♦ No real (-) effect on fertility
5) Cervix function
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♦ ____________________________________________ (amount varies between species)
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Cow: two types of mucous (Fig 12-3)
♦ Sialomucin : low viscocity, secreted by basal cells of crypts
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“Privileged pathway” for sperm
♦ Sulfomucin: high viscocity, secreted by apical epithelial portions of crypts
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Sperm washed out of tract with contact
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Filter non-motile sperm??
6) Sperm transport through tract (uterus/oviduct)
♦ ___________________________________________________________________
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Seminal plasma PGF2α & PGE2
•
Unclear of what drives directionality of sperm flow
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Unclear of what drives directionality of sperm flow
♦ Rapid phase: sperm at oviduct in minutes (Function??)
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♦ Transport phase:
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118 ________________________________________________________________
ANS 3319C Reproductive Physiology and Endocrinology
Fertilization
♦ Sperm capacitation (Fig 12-4)
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Ejaculated sperm coated with proteins from seminal plasma
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______________________: proteins striped away in female tract
♦ __________________________________________________
♦ Species differences in rate & location
7) Fertilization events
♦ Sperm acquisition of hyperactivity
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♦ Sperm binding to zona pellucida (Fig 12-6)
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Zona pellucida (ZP) glycoproteins
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Specific sperm membrane proteins: bind to zona
♦ Primary zona binding region (ZBR): ZBR binds to ZP3
♦ Secondary zona binding region: acrosome reaction promoting ligand (ARPR)
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119 ANS 3319C Reproductive Physiology and Endocrinology
Fertilization
♦ Acrosome reaction (Fig 12-7)
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Sperm penetration of zona
♦ Sperm membrane fuses with outer acrosomal membrane
♦ ______________________________: formation of vesicles due to membrane fusion
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Proacrosin: inactive form of acrosin, aids sperm binding to zona
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Acrosin: hydrolizes zona proteins (+) zona penetration
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Flagellar action of tail moves sperm through zona
Exposure of sperm equatorial segment
♦ Fuses with oocyte plasma membrane
♦ Fertilization (Fig 12-8)
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♦ Requires fusion of equatorial segment & oocyte plasma membrane
120 ANS 3319C Reproductive Physiology and Endocrinology
Fertilization
121 ANS 3319C Reproductive Physiology and Endocrinology
Fertilization
♦ Cortical reaction
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Granules on periphery of oocyte plasma membrane undergo exocytosis
♦ Contents released into perivitelline space è ________________________________
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(+) biochemical changes to zona è ____________________________________
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_________________: prevents additional sperm binding oocyte plasma membrane
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Species differences in absence/presence zona & vitelline blocks
♦ Decondensation of sperm nucleus
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Reduction of disulfide cross links è nuclear material released
♦ Formation of male pronuceli
♦ Syngamy : ____________________________________________________________________
8) Sperm life span in female tract
♦ Domestic animals & humans (days)
Table 12-‐1 Duration of fertilizing ability of sperm within female reproductive tract of various species Species Fertile Life (days) Bitch 9-‐11 Camelids (Llama, alpaca, camel) 4-‐5 Cow 1.5-‐2 Mare 4-‐5 Woman 5-‐6 ♦ Superfecundation
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Bitch mated by several males during estrus
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♦ Probability of conception in women (Fig 12-9)
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122 Closer copulation is to ovulation, é chance of pregnancy