Egg

The egg, or ovum, is the female reproductive cell. It is released from the ovaries and travels through the fallopian_tubes to the uterus, where it may be fertilized by [sperm](male 1/sperm.md).

Structure

• Nucleus: Contains genetic material.
• Cytoplasm: Stores nutrients.
• Zona pellucida: Protective outer layer that prevents polyspermy and facilitates species-specific fertilization.
• Cortical granules: Release enzymes upon fertilization to prevent multiple sperm from entering.
• Mitochondria: Provide energy for early development stages.

Related Topics

• Fertilization
• Ovaries
• Fallopian Tubes
• Uterus
• [Sperm](male 1/sperm.md)

Additional Biological Details

Cell Type

The egg is a eukaryotic cell, characterized by its nucleus and organelles. This distinguishes it from prokaryotic cells like bacteria.

Size Range

Egg sizes vary dramatically across species:

• Humans: ~0.05-0.1 mm in diameter.
• Chickens: ~39-52 mm long, including the shell.
• Whales: Larger than human eggs, though fertilized internally.

Zona Pellucida Function & Components

The zona pellucida is composed of glycoproteins (ZP1, ZP2, ZP3) that play roles in sperm binding and preventing polyspermy.

Oogenesis Process

Oogenesis is the process of egg cell formation:

1. Primordial Follicle: Contains primary oocytes arrested in prophase I.
2. Growth: Follicles develop, and meiosis resumes during ovulation.
3. Maturation: Meiosis II completes only after fertilization.

Writing Tips

• Use sensory details to describe the egg's journey through the fallopian tubes.
• Highlight the interplay between the egg and sperm during fertilization.
• Incorporate metaphors, such as the egg as a "vessel of life" or "cradle of potential."

Example

"The egg, cradled within the rhythmic embrace of the fallopian tube, seemed to pulse with anticipation, its protective shell shimmering like a pearl in the ocean of life."