Spermatogenesis and Fertilisation

sperm production and storage

• from puberty, sperm produced constantly in seminiferous tubules

• each spermatazoa takes 60-75 days to fully develop

• mature sperm stored in epididymis

sertoli cells

• support stem cells and developing sperm

leydig cells

• between seminiferous tubules

• produce androgens

effects of LH and FSH and androgens

• LH stimulates leydig cells to produce androgens

• FSH and androgens stimulate sertoli cells and spermatogenesis

spermatogenesis vs spermiogenesis

• spermatogenesis→ diploid spermatogonia undergo mitosis and meiosis to produce haploid spermatids

• spermiogenesis→ spermatids change shape to form spermatozoa

spermatogenesis

1. primary spermatocytes undergo meiosis I

2. secondary spermatocytes undergo meiosis II

3. spermatids are haploid

semen

• typical ejaculate→ 2-5

• typical sperm count→ 20-250 million/ml

where does fertilisation generally occur

fallopian tube

what happens during fertilisation

• acrosome on head of sperm breaks through zona pellucida of the oocyte

• secondary oocyte completes second meiotic division with fusion of sperm

• fertilised oocyte divides as it is swept along fallopian tube by action of cilia

blastocyst

• day 5→ dividing cells separating into inner cell mass

• goes on to form foetus and a trophoblast→ forms placenta

when does implantation occur

day 7