fertilization

What is insemination?

Deposition of male gametes into the female genital tract; sperm must travel from vagina to ovarian end of uterine tube for fertilization, possible due to sperm motility and uterine/tubal contractions.

Describe the process of oocyte transport during ovulation.

Fimbriae of uterine tube approach ovary; their sweeping action and fluid currents move secondary oocyte into infundibulum; oocyte moves into ampulla via peristalsis.

How are sperms transported during ejaculation?

Peristaltic contractions of ductus deferens move sperm from epididymis to urethra.

What forms semen?

Sperm + seminal plasma (secretions from seminal glands, prostate, bulbourethral glands).

List the tasks of seminal plasma.

1. Create alkaline pH in vagina
2. Coagulate ejaculate, form sperm deposit
3. Coat sperm to inhibit female immune response
4. Prostaglandins induce uterine/tubal contractions
5. Activate & augment sperm motility (proteins + fructose)
6. Supply nutrients

What is vesiculase and its function?

Enzyme from seminal glands; coagulates semen forming cervical plug to prevent backflow.

How does ovulation affect cervical mucus?

Increases amount and reduces viscosity, aiding sperm transport.

What role do prostaglandins in semen play?

Stimulate uterine motility, moving sperm to ampulla.

What is sperm motility speed?

2-3 \text{ mm/min} slower in vagina (acidic), faster in uterus (alkaline). About 200 reach ampulla.

List the steps sperm undergo before fertilization.

1. Storage in epididymis (acquire motility)
2. Physiological activation (ejaculation + glandular secretions)
3. Capacitation
4. Acrosome reaction

Define capacitation.

Functional maturation of sperm in female genital tract (~7 hrs). Regulated by \text{src} kinase.

What changes occur during capacitation?

Removal of glycoprotein coat & seminal proteins from acrosome; no morphologic change but activity increases; occurs in uterus/tubes via interleukin-6.

Where and how does the acrosome reaction occur?

Near secondary oocyte, likely due to corona radiata & oocyte substances; sperm plasma membrane fuses with acrosomal membrane, releasing enzymes (hyaluronidase, acrosin, zona lysin, neuraminidase) for penetration.

Define fertilization and its site.

Fusion of male & female gametes forming zygote; occurs in ampulla of uterine tube.

What molecules are involved in sperm chemotaxis and gamete recognition?

Carbohydrate- and protein-binding molecules on gamete surfaces.

List the 3 phases of fertilization.

1. Penetration of corona radiata
2. Penetration of zona pellucida
3. Fusion of oocyte & sperm membranes

What happens after the 3 phases of fertilization?

Zona reaction (zona pellucida permeability change) & injection of sperm nucleus + middle piece into oocyte cytoplasm.

What enables penetration of corona radiata?

Sperm hyperactivity, hyaluronidase, tubal mucosal enzymes.

Which enzymes help penetrate zona pellucida?

Acrosin, esterases, neuraminidase.

What happens during zona reaction?

Cortical granules from oocyte released into perivitelline space \to changes zona pellucida to block polyspermy.

What enters the oocyte cytoplasm after membrane fusion?

Head & tail of sperm; plasma membrane & mitochondria remain outside.

What happens during completion of 2nd meiotic division of oocyte?

Forms mature oocyte + 2nd polar body; nucleus becomes female pronucleus.

How is male pronucleus formed?

Sperm nucleus enlarges in oocyte cytoplasm; tail degenerates.

What occurs before first cleavage?

Male & female pronuclei replicate DNA; pronuclear membranes break down; chromosomes arrange for mitosis; pronuclei fuse \to zygote with 46 chromosomes.

List the 4 results of fertilization.

1. Completion of 2nd meiosis
2. Restoration of diploid number (46)
3. Sex determination
4. Initiation of cleavage

Differentiate between dizygotic and monozygotic twins.

Dizygotic: 2 ova fertilized by different sperm \to 2 zygotes. Monozygotic: 1 fertilized ovum splits \to identical twins.

Define superfecundation and superfetation.

Superfecundation: 2+ ova from same cycle fertilized by sperm from separate acts. Superfetation: 2nd ovum fertilized during pregnancy \to fetuses of different ages.