Chapter 44: Structure and Function of the Female Reproductive System

The organization of the uterus is detailed, emphasizing its three layers—the outer perimetrium, the dense muscular myometrium, and the functional innermost endometrium, which undergoes profound changes throughout the cyclic process. The menstrual cycle itself is governed by an intricate feedback loop orchestrated by gonadotropin-releasing hormone (GnRH) from the hypothalamus, pituitary hormones like follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and the ovarian sex steroids: estrogens (E1, E2, E3) and progesterone (EPT). These hormones drive the maturation and release of the ovum, followed by the formation of the corpus luteum, which sustains the secretory changes in the endometrium. The text extensively covers menopause, defined by the cessation of ovarian function and estrogen decline, which results in symptoms such as vasomotor instability ("hot flashes") and long-term health risks, notably osteoporosis due to increased bone resorption and elevated cardiovascular disease risk. Based on findings from pivotal studies, including the Women's Health Initiative (WHI), current recommendations for Hormone Therapy (HT) stress individualized risk assessment, prescribing the lowest effective dose for the shortest duration necessary, primarily for relieving debilitating menopausal symptoms in recently postmenopausal individuals. Finally, the chapter examines the mammary glands, explaining how estrogen promotes ductile growth and progesterone stimulates alveolar tissue, detailing the hormonal mechanisms—prolactin for milk production and oxytocin for ejection—that facilitate lactation.