Seminiferous tubules

Seminiferous tubules are the tubes located within the testes where most of spermatogenesis, sperm production and maturation, takes place. Here, germ cells develop into spermatozoa by interacting with Sertoli cells. The seminiferous tubules are the site of the meiosis, or cell devision, which kicks off the creation of male gametes.

What are the seminiferous tubules?

The seminiferous tubules are a collection of small tubes inside the testicles where sperm are created and matured.

There are around 500–750 coiled seminiferous tubules inside of each testicle. These tubules, which may be up to 70 cm long, connect to the rete testis, a separate network of tubes that transport the sperm to the epididymis.

The seminiferous tubules take up about two-thirds of the space in the testicles. Their increase in size during puberty contributes to the growth of the testicles during that period.

Testosterone-producing Leydig cells are located between the seminiferous tubules, making up about 12% of the testicle. The tubules also contain Sertoli cells, which support and protect the developing sperm cells during spermatogenesis.

Sperm go through several developmental stages in the seminiferous tubules. Undifferentiated germ cells divide several times before undergoing a process of maturation, in which they develop a nucleus, acrosome, and the beginnings of a tail. Sperm are transported out of the seminiferous tubules via fluid secreted by the Sertoli cells, and finally gain motility in the epididymis.

Types of seminiferous tubules

Seminiferous tubules appear as two types, convoluted (coiled) and straight. Sperm production occurs in the coiled tubules, which make up the majority of the tubules. The ends of the coils become short, straight sections of the tubules. These lead to the rete testis and then to the epididymis, where sperm mature before they eventually leave the body.

Seminiferous tubules and male fertility

The seminiferous tubules are essential for male fertility because they produce sperm. Degeneration of the seminiferous tubules can lead to failed sperm production and loss of fertility, and may be related to:

The Sertoli cells in the seminiferous tubules also play an important role by forming the blood-testis barrier. This barrier protects developing sperm from the body’s immune system, and damage to the barrier can harm sperm production and fertility.

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