Male Reproductive System 2010 - Copy

Male Reproductive System 2010 - Copy - 1 Male Reproductive...

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1 Male Reproductive System 2010 The male reproductive system consists of the testes, their associated ducts and accessory glands, and the intromittent organ, the penis. Testis : Each testis is surrounded by dense CT, called the tunica albuginea . On the posterior surface the tunica albuginea is thickened to form the mediastinum testis which gives off CT septae that divide the testis into 200-300 lobules. Each lobule contains 1-4 seminiferous tubules enmeshed in loose CT that contains blood vessels, lymphatics, and nerves. The bulk of testicular tissue is made of these tubules. (The combined length of these seminiferous tubules is nearly 2000 feet, much longer than the Empire State Building is high). Outside the tunica albuginea and covering the tunica albuginea is a serosal (mesothelium) sac, called the tunica vaginalis . (This is really a remnant of the abdominal peritoneum. In the embryo, the testes develop in the abdominal retroperitoneal space near the kidneys and descend to the scrotum before birth). Seminiferous tubules are highly convoluted and they are surrounded by a thick basal lamina (basement membrane). Outside the basal lamina (or, if you wish, underneath the basal lamina) is CT which contains not only fibroblasts but also flattened smooth muscle cells called myoid cells or peritubular contractile cells. Also, within this CT that separates the seminiferous tubules are the interstitial cells of Leydig which produce testosterone. ( See below). The seminiferous tubules are lined by a special stratified epithelium call seminiferous epithelium which consists of two types of cells: the Sertoli or supporting cells and the cells that constitute the spermatogenic line (or sperm cell line ). It is this sperm cell line that creates the stratified appearance. The epithelium contains several stages in the developmental sequence (called spermatogenesis) that leads to mature spermatozoa. The earliest of these cells is the primitive germ cell called the spermatogonium (pl. spermatogonia). At puberty, these spermatogonia begin dividing by mitosis producing more spermatogonia some of which will remain as stem cells and some of which will undergo meiosis to become haploid spermatocytes. The spermatogonia cells rest on the basal lamina. They are relatively small cells with densely stained, round nuclei. Spermatogonia that will undergo meiosis differentiate into primary spermatocytes which are diploid in chromosomes but have 4N of DNA. Primary spermatocytes are larger than the stem cells and their nuclei are filled with clumped chromatin
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2 as they are in various stages of meiosis. (In human males, prophase I lasts about 22 days, so most of the cells we see in the seminiferous tubules will be primary spermatocytes. At the completion of meiosis I, secondary spermatocytes are formed which are haploid in chromosome number and 2N in DNA. (Remember anaphase I reduces the chromosome number to haploid, but the chromosomes still consist of two sister chromatids, hence 2N in
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This note was uploaded on 11/08/2011 for the course SCIENCE 3254 taught by Professor Dr.shoupe during the Spring '11 term at Fort Valley State University .

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Male Reproductive System 2010 - Copy - 1 Male Reproductive...

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