Anatomy and Physiology Answer Key

A conducts sperm to the urethra b stores urine c

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Unformatted text preview: tion of the membrane that forms a fast block to further sperm entry. (d) Cortical reaction: A permanent change in the egg surface that provides a slow (permanent) block to sperm entry. Involves the release of cortical granules into the perivitelline space, followed by the release of substances from the granules that raise and harden the vitelline layer. (e) Fusion of egg and sperm nuclei: Results in the formation of a diploid zygote and initiates the rapid cell division that follows fertilization. (e) Urethra (f) Testis (g) Scrotal sac (scrotum) (a) Spermatogenesis (gametogenesis is also correct). (b) FSH and testosterone (reference to ICSH which controls testosterone secretion is also appropriate). (c) Seminiferous tubules of the testes. (d) Process completed in the epididymis. Sperm cannot move easily in an acid environment. The alkaline prostate secretions neutralize the acidity of the vaginal secretions providing conditions suitable for the sperm to move. About 100-400 million sperm are produced because only a very small percentage of them eventually reach the ovum (remember that the sperm must negotiate the cervix and then find their way into the fallopian tube). Note: Although only one sperm is needed to fertilize the egg, the combined action of the enzymes from a large number of sperm is needed in order to help digest the jelly-like barrier around the egg. 2. It is necessary to prevent fertilization of the egg by more than one sperm because this would result in too many chromosomes in the zygote (making the zygote non-viable or unable to survive). Triploidy (a condition resulting from two sperm fertilizing an egg) is frequently found among spontaneous miscarriages. 3. (a) Oocyte is arrested in metaphase of meiosis II after it has already undergone the first meiotic division. (b) Meiotic division proceeds to completion if the egg is fertilized (i.e. fertilization triggers completion). 4. (a) Zygote nucleus: sperm: 50%, egg: 50% (b) Zygote cytoplasm: sperm: 0%, egg: 100% 5...
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This document was uploaded on 01/28/2014.

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