The Testes

• The testes are surrounded by a peritoneal evagination on the anterior and lateral surfaces - the tunica vaginitis
• The capsule covering the testis is called the tunica albuginea due to the large number of collagen fibers it contains
• On the posterior side the tunica albuginea extends for a short distance to form a connective tissue plate - the mediastinum testis
• Connective tissue septae from the mediastinum radiate towards the tunica albuginea and divide the testis into many lobules
• Each lobule contains one to four seminiferous tubules/contorti
• These tubules are contorted loops that begin and end at the mediastinum and then change into the short straight tubules - the tubuli recti
• The latter opens into a network of spases in the mediastinum, called the rete testis
• From the rete testis the ductuli efferentes arise
• At this point arteries and nerves enter, while veins and lymphatic vessels exit the testis
• The interstitial connective tissue, containing the Leydig cells, are found between the seminiferous tubules

• Frontiers in Zoology 2005, 2:12doi:10.1186/1742-9994-2-12

• The epithelium lining the tubules appear stratified in cross-section
• The are surrounded by a few layers of smooth, muscle-like myoid cells on the outside
• There are 2 types of seminiferous/germinal epithelium:
  1. Spermatogenic cells - divide and give rise to sperm
  2. Sertoli cells - have a nutritional and supporting function

Spermatogenesis and spermatogenic cells

• Spermatogenesis is the process in which basal cells of the seminiferous tubules divide and differentiate into sperm
• As the cells differentiate the different cells are gradually pushed towards the lumen
• The dividing cells developing from the spermatogonia type B remain connected to one another by means of cytoplasmic bridges
• These intercellular bridges detach towards the end of spermatogenesis

Spermiogenesis

• This process is the final development of the spermatid into a sperm
• The spermatids come to lie between the long luminal processes of the Sertoli cells
• This process takes 64 days to complete

Structure of mature spermatozoa or sperm

• A sperm comprises a head, neck and tail
• The head consists mainly of a dark oval nucleus surrounded by a thin layer of cytoplasm
• Two centrioles are found in the neck
• The tail is subdivided into three sections:
  1. Middle part - thickest part
  2. Principal part
  3. End part

Sertoli Cells

• These cells are located between the spermatogenic cells
• They extend from the basement membrane to the lumen
• The nucleus is round to oval with indentations
• The spermatogonia are located between the lateral processes and basement membrane of the Sertoli cells
• The other stages of sperm development take place on the luminal side of the lateral processes
• Toward the luminal side the cells contain long processes against which sperm are located
• These cells have a supporting function

• They are short, straight and open into the rete testis
• Only Sertoli cells line these tubules

• Consists of anastomosing canals and spaces located in the mediastinum
• These spaces are lined with simple cuboidal and columnar epithelium

• Located between the seminiferous tubules
• This connective tissue contains blood and lymphatic vessels, interstitial or Leydig cells
• The Leydig cells are often found in small groups
• They have a large diameter and have oval nuclei with a pale appearance
• Secretes male sex hormones or androgens