Chapter 45 Human Reproduction and Development

Chapter 45 Human Reproduction and Development - Chapter 45...

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Chapter 45 Human Reproduction and Development I. Human Reproductive System A. Overview 1 Male gonads (testes) produce sperm plus hormones for reproductive function and secondary sexual characteristics. 2 Female gonads (ovaries) produce eggs plus reproductive hormones. 3 All gonads are similar in form until the seventh week of development; they do not become functional until early adolescence. B. Male Reproductive Organs 1 Where Sperm Form a. The testes reside in the scrotum, which is a few degrees cooler than body temperature for proper sperm development. b. Each testis is divided into about 300 lobes, each of which contains two or three seminiferous tubules where sperm are continuously formed beginning at puberty. 1) Diploid spermatogonia undergo mitosis Æ primary spermatocytes, which undergo meiosis I Æ haploid secondary spermatocytes, which undergo meiosis II Æ haploid spermatids Æ mature sperm. 2) Sertoli cells in the tubule provide nourishment and chemical signals to the developing sperm. 3) Each sperm has a head (nucleus and acrosome), midpiece (mitochondria), and tail (microtubules). 2 How Semen Forms a. Sperm move from a testis Æ epididymis (for maturation and storage) Æ vas deferens Æ ejaculatory ducts Æ urethra. b. The sperm-bearing fluid—semen—is formed by secretions from the seminal vesicles (fructose and prostaglandins) and the prostate (buffers against acidic vagina). c. The bulbourethral glands secrete a mucus-rich fluid into the vagina during sexual arousal. C. Hormonal Control of Male Reproductive Functions 1 Testosterone, produced by interstitial cells in the testes, stimulates spermatogenesis, the formation of reproductive organs and secondary sex characteristics, and helps to develop and maintain normal (or abnormal?) sexual behavior. 2 Luteinizing hormone is released from the anterior pituitary (under prodding by GnRH from the hypothalamus) and stimulates testosterone production. 3 GnRH also causes the pituitary to release FSH, which stimulates the production of sperm, beginning at puberty. D. Female Reproductive Organs 1 Two ovaries in the lower abdominal cavity release eggs (monthly) and secrete estrogen and progesterone.
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