Ansc431%20spermatogenesis%20note%2007

Ansc431%20spermatogenesis%20note%2007 - Spermatogenesis...

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Spermatogenesis Yao ASCI 431 Advanced Reproductive Biology Lecturer: Humphrey Yao hhyao@uiuc.edu Topic: Spermatogenesis I. The Site of Spermatogenesis and the Functional Cell Types Participating (Slides 3-5) Spermatogenesis is the process of producing sperm with half the number of chromosomes (haploid) as somatic cells (diploid). The process of spermatogenesis then allows the recombination of male and female haploid gametes at fertilization. This provides genetic contributions from both parents without increasing the number of chromosomes each generation. Spermatogenesis occurs in medullary sex cords that are called seminiferous tubules (totaling about 3 miles in length in the bull). 1) The germ cells progress first from the diploid to haploid state (meiosis) and then change shape to become spermatozoa (spermiogenesis). 2) Sertoli cells, the only somatic cell in the seminiferous tubules, provide: Support for germ cells The environment for germ cells to develop and mature Substances initiating meiosis or the reduction from diploid to haploid cells Hormonal signals effecting pituitary gland control of spermatogenesis II. Spermatogenesis in the Sexually Mature Male (Slide 6) The gametogenic function of the testes is to produce the male gametes or spermatozoa. This process is termed, spermatogenesis. The sites of spermatozoa production are the seminiferous tubules. The spermatozoa originate from precursor stem cells that are called spermatogonia, and these cells line the basement membrane of the seminiferous tubule. Spermatogenesis can be divided into three portions: 1. Proliferative phase – spermatogonia stem cell renewal and proliferation 2. Meiosis -- production of the haploid spermatocytes 3. Spermiogenesis -- "metamorphosis" of spermatids into spermatozoa 1. Proliferative Phase: This phase begins with the division of the spermatogonia that line the seminiferous tubule, near the basement membrane. Spermatogonia originate at puberty by the proliferation of the gonocytes and are the descendants of the primordial germ cells . One or two divisions of spermatogonia occur to maintain their population in a stem cell pool. Of the cells resulting from these mitotic divisions, some spermatogonia stay in the "resting" pool, while the remaining type A spermatogonia proliferate several times and undergo 1 to 5 stages of division and differentiation. After the last division, the resulting cells are termed primary spermatocytes, which will enter the meiosis phase. Page 1 of 5
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Spermatogenesis Yao The primary spermatocytes then undergo the first of the two meiosis divisions. The first meiosis division (or meiosis I) produces two haploid secondary spermatocytes. The secondary spermatocytes undergo the second meiosis (meiosis II) and produce the spermatids.
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This note was uploaded on 04/10/2008 for the course ANSC 431 taught by Professor Bahr during the Spring '07 term at University of Illinois at Urbana–Champaign.

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Ansc431%20spermatogenesis%20note%2007 - Spermatogenesis...

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