The sperm is called the male reproductive cell (gamete). Its size (excluding tail length) is much smaller than the size of the zygote. The microscopic structure of the sperm is due to the need to travel a relatively large distance to reach the egg. It should be noted that this cell has the smallest size in comparison with all human cells.
Sperm structure
The gamete includes the head, neck, middle part (body) and tail. The front of the oval head contains the so-called acrosome. Its composition includes enzymes, through which the egg membrane dissolves. Behind the acrosome is a nucleus that contains twenty-three male chromosomes. During fertilization, they combine with twenty-three female chromosomes contained in the egg. In this case, the fertilizing sperm brings only the X or Y chromosome, thus determining the sex of the child.
The neck of the gamete performs a connecting function between the head and body. The mobility of the neck allows the head to oscillate during the movement of the sperm.
The body of the cell is made in the form of an axial filament, which consists of mitochondria and microtubules.
The tail continues the middle part (body) and includes microtubules coated with cytoplasm.
The normal structure of the sperm is characteristic of half of all those present in sperm. It should be noted that the presence of defects does not affect the genetic material of the gamete. In this case, the defective structure of the sperm can affect its ability to reach the egg.
The production of these cells occurs in the convoluted, covered with spermatogenic epithelium tubules of the testicles. These tubules then go into the direct tubules. They, in turn, form the epididymis. The sperm must pass through all the tubules. Thus, its full maturation occurs. The epididymis passes into the duct, which goes along the inguinal canal and enters the abdominal cavity. In this case, the duct flows into the seminal vesicles located behind the bladder. In the seminal vesicles , sperm accumulate and mix with the secretion of their walls. The composition of the secret includes the necessary nutrients that contribute to the promotion of sperm to the egg. According to the vas deferens, male reproductive cells from the seminal vesicles enter the prostate gland. Here they are mixed with her secret. Chemical compounds and nutrients create an alkaline environment for sperm. The result is a suspension called sperm. When male ejaculation occurs, it enters the urethra from the vas deferens, and then is expelled from the body with force.
The volume of ejaculate is considered normal within three to five milliliters, while the number of sperm per milliliter of sperm should be at least twenty million. In the normal state of the genitals, a man should not have sperm aggregation (areas of large congestion). Sometimes such areas can be identified visually - they are distinguished by a large whiteness and density.
At the time of ejaculation, a huge amount of sperm gets onto the cervix of the female uterus. However, only half of them are able to pass the mucous plug in the channel of the uterine neck. Of this half of the sperm, in turn, only a small part is able to reach the mouth of the uterine tubes. In this case, the egg is located in one tube of the uterus. As a result, even less sperm remains on the way to the ovum, of which not all fall into the fallopian tube. Thus, eggs can only reach about two hundred male cells.
How long do sperm live
For several hours, the gametes remaining in the vagina are destroyed by the acidic environment of the vaginal secretions. In the cervix, the sperm can live from three to five days (sometimes longer), depending on the amount of cervical mucus.