1. The Reproductive Systems

2. Reproduction Life is defined by its ability to reproduce
The cells of our body can reproduce to make two identical copies (mitosis)
This was the only means of reproduction for a long time
To increase the spread of beneficial genes, a new type of reproduction was evolved called sexual reproduction

3. Meiosis
Sexual reproduction requires a new type of cell division: meiosis
Normal human mitosis takes one cell with 46 chromosomes and produces two cells with 46 chromosomes
Meiosis instead produces four cells with 23 chromosomes
1 of each instead of 2 of each
These cells are called haploid, and two haploid cells will make a new whole cell

4. Fertilization Haploid sex cells are called gametes
Human gametes are sperm cells (male) and egg cells (female), which are produced by the gonads
The human reproductive systems have two purposes:
Initiate fertilization (combine a sperm cell with an egg cell)
Keep this newly-created life form in a safe place until it is able to live on its own (pregnancy)

5. Gamete Formation
In men, gamete formation is called spermatogenesis and takes places in the testes
Spermatogenesis requires a precise temperature which is less than normal body temperature, so the testes are placed in a sac of skin called the scrotum
Men produce millions of sperm a day after puberty
In women, gamete formation is called oogenesis and takes place in the ovaries
In women, all gametes have begun their formation by the time the baby is born, and will only release a few hundred during her lifetime

6. Sex Hormones
The primary mediator of the reproductive system is sex hormones, also produced by the gonads
Male gonads: testes (singular: testis)
Female gonads: ovaries
The gonads produce sex hormones, primarily testosterone (men) and estrogen and progesterone (women)
Actually a broad array of hormones in both

7. Hormonal Activities Sex hormones have major effects on the body
Development of reproductive organs and secondary sexual characteristics
Change brain behavior (e.g. testosterone supposedly increases aggression, though it’s not clear that it does)
Make sexual activity appealing
Sex hormones have strong effects on the limbic system, and the frontal lobe must spend its teenage years learning to cope with hormone-originated impulses
This is why teenagers are idiots

8. Reproductive Organs
The gonads produce the gametes, but other organs are involved in the meeting of the gametes
Male organs are devoted to producing, processing, and delivering sperm cells
Female organs are for receiving semen and growing and nourishing the fetus once it is formed

9. Male Reproductive Organs
The primary male reproductive organs are the testes that produce sperm and testosterone
The other major organ is the penis, used to deliver sperm to inside the woman
The tubes running from the testes to the penis are called the vas deferens, and these also meet with the urethra which carries urine

10. Accessory Male Organs
The other male reproductive organs help create semen, which is a mixture of sperm cells with sugars, mucus, and alkaline chemicals to enable them to survive inside the woman
The vagina is acidic and generally hostile to life, so that it does not become infected
The most well-known of these is the prostate, which produces the watery alkaline fluid of semen
Enlargement can cause discomfort, also prone to cancer

11. Female Reproductive Organs
The female ovaries are attached via the oviducts to the uterus
The oviducts were formerly known as the Fallopian tubes
The uterus’s connection to the exterior of the body is a muscular canal called the vagina
The vagina has a small penislike organ called the clitoris at the anterior portion

12. Why Do Women Have A Clitoris?
Answer: The same reason men have nipples!

13. Pregnancy
The actual fertilization event occurs in the oviduct, which is where the egg cell is initially placed at the peak of the ovarian cycle
If fertilized, the egg is migrated into the uterus where it becomes implanted
The uterus then develops an organ called the placenta which nourishes the fetus
The fetus develops for 9 months before being pushed out of the vagina by uterine contractions, a painful and occasionally lethal process

14. Ovarian Cycle
The ovaries do not secrete estrogen and progesterone at a fixed level
During the ovarian cycle, estrogen and progesterone levels rise, triggering a release of an egg cell, which is called ovulation
If no sperm is present to fertilize the egg, the estrogen and progesterone levels will drop
This causes menstruation

15. Menstruation
The increasing hormones from the ovarian cycle trigger growth of the inner lining of the uterus, which is called the endometrium
Once the estrogen and progesterone levels fall, the endometrium disintegrates and leaks out of the vagina, a process called menstruation
When fertilization occurs, hormonal levels remain high so there is no menstruation
This is how the woman’s body is aware it is pregnant
Hormonal contraceptives trick the body into thinking it’s pregnant when it’s not (“The Pill,” “The Shot,” etc.)

16. Contraception
Many female contraceptive technologies are hormonal, in that they deceive the body by creating artificial hormone levels
These have an advantage of not interrupting the parasympathetic nervous system’s attempt to relax you into having sex
Barrier methods such as condoms also prevent pregnancy and also prevent excessive mucousa-to-mucousa contact
Mucosal layers of the genitals may carry bacterial and/or viral sexually transmitted diseases (STDs)

17. That’s our show!
There is no new content (aside from labs) for the semester!
Next week is exam #3
The following week is the last week with the cumulative final exam!