Week 5 Study Guide6

Week 5 Study Guide6 - Lecture#8-9 Lecture Outline Male...

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Lecture #8-9: 2/2/10 Lecture Outline: Male Reproductive System Male Anatomy Male Gametogenesis Male Hormones Androgens: Dehydroepiandrosterones (DHEAs) Androstenedione Testosterone Dihydrotestosterone (DHT) Synthesis Effects Regulation Sexual Development Female Reproductive System Anatomy Fetal Sexual Differentiation Sex Chromosome Non-Disjunction Male Reproductive System In both sexes, the gonads are stimulated and sustained by the gonadotropins, Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH), secreted by the anterior pituitary. The secretion of the gonadotropins, in turn, is stimulated by the hypothalamic Gonadotropin Releasing Hormone (GnRH). Puberty commences the secretion of GnRH from the hypothalamus and thus triggers the development of the gonads and in the case of males, spermatogenesis. The sex hormones generated by this pathway negatively feedback and regulate the secretions from the hypothalamus and anterior pituitary. In the male reproductive system, testosterone inhibits gonadotropin release, and LH secretion primarily. In addition to the androgens, FSH secretion is also regulated by inhibin, which is discussed in further detail below. Anatomy The male reproductive system consists of the internal accessory glands and ducts and the external genitalia. The external genitalia consist of the penis and the scrotum. The penis consists of the corpus spongiosum and two corpora cavernosa. Refer to Figure 27 . The two types of corpora are spongy, erectile tissues that become engorged with blood during penile erection. The corpus spongiosum also contains the urethra, which is the passageway for urine and semen, though never simultaneously. The tip of the penis is called the glans and it is covered by a layer of skin, called the prepuce or the foreskin, which may be surgically removed through circumcision. The scrotum is a sac that contains the testes, which descend from the abdominal cavity during fetal development. The testes need to be kept in an external environment because healthy sperm development necessitates a cooler temperature, about 2-3˚F lower than the core
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body temperature. If one or both testes fail to descend into the scrotum during fetal development, a condition called cryptorchidism develops and sperm production is hampered or altogether inhibited, causing infertility. Nevertheless, those who suffer from cryptorchidism are capable of producing normal levels of androgens. A B Figure 27. Male Reproductive Anatomy. The male accessory glands include the prostate gland, the seminal vesicles, and the bulbourethral gland, which is also known as the Cowper’s gland. As it is seen in Figure 27-A above, the urethra has two branches that converge in the center of the prostate gland. The anterior branch opens to the bladder whereas the dorsal branch opens to the seminal vesicle and the ejaculatory duct leading to the vas deferens. Thus, the urethra is a passageway for both urine
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Week 5 Study Guide6 - Lecture#8-9 Lecture Outline Male...

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