Gametogenesis

Also called

spermatogenesis · oogenesis · spermatogonia · primary spermatocyte · secondary spermatocyte · spermatids · spermiogenesis · sperm · oogonia · primary oocyte · secondary oocyte · ovum · polar body · meiosis in gametes · haploid gametes · diploid to haploid · युग्मकजनन · शुक्रजनन · अंडजनन

Topics

• Gametogenesis makes haploid gametes from diploid germ cells: spermatogenesis in the testis, oogenesis in the ovary.
• Spermatogonia (2n = 46) multiply by mitosis; some grow into primary spermatocytes that enter meiosis at puberty.
• Meiosis I gives two haploid secondary spermatocytes (n = 23); meiosis II gives four equal spermatids.
• Spermiogenesis turns each spermatid into a sperm: head with acrosome, middle piece full of mitochondria, tail.
• Oogenesis begins before birth: oogonia multiply in the foetal ovary, start meiosis I and stop at prophase I.
• Each arrested primary oocyte is wrapped by granulosa cells as a primary follicle; no oogonia form after birth.
• At puberty one follicle a month completes meiosis I: a large secondary oocyte and a tiny first polar body.
• Meiosis II finishes only when a sperm enters the secondary oocyte, giving one ovum and a second polar body.
• One spermatogonium yields four sperm; one oogonium yields one egg plus polar bodies that degenerate.

About this model

A GLB file of about 477 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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