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Human Reproduction

Human Reproduction. Spermatogenesis. Spermatogenesis. Sperm production begins during puberty and is stimulated by the release of hormones Sperm production is controlled by the hypothalamus and ant. Pituitary through negative feedback. Spermatogenesis.

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Human Reproduction

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  1. Human Reproduction Spermatogenesis

  2. Spermatogenesis • Sperm production begins during puberty and is stimulated by the release of hormones • Sperm production is controlled by the hypothalamus and ant. Pituitary through negative feedback

  3. Spermatogenesis • Hypothalamus releases gonadotropin releasing hormone (GnRH) which triggers ant. pit. To release FSH and LH • FSH triggers seminiferous tubules to produce sperm • LH triggers testosterone production by Leydig cells (interstitial cells) which increases sperm production

  4. Testosterone • Produced by interstitial cells in the Testes • Also responsible for Secondary sex chars. • Voice Deepens • Body Hair • Strengthening of muscles • Sex drive

  5. Hormonal control

  6. Spermatogenesis: The making of sperm • Seminiferous tubules in the testes are the site of sperm cell production • Lumen of tubules is lined with spermatogonia • 46 chromosomes • Undergo mitosis to form primary spermatocytes • primary spermatocytes undergo meiosis to produce secondary spermatocytes(46 Chromosomes *) and eventually spermatids (23 chromosomes) • One primary spermatocyte will eventually produce four sperm cells

  7. Spermatogenesis • Spermatogenesis occurs at the onset of puberty • Several hundred million produced/day • Formation of a mature sperm cell takes about 70 – 80 days • Sperm cells mature in the epididymis • Develop flagella and begin to swim within 4 days

  8. Spermatogenesis

  9. Mature Sperm

  10. Human Reproduction Oogenesis

  11. Oogenesis • All follicles are produced in the ovaries during the first during the 1st six months of fetal development • Max. of 7 million produced • 2 million left at birth • 400,000 at onset on puberty • Approx. 400-500 mature ova develop and are released during the reproductive years

  12. Oogenesis • Follicles consist of two types of cells: • Primary oocyte • Granulosa cells • Clusters of these cells are called primordial follicles • Granulosa provide nutrients, chemical signals, and protection for the developing follicle

  13. Oogenesis • 6-20 primary follicles begin to mature each month • Only one follicle fully matures and is released from one ovary each month during reproductive years

  14. Ovulation • The ovum is released out of the ovary and will move into the fallopian tube • Remaining follicular cells change and become the corpus luteum • Secretes progesterone and estrogen • If ovum remains unfertilized, corpus luteum degenerates and new cycle will begin

  15. Hormonal control • Cyclic process in females (continuous in males) • Hypothalamus secretes GnRH • Stimulates LH and FSH in ant. Pit. • Effects of LH and FSH on ovaries varies during the cycle

  16. The Ovarian Cycle • 28 days long, divided into 3 phases • Follicular phase (12 days) • Luteal phase (11 days) • Menstrual phase (approx. 5 days)

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