1. Human Reproductive System

2. 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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3. Oogenesis
Occurs in the ovaries—results in the production of 1 egg (and 3 polar bodies)
Begins when the female is an embryo—all primary oocytes form before birth and remain “frozen” in this stage indefinitely
1,000,000 primary oocytes at birth; only 200,000 left by puberty (rest have degenerated). Over a woman’s reproductive lifetime, only 450 eggs complete oogenesis.
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4. Oogenesis
Each month after puberty, one primary oocyte completes Meiosis I and begins Meiosis II
Meiosis II is completed only after fertilization occurs.
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5. Oogenesis Characterized by unequal division of cytoplasm.
Why does it make sense for this to happen?
Allows for more nutrients to be available to the egg in case fertilization occurs.
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6. 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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7. Spermatogenesis The midpiece contains lots of mitochondria—why?
The sperm have a long journey  they need a lot of energy (hence the need for lots of mitochondria)
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8. 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 the following glands:
Bulbourethral gland
Prostate gland
Seminal vesicles
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9. Male Reproductive System
Secretions of these 3 glands, contribute to the semen
Bulbourethral glands - produce an alkaline solution to neutralize acidity of urethra
Prostate gland – clotting enzyme to make semen gelatinous, solution to make environment in uterus more “friendly”
Seminal vesicles – solution that contains food (fructose) for the sperm.
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10. Pathway of Semen Epididymis  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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11. 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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12. Female Reproductive Hormones
See hormone chart in notes
GnRH released from hypothalamus causes the release of LH and FSH from the pituitary gland
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
Image taken without permission from
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13. Female Menstrual Cycle
Each month, a woman’s body prepares for the possible fertilization of an egg
Ovarian Cycle = an egg matures (from a primary oocyte) 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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14. Female Menstrual Cycle
An oocyte & the cells around it = follicle
Usually, only one follicle fully matures during each ovarian cycle
Ovulation – release of egg from ovary triggered by a surge of LH.
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15. Female Menstrual Cycle
The corpus luteum is the remaining cells of the follicle
Continues to produce estrogen and progesterone for approximately 2 weeks  maintains the thickness of the endometrium
If no fertilization occurs, it degenerates  endometrium is no longer maintained.
This starts the whole cycle over again.
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16. 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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17. Female Menstrual Cycle
If fertilization occurs, the embryo secretes HCG which maintains the corpus luteum
Eventually cells derived from embryo will secrete estrogen and progesterone to take over for the corpus luteum
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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