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The Reproductive System

The Reproductive System. Gonads – primary sex organs Testes in males Ovaries in females Gonads produce gametes (sex cells) and secrete hormones Sperm – male gametes Ova (eggs) – female gametes. Male Reproductive System. Scrotum Divided sac of skin outside the abdomen

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The Reproductive System

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  1. The Reproductive System • Gonads – primary sex organs • Testes in males • Ovaries in females • Gonads produce gametes (sex cells) and secrete hormones • Sperm – male gametes • Ova (eggs) – female gametes

  2. Male Reproductive System

  3. Scrotum • Divided sac of skin outside the abdomen • Maintains testes at 3°C lower than normal body temperature to protect sperm viability External Genitalia

  4. Penis Delivers sperm into the female reproductive tract • Regions of the penis • Shaft, Glans penis (enlarged tip) , Prepuce (foreskin), Folded cuff of skin around proximal end Often removed by circumcision

  5. Ductus Deferens (Vas Deferens) Testes • Carries sperm from the epididymis to the ejaculatory duct • Moves sperm by peristalsis • Vasectomy – cutting of the ductus deferens at the level of the testes to prevent transportation of sperm

  6. Epididymis • Comma-shaped, tightly coiled tube • Found on the superior part of the testis and along the posterior lateral side • Functions to mature and store sperm cells (at least 20 days) • Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens

  7. Seminal Vesicles • Located at the base of the bladder • Produces a thick, yellowish secretion (60% of semen) • Fructose (sugar) • Vitamin C • Prostaglandins • Other substances that nourish and activate sperm

  8. Encircles the upper part of the urethra • Secretes a milky fluid • Helps to activate sperm • Enters the urethra through several small ducts Prostate Gland

  9. Mixture of sperm and accessory gland secretions • Advantages of accessory gland secretions • Fructose provides energy for sperm cells • Alkalinity of semen helps neutralize the acidic environment of vagina Semen

  10. The only human flagellated cell • DNA is found in the head Anatomy of a Mature Sperm Cell

  11. Ovaries • Duct System • Uterine tubes (fallopian tubes) • Uterus • Vagina • External genitalia Female Reproductive System

  12. Female Reproductive System

  13. Labia – skin folds • Clitoris • Contains erectile tissue • Corresponds to the male penis External Genitalia (Vulva)

  14. Composed of ovarian follicles (sac-like structures) • Structure of an ovarian follicle • Oocyte • Follicular cells Ovaries

  15. Receive the ovulated oocyte • Provide a site for fertilization • Attaches to the uterus • Does not physically attach to the ovary Uterine (Fallopian) Tubes

  16. Fimbriae – finger-like projections at the distal end that receive the oocyte • Cilia inside the uterine tube slowly move the oocyte towards the uterus (takes 3–4 days) • Fertilization occurs inside the uterine tube Uterine Tube Function

  17. Located between the urinary bladder and rectum • Hollow organ • Functions of the uterus • Receives a fertilized egg • Retains the fertilized egg • Nourishes the fertilized egg Uterus

  18. Endometrium • Inner layer • Allows for implantation of a fertilized egg • Sloughs off if no pregnancy occurs (menses) • Myometrium – middle layer of smooth muscle • Serous layer – outer visceral peritoneum Walls of the Uterus

  19. Hormones • Female • Follicle Stimulating Hormone (FSH) • Luteinising Hormone (LH) • Oestrogen • Progesterone (P) • Human Chorionic Gonadotropin (HCG) • Male • FSH • LH • Testosterone (T)

  20. Hormones in common-FSH and LH • In females • Oestrogen and P will flucuate • When FSH and LH added triggers monthly cycle • 2 cycles • Ovarian • Uterine • In Males, puberty hypothalmus triggers pituitary • FSH and LH secreted • FSH triggers sperm production • LH triggers T production • Negative feedback

  21. Ovarian Cycle • Monthly cycle • Hypothalmus→ Ant. Pit. → releases FSH/LH • FSH for egg development • Egg produces oestrogen, stimulates uterus and neg. feedback

  22. Uterine Cycle • Oestrogen peaks, LH stimulated • Causes ovulation • Corpus luteum secretes P • Builds endometrium • Inhibits LH/FSH • When FSH/LH levels fall, P/oestrogen levels fall • Endometrium discarded • If egg fertilized, embryo secretes hormone that maintains P levels

  23. Gametogenesis • Process of making gametes • What do you know?

  24. Basics • For both sexes • Multiplication by mother cells • Growth • Maturation (meiosis) • Meiosis I - 2ºspermatocytes/ 2º oocytes • Meiosis II – spermatids/ ova

  25. Sperm production • Seminiferous tubule (mother cell) • Mitotic division • Makes way to epidymis where stored/matured

  26. Ova Production • Starts before birth • At puberty have about 250,000 • Ovulate every 28 days till menopause

  27. Primary follicle – contains an immature oocyte • Graafian (vesicular) follicle – growing follicle with a maturing oocyte • Ovulation – when the egg is mature the follicle ruptures • Occurs about every 28 days • The ruptured follicle is transformed into a corpus luteum Ovarian Follicle Stages

  28. Compare the processes of spermatogenesis and oogenesis.

  29. Fertilization • What do you know? • How does it occur?

  30. Fertilization in Mammals • Occurs internally, in fallopian tubes • Sperm deposited in vagina and travel to egg • At egg sperm must pass follicular ring and zonapellucida • Acrosome • Cortical reaction • Assures only one sperm will enter • Why important? • Sperm presence triggers meiosis II of ova, polar body released • Fertilization Animation

  31. Invitro Fertilization • IVF= fertilizes egg outside the body • Why do it?

  32. Infertility • Female • Sperm death • Uterus prevents implantation • Blockage of duct • Egg failure • Male • Impotence • Abnormal sperm • Short-lived sperm • Low #’s • blockage

  33. Steps • Menstration stopped • FSH injected for super-ovulation • Semen sample • Eggs removed from ovary • Mix • Incubate • Transfer- up to 3

  34. For tomorrow… • We will have an ethics debate • You will be divided up into smaller discussion groups of 4. • Two will be in favor and two against • We will follow-up with a class discussion

  35. Pregnancy and early development • Fertilized embryo travels to uterus • Implantation at day 7 (100 cells) • Cells form blastomere • Mass in middle becomes baby

  36. Gestation • 40 weeks • Embryo/fetus surrounded by amniotic sac/fluid • Outer layer of cells from blastomere develops into those and placenta

  37. Placenta • Connection point for mom and baby • Blood never mixes • Why? • What is exchanged here?

  38. Placenta cont… • Becomes endocrine gland • Produces HCG (pregnancy tests) • Maintains corpus luteum, keeps P and oestrogen levels up • Placenta takes over production after 16 wks • If levels drop pregnancy levels drop, aborts

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