Sperm Transport, Capacitation, Fertilization
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 • Rodents: gel plug produced for vagina, prevents retrograde sperm loss ♦ Cervix: Pig • Gel fraction: ê retrograde sperm loss ♦ Cervical lumen into uterus: horse • 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) • ______________________________________________________________________ • ______________________________________________________________________ • Digest some sperm (foreign to female) ♦ No real (-) effect on fertility 5) Cervix function ♦ _________________________________________________________________________ ♦ _________________________________________________________________________ ♦ ____________________________________________ (amount varies between species) • Cow: two types of mucous (Fig 12-3) ♦ Sialomucin : low viscocity, secreted by basal cells of crypts • “Privileged pathway” for sperm ♦ Sulfomucin: high viscocity, secreted by apical epithelial portions of crypts • Sperm washed out of tract with contact ∗ Filter non-motile sperm?? 6) Sperm transport through tract (uterus/oviduct) ♦ ___________________________________________________________________ • Seminal plasma PGF2α & PGE2 • Unclear of what drives directionality of sperm flow • Unclear of what drives directionality of sperm flow ♦ Rapid phase: sperm at oviduct in minutes (Function??) • ________________________________________________________________ ♦ Transport phase: • 118 ________________________________________________________________ ANS 3319C Reproductive Physiology and Endocrinology Fertilization ♦ Sperm capacitation (Fig 12-4) • Ejaculated sperm coated with proteins from seminal plasma • ______________________: proteins striped away in female tract ♦ __________________________________________________ ♦ Species differences in rate & location 7) Fertilization events ♦ Sperm acquisition of hyperactivity • _____________________________________________________ ♦ __________________________________________________ ♦ Sperm binding to zona pellucida (Fig 12-6) • Zona pellucida (ZP) glycoproteins ♦ ______________________________________________________________________ ♦ ______________________________________________________________________ • 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) • ___________________________________________________________________ ∗ ________________________________________________________________ 119 ANS 3319C Reproductive Physiology and Endocrinology Fertilization ♦ Acrosome reaction (Fig 12-7) • Sperm penetration of zona ♦ Sperm membrane fuses with outer acrosomal membrane ♦ ______________________________: formation of vesicles due to membrane fusion • • ______________________________________________________________________ • ______________________________________________________________________ ∗ Proacrosin: inactive form of acrosin, aids sperm binding to zona ∗ Acrosin: hydrolizes zona proteins (+) zona penetration ∗ Flagellar action of tail moves sperm through zona Exposure of sperm equatorial segment ♦ Fuses with oocyte plasma membrane ♦ Fertilization (Fig 12-8) • __________________________________________________________________________ • __________________________________________________________________________ ♦ 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 • Granules on periphery of oocyte plasma membrane undergo exocytosis ♦ Contents released into perivitelline space è ________________________________ • (+) biochemical changes to zona è ____________________________________ • _________________: prevents additional sperm binding oocyte plasma membrane • Species differences in absence/presence zona & vitelline blocks ♦ Decondensation of sperm nucleus • 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 • Bitch mated by several males during estrus ♦ _______________________________________________________________________ ♦ _______________________________________________________________________ ♦ Probability of conception in women (Fig 12-9) • __________________________________________________________________________ • __________________________________________________________________________ ♦ _______________________________________________________________________ • 122 Closer copulation is to ovulation, é chance of pregnancy
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