What Is Sperm Definition Structure Diagram and Role in Fertilization
The male reproductive cell is known as sperm or male gamete, in an organism that undergoes sexual reproduction i.e. in anisogamous form. Sperms are motile in nature with flagellum in the case of animals, which is also called spermatozoa, whereas a few red algae and fungi produce non-motile sperm cells which are commonly known as spermatia. Few flowering plants like ferns and some gymnosperms also produce motile sperm while some produce non-motile sperm inside the pollen.
The process of the formation of sperm is known as spermatogenesis. In the case of amniotes like reptiles and mammals sperm formation takes place in the seminiferous tubules of the testes. Sperm cell formation includes various steps like the formation of spermatogonia and it gets differentiated into spermatocytes. Further, these spermatocytes undergo meiosis division and form spermatids. This whole process of formation of sperm takes three months to complete.
Structure of Sperm
Sperm is differentiated into three parts i.e. head, neck, middle piece and tail. The plasma membrane covers the whole body of sperm.
Structure of Sperm:
A. Head Region: They contain acrosome at the apical end, which contains several important enzymes that help the entry of sperm into the ovum. Further, this head region is followed by a haploid elongated nucleus.
B. Middle Region: This region has multiple mitochondria, and these mitochondria provide energy for the movement of sperm, in order for fertilization to take place.
C. Tail Region: This region has a flagellum that protrudes out of the cell body and is helpful in providing vigorous motility to the sperms. This region of sperm helps in swimming by which they can reach towards the ovum. Approximately 200-300 million sperms are ejaculated at once.
Important Role of Different Regions of Sperm:
Each region of sperm has its specific functions, like:
A. Head region contains acrosomes which contain several important enzymes and these enzymes help to enter the egg during fertilization.
B. Mitochondria present in sperm cells provides energy and this energy is used to navigate in the female genital tract.
C. Tail part of sperm helps in locomotion, by which the fertilization process takes place.
D. Sperm has two types of chromosome either X or Y type and these chromosomes are responsible for determining individual sex.
Place Where Sperm are Created:
Sperms are stored, transported and produced in the male reproductive system. Reproductive organs of male are on both the interior and exterior of the pelvic cavity.
Male reproductive organs include the following parts:
A. The testes:
B. The duct system: The duct system contains epididymis and vas deferens also known as sperm duct.
C. The accessory glands: This gland includes seminal vesicles and prostate gland
D. The penis: Through this transfer of sperm occurs during the copulation process.
Production of sperm occurs in the testicles. At the time of puberty, a man can produce a million sperm every day and the size of sperm varies from 0.002 to 0.003 inches. Tubes that are present in the testicles are known as seminiferous tubules which also includes testosterone. Further male sex hormone produced by the male reproductive system causes semen to turn into sperm. Sperm has a tail, which helps in pushing the sperm into a tube behind the testes called the epididymis. Movement of sperm occurs for five weeks in the epididymis region and in this stage, they complete their development. Sperm moves out of epididymis to vas deferens.
Transfer of Sperm into Female Reproductive Tract
The human male produces semen during mating and ejaculation processes, which is done by the penis. Sperms are microscopic in nature and each drop of semen contains thousands of sperms. When the ejaculation process takes place inside the female vagina or genitals, in that case, the movement of sperm takes place from the cervix to the uterus.
At the time of ejaculation approx 300 million sperms are produced but among this 300 million only 1% are able to make their way into the cervix as the remaining are killed by acidic fluid near the vagina. 1% of sperm are able to find their path towards the oviduct, a place where ovaries release their eggs towards the uterus. Out of this, only a few make their way to the fallopian tube and the rest of them die because of the mucus lining in the uterotubal junction.
After going through so many obstacles, inside the female reproductive system, only one sperm manages to do the fertilization process.
Accessory Gland in Male Reproductive System
The accessory glands in males are seminal vesicles and the prostate gland, and these glands secrete fluids that helps in lubrication of the duct system and also nourishes sperm. The major function of the urethra is to carry sperm in the form of semen to the outside of the body with the help of the penis and it is also considered as a part of the urinary system as it is also the channel through which the urination process takes place.
FAQs on Sperm Structure and Function in Human Reproduction
1. What is sperm?
Sperm is the male reproductive cell, or male gamete, responsible for fertilizing the female egg. In humans and many animals, sperm is produced in the testes and carries half the genetic material (23 chromosomes in humans). During fertilization, a sperm cell fuses with an ovum to form a zygote, which develops into a new individual.
2. What are the parts of a sperm cell and their functions?
A sperm cell has three main parts: the head, midpiece, and tail, each with a specific function.
- Head: Contains the nucleus with genetic material and the acrosome, which has enzymes to penetrate the egg.
- Midpiece: Packed with mitochondria that produce ATP for movement.
- Tail (flagellum): Enables motility, allowing the sperm to swim toward the egg.
3. How is sperm produced in the male body?
Sperm is produced through a process called spermatogenesis in the seminiferous tubules of the testes.
- It begins with spermatogonia (diploid stem cells).
- These undergo meiosis I and II to form haploid spermatids.
- Spermatids mature into functional spermatozoa.
4. What is the function of sperm?
The primary function of sperm is to deliver male genetic material to the egg for fertilization. Specifically, sperm cells:
- Carry half of the genetic information (haploid set of chromosomes).
- Use their flagellum for movement toward the egg.
- Release acrosomal enzymes to penetrate the egg’s protective layers.
5. What is the difference between sperm and ovum?
The main difference between sperm and ovum is that sperm is the small, motile male gamete, while the ovum is the large, non-motile female gamete.
- Sperm: Produced in testes, flagellated, contains minimal cytoplasm.
- Ovum: Produced in ovaries, spherical, rich in cytoplasm and nutrients.
- Sperm determines the sex of the offspring (X or Y chromosome), while the ovum always carries an X chromosome.
6. How does sperm fertilize an egg?
Sperm fertilizes an egg by penetrating its outer layers and fusing with its plasma membrane.
- Sperm undergoes capacitation in the female reproductive tract.
- The acrosome reaction releases enzymes to digest the zona pellucida.
- The sperm membrane fuses with the egg membrane.
- The nuclei merge to form a diploid zygote.
7. How long can sperm survive in the female body?
Sperm can survive up to 3–5 days in the female reproductive tract under optimal conditions. Their survival depends on:
- The presence of fertile cervical mucus.
- Hormonal conditions during the ovulatory phase.
- Protection from the acidic vaginal environment.
8. What chromosome does sperm carry?
A sperm cell carries either an X or a Y chromosome along with 22 autosomes. Since sperm is haploid, it contains 23 chromosomes in total.
- X-bearing sperm + X ovum → XX (female).
- Y-bearing sperm + X ovum → XY (male).
9. What affects sperm count and quality?
Sperm count and quality are influenced by hormonal, environmental, and lifestyle factors. Key factors include:
- Levels of testosterone and other reproductive hormones.
- Exposure to heat, radiation, or toxins.
- Lifestyle factors such as smoking, alcohol use, and poor nutrition.
- Medical conditions like varicocele or infections.
10. What is sperm motility and why is it important?
Sperm motility is the ability of sperm cells to move efficiently toward the egg. Motility depends on the proper function of the flagellum and sufficient ATP production by mitochondria.
- Progressive motility: Forward movement toward the egg.
- Non-progressive motility: Movement without forward progression.
