The Testes

testesThe word comes from the Greek word “orchis”. The testes is the male hormone gland and is important for sexual function and normal, everyday male function.

There are two testes that are oval shaped like a plum measuring around 2.5-3 cm across and 4-5cm in length. They have a smooth surface with the left testes positioned slightly lower than the right. They weigh around 15g each and are suspended outside of the body in a sac called the scrotum.

Each Testes are divided into 400 segments called lobules (1). Each lobule has 2-4 seminiferous tubules. Each Testes has between 600 and 1200 seminiferous tubules totalling 400 metres in length in the whole testes. Each individual seminiferous tubule is around 50cm in length.  These seminiferous tubules have three main functions:

Sertoli cells line the seminiferous tubules with Sertoli cells which act as a kind of “nursery” for the developing sperm. It is crucial that they maintained in the correct temperature. The complex process of maturing sperm is called meiosis i.e. the making of sex cells. During meiosis, cells, are created with only half the number of chromosomes. These are called gametes or sperm. Surrounding these tubules are Leydig cells that make and excrete testosterone and other hormones.

seminiferous tubulesThe seminiferous tubules have two parts to each; a straight (4) and a convoluted section (2). The straight section allows mature sperm to leave the testicles. In the convoluted section, meiosis takes place. The reason for their complex construction is thought to be so that the tubules prevent large molecules from entering, one of the body’s ways of stopping an immune response.

The seminiferous tubules open out into a series of larger tubes or channels called the tete testis (6). Here the sperm are transported from the testes to the sperm transport ducts of the penis, the efferent ducts.