Human Reproductive System. Gametogenesis Occurs in the gonads (ovaries and testes) Meiosis that...
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Transcript of Human Reproductive System. Gametogenesis Occurs in the gonads (ovaries and testes) Meiosis that...
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Human Reproductive SystemHuman Reproductive System
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Gametogenesis
• Occurs in the gonads (ovaries and testes)
• Meiosis that results in the production of gametes (haploid) from germ cells (diploid cells)
• Spermatogenesis and Oogenesis
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Oogenesis
• Occurs in the ovaries—results in the production of 1 egg (and 3 polar bodies)
• Begins when the female is an embryo —
• Oocytes form before birth and remain “frozen” in this stage indefinitely
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Oogenesis
• Each month after puberty, one oocyte completes Meiosis I and begins Meiosis II
• Meiosis II is completed only after fertilization occurs.
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Oogenesis
• Unequal division of cytoplasm.
• Allows for more nutrients to be available to the egg in case fertilization occurs.
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Spermatogenesis
• Occurs in the testes in the seminiferous tubules—results in the production of 4 sperm
• Mature in the epididymis and gain motility
• Produced constantly after puberty
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Spermatogenesis
• The sperm contains lots of mitochondria (powerhouse of the cell) —why? – The sperm have a long journey they need a
lot of energy (hence the need for lots of mitochondria)
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Male Reproductive System
• Testes – where spermatogenesis takes place
• Epididymis – where sperm mature
• When sperm leaves the body, it will go up the vas deferens, past glands
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Male Reproductive System
• Secretions of glands contribute to the semen– produce an alkaline solution to
neutralize acidity of urethra– solution that contains food
(fructose) for the sperm.
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Pathway of Semen
• Epididymis (testes) Vas Deferens Urethra
• A vasectomy is a procedure in which the vas deferens is cut so that the man will no longer be able to father children.
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Female Reproductive System
• Ovaries – where oogenesis takes place
• Oviduct (Fallopian Tube) – where fertilization takes place
• Uterus – where the embryo grows and develops
• Vagina – birth canal
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Female Reproductive Hormones
• LH and FSH act on the ovaries and cause them to produce estrogen and progesterone– Feedback mechanisms will be
discussed in the next few slides
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Female Menstrual Cycle
• Each month, a woman’s body prepares for the possible fertilization of an egg
• Ovarian Cycle = an egg matures and is released
• Uterine Cycle = the endometrium (lining) of the uterus builds up (becomes ready to have a fertilized egg implant) then breaks down (if no fertilization occurs).
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Female Menstrual Cycle
• Ovulation – release of egg from ovary triggered by a surge of LH.
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Female Menstrual Cycle
• Day 1 = first day of a woman’s period
• Hormonal control is complicated!– During different times of
the cycle, Estrogen can either stimulate or inhibit other hormones
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Female Menstrual Cycle• If fertilization occurs, the embryo secretes
HcG which maintains the lining of the uterus – hCG is what is tested for in pregnancy tests
• Birth control pills are synthetic progesterone and estrogen that “trick” the body into thinking the woman is pregnant – no ovulation occurs
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