1. Making hormones, gametes and little babies
Reproductive System
Making hormones, gametes and little babies

2. The circle of Life male embryo zygote embryo female embryo Gender
Conception
female fetus
male fetus
Mature ovum
Birth
Mature female
Immature female
Mature sperm
Immature male
Mature male
Puberty
Gameteogenesis

3. Male reproductive system
Reproductive system = gonads + tubes
Male gonad = testes
Testes make gametes (sperm)
Testes make hormones to regulate sperm production
Tubes provide pathway for sperm to be excreted

4. Spermatogenesis
Male gametogenesis = process to produce sperm (male gametes)
Normal adult male = 400 million sperm/day
Sperm produced in seminiferous tubules in the testes
Testosterone is made by interstitial cells in the testes

5. spermatogenesis Spermatogenesis = meiosis
Process starts with spermatogonium in outside of tubule wall
Mitosis results in two spermatogonium, one remains in basement layer
Meiotic divisions occur as developing sperm moves to tubule lumen
Final result is 4 haploid spermatozoa

6. spermatogenesis Male gamete = sperm
Sperm are specialized for mobility and among the smallest cells in the human body
Structure
Head contains DNA (in form of 23 chromosomes) and enzymes for penetration of egg
Midpiece contains mitochondria to produce energy for movement (in the form of ATP)
Tail is a flagellum that propels the sperm through the liquid medium of the female reproductive tract

7. spermatogenesis Rate of sperm production is controlled by hormones
Brain hormones = GnRH, LH, FSH
Gonad hormones = testosterone + inhibin
Negative feedback is primary control

8. Spermatogenesis + negative feedback
Negative Feedback in spermatogenesis
Brain hormones stimulate gonad hormones
Gonad hormones inhibit brain hormones
 brain hormones stimulate  gonad hormones
gonad hormones cause brain hormones
brain hormones cause gonad hormones
gonad hormones cause brain hormones

9. Female reproductive system
Reproductive system = gonads + tubes
Female gonad = ovary
Ovaries make gametes (ova/egg)
Ovaries make hormones to regulate egg production and prepare the uterus for fertilization
Tubes provide pathway for sperm to get in and fetus to get out

10. Oogenesis
Female gametogenesis = process to produce female gametes (eggs/ova)
Females normally release 1 egg/28 days in ovary
Cells in developing follicle produce estrogen
Cells in post-ovulation follicle produce progesterone

11. oogenesis Oogenesis = meiosis
Primary oocytes begin meiosis before birth
After puberty, one cell/month continues meiosis
One meiotic division occurs before ovulation, with unequal division of cytoplasm (one big cell/one small cell)
After fertilization, second meiotic division occurs
Final result = 1 viable haploid cell + 3 small polar bodies

12. Oogenesis Egg develops as part of follicle
Follicle = ovum + hormone-producing cells + protective cells
Corpus luteum = follicle after ovum is released

13. oogenesis
Egg development and uterine development are regulated by hormones
Brain hormones = GnRH, LH, FSH
Ovarian hormones = estrogen + progesterone
Egg and uterine development regulated by negative feedback, ovulation is regulated by positive feedback

14. Oogenesis + negative feedback
Negative Feedback in oogenesis
FSH + LH stimulate estrogen + progesterone
estrogen + progesterone inhibit  FSH + LH
Estrogen – from follicle cells – stimulates egg development + development of uterine lining
Progesterone – from corpus luteum – maintains developed uterine lining
When progesterone decreases, uterine lining breaks down (menstruation)
When fertilization occurs, corpus luteum is maintained, progesterone produced and uterine lining maintained

15. Oogenesis + oral contraceptives
Increasing levels of progesterone decreases production of LH (negative feedback)
Decreased LH prevents ovulation
Artificial increase in progesterone prior to ovulation will prevent ovulation by decreasing LH
Most oral contraceptives (birth control pills) use this strategy