Anatomy & Physiology

Anatomy & Physiology Study Guide • Major anatomical landmarks of the uterus include the body, isthmus, cervix, external orifices, uterine cavity, cervical canal, and internal orifices. The uterine wall consists of an inner endometrium, a muscular myometrium, and a superficial perimetrium. • A typical 28-day uterine, or menstrual, cycle begins with the onset of menses and the destruction of the functional zone of the endometrium. This process of menstruation continues from one to seven days. • After menses, the proliferative phase begins. The functional zone undergoes repair/thickens. The secretory phase follows the proliferative phase, during which uterine (endometrial) glands enlarge. Menstrual activity begins at menarche and continues until menopause. • The vagina is a muscular tube extending between the uterus and the external genitalia. A thin epithelial fold, the hymen, partially blocks the entrance to the vagina until physical distortion (often associated with sexual intercourse) ruptures the membrane. • The components of the vulva are the vestibule, labia minora, paraurethral glands, clitoris, labia majora, and lesser and greater vestibular glands. • A newborn infant can gain nourishment from milk secreted by maternal mammary glands. • Hormonal regulation of the female reproductive cycle involves the coordination of the ovarian and uterine cycles. • Estradiol, the most important estrogen, is the dominant hormone of the follicular phase. Ovulation occurs in response to a mid-cycle surge in LH. • The hypothalamic secretion of GnRH occurs in pulses that trigger the pituitary secretion of FSH and LH. FSH initiates follicular development and activated follicles and ovarian interstitial cells produce estrogens. High estrogen levels stimulate LH secretion, increase pituitary sensitivity to GnRH, and increase the GnRH pulse frequency. Progesterone, one of the progestins, is the principal hormone of the luteal phase. Fluctuations in estrogen and progesterone levels are responsible for the maintenance of the uterine cycle. The autonomic nervous system influences male and female sexual function: • During (male) sexual arousal, erotic thoughts, sensory stimulation, or both lead to parasympathetic activity that produces erection. Stimuli accompanying sexual intercourse leads to emission and ejaculation. Contractions of the bulbospongiosus muscles are associated with orgasm. • The events of female sexual function resemble those of male sexual function, with parasympathetic arousal and skeletal muscle contractions associated with orgasm. With age, decreasing levels of reproductive hormones cause functional changes: • Menopause (the time that ovulation and menstruation cease) typically occurs at ages 45–55. The production of GnRH, FSH, and LH rise, whereas circulating concentrations of estrogen and progesterone decline. • During the male climacteric, at ages 50–60, circulating testosterone levels fall, and FSH and LH levels rise. The reproductive system secretes hormones affecting growth and metabolism of all body systems. Achieve Page 352 of 368 ©2018