Spermatogenesis and Sperm

16 mars 2023

Spermatogenesis is the process of sperm production in male animals, including humans. It is the process by which male gametes or spermatozoa are formed from precursor cells known as spermatogonia. The production of sperm is essential for sexual reproduction and continuation of the species.

Sperm: Definition, Composition, and Role 

Sperm, also known as spermatozoa, are the male reproductive cells or gametes that are responsible for fertilization of the female egg cell during sexual reproduction. Spermatozoa are produced in the testes of male animals, including humans, through a process called spermatogenesis.

Composition of Sperm:

Sperm is composed of three main parts: the head, the midpiece, and the tail. The head contains the genetic material or DNA of the sperm, while the midpiece contains the mitochondria, which provide energy for the sperm's movement. The tail, also known as the flagellum, is responsible for the propulsion of the sperm.

In addition to these main parts, sperm also contains various enzymes and proteins that aid in the fertilization process. These include enzymes that help the sperm penetrate the female egg cell and proteins that help protect the sperm from the female's immune system.

Place of Unwinding of Spermatogenesis:

Spermatogenesis occurs in the testes of male mammals.

The testes are two oval-shaped glands located in the scrotum, which is a sac that hangs outside the body. The testes are responsible for the production of testosterone, the male sex hormone, and the production of sperm.

Spermatogenesis takes place within the seminiferous tubules, which are coiled tubes that make up the bulk of the testes.

Steps of Spermatogenesis:

Spermatogenesis is a complex process that occurs in several stages. These stages include:

1. Spermatogonial phase: This phase involves the division of spermatogonia, which are precursor cells of sperm, into two daughter cells, one of which remains a spermatogonium, while the other becomes a primary spermatocyte.

2. Meiotic phase: During this phase, the primary spermatocyte undergoes meiosis I and produces two secondary spermatocytes, each with 23 chromosomes.

3. Post-meiotic phase: During this phase, the secondary spermatocytes undergo meiosis II, which results in the production of four haploid spermatids, each with 23 chromosomes.

4. Spermiogenesis: This is the final stage of spermatogenesis, in which the spermatids undergo a series of changes to form mature spermatozoa. This process involves the formation of the acrosome, the elongation of the nucleus, and the development of the tail.

Conditions Necessary for Spermatogenesis:

Several conditions are necessary for spermatogenesis to occur. These include:

1. Testosterone: Testosterone is the male sex hormone that stimulates the development of male sexual characteristics and is necessary for spermatogenesis.

2. Follicle-stimulating hormone (FSH): FSH is a hormone produced by the pituitary gland that stimulates the production of sperm in the testes.

3. Temperature: The testes must be maintained at a temperature slightly lower than the core body temperature for spermatogenesis to occur. This is why the testes are located outside the body in the scrotum.

Semen Transport from Production to Ejaculation:

After the spermatozoa are produced, they are transported from the seminiferous tubules to the epididymis, a coiled tube located on the posterior aspect of each testis. The epididymis is responsible for the maturation and storage of spermatozoa. From the epididymis, the spermatozoa are transported to the vas deferens, a muscular tube that connects the epididymis to the ejaculatory duct. During ejaculation, the vas deferens contracts to propel the spermatozoa into the urethra, which is the tube that carries urine and semen out of the body.

From the urethra, the spermatozoa enter the female reproductive system through the vagina and then travel through the cervix and uterus to reach the fallopian tubes, where fertilization occurs.

The movement of spermatozoa through the female reproductive system is aided by several factors, including the viscosity of the cervical mucus, the contractions of the uterine and tubal muscles, and the presence of sperm-activating substances in the female reproductive tract.

Abnormalities due to Blockage or Absence of Spermatogenesis:

Several abnormalities can occur due to blockage or absence of spermatogenesis. These include:

1. Azoospermia: This is the absence of sperm in the semen due to a blockage in the reproductive tract or a failure of the testes to produce sperm.

2. Oligospermia: This is a condition in which there is a low sperm count in the semen.

3. Varicocele: This is a condition in which the veins that drain the testes become enlarged, leading to reduced blood flow and oxygenation in the testes. Varicoceles are a common cause of male infertility and may lead to reduced sperm production and quality. Treatment options for varicoceles include surgery or embolization to repair the damaged veins and restore proper blood flow to the testes.   

Other abnormalities that can arise from blockage or absence of spermatogenesis include retrograde ejaculation, in which semen is ejaculated into the bladder instead of out of the penis, and ejaculatory duct obstruction, in which the ducts that carry semen from the seminal vesicles to the urethra are blocked.

These conditions may also lead to male infertility and can be treated with surgical intervention or medication, depending on the underlying cause. It is important for men experiencing infertility to seek medical attention to identify the cause and explore potential treatment options.