Introduction The male reproductive system has three principal functions: 1. The differentiation and maintenance of the primary and secondary sex characteristics under the influence of the hormone testosterone, made in the testes. 2. Spermatogenesis: The creation of the male gametes…
The organs of pregnancy The placenta serves as the point of exchange between the circulatory systems of the mother and fetus; it is also a hormone-producing organ ( Fig. 35.1 A). The fully developed placenta is a round oval organ…
Introduction The menstrual cycle defines the reproductive years of a woman’s life. It begins with menarche (the onset of menstruation) at about age 8 to 13 years and ends with menopause, which begins at about age 50 years. Evolutionarily, the…
Introduction The word skeleton comes from the Greek skellein, meaning to dry up; a dried-up body (skeleton soma) is one with only the bones remaining. Thus etymologically, but also in our cultural imagination, our bones refer to death. However, the…
Introduction Calcium plays a fundamental role in the physiology of all living organisms. At the macroscopic level, calcium is essential to maintaining the structural integrity of the skeleton. At the molecular level, calcium is central to several physiologic processes, including…
Introduction The adrenal gland plays a pivotal role in human endocrine physiology. It is subdivided into two sections, which function separately and originate from different embryonic tissues. The outermost shell of the adrenal gland, the adrenal cortex, is divided into…
Introduction The thyroid—named from the Greek thureoeides , meaning “shield-shaped”—bears two essential responsibilities in the endocrine system: Maintains metabolic rate necessary for heat generation in warm-blooded species. Promotes normal growth and development from fetal life into childhood. Roughly 5% of…
Introduction The hypothalamus and pituitary gland constitute an elegant center of hormonal control known as the hypothalamic-pituitary axis (HPA). Each hormone controlled by the pituitary is regulated separately along its own pathway, or “axis.” The HPA integrates information from the…
Introduction In the 1920s, Frederick Banting and Charles Best isolated insulin and made possible the treatment and survival of millions of diabetics. This helped initiate the era of modern medicine, in which the empiricism of the 18th century and its…
D.L. is a 9-year-old female who is being seen by her pediatrician for the fifth time this summer. She has been seen for multiple gastrointestinal (GI) complaints including abdominal pain, bloating, and frequent nausea. Her mother is worried because she…