𧬠Gametogenesis is the process by which haploid gametes (sperm in males π§βπ¦±β‘οΈπ§¬ and ova in females π©βπ¦°β‘οΈπ§¬) are formed from diploid precursor cells.
It involves mitosis, meiosis, and differentiation, ensuring gametes carry half the genetic material ready for fertilisation.
βοΈ Male Gametogenesis: Spermatogenesis
- Occurs in the seminiferous tubules of testes.
- Onset: Begins at puberty and continues lifelong.
- Duration: β³ ~64β72 days from start to mature sperm.
π Mitotic Proliferation (Spermatocytogenesis)
- Spermatogonia: Diploid stem cells undergo mitosis in basal compartment.
- Differentiate into primary spermatocytes β move to adluminal compartment.
π Meiosis
- Primary Spermatocytes: Undergo meiosis I β 2 haploid secondary spermatocytes.
- Secondary Spermatocytes: Complete meiosis II β haploid spermatids.
βοΈ Spermiogenesis (Differentiation)
- Spermatids mature into spermatozoa through:
- π― Acrosome formation (enzymes to penetrate ovum).
- π¦ Nuclear condensation + flagellum development.
- πͺΆ Cytoplasm shed β streamlined shape.
π Hormonal Regulation (Male)
- FSH: Stimulates Sertoli cells β support spermatogenesis.
- LH: Acts on Leydig cells β testosterone production.
- Testosterone: Essential for maturation and maintenance.
π§© Sperm Structure
- Head: DNA + acrosome (enzymes).
- Midpiece: β‘ Packed with mitochondria for motility energy.
- Tail: π Flagellum propels sperm toward ovum.
βοΈ Female Gametogenesis: Oogenesis
- Occurs in the ovaries.
- Onset: Begins in fetal life πΆ β pauses β resumes at puberty.
- Completes only if fertilisation occurs.
π Stages of Oogenesis
A. πΆ Fetal Stage
- Oogonia: Diploid β mitosis β primary oocytes.
- Primary oocytes enter meiosis I β arrested in prophase I within primordial follicles.
B. π Puberty to Menopause
- Hormonal signals restart meiosis during cycles.
- Primary oocyte: Completes meiosis I β secondary oocyte + polar body.
- Secondary oocyte: Arrested in metaphase II β ovulated.
C. π Completion Upon Fertilisation
- If sperm penetrates, meiosis II completes β mature ovum + second polar body.
π Hormonal Regulation (Female)
- FSH: Follicular growth + oocyte development.
- LH: Ovulation trigger.
- Estrogen & Progesterone: Cycle regulation + endometrial preparation.
π Follicular Development
- Primordial Follicle: Primary oocyte inside.
- Graafian Follicle: Mature follicle ready for ovulation.
- Ovulation: Secondary oocyte released, captured by fallopian tube.
βοΈ Comparative Summary: Spermatogenesis vs. Oogenesis
Feature |
βοΈ Spermatogenesis |
βοΈ Oogenesis |
Location |
Testes (seminiferous tubules) |
Ovaries |
Onset |
Puberty |
Fetal life |
Duration |
Lifelong |
Until menopause |
Gametes |
Millions daily |
1 ovum per cycle (if fertilised) |
π₯ Clinical Implications
- Infertility:
βοΈ Low sperm count/motility or
βοΈ Oocyte maturation/hormonal issues.
- Assisted Reproduction (IVF): Knowledge of gametogenesis guides egg retrieval & fertilisation.
- Genetic Risks: Abnormal meiosis β aneuploidy (e.g. Down syndrome, Turnerβs).