Fertilization

Fertilization

The union of male and female gametes

Zygote

The first diploid cell formed after gamete fusion

Sperm maturation

The process where sperm acquire motility and fertilizing ability in the epididymis

Capacitation

Biochemical changes in sperm in the female tract that enable zona pellucida binding

Hyperactivation

Vigorous

Zona pellucida

Glycoprotein-rich extracellular matrix surrounding the oocyte

ZP3

Glycoprotein that mediates species-specific sperm binding

Acrosome reaction

Release of enzymes (acrosin

Calcium oscillations

Sudden increases in intracellular calcium during oocyte activation

Oocyte activation

The process triggered by sperm entry

Pronucleus

Haploid nucleus formed in the oocyte and sperm after fertilization

Syngamy

Fusion of male and female pronuclei into a diploid zygote

Polyspermy

Entry of multiple sperm into the oocyte

Fast block

Immediate electrical membrane change preventing multiple sperm entry

Cortical reaction (slow block)

Release of cortical granules modifying the zona to prevent polyspermy

Pronuclear migration

The movement of male and female pronuclei toward each other

First mitotic division

Zygote divides into two blastomeres

Uterine contractions

Help sperm migration toward the oocyte

Sperm reservoir

Site in the epididymis where mature sperm are stored until ejaculation

Birds' fertilization

Sperm stored in tubular structures in the oviduct for extended viability

External fertilization

Gametes released into the aquatic environment for fertilization (fish

ICSI (Intracytoplasmic Sperm Injection)

ART technique where sperm is directly injected into the oocyte

In vitro fertilization (IVF)

Fertilization performed outside the body

Assisted reproductive technologies (ART)

Techniques to aid reproduction

Zona reaction

Hardening of the zona pellucida after sperm entry to block polyspermy

Maternal histones

Replace sperm protamines during pronuclear formation

Oocyte membrane proteins

Juno and CD9

Species-specific adaptations

Differences in fertilization mechanisms across species

Cattle and sheep

Sperm deposited in the vagina during mating

Pigs

Sperm deposited in the cervix due to the boar’s corkscrew-shaped penis

Dogs and rodents

Sperm deposited directly into the uterus

Horses

Specialized epithelial cells in the uterine tube guide sperm to the oocyte

Fish

External fertilization requiring synchronized gamete release

Birds

Sperm stored in tubular structures in the oviduct

Calcium ionophores

Used in ART to artificially induce oocyte activation

Zona pellucida hardening

Occurs after cryopreservation

Cryopreservation

Freezing embryos for later use in reproduction

Male infertility

Diagnosed by testing for capacitation or acrosome reaction defects

Contraceptive research

Targets zona glycoproteins (ZP3) for immunocontraception

Genetic editing

CRISPR-Cas9 used at the zygote stage for gene modifications