The remaining cases of complete isosexual precocity are caused by central nervous system (CNS) lesions. These lesions include neoplasms, trauma, hydrocephalus, postinfectious encephalitis, congenital brain defects, tuberous sclerosis and neurofibromatosis…
The risk of pregnancy without contraception is 2–4% for each unprotected act of intercourse. In 100 women using no contraception, 85 pregnancies occur per year. Approximately half of all pregnancies…
Development of the breast The human mammary gland is derived from ectoderm. It is first visible in the 4-week embryo as a bud or nodule of epithelial tissue appearing along…
Ovary The ovary has two distinct functions: germ cell production and steroid hormone biosynthesis. Germ cell support occurs in microscopic structures known as ovarian follicles. Resting follicles each contain a…
Thyroid gland Maternal thyroid hormone is critical for normal embryonic and fetal development. Among the hepatic proteins stimulated by the elevated circulating levels of estrogen in pregnancy is thyroid-binding globulin…
Chromosomes Human chromosomes are complex structures consisting of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein. Each single helix of DNA is bound at each end with a telomere and…
The egg At ovulation, the egg is arrested in metaphase of the second meiotic division (Chapter 4). It is surrounded by a proteinaceous sphere called the zona pellucida. Those granulosa…
Successful reproduction is the ultimate definition of evolutionary fitness. Because fertilization occurs within the reproductive tract of humans, intimate contact between male and female is necessary for spontaneous conception to…
Gametogenesis and steroidogenesis proceed in a continuous fashion in the postpubertal human male. In contrast, the postpubertal human female exhibits repetitive cyclic changes in the hypothalamic–pituitary–ovarian axis that allow: (i)…
