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)…
Internal genitalia Unlike the bipotential gonads and external genitalia, the male and female internal genitalia arise from separate duct systems (Fig. 6.1). Development of these structures occurs in parallel and…
Erection, emission and ejaculation An erection is a complex neuropsychologic event. It occurs when blood rapidly flows into the penis and becomes trapped in its spongy chambers. The three systems…
Puberty is the process by which the immature individual will acquire the physical and behavioral attributes that allow him or her to reproduce. In males, puberty is largely the response…
Puberty is the process by which the immature individual will acquire the physical and behavioral attributes that allow him or her to reproduce. In girls, puberty is largely the response…
Testes The testes have two distinct functions: spermatogenesis and androgen production. Spermatogenesis occurs within distinct structures called seminiferous tubules (Fig. 8.1). These tubules lie coiled within lobules whose ducts all…
