• Oocyte picked up from peritoneal cavity by cilia on fimbria
• Transported to ampulla via oviductal cilia and contractions of the tubule wall
• Takes ~25 min to reach ampulla

• Several hundred million sperm enter vagina
• Only several hundred reach ampulla
• barriers = cervix and cervical mucus
• Transported to ampulla via flagellar activity, uterine cilia and contractions of the uterine walls
• Reach fallopian tubes within minutes

• Oocyte = 24 hrs
• Spermatozoa = 24 hrs (small % viable for several days)

Sperm Capacitation (acquiring ability to fertilize)

• Beat pattern changes
• Closer to ampulla, faster they beat

Binding to Zona Pellucida and Acrosome Reaction (Fig 1)

• Fertilization = when sperm head fuses with the egg plasma membrane
• Sperm stops moving
• Microvilli on surface of oocyte membrane engulfs the spermatozoan
• Following membrane fusion:
• (1) oocyte must prevent polyspermy
• within seconds to minutes, the egg plasma membrane undergoes quick charge change
• within minutes, cortical granules are released into perivitilline space
• cortical granules wipe off the glycoprotein receptors preventing the binding of additional sperm
• (2) oocyte completes M2 (2-3hrs) and excretes 2^nd polar body
• (3) male pronucleus forms (4-7hrs)
• tail components disintegrate
• sperm head decondenses
• nuclear memb breaks down, chromatin decondenses, protamines replaced with histones, pronucleus memb forms, DNA synthesis commences
• egg DNA also forms nuclear envelope
• (4) 1^st cleavage division (~20 hrs post fertilization)
• DNA synthesis occurs in both male and female pronucleus
• with onset of 1^st cleavage division, nuclear envelopes disappear and chromosome mix on the 1^st mitotic division

• Parthogenesis Þ egg development without fertilization
• normal individuals result in many species, but in mammals, oocytes die in early embryogenesis
• failure due to genetic imprinting
• certain portions of genome function differently depending upon whether they are maternally or paternally inherited