Reproductive System

Reproductive System Males Sex Organ: Penis In males, the testes produce testosterone which causes sperm production to occur. In addition, testosterone causes further development of the penis, prostate gland, deeper voice, broader shoulders, and increased upper body muscle mass. Sperm live in the testes for approximately 30 days, after which their mortality causes an increase in testosterone to produce more sperm.

Females Sex Organ: Ovaries/Vagina In females, hormonal cycles occur in both estrogen and progesterone. On an approximately 28 day cycle, one ovary will release an ovum (egg) to potentially become fertilized and produce a new life. The development of the egg and the inner lining of the uterus, the organ where the fetus will develop, are caused by fluctuations in the hormones estrogen and progesterone.

Menstruation At the beginning of the cycle, estrogen and progesterone levels that are very low begin to rise and around day 14 of the cycle, there is a slight surge in estrogen as the egg is released from the ovary (ovulation). Levels of estrogen and progesterone rise causing the uterine lining to thicken in preparation for a potentially fertilized egg. If the egg is not fertilized, progesterone levels drop, the uterine lining dies, and muscle contractions of the uterus cause the lining to exit the body through the vagina thereby starting her “menstrual cycle or period.” Once estrogen and progesterone levels drop below a particular level the cycle (feedback loop) begins again.

Fertilization Fertilization occurs when a sperm meets a egg creating a zygote. Once an egg is fertilized, it will bury into the uterine lining. The developing embryo produces a chemical called human chorionic gonadotropin (hCG). The hCG circulates in the blood and is filtered out in the urine. The presence of hCG triggers a positive response on an Early Pregnancy Test (EPT). Once the embryo is embedded in the uterine lining (implantation), a temporary organ known as the placenta will develop. Cell division in the embryo will increase as different organs and organ systems develop until the fetus is born.

Development There are 3 stages of birth 1. Contractions/breaking of water 2. Expulsion of the baby/birth 3. Expulsion of the placenta/afterbirth After birth, children go through several different developmental changes including infancy (birth – 2 years), childhood (2-13 years), adolescence (13 – 18/20 years), and finally adulthood (20 years until death).