Difference Between Sperm and Semen

Main Difference – Sperm vs Semen

Sperm and semen are two components that are produced by the male reproductive system of animals. Sperms are the reproductive cells of males. They are contained in the semen. The main difference between sperm and semen is that sperm is the only cellular component of the semen whereas semen is the liquid carrier of sperms. Sperms are microscopic cells with a haploid nucleus. They carry the genetic information of males to the egg cell of the female. Semen is also called the seminal fluid that contains millions of sperms. Semen is a viscous liquid that nourishes sperms and keeps them motile.

Key Areas Covered

1. What is a Sperm
     – Definition, Structure, Role
2. What is Semen
     – Definition, Components, Role
3. What are the Similarities Between Sperm and Semen
     – Outline of Common Features
4. What is the Difference Between Sperm and Semen
     – Comparison of Key Differences

Key Terms: Haploid Nucleus, Gonads, Male Reproductive Cells, Reproduction, Semen, Seminal Vesicles, Sperm

What is a Sperm

Sperm refers to a male reproductive cell. Sperms are small, compact cells that are highly adapted to their function – fertilization of the female egg cell. Males continuously produce sperm cells throughout their lifetime, starting from puberty. Sperms are produced in a process called spermatogenesis that occurs in the gonads. Primary spermatocytes are diploid and each gives rise to four mature sperm cells or spermatozoa. The structure of a typical human sperm cell is shown in figure 1.

Figure 1: Sperm Cell Structure

The three sections of a typical sperm cell are head, middle region, and tail. The head consists of a haploid nucleus, pair of centrioles, and an acrosome cap. The haploid nucleus contains a single set of chromosomes of the species. A human sperm nucleus contains 23 chromosomes. The hydrolytic enzymes that help to penetrate the jelly coat of the egg cell are contained in the acrosome cap. A large number of mitochondria are concentrated in the middle part of the sperm. They produce the energy required by the mobility of the tail. The tail is made up of a single flagellum in humans. The motile sperms of the algae and seedless plants are shown in figure 2.

Figure 2: Motile Sperms of Algae and Seedless Plants

Plants also produce sperms as their male reproductive cells. Algae and other seedless plants produce motile sperms while flowering plants produce non-motile sperms.

What is Semen

Semen refers to the reproductive fluid of males, which contains sperms in suspension. It is also called the seminal fluid. Though sperms are the major cellular component of the semen, it also contains some other important substances as well. Semen provides nourishment to sperms and a medium to swim. The human sperms cells suspended in the semen is shown in figure 3.

Figure 3: Sperms in the Semen under x1000 Magnification

 The discharging process of semen by males is called the ejaculation. When the sperms pass through the ejaculatory ducts, they are mixed with different secretary fluids from seminal vesicles, prostate, and the bulbourethral glands. These fluids along with the sperms collectively form the semen. A yellowish, viscous fluid is produced in the seminal vesicles. It is rich in fructose. The fluid from the seminal vesicles accounts for the 70% of the total volume of the semen. A whitish, thin fluid is produced by the prostate glands that contain proteolytic enzymes, lipids, citric acid, and phosphatase. It accounts for the 25 – 30 % of the volume of the semen. The bulbourethral glands produce a colorless fluid to lubricate the lumen of the urethra. This fluid takes around 1% of the total semen volume. Each ejaculation releases around 200 – 500 million sperms in humans. Sperms take 2 – 5% of the total volume of the semen. Around 3.4 mL of semen is released by humans per ejaculation. The color of the semen is whitish-gray. The semen also has an opalescent appearance due to the presence of sperms. The semen of a dog is shown in figure 4.

Figure 4: Dog Semen
Sperm-Rich Fraction (left) and Prostatic Fraction (right)

Primarily, semen comprises water, proteins, fructose, cholesterol, citric acid, ascorbic acid, lactic acid, minerals, vitamin B12, blood group antigens, nitrogen, and uric acid. The major component of the semen is albumin and free amino acids, which takes about 50% of the semen. The amount of fructose in semen determines the fertility. Semen also contains catecholamines such as adrenaline, noradrenaline, and dopamine. Catecholamines determine the sperm count, mobility of sperms as well as the overall fertility. 

Similarities Between Sperm and Semen

• Sperm and semen are two components produced by the male reproductive system.
• Both sperm and semen play a major role in fertilizing the female egg cell.

Difference Between Sperm and Semen

Definition

Sperm: Sperm is a male reproductive cell.

Semen: Semen is the reproductive fluid of males, which contains sperms in suspension.

Occurrence

Sperm: Sperms are produced by both animals and plants.

Semen: Semen is produced by male animals and hermaphrodites.

In Humans

Sperm: Sperms are produced by the spermatozoa in the testis.

Semen: Semen is a collection of fluids produced by seminal vesicles, prostate gland, and bulbourethral glands. 

Structure

Sperm: Sperm is a microscopic cell that contains an oval-shaped head with a long tail.

Semen: Semen is a viscous liquid, which is typically whitish-gray in color.

Significance

Sperm: Sperms are the only cellular component of the semen.

Semen: Semen is the liquid carrier of sperms.

Function

Sperm: Sperm carries genetic information of a male to an egg cell of the same species for fertilization.

Semen: Semen carries sperms while nourishing them and keeping their mobility.

Visibility

Sperm: Sperms are not visible to the naked eye.

Semen: Semen is visible to the naked eye.

Conclusion

Sperm and semen are two components produced by the male reproductive system. Sperm is the haploid, male, reproductive cell. Semen is the fluid that carries sperms. It nourishes the sperms and helps in their mobility. Both sperm and semen are involved in the successful fertilization of a female egg cell. The main difference between sperm and semen is the relationship and function of each factor during reproduction.

Reference:

1. Alberts, Bruce. “Sperm.” Molecular Biology of the Cell. 4th edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. Mandal, MD Dr. Ananya. “What is Semen?” News-Medical.net, 8 Oct. 2014, Available here.

Image Courtesy:

1. “Complete diagram of a human spermatozoa en” By Mariana Ruiz Villarreal (Public Domain) via Commons Wikimedia 
2. “Plant sperm” By Tameeria at English Wikipedia – Transferred from en.wikipedia to Commons by Vojtech.dostal., (Public Domain) via Commons Wikimedia
3. “Spermatozoa-human-1000x” By No specific author – Own work (Public Domain) via Commons Wikimedia
4. “Collected dog semen” By Wuffy4252 – Own work (CC BY-SA 4.0) via Commons Wikimedia

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