Describe spermatogenesis with a flow chart. How is it controlled by hormones?
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define in one line. Spermatogenesis is the formation of haploid sperms from diploid spermatogonia in the seminiferous tubules, beginning at puberty.
2 · Multiplication and growth. Spermatogonia (2n) multiply by mitosis; some become primary spermatocytes (2n).
3 · Meiosis. Meiosis I gives two secondary spermatocytes (n); meiosis II gives four spermatids (n).
4 · Spermiogenesis and spermiation. Spermatids change into sperms; the sperm heads stay in Sertoli cells until they are released by spermiation.
5 · Draw the flow chart. [Flow chart: spermatogonium → primary spermatocyte → secondary spermatocytes → spermatids → sperms, with 2n or n at each stage]
6 · Hormonal control.
GnRH from the hypothalamus acts on the anterior pituitary.
LH → Leydig cells → androgens → spermatogenesis.
FSH → Sertoli cells → factors that help spermiogenesis.
7 · Close in one line. So each primary spermatocyte gives four sperms, under the control of GnRH, LH and FSH.
Scoring tip: Write 2n or n beside every stage of the flow chart. Examiners look for the step where meiosis halves the number.
