Editing Anatomy and Physiology (section)

== Reproductive System and Selected Life-Span Changes ==

Female structures include the ovaries (oocytes, estrogen, progesterone), fallopian tubes (usual site of fertilization), uterus, cervix, and vagina. Male structures include the testes (sperm and testosterone), epididymis, vas deferens, seminal vesicles, prostate, and penis. The menstrual cycle is regulated by follicle-stimulating hormone and luteinizing hormone from the anterior pituitary, with ovulation at roughly day 14 of a 28-day cycle.

Selected physiologic changes in '''pregnancy''': plasma volume rises more than red cell mass, producing physiologic anemia of pregnancy; cardiac output and heart rate increase; the enlarged uterus can compress the inferior vena cava in the supine position, so left lateral positioning improves venous return and placental perfusion; progesterone relaxes smooth muscle, contributing to reflux, constipation, and urinary stasis.

Selected changes with '''aging''': decreased skin elasticity and subcutaneous fat, reduced bone density, decreased lung elasticity and cough effectiveness, stiffer arteries with higher systolic pressure, reduced glomerular filtration rate and drug clearance, decreased gastric acid, and blunted thirst sensation. These changes explain higher risk of falls, dehydration, pneumonia, adverse drug reactions, and atypical presentation of illness in which confusion may be the only sign of infection.