REPRODUCTIVE SYSTEM

Male  

 Reproductive  

System is illustrated to the right. Sperm are produced in the testes located in thescrotum. Normal body temperature is too hot thus is lethal to sperm so the testes are outside of the abdominal cavity where the temperature is about 2° C (3.6° F) lower. Note also that a woman’s body temperature is lowest around the time of ovulation to help insure sperm live longer to reach the egg. If a man takes too many long, very hot baths, this can reduce his sperm count. Undescended testes (testes are supposed to descend before birth) will cause sterility because their environment is too warm for sperm viability unless the problem can be surgically corrected. (Undescended testes are also very prone to developing cancer, thus if they cannot be surgically moved, they probably will need to be removed.)   

THE FEMALE REPRODUCTIVE SYSTEM 

The female reproductive system is illustrated to the right. “Eggs” are produced in the ovaries, but remember from our discussion of meiosis, that these are not true eggs, yet, and will never complete meiosis and become such unless/until first fertilized by a sperm. Within the ovary, a follicle consists of one precursor egg cell surrounded by special cells to nourish and protect it. A human female typically has about 400,000 follicles/potential eggs, all formed before birth. Only several hundred of these “eggs” will actually ever be released during her reproductive years. (As just an example, if a woman would ovulate from age 15 to age 55, which is a long time, that’s 40 years. If we’d assume 13 28-day cycles per year, that would be 40 × 13 = 520 potential times an “egg” could be released.) Normally, in humans, after the onset of puberty, due to the stimulation of follicle-stimulating hormone (FSH) one “egg” per cycle matures and is released from its ovary. Ovulation is the release of a mature “egg” due to the stimulation ofleutenizing hormone (LH), which then stimulates the remaining follicle cells to turn into a corpus luteumwhich then secretes progesterone to prepare the uterus for possible implantation. If an egg is not fertilized and does not implant, the corpus luteum disintegrates and when it stops producing progesterone, the lining of the uterus breaks down and is shed.