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Sperm - Function, Parts, and Factors Affecting Sperm Health

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Sperm is the male reproductive cell that infuses with the female reproductive cell (ovum) to facilitate reproduction. To know more, read the article below.

Medically reviewed by

Dr. Raveendran S R

Published At August 12, 2022
Reviewed AtOctober 19, 2023


Sperm is the small, compact reproductive cell in males that is manufactured by the testicles. It is formed through a process known as spermatogenesis, which takes place in the seminiferous tubules present in the testicles. The seminiferous tubules are coiled tubes situated within the testes (they produce sperm cells).The core function of sperm is reproduction. This is achieved by uniting or fusing with the female reproductive cell (the egg or ovum) and fertilizing it. The fertilized egg is called a zygote. This zygote then transforms into 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 which are as follows:

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

  • The Tail: The tail is the motile part of the sperm. It is also called the flagellum. It enables the swimming motion of the sperm towards the egg and aids in the penetration of the egg.

How Does the Sperm Fuse With the Ovum?

The sperm present in the semen is expelled when a man ejaculates after sex. When the semen makes its way into the vagina, sperm cells swim up into the cervix and uterus until they reach the ovum. If a single sperm cell penetrates the outer covering of the ovum, it then results in a few processes that result in the formation of a fertilized egg. The tip of the sperm head consists of a specialized vesicle called the acrosome or acrosomal vesicle. This vesicle encompasses enzymes that aid in the penetration of the sperm cell into the outer coating of the ovum. The enzymes are also released in what is referred to as the acrosome reaction. The genetic material from the sperm and the egg merge 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 thrive. In dry conditions, such as dried-up semen on hard surfaces like beds, the sperm dies almost as soon as the semen becomes dry. Sperm cells generally thrive in warm, wet environments. They may live for a long time in wet environments like pools and tubs.

A sperm cell may live up to five days in the female body. When stored in a frozen state, sperm cells can thrive for months and years and are capable of fertilization once thawed.

How Many Sperm Cells Are Released During Ejaculation?

Nearly 100 million sperm cells are expelled every time a man ejaculates. With time and increasing age, this number may decrease significantly, and so does the quality of the sperm. However, the sperm is 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 needs 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 on their way to reach the ovum, and even then, the possibility of penetrating the ovum is usually less. Generally, only the healthiest sperm cell out of all the millions has the best chance of reaching the ovum and penetrating it.

What Factors Determine Sperm Health?

Healthy sperm is an important prerequisite for the fertilization of the egg. The definition of health with regard to sperm cells corresponds to their fertility, which is determined by the following:

  • Sperm Quantity: Fertility depends on the number of sperm cells expelled in a single ejaculate. It is estimated that 15 million sperm cells must be present in every milliliter to increase the chances 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 impregnate an ovum resulting in pregnancy than a sperm cell with a different or abnormal structure.

  • Sperm Motility: The motility or movement presented by a sperm cell is crucial for fertilization. It is necessary for the sperm to propel forward through the vagina, cervix, and uterus; and into the ovum. About 40 percent 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?

Physiological Causes:

  • Age: As men grow older, there is a deterioration in the quality and quantity of the sperm they produce. While they are still capable of fertilizing the ovum, their overall fertility is low when compared to young men.


Disorders in the parts of the brain that are responsible for the manufacturing of testosterone and sperm (hypothalamus, pituitary gland), such as tumors and hormonal diseases, sperm transport disorders, and diseases of the testicles can result in male fertility issues.

Environmental Conditions:

Environmental conditions and compounds within the environment can cause contamination and alter the body’s normal functioning which can have an impact on the regular sperm functions, resulting in reduced fertility.

How Can Male Fertility Be Evaluated?

A semen analysis is a test that is commonly done to assess fertility in accordance with specific parameters. For example, the semen analysis can determine:

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

  • Quantity of Semen: The quantity of semen that is expected to be present is about two to six milliliters of semen with each ejaculation.

  • Thickness of Semen: Semen is usually thick upon release and turns less viscous within 10 to 15 minutes of ejaculation. This aids in sperm motility.

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

  • Concentration of Sperm: Sperm concentration, or sperm density, is described as the number of sperm cells present 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.


Sperm cells are reproductive cells in males that are manufactured in the testicles. These cells swim and fertilize the female reproductive cell, called an egg or oocyte. Sperm count and sperm motility are the two major factors that can impact male fertility. While the basic concept of sex and pregnancy is not lost in most people, it is not quite so cut-and-dried. Having a basic knowledge about 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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Dr. Raveendran S R
Dr. Raveendran S R



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