Archive for December 29th, 2009


Remember to view and download the full article (this has been cut short and the diagrams have been omitted) at – all articles are available free!


Spermatogenesis is the biological process whereby spermatogonia (the germ cell) develop into spermatozoa (the mature sperm cells). This process takes place in the seminiferous tubules of the testes; this is the starting point for spermatogenesis. Stem cells adjacent to the inner tubule wall divide, beginning at the walls and proceeding into the innermost part, or lumen producing immature sperm. Maturation occurs in the epididymis where sperm develop a tail and become motile.

Anatomy of the Testes

Seminiferous tubules comprise the majority of the structure of the testes. The remaining spaces between the tubules are occupied by interstitial tissue.

Interstitial Tissue

The interstitial tissue comprises mainly of blood vessels, lymph gaps, connective tissue and Leydig cells (specialised cells found in interstitial tissue adjacent to seminiferous tubules). Mast cells and macrophages are also present in small numbers.

Leydig Cells – These cells have an abundance of smooth endoplasmic reticulum and no rough endoplasmic reticulum, along with large amounts of mitochondria, lipid droplets and centrioles. They also have a prominent Golgi complex. Another cell specific feature is the receptors they have on their cell membrane that are highly specific to luteinising hormone (LH) – This differentiates them from other testicular cells, as they are the only cells to have these receptors.

Follicle-stimulating hormone (FSH) increases the response of Leydig cells by increasing the number of LH receptors expressed on their surface. The LH receptors when stimulated secrete steroidal hormones such as testosterone. Testosterone has a key role in the development of spermatozoa (spermatogenesis).

Seminiferous Tubules

Typical seminiferous tubules include the Sertoli cells and germ cells. The epithelium of these tubules is known as the germinal epithelium. The seminiferous tubules have a fluid filled lumen; mature spermatids are released into this lumen as fully mature spermatozoa. Myoid cells surround the basement membrane of seminiferous tubules; they are contractile in nature and their contractions move sperm along the seminiferous tubules.

Sertoli Cells

Sertoli cells have a main function in the nurturing of spermatozoa through their early stages of development from germ cells right up to their mature spermatid form (before being released into the seminiferous tubules to become spermatozoa). Sertoli cells therefore have a prime role in the co-ordinating of spermatogenesis – without Sertoli cells, spermatogenesis cannot take place.

Near the base of the cells in their lateral walls, tight junctions join Sertoli cells to one another. The formation of tight junctions means that inter-cellular diffusion of material is prevented. The tight junctions form a complete barrier that divides the tubule into a basal compartment and an adluminal compartment. Different types of germ cells occupy the different compartments. This barrier forms a blood-testes barrier, which isolates spermatocytes from the rest of the body, allowing for the environmental conditions required for spermatogenesis.

An important feature of the blood-testes barrier is that it prevents immune cells from reaching the haploid cells produced during spermatogenesis. This is important because the haploid cells are not recognisable as ‘self’ cells, meaning if the immune cells could reach them, they would destroy them. If damage were to occur to the tight junctions forming the blood-testes barrier, immune cells would be able to come into contact with the germ cells triggering an immune response and the production of antibodies causing the sperm cells to become non-functional – resulting in infertility of the male. Sertoli cells are also unable to proliferate; the body is unable to replace any lost Sertoli cells.

Sertoli cells have cell-membrane receptors specific for FSH, which when stimulated increases production of cyclic AMP

They are also able to convert cholesterol to pregnenolone, which is then converted to testosterone. They also produce specific proteins such as androgen binding protein under the influence of FSH and testosterone.


Below is only the introduction to this article on cryptorchidism, if you are interested and this is what you were looking for, then head over to our website, where you can download this article and many more for free! If you don’t want to download them, then it is possible for you to view them online in your browser!

Also remember to check out the new questions being added all the time, you can see which articles have questions by searching the index, where you will see a link next to the article like this [Questions]


Cryptorchidism is a disorder where either one or both testes fail to descend and are therefore absent from the scrotum.  This usually occurs during foetal development when the testes begin their movement or descent from an abdominal position through the inguinal canal into the scrotum. Because the testes have failed to descend and therefore remain within the body, the temperature is too hot for sperm production to occur, rendering the male infertile.

There are however varying levels of cryptorchidism:

• Undescended testicles may later fully descend (usually within 1 year) leaving the male without fertility problems

• Testicles which have not fully descended but have partially reached the scrotum may be able to produce some sperm

• Only on testicle may not descend, but as the other will have fully descended the male will be fertile

• If both testicles fail to descend (bilaterally cryptorchid testes) then the male is infertile

Only sperm production is affected however (due to the high body temperature) which means that the natural hormone production of the testes are unaffected, the male will still behave normally therefore and express normal sexual behaviour.

The possible outcomes of testes failure to descend:

• Testis could be found anywhere along the “path of descent” from high in the posterior (retroperitoneal) abdomen, just below the kidney, to the inguinal ring

• Testis could be found in the inguinal canal

• Testis could be ectopic, that is, found to have “wandered” from that path, usually outside the inguinal canal and sometimes even under the skin of the thigh, the perineum, the opposite scrotum, and femoral canal

• Testis could be undeveloped (hypoplastic) or severely abnormal (dysgenetic);

• Testis could have vanished – May therefore be anorchid or monorchid (Not formed)