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BIOLOGY FORM 5 CHAPTER 4 - 4.1C Spermatogenesis & 0ogenesis
Spermatogenesis and oogenesis are the processes by which gametes (sperm and eggs) are produced in the male and female reproductive systems. Spermatogenesis occurs in the seminiferous tubules of the testes and involves the production of sperm through meiosis and differentiation. Oogenesis begins during embryonic development with the formation of oocytes, and involves meiosis, follicular growth, and ovulation of a secondary oocyte from the ovaries each menstrual cycle. Fertilization occurs when a sperm fuses with an egg in the fallopian tubes, forming a zygote.
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BIOLOGY FORM 5 CHAPTER 4 - 4.1C Spermatogenesis & 0ogenesis
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- 2. Formation of gametes A. Spermatogenesis B. Oogenesis
- 3. Sexual Reproduction inHuman testis meiosis meiosis sperms ovary eggs (ova) fertilization zygote embryo foetus baby
- 4. Gametogenesis • Formationof haploid gametes (n) –sperm, ovum • Takes place - testis & ovary (gonad)
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- 6. Spermatogenesis • Productionof sperm • Occurs in male testis (testes) • Begins at puberty (ages of 11 to 15 )
- 7. • Sperm: Malesex cell (gamete)
- 8. SPERMATOGENESIS • 100to 200 million sperms are made a day • Happens in seminiferous tubules of testis
- 9. Gonads make gametes! Testes make sperm
- 17. Spermatogenesis – occursin the seminiferous tubule (testis)
- 19. Fig. 46-12c Primordialgerm cell in embryo Differentiation Spermatogonium Mitosis Primary spermatocyte Meiosis I Secondary spermatocyte Meiosis II Early spermatid Differentiation (Sertoli cells provide nutrients) Sperm 2n 2n 2n n n n n n n n n n n spermatogenesis
- 20. spermatogenesis Primordium germcell Spermatogonium Differentiation Primary Spermatocyte Secondary Spermatocyte Spermatid Spermatozoa Mitosis Meiosis I Meiosis II Differentiation
- 21. Fig. 46-12b Epididymis Seminiferous tubule Sertoli cell nucleus Testis Cross section of seminiferous tubule Spermatogonium Primary spermatocyte Secondary spermatocyte Spermatids (two stages) Sperm Lumen of seminiferous tubule
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- 25. Mature Spermatozoa tail acrosome nucleus mitochondria head Midpiece (with mitochondria)
- 31. • Animation offlagella propelling sperm.
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- 35. Male Infertility •Over the past 30 years, the sperm content of semen has dropped dramatically • In the 1970s sperm content of an average ejaculate was ~100 million / mL; now it is ~60 million / mL • It is thought that low sperm count is attributable to drug usage, alcohol abuse, cigarette smoking and possibly industrial and environmental toxins
- 36. Male Reproductive System • Hormones involved: –FSH stimulates the Sertoli to facilitate sperm development. –LH stimulates Leydig cells to secrete testosterone. • Negative feedback inhibition applies to FSH and LH secretion.
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- 38. • Egg (Ovum):Female sex cell.
- 39. Oogenesis • Productionof ovum • Occurs in Female ovary • starts at embryonic stage
- 40. Gonads make gametes! Ovaries make eggs
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- 43. Oogenesis Mitosis &Growth Meiosis1 5 or 6 weeks after female zygote forms, some cells in embryo’s ovary undergo mitosis to produce diploid oogonia By 24 weeks, the embryo contains millions of oogonia From then until 6 weeks after birth, the oogonia undergo a first meiotic division to form primary oocytes. They remain arrested at Prophase 1 at birth. Most of the primary oocytes disappear – by puberty about 400 000 remain. Each month from puberty to menopause, 1 primary oocycte completes Meiosis1 & Meiosis II till Metaphase II.
- 44. Oogenesis Primordium germcell Differentiation Oogonium mitosis Primary oocyte Meiosis I Secondary oocyte + polar body Meiosis II Sperm Ovum + polar body
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- 46. Fig. 46-12f Ovary Primary oocyte within follicle Ruptured follicle Growing follicle Mature follicle Ovulated secondary oocyte Corpus luteum Degenerating corpus luteum
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- 51. OOGENESIS • Themeiotic division commenced as an embryo now completes. • This results in a large secondary oocyte and a tiny polar body
- 53. Uterine tube Ovary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Secondary oocyte © 2007 Landrum B. Shettles Ovulation • The release of an ovum from an ovary
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- 60. Ovum • Iovum released per month. • Women release about 500 ova in a lifetime. • Larger • Stationary • contain food reserves (lipids, proteins, carbohydrates) to nourish the embryo after fertilisation
- 62. The Fallopian Tube/ Oviduct • receives the secondary oocyte, • which moves by peristalsis and ciliary beating toward the uterus – fertilization occurs in the fallopian tube Inside the fallopian tube
- 64. Human Gametes muchsmaller (~0.05mm) much larger (~0.1mm) tadpole-like (with head & tail) spherical in the head toward center strongly mobile by its tail not able to move by itself Size Shape Position of nucleus Movement Sperm Ovum
- 66. Removing an ovariancyst!
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