Sperm - Function, Parts, and Factors Affecting Sperm Health

What Is Sperm?

Sperm is the small, compact reproductive cell in males produced by the testicles. It is formed during a process known as spermatogenesis, which is carried out in the seminiferous tubules present in the testicles. The seminiferous tubules are coiled tubes located within the testes - they produce sperm cells.

What Is the Function of Sperm?

The primary function of sperm is reproduction. It does this by uniting or fusing the female reproductive cell (the egg or ovum) and fertilizing it. The fertilized egg is a zygote. This zygote then becomes an embryo and eventually grows and develops in the womb into a fetus.

What are the Parts of a Sperm Cell?

The sperm cell is composed of two parts:

• The Head: The head of the sperm contains a condensed nucleus, within which DNA is present. This DNA combines with the DNA present in the female egg to create a unique individual with a combination of traits from both parents.

• The Tail: The tail is the motile portion of the sperm. It is also called the flagellum. It facilitates the swimming motion of the sperm towards the egg and the penetration of the egg.

How Does the Sperm Fuse With the Ovum?

The sperm is present in the semen released when a man ejaculates after sex. When the semen is released into the vagina, sperm cells swim up into the cervix and uterus until they reach the ovum. If a single sperm cell can penetrate the outer covering of the ovum, it then results in some processes that result in the formation of a fertilized egg. The tip of the sperm head contains a specialized vesicle called the acrosome or acrosomal vesicle. This vesicle contains enzymes that help the sperm cell penetrate the outer coating of the ovum. The enzymes are also released in what is known as the acrosome reaction. The genetic material from the sperm and the egg combine to form a zygote, which continuously divides within the uterus and grows and develops into an embryo, then a fetus, and finally a neonate (newborn).

How Long Can Sperm Survive?

The survival rates of sperm depend on the environment in which they are present.

• In dry conditions, such as dried-up semen on hard surfaces such as beds, the sperm die almost as soon as the semen is dry.

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• Sperm cells generally thrive in warm, wet environments. They may live longer in wet environments like pools and tubs.

• A sperm cell may last up to five days in the female body.

• When stored in the frozen state, sperm cells can last months and years and are capable of fertilization once thawed.

How Many Sperm Cells Are Released During Ejaculation?

Nearly 100 million sperm cells are released every time a man ejaculates. With time and increasing age, this number may reduce significantly, as will the quality of the sperm. However, they are still capable of fertilizing an egg and causing pregnancy.

Why Is the Number of Sperm Cells Released During Ejaculation So Large?

Although fertilization of an ovum requires just one sperm, the chances of a single sperm cell fertilizing the egg are low. Of the millions of sperm cells produced, only a few may survive long enough to reach the ovum, and even then, the possibility of penetrating the ovum is limited. Generally, only the healthiest sperm cell out of all the millions has the best shot at reaching the ovum and penetrating it.

What Factors Determine Sperm Health?

Healthy sperm is a prerequisite to the fertilization of the egg. The definition of health with regards to sperm cells corresponds to its fertility, which is determined by:

• Sperm Quantity: Fertility depends on the number of sperm cells released in a single ejaculate. An estimated 15 million sperm cells must be present in every milliliter to increase the odds of fertilization and pregnancy.

• Sperm Structure: The normal sperm structure with an oval head and a tail, complete with the nucleus and acrosomal vesicle, is more likely to improve pregnancy chances than a sperm cell with a different or abnormal structure.

• Sperm Motility: The motility or movement presented by a sperm cell is vital for fertilization. It is necessary to propel the sperm forward through the vagina, cervix, and uterus; and into the ovum. About 40 % of sperm cells should be motile for a man to be considered fertile.

What Are the Do’s and Don’ts to Ensure Healthy Sperm?

What Are the Causes of Male Fertility Issues?

1. Physiological Causes:

• Age: As men grow older, the quality and quantity of the sperm they produce decreases. While they are still capable of fertilizing the ovum, their overall fertility is less than younger men.

2. Illnesses:

• Disorders in the parts of the brain that are responsible for testosterone and sperm production (hypothalamus, pituitary gland) such as tumors and hormonal diseases.

• Sperm transport disorders.

• Diseases of the testicles.

3. Environmental Conditions:

• Environmental conditions and compounds within the environment can cause contamination and alter the body’s normal functioning, including regular sperm functions, resulting in reduced fertility.

How Can Male Fertility Be Evaluated?

A semen analysis is a test commonly done to assess fertility in accordance with specific parameters.

For example, the semen analysis can determine:

• Structure and Morphology of Semen: The general appearance and the shape and size of the sperm cell are essential parameters of fertility that can be assessed with a semen analysis.

• Quantity of Semen: The ideal quantity should be about 2-6 milliliters of semen with each ejaculation.

• Thickness of Semen: Semen is usually thick upon release and grows thinner within 10 - 15 minutes of ejaculation. This helps with sperm motility.

• Motility of the Sperm: The number of sperm that can move and the direction and manner of movement are assessed. Ideally, about 40 % of sperm should be able to move towards the uterus along a straight path.

• Concentration of Sperm: Sperm concentration or sperm density is described as the number of sperm cells per milliliter of semen (measured in millions). Around 15 million sperm cells should be present in a milliliter of semen in a normal, fertile man.

Conclusion

While the basic concept of sex and pregnancy is not lost on most people, it is not quite so cut-and-dried. Understanding the structure, function, and method of action of sperm cells could make a world of difference in couples planning for pregnancy. It will lead to a better understanding and better quality of life.

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