Human Reproductive SystemHuman Reproductive System

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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