Lecture Notes for Bio 106

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Reproductive roles Male’s job is to get the sperm to the egg The sperm are specialized to deliver the male’s genes to the egg Female’s job is to produce a gamete (egg) containing the female’s genes Egg is specialized to nourish the embryo Egg is large and contains nutrients Egg must be moved along Female must also nourish and protect the embryo and fetus This is the job of the uterus Male reproductive strategy: Produce millions of gametes and hope that one makes it to the egg Female reproductive strategy: Invest heavily in one gamete and nourish and protect it Egg Cell (Ovum; 1 copy each chromosome) Sperm Cell (1 copy of each chromosome) MEIOSIS (a type of cell division that begins with a cell with 2 copies of each chromosome and ends with 4 cells with 1 copy of each chromosome) FERTLIZATION (Fusion of Egg and Sperm nuclei; creates a cell with 2 copies of each chromosome)

Zygote (cell formed by fusion of egg and sperm; has 2 copies of each chromosome; will develop into new individual) Ovary (in female) Testis (in male)

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Gonads: a. Testes in male b. Ovaries in females 1. produce gametes Male = sperm Female = ovum or egg join zygote; new individual 2. produce sex hormones testosterone estrogen + progesterone Male Reproductive System Testes located in scrotum why? sperm don't survive well at body temperature is 3-4o F cooler temp kept constant by reflex how? – pass through the inguinal canal before birth hole usually closed over with connective tissue possible problems 1. cryptorchidism failure of the testes to descend if not corrected, results in sterility corrected by surgery or by administering hormones 2. inguinal hernia inguinal canal does not completely close intestine may push into opening correct with surgery more common in men but may occur in women

Inside Testes 1. seminiferous tubules about 1000 site where sperm are produced by a process called spermatogenesis produce 100 million+ sperm each day from puberty until death spermatogenesis A. takes place in an orderly progression from the outside edge of seminiferous tubule to inside (lumen) B. involves changes in genetic information and changes in the shape and functioning of cell sperm carry father’s genetic contribution to next offspring body cells have 2 copies of each chromosome (1 from Mom & 1 from Dad) gametes (egg or sperm) can have only 1 copy of each chromosome meiosis = the type of cell division that produces gametes 1 cell with 2 copies of each chromosome Meiosis spermatogenesis 4 cells with 1 copy of each chromosome Sperm Structure

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designed to deliver male’s genetic contribution to next generation 1. Head – contains male’s genetic contribution to next generation; almost all nucleus 2. Acrosome – a sac containing enzymes to will allow the sperm to digest the outer layers around egg so sperm nucleus can reach egg nucleus 3. Mitochondria – energy to fuel the trip to egg 4. Tail (or flagellum)—has contractile fibers for motility; allows the sperm to swim to egg 2. interstitial cells - produce male sex hormone - testosterone Still in testis – between seminiferous tubules Beginning at puberty these cells secrete testosterone They are stimulated to secrete testosterone by LH, a hormone produced by the anterior pituitary gland LH (from anterior pituitary) stimulates the release of testosterone

HORMONES chemical messengers produced by certain glands and released into the blood hormone reaches all cells only cells with a receptor for that hormone can respond a cell responds by doing what that cell does it might divide it might produce a chemical it might increase rate of certain chemical reactions so hormones have different effects on different cells cells without receptors for that hormone cannot respond

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Cell 1 (with receptor) Effect 1 Cell 2 (with receptor) Effect 2 Hormone Into blood supply throughout body Cell 3 (with receptor) Effect 3 Cell 4 (no receptor) No Effect Testosterone causes: development of male reproductive...
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