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BIOL 302 – Male Reproductive System

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BIOL 302
Mungo Marsden

BIOL 302 – Male Reproductive System Consists of:  Testes  Ducts  Exocrine glands  Glands Testes  Double external layer: tunica vaginalis (parietal – outer; visceral – inner)  Capsule: tunica albuginea  Septa that emanate from this capsule (tunica albuginea) to subdivide the testis into lobules. Lobules have seminiferous tubules surrounded by connective tissue that produce sperm.  The septa converge towards the midline of the posterior border, meeting along a thickening of the tunica albuginea called the mediastinum testis.  Rete testes: network of delicate tubules located in the hilum of the testicle that carries sperm from the seminiferous tubules to the efferent ducts.  Ductus efferentes: The efferent ducts connect the rete testis with the initial section of the epididymis.  Epididymis: a highly convoluted duct behind the testis, along which sperm passes to the vas deferens.  Vas deferens: the duct that conveys sperm from the testicle to the urethra. Seminiferous Tubule  Seminiferous tubules are located in the testes, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa. The epithelium of the tubule consists of Sertoli cells, which are tall, columnar type cells that line the tubule. In between the Sertoli cells are spermatogenic cells, which differentiate through meiosis to sperm cells.  Site of spermatogenesis (production spermatozoa) and spermiogenesis (maturation of spermatozoa). It is a peripheral to central maturation (new cells in periphy and mature as they move to the centre).  Spermatogonia type A  spermatogonia type B  spermatocytes  spermatids  spermatozoa o Spermatogonia Type A: On basement membrane, small round nuclei, fine chromatin grains and one or two nucleoli. They are stem cells to divide to form both type A and type B spermatogonia. o Spermatogonia Type B: On basement membrane, pale cytoplasm, round nuclei with chromatin granules of variable size which attach to nuclear membrane and one nucleolus. They do not function as stem cells and always form primary spermatocytes. o Primary Spermatocytes: Large round pale nuclei, visible chromosomes, middle of epithelium. They appear larger than spermatogonia. The completion of the first meiotic division results in the formation of secondary spermatocytes. o Secondary Spermatocytes: They are smaller than primary spermatocytes. They rapidly enter and complete the second meiotic division and are therefore seldom seen in histological preparations. Their division results in the formation of spermatids. o Spermatids: small round nuclei, not a lot of cytoplasm, close to lumen. They are small with an initially very light (often eccentric) nucleus. The chromatin condenses during the maturation of the spermatids into spermatozoa, and the nucleus becomes smaller and stains darker. o Spermatozoa: elongated, condensed nuclei, no cytoplasm, close to lumen  Sertoli Cells: support and nutrition of germ cells. Tall cells in vertical orientation, pale nuclei, prominent nucleolus, nuclei middle of epithelium  The seminiferous tubule is lined by a stratified epithelium, lined by a basal membrane and covered by a sheath of connective tissue. The connective tissue contains fibroblasts and myoid cells. The myoid cells are contractile, and produce gentle peristaltic waves in the tubules.  The Sertoli cells have pale nuclei and dense nucleoli. The spermatogonia and the nuclei of the Sertoli cells lie on the basal membrane. The nuclei of these cells are pale, with prominent nucleoli.  Primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa are in the adluminal compartment.  The lumen also contains some spermatozoa, and cellular debris.  Leydig cells: located in the interstitial tissue between the convoluted seminiferous tubules, they surround blood and lymph vessels. They constitute the endocrine component of the testis. They synthesize and secrete testosterone. They are vacuolated and have have smooth ER and Golgi bodies. Leydig cells occur in clusters, which are variable in size and richly supplied by capillaries. The cytoplasm is strongly acidophilic and finely granular. The nucleus is large, round and often located eccentric in the cell. Tubes and Ducts Consists of:  Rete testes  Ductuli efferentes  Epididymis  Ductus deferens (vas deferens) Function:  Move sperm from testes to exterior for ejaculation  Modify sperm  Add fluids to ejaculate Basic structure of all tubes and ducts:  Mucosa: pseudostratified epithelium, lamina propria  No submucosa  Muscularis externae: smooth muscle Rete Testes  Function: Collect sperm from semiferous tubules; spermatozoa pass through the rete testes to the ductili efferentes  Convoluted ducts  Mucosa: simple cuboidal/low columnar epithelium  Looks like trabecular bone Ductuli Efferentes  Function: resorption of fluids from seminiferous tubules  Convoluted ducts  Mucosa: cuboidal/columnar epithelium – columnar are ciliated, cuboidal are absorptive – the two cell heights give a wavy appearance  Leave the retes testes and open into the epididymis  Muscularis externae: layer of smooth muscle  Connective tissue around smooth muscle Epididymis  Highly convoluted tubules  Function: maturation of sperm (gain motility and ability to fertilize), store sperm  Mucosa: pseudostratified epithelium with stereocilia, lumen has sperm  Muscularis externae: smooth muscle Vas Deferens  Connects the epididymis (where sperm is matured) to the urethra (where sperm is ejaculated). It is a muscular tube that propels the sperm to the urethra through peristalsis contractions where it exits the body.  Mucosa: pseudostratified epithelium with stereocilia, lamina propria  Muscularis externae: three layers of smooth muscle (longitudinal, circular, longitudinal)  Small lumen compared to layers of smooth muscle Accessory Reproductive Glands Prostate Gland  Function: secrete a slightly alkaline fluid, milky or white in app
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