A sperm cell or spermatozoon is the male reproductive cell that is produced in the male’s testicles. Sperm cell units with the female egg cell to produce a diploid zygote.
The sperm cells are formed through the process called spermatogenesis in the seminiferous tubules of the testes. In the final phase of sperm cell production, the sperm passes into the epididymis near the top of the testicles. The epididymis acts as a holding bay, where the sperm cell can continue to mature and gain its ability to swim.
A sperm cell is known as a haploid cell. Haploid cells have half the chromosomes (one of each pair) and in humans this is 23 chromosomes.
In 1677, Antonie van Leeuwenhoek was the first person to describe the sperm cell in detail. They are elongated cells with a head, body and tail and the whole body of sperm is covered by a layer of the plasma membrane with the length of approximately 50 - 60 microns.
1. Head
The head is an oval shaped structure, size ranges from 5 to 8 µm. The head is covered by a cap-like structure called acrosome which accounts for 40% to 70% of total sperm head area. Acrosome contains proteolytic enzymes that help to penetrate the outer layer of egg, allowing the sperm to enter easily. The human sperm cell nucleus contains 23 chromosomes. This is the only part of the sperm that enters into the egg cell. When this haploid cell fertilizes with the egg, it produces a diploid zygote containing 46 chromosomes.
2. Body
The body or neck also called the midpiece are the parts that can be found between the head and the tail. The body measured between 6 - 12 microns, the midpiece is little longer than the head. Inside the body there are 50 - 75 mitochondria’s. Mitochondria provide the sperm cell with the energy required by the tail to allow the female reproductive system.
3. Tail
The tail or flagellum of the sperm makes up 80% of its entire length, about 50 µm. The main function of the tail is to allow sperm motility, it achieves this by slithering, snake-like movement. The tail contains a structure called axoneme, which is made of tiny structures called microtubules. The axoneme has 9 pairs of microtubules around and 2 single microtubules in the center. The movement of the tail is controlled by dynein proteins.
1. Head
Head: Head is the front part of the sperm cell containing a cap-like structure called acrosome.
Nucleus: The human sperm cell contains genetic material 23 chromosomes from the male parent.
Acrosome: Acrosome contains proteolytic enzymes that help to penetrate the outer layer of egg.
2. Body
Mitochondria: Mitochondria wraps around the axoneme to form the mitochondrial sheath.
Terminal Disc: This is a ring shaped structure located between the middle piece or body and tail.
Plasma Membrane: A thin lipid layer that surrounds the entire sperm cell. It protects the internal components.
3. Tail
Flagellum: It extends from the neck and the mid-piece through the tail of the sperm, enabling it to move the entire sperm cell.
Axoneme: Axoneme is inside the flagellum that helps the sperm move. It contains nine pairs of microtubule doublets arranged peripherally with a central pair of microtubules.
Spermatogenesis is the process by which sperm cells are formed in the testes. Testes contain many tightly coiled tubes called seminiferous tubules. Sperms are produced in these tubules. There are some specialized cells present among these tubules called Sertoli cells, which provide nutrients to the developing sperm cells.
The sperm production process begins with spermatogonia, which are immature sperm cells, they multiply by mitosis process. Some spermatogonia remain as the stem cells, while others develop into primary spermatocytes.
Primary spermatocytes further undergo meiosis I and form the secondary spermatocytes. In this stage chromosome number is reduced by 46 to 23. Secondary spermatocytes further undergo meiosis II and form the haploid spermatids. Spermatids then change their shape and structure to become mature sperm. This process is called spermiogenesis.
During the process of spermiogenesis, the nucleus forms the head of the sperm cell and tail develops to help the sperm move. The mature sperm cells are called spermatozoa and these cells are stored in the epididymis, where they undergo further maturation.
The main function of the sperm cells is to fertilize the female egg. The fusion of a sperm cell with a matured egg forms a zygote which is further divided to form an embryo. During this process sperm cells contribute a haploid set of chromosomes (23 chromosomes).
There are several defects that can occur to the sperm cells. Here are some most frequent diseases and defects in the sperm cells;
Azoospermia: It is a condition where sperms are completely absent in the ejaculate. This might be due to the result from problems in the sperm production or blockage in the reproductive tract.
Oligozoospermia: Low sperm concentration in the ejaculate. Low sperm count may reduce the chances of fertility. Hormone abnormalities, genetic disorders, infections, varicocele, medications and toxins are major causes of this condition.
Asthenozoospermia: Asthenozoospermia is a condition that occurs due to reduced sperm motility. Reduced sperm motility can decrease the ability of sperm to reach and fertilize the egg.
Teratozoospermia: Teratozoospermia condition is characterized by abnormal sperm morphology (shape and structure). Abnormal sperm may cause difficulty in penetrating the barriers of the egg for fertilization.
DNA fragmentation: Sperm DNA fragmentation is the broken or damages in the DNA. DNA fragmentation can reduce fertility, embryo development and increase the risk of abnormalities in the off-spring. Common causes of DNA fragmentation are oxidative stress, infections, varicocele, regular smoking, toxins and advanced aging.
The sperm cells are formed through the process called spermatogenesis in the seminiferous tubules of the testes. In the final phase of sperm cell production, the sperm passes into the epididymis near the top of the testicles. The epididymis acts as a holding bay, where the sperm cell can continue to mature and gain its ability to swim.
A sperm cell is known as a haploid cell. Haploid cells have half the chromosomes (one of each pair) and in humans this is 23 chromosomes.
Structure of the Sperm Cell
In 1677, Antonie van Leeuwenhoek was the first person to describe the sperm cell in detail. They are elongated cells with a head, body and tail and the whole body of sperm is covered by a layer of the plasma membrane with the length of approximately 50 - 60 microns.
1. Head
The head is an oval shaped structure, size ranges from 5 to 8 µm. The head is covered by a cap-like structure called acrosome which accounts for 40% to 70% of total sperm head area. Acrosome contains proteolytic enzymes that help to penetrate the outer layer of egg, allowing the sperm to enter easily. The human sperm cell nucleus contains 23 chromosomes. This is the only part of the sperm that enters into the egg cell. When this haploid cell fertilizes with the egg, it produces a diploid zygote containing 46 chromosomes.
2. Body
The body or neck also called the midpiece are the parts that can be found between the head and the tail. The body measured between 6 - 12 microns, the midpiece is little longer than the head. Inside the body there are 50 - 75 mitochondria’s. Mitochondria provide the sperm cell with the energy required by the tail to allow the female reproductive system.
3. Tail
The tail or flagellum of the sperm makes up 80% of its entire length, about 50 µm. The main function of the tail is to allow sperm motility, it achieves this by slithering, snake-like movement. The tail contains a structure called axoneme, which is made of tiny structures called microtubules. The axoneme has 9 pairs of microtubules around and 2 single microtubules in the center. The movement of the tail is controlled by dynein proteins.
Parts of the Sperm Cell
1. Head
Head: Head is the front part of the sperm cell containing a cap-like structure called acrosome.
Nucleus: The human sperm cell contains genetic material 23 chromosomes from the male parent.
Acrosome: Acrosome contains proteolytic enzymes that help to penetrate the outer layer of egg.
2. Body
Mitochondria: Mitochondria wraps around the axoneme to form the mitochondrial sheath.
Terminal Disc: This is a ring shaped structure located between the middle piece or body and tail.
Plasma Membrane: A thin lipid layer that surrounds the entire sperm cell. It protects the internal components.
3. Tail
Flagellum: It extends from the neck and the mid-piece through the tail of the sperm, enabling it to move the entire sperm cell.
Axoneme: Axoneme is inside the flagellum that helps the sperm move. It contains nine pairs of microtubule doublets arranged peripherally with a central pair of microtubules.
Process of Sperm Production
Spermatogenesis is the process by which sperm cells are formed in the testes. Testes contain many tightly coiled tubes called seminiferous tubules. Sperms are produced in these tubules. There are some specialized cells present among these tubules called Sertoli cells, which provide nutrients to the developing sperm cells.
The sperm production process begins with spermatogonia, which are immature sperm cells, they multiply by mitosis process. Some spermatogonia remain as the stem cells, while others develop into primary spermatocytes.
Primary spermatocytes further undergo meiosis I and form the secondary spermatocytes. In this stage chromosome number is reduced by 46 to 23. Secondary spermatocytes further undergo meiosis II and form the haploid spermatids. Spermatids then change their shape and structure to become mature sperm. This process is called spermiogenesis.
During the process of spermiogenesis, the nucleus forms the head of the sperm cell and tail develops to help the sperm move. The mature sperm cells are called spermatozoa and these cells are stored in the epididymis, where they undergo further maturation.
Functions of the Sperm Cells
The main function of the sperm cells is to fertilize the female egg. The fusion of a sperm cell with a matured egg forms a zygote which is further divided to form an embryo. During this process sperm cells contribute a haploid set of chromosomes (23 chromosomes).
Sperm cell diseases and defects
There are several defects that can occur to the sperm cells. Here are some most frequent diseases and defects in the sperm cells;
Azoospermia: It is a condition where sperms are completely absent in the ejaculate. This might be due to the result from problems in the sperm production or blockage in the reproductive tract.
Oligozoospermia: Low sperm concentration in the ejaculate. Low sperm count may reduce the chances of fertility. Hormone abnormalities, genetic disorders, infections, varicocele, medications and toxins are major causes of this condition.
Asthenozoospermia: Asthenozoospermia is a condition that occurs due to reduced sperm motility. Reduced sperm motility can decrease the ability of sperm to reach and fertilize the egg.
Teratozoospermia: Teratozoospermia condition is characterized by abnormal sperm morphology (shape and structure). Abnormal sperm may cause difficulty in penetrating the barriers of the egg for fertilization.
DNA fragmentation: Sperm DNA fragmentation is the broken or damages in the DNA. DNA fragmentation can reduce fertility, embryo development and increase the risk of abnormalities in the off-spring. Common causes of DNA fragmentation are oxidative stress, infections, varicocele, regular smoking, toxins and advanced aging.