Testis

 

  

 
Testis explanatory video

 The testis is invested with a coat known as the tunica albuginea.  This coat is fibrous in nature.  The tunica vaginalis testis is a prolongation of the peritoneal covering of the testis during embryological descent of the testis  from the abdominal cavity into the scrotal canal.  The testis is further divided into lobules by the septula testis.  Each lobule contains numerous tubules known as seminiferous tubules.  The tubules are convoluted peripherally but they straighten out medially entering the rete testis where the ductuli are formed commencing on the superior pole of the testis at the head of the epididymis.  The ductuli efferentia later on become fused into one single duct in the region of the body of the epididymis.  This single duct is highly coiled and when straightened out can run for about 6 meters in length.  The duct finally leads on to the tail of the epididymis where it straightens out as the ductus deferens.

Cross section of the testis shows the seminiferous tubules containing germinal epithelium of the cuboidal variety.  The epithelium is stratified since it consist of many layers of cells.  There are cells in the periphery and the layers follow from the periphery to the center of the tubule (see diagram).  The cells in the periphery are quite large.  They have prominent nuclei.  They are basophilic and are called spermatogonia.

There are two types of spermatogonia

(1)   dark type

(2)   light type

 The dark type is darkly staining and more basophilic than the light type spermatogonia.

            The light type is divided into 2 types

(1)   type A

(2)   type B

 The next layer of cells are the spermatocytes.  These arise from the light type B cells by homotypical (mitotic) division.  Light type A cells give rise again to both types A and B by mitosis and the A further divides into B while B is transformed into spermatocytes in a recycling process.

       Spermatocytes are further divided into

(1)   primary spermatocytes

(2)   secondary spermatocytes

 The supporting cells or Sertoli cells are usually found as large cells in the periphery of the seminiferous tubules.  They have clear cytoplasm and are therefore light staining.

 The interstitial cells of Leydig are found in the interstices.  These are located around the basement membrane surrounding the seminiferous tubules.  They are thought to produce testosterone and estradiol.

Cells in testis

 

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  Electronic School of Medicine
Creator: Oluwole Ogunranti

 
              

Testis microscope video     Double click for full screen

 

 

 

 

Seminiferous tubule and sperm production

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

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