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8 Cards in this Set
- Front
- Back
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How many sperm are produced a day, and how long does it take? |
100 million 64 days |
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What do sperm start out from? |
At puberty, spermatagonia (2n diploid cells) located in the basal compartment of the wall of the seminiferous tubule will be initiated and divide mitotically |
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Describe what initial division of germ cells produces? |
Type A and Type B cells **Dark type A cells replenish spermatagonia stores **Light type A cells become type B cells **Type B cells move into the adluminal compartment and become primary spermatocytes |
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Describe the types of division the germ cell undergoes |
Spermatagonia A (mitosis) Spermatagonia B (mitosis) Primary spermatocyte. Migrates to adluminal compartment. (1st meiosis) Secondary spermatocyte (2nd meiosis) Spermatids (mature) Spermatozoa During development the cells of the spermatogenic series are supported by Sertoli cells |
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What is spermiogenesis? |
The process by which spermotids are transformed into mature spermatozoa
No further division, only differentiation |
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Describe the main changes of spermiogenesis |
1. Golgi apparatus makes large, membrane-bound vesicle 2. Acrosomal vesicle is applied to pole of developing nucleus to become the acrosomal head cap. 3. Both centrioles migrate to opposite end to acrosomal head cap. 4. One centriole elongates to form flagellum 5. Cytoplasm migrates to surround first part of flagellum 6. Any excess cytoplasm phagocytosed by Sertoli cells |
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What then happens to mature spermatozoa? |
Lack of motility renders them sterile. Released from Sertoli cells by spermiation. In the epididymis, the spermatazoa gain motility and become capable of fertilisation |
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Outline the regulation of spermatogenesis |
GnRH is released from hypothalamus via hypophyseal portal tract GnRH acts on anterior pituitary to stimulate release of FSH and LH LH acts on Leydig cells, bringing about synthesis of testosterone Testosterone and FSH act on Sertoli cells to aid development of gametes Once spermatogenesis reaches sufficient levels, Sertoli cells produce inhibin which has a negative feedback effect on FSH secretion. |
