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Human Reproduction. Topic 11.4. I. Human Reproduction: Males A. The testes produce gametes and hormones 1. Spermatogensis occurs within the testes, in the seminiferous tubules 2. Spermatagonia divide by mitosis to form more spermatagonia
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Human Reproduction Topic 11.4
I. Human Reproduction: Males A. The testes produce gametes and hormones 1. Spermatogensis occurs within the testes, in the seminiferous tubules 2. Spermatagonia divide by mitosis to form more spermatagonia 3. Some spermatagonia become primary spermatocytes which undergo spermatogenesis (sperm production by meiosis) 4. Primary spermatocytes produce secondary spermatocytes, which produce spermatids 5. Four haploid spermatids are produced by one diploid primary spermatocyte
6. Spermatids differentiate into a mature sperm by developing a flagellum, an enzyme cap (the acrosome) which is derived from the Golgi complex, and shedding cytoplasm a. The sertoli cells phagocytize much of the cytoplasm of the spermatid and have FSH receptors - FSH helps promote the increased production of testosterone by the interstitial cells of the seminiferous tubules b. The midpeice is located between the head and the flagellum, and is supplied with mitochondria
7. Sperm develop at a temperature lower than the core body temperature in the scrotum 8. The inguinal canals connect the scrotum to the pelvic cavity and contain the vessels, nerves, and ducts
B. A series of ducts store and transport the sperm 1. Sperm leave the seminiferous tubules and moves into tubules of the epididymis 2. Sperm mature in the epidiymis and may be stored there 3. Sperm are ejaculated from the epididymis into the vas deferens. 4. The vas deferens leads to the ejaculatory duct, which passes through the prostate gland and empties into the urethra 5. The urethra may carry urine or semen, and passes out through the penis
C. The accessory glands produce the fluid portion of semen 1. A single ejaculate of about 3.5 mL of semen contains about 400 million sperm cells 2. The paired seminal vesicles secrete a fluid rich in fructose and prostaglandins 3. The single prostategland, located under the bladder, secretes an alkaline fluid rich in prostoglandins a. This basic fluid helps to neutralize the acidic environment of the vagina 4. The paired bulbourethralglands produce a mucous secretion which lubricates the penis, facilitating penetration
D. The penis transfers sperm to the female 1. The glans is the enlarged tip of the penis a. The prepuce, or foreskin, is removed from the glans in a circumcision 2. The cavernous bodies are three columns of erectile tissue 3. During arousal, the arteries in the cavernous bodies dialate, which causes swelling which prevents venous drainage of the penis E. The hypothalamous, pituitary, and testes interact to regulate male reproduction 1. At about age 10, the hypothalamus secretes gonadotropin-releasing hormone (GnRH)
2. GnRH stimulates the anterior pituitary to secrete FSH (follicle stimulating hormone) and LH (lutenizing hormone) a. FSH stimulates development of the seminiferous tubules b. LH stimulates the interstitial cells to secrete testosterone 3. Inhibin, secreted by the sertoli cells, inhibits FSH production (another example of feedback) 4. Testosterone stimulates spermatogenesis, growth, and development of the male primary and secondary sexual characterisics a. Male secondary sex characteristics include facial and chest hair, deepened voice, more pronounced adam’s apple and inc. muscle mass
