Fertilization

Fertilization

Union of male and female gametes resulting in a zygote that begins embryonic development.

Sperm Maturation

Occurs in the epididymis, where sperm acquire motility and the ability to bind to an oocyte.

Sperm Deposition

Site of sperm release varies among species and affects fertilization efficiency.

Cattle and Sheep Sperm Deposition

Occurs in the vagina during natural mating.

Pig Sperm Deposition

Occurs in the cervix due to the corkscrew-shaped penis of the boar.

Dog and Rodent Sperm Deposition

Occurs in the uterus during copulation.

Capacitation

Biochemical transformation of sperm in the female reproductive tract, enabling fertilization.

Capacitation Changes

Includes removal of cholesterol and glycoproteins, increased membrane fluidity, and hyperactivated motility.

Zona Pellucida

Glycoprotein-rich extracellular matrix surrounding the oocyte, mediating sperm binding.

ZP3

Glycoprotein in the zona pellucida responsible for species-specific sperm binding.

Acrosome Reaction

Release of acrosomal enzymes like acrosin and hyaluronidase to digest the zona pellucida.

Oocyte Activation

Triggered by sperm fusion, leading to calcium oscillations and completion of Meiosis II.

Fast Block to Polyspermy

Immediate electrical change in the oocyte membrane preventing further sperm entry.

Slow Block to Polyspermy

Release of cortical granules modifying the zona pellucida to block additional sperm.

Pronuclei Formation

Male and female pronuclei form and migrate toward each other before syngamy.

Syngamy

Fusion of paternal and maternal chromosomes, marking the formation of the zygote.

Bird Fertilization

Internal fertilization with long sperm storage in oviductal tubules, allowing multiple fertilizations.

Marine Species Fertilization

External fertilization requiring synchronized gamete release.

Horse Fertilization

Uterine tube epithelial cells actively guide sperm to the oocyte.

In Vitro Fertilization (IVF)

Used in cattle breeding to enhance genetic diversity.

Intracytoplasmic Sperm Injection (ICSI)

Technique to overcome male infertility by directly injecting sperm into the oocyte.

Spermatogenesis

Occurs in seminiferous tubules, producing haploid spermatids from diploid spermatogonia.

Spermiogenesis

Final stage of spermatogenesis, involving acrosome formation, nuclear condensation, and flagellum development.

Epididymal Maturation

Acquisition of motility and fertilization ability in the epididymis.

Sperm Reservoir

Storage site for sperm in the cauda epididymis, preventing premature capacitation.

Vaginal Sperm Deposition

Requires sperm to pass through the cervix, which filters out defective sperm.

Cervical Sperm Deposition

Direct deposition in pigs, bypassing vaginal acidity.

Uterine Sperm Deposition

Occurs in dogs, rodents, and birds, shortening sperm travel distance.

Active Sperm Motility

Aids sperm in navigating the female reproductive tract.

Uterine Contractions

Assist sperm movement toward the oviduct.

Selective Passage

Female reproductive tract filters out defective sperm, guiding viable ones.

Capacitation Steps

Includes cholesterol removal, ion fluxes, and hyperactivated motility.

Hyperactivation

Vigorous, asymmetrical tail movement aiding sperm penetration.

Zona Pellucida Composition

Differs among species, affecting sperm recognition.

Acrosin and Hyaluronidase

Enzymes released during acrosome reaction to digest the zona pellucida.

Fusion Proteins

In mammals, Izumo1 (sperm) and Juno (oocyte) mediate membrane fusion.

Cortical Reaction

Slow block to polyspermy by modifying the zona pellucida.

Calcium Oscillations

Triggered by sperm entry, essential for oocyte activation.

Mitochondria

Derived solely from the oocyte, providing energy for embryonic development.

Zygotic Genome Activation (ZGA)

Initiation of transcription from the zygotic genome.

Blastomeres

Daughter cells of the zygote, capable of forming any cell type.

Pronuclear Migration

Guided by microtubules to ensure proper alignment.

Assisted Reproductive Technologies (ART)

Includes IVF and ICSI to aid reproduction.

Infertility Causes

Can result from defective capacitation, acrosome reaction, or pronuclear migration.

Livestock Breeding

Artificial insemination and embryo transfer improve reproductive success.

Genetic Editing

CRISPR-Cas9 targets zygote stage for genetic modifications.

Contraceptive Research

Targets zona pellucida or fusion proteins for non-hormonal contraception.

Polyspermy Prevention

Critical for ensuring normal chromosomal content and embryo viability.

Syngamy Timing

Varies across species, affecting early embryonic development.

Sperm Storage in Birds

Allows fertilization over multiple ovulations.

Uterine Tube in Horses

Epithelial cells actively assist sperm guidance.

IVF Media

Designed to mimic natural capacitation and fertilization conditions.

Fast vs. Slow Polyspermy Block

Membrane potential change vs. cortical reaction.

Male Pronucleus Formation

Decondensation of paternal DNA into transcriptionally active form.

Female Pronucleus Formation

Completion of Meiosis II and extrusion of second polar body.

Cytoplasmic Contributions

Oocyte provides essential organelles and nutrients for early development.

First Mitotic Division

Formation of two identical blastomeres marking the start of embryogenesis.

Species-Specific Variations

Each species exhibits adaptations in fertilization mechanisms.

Retrograde Sperm Loss

Many sperm are lost due to backflow in species like bulls and stallions.

Sperm Storage Tubules in Birds

Allow prolonged sperm viability for multiple fertilization events.

Cattle vs. Pig Pronuclear Fusion

Timing differences due to cytoplasmic organization.

Cortical Granules

Modify the zona pellucida to prevent additional sperm entry.

Mitochondrial Inheritance

Exclusively maternal, as sperm mitochondria are degraded.

Embryo Transfer (ET)

Transfers early embryos to recipient females for gestation.

Sperm Binding Specificity

ZP3 ensures species-specific fertilization.

Environmental Cues in Fish

External fertilization is triggered by changes in water salinity or ions.

CRISPR in Livestock

Used for genetic trait modifications.

Calcium Ionophores

Used in ART to induce oocyte activation artificially.

Cattle Capacitation

Takes several hours due to reproductive tract adaptations.

Pigs and Polyspermy

More common due to high sperm numbers reaching the oocyte.

Fish Fertilization

Fast block to polyspermy via membrane depolarization.

Bird Blastodisc

Localized site of early embryonic development.

Maternal RNA in Zygote

Controls early development before zygotic genome activation.

ICSI vs. IVF

ICSI bypasses natural fertilization barriers by injecting sperm directly into the oocyte.