| Lab 16 Male Reproductive System: 1) Index 2) Introduction 3) Things to Identify 4) The Testes 5)Tubuli Recti and Rete Testes 6) Efferent ducts and Ductus Epididymis 7) Ductus Deferens 8)Seminal Vesicle 9) Prostate Gland 10) Penis 11) Practical |
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The
Testes
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# 163 - Testis, human, 1.5 mm, h-e # 164 - Testis, human, sec., Mallory stain # 231 - Testis, epididymis, mature, iron hematoxylin, l.s. |
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The testis has a dense connective tissue capsule, the tunica albuginea. In the region of the mediastinum testis, the tunica albuginea is thickened and is penetrated by blood vessels and nerves. Septa pass inward from the mediastinum, dividing the testis into lobules. Observe the seminiferous tubules cut in various planes of section. Each tubule is enclosed within a basement membrane (basal lamina) which appears moderately thick and glassy. Surrounding the basement membrane is a layer of collagenous connective tissue which increases in thickness with age. The stratified epithelium of the tubule is composed of seminiferous tubules and the spermatogenic cells. The pillar-like Sertoli cells extend from basement membrane toward the lumen of the tubule. These cells are difficult to see, however. They are most readily identified by their nuclei, which are elongated and stain evenly due to a relative absence of heterochromatin. Their nucleoli are large and distinct, and are probably their most obvious characteristic. The Sertoli cell nuclei are found within the first, or more often within the second tier of cells. Spermatozoa may be seen embedded within the cytoplasm of Sertoli cells. What role do these cells play during spermiogenesis? Spermatogenesis proceeds in waves of activity along the tubule. Various cell types will be found grouped in different segments. Thus, one may find sperm heads embedded in Sertoli cells in one segment and clusters of spermatids in another. The lumen of the tubule contains spermatogonia, a few desquamated spermatids and some cellular debris. Identify spermatogonia, primary spermatocytes and spermatids. The newly formed spermatids lie close to the lumen and contain relatively small, round, dark, central nuclei. Review the process of spermiogenesis (see pp. 641-645 in Ross). Identify the maturing spermatozoa in both sections of your slide of the testis. Distinguish between the terms spermatogenesis and spermiogenesis. Look for clusters of interstitial cells (Leydig cells) in the C.T. between seminiferous tubules. These are large cells with spherical nuclei and prominent nucleoli. These cells secrete what? The tunica albuginea appears as a broad band of connective tissue. The nuclei of the Sertoli cells and their prominent nucleoli are clearly demonstrated. Identify spermatogonia, primary spermatocytes, and spermatids. The interstitial cells have a vacuolated cytoplasm characteristic of steroid hormone-secreting cells. Spermatozoa are found near the lumen of the seminiferous tubules with their heads embedded in the cytoplasm of the Sertoli cells. REFERENCES:Gartner, p. 368-371Ross, p. 666-669 DiFiore, pp. 378 - 281 Wheater pp. 324 - 326
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This is a low power image of the Testes. The blue arrow is pointing to the Dense Connective tissue capsule of the testes called the Tunica Albuginea. The area of the Tunica Albuginea that is thickened and pierced by blood vessels is known as the Mediastinum Testes. The Red arrow is pointing to the functional units of the testes called the Seminiferous Tubule. It is here where the cells that give rise to sperm are located. Red arrow - Seminiferous Tubules Blue arrow - Tunica Albuginea
Here is a closer look at the Seminiferous Tubules. The yellow arrows are pointing to the Basement Membrane which outlines the seminiferous tubule. This gets thicker as humans age. The red arrows are pointing to cells located in the Connective tissue located in between the seminiferous tubules called the Interstitial Cells of Leydig. They are responsible for producing Testosterone. The green arrow is pointing to the length of the epithelium of the seminiferous tubule where the spermiogenic cells are located. The blue arrow is pointing to another type of cell located with in the tubules called Sertoli Cells. They can be characterized by their relatively large nuclei and DARK STAINING NUCLEOLUS. These cells support and protect the developing sperm cells. Yellow arrows - Basement Membrane of Seminferous Tubule. Red arrow - Interstitial Cells of Leydig Green arrow - Epithelium of Seminferous Tubule Blue arrow - Sertoli Cells This is another look at the Seminiferous Tubule. The Red arrow are showing Interstitial Cells of Leydig. The white arrows are indicating Sertoli Cells with their characteristic Dark staining Nucleolus. The blue arrow is pointing to the region of the seminferous tubule where Spermatogenesis takes place, which is the differentiation of Spermatogonia to Primary Spermatocytes. The Green arrow is pointing to the region of the seminiferous tubule where Spermiogenesis takes place which is the differentiation of Spermatids to Spermatozoa (sperm). Red arrows - Interstitial Cells of Leydig White arrow - Sertoli Cells Blue arrow - Area of Spermatogenesis Green arrow - Area of Spermiogenesis |
Testes
Seminiferous Tubule
Seminiferous Tubules |
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Developing Cells of Seminiferous Tubule This is a high magnification of the cells located in the epithelium of the Seminiferous Tubule. The yellow arrow is pointing to a Sertoli cells, again easily recognizable by it's Dark staining NUCLEOLUS. The red arrow is pointing to the first cells of spermatogenesis and located closest to the basement membrane called Spermatogonia. The next set of cells located a little higher up in the epithelium are the Primary Spermatocytes, indicated by the blue arrow. They have a characteristic "DARK SPOTS" look in their nucleus, which are from the dark staining regions with in the nucleus of the developing cells. The spermeogenic cells develop in groups attached to each other and this is easily seen with the primary spermatocytes. The next type of cells are the Spermatids, (green arrows) which are located closest to the lumen and are rounded and sometimes have the heads of the Spermatozoa (black arrows), imbedded into them as they are developing in spermiogenesis.
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