The female gamete is called. Features of the structure and movement of sperm
From our article you will learn what a gamete is. This is a special cell whose functions are strictly specialized. What are they? Let's figure it out together.
What is a gamete: definition
Translated from Greek, this term means “wife” or “husband.” This defines its meaning as precisely as possible. A gamete is a sex cell. In nature, there are two varieties of it - male and female.
In any case, gametes are formed as a result of the division of primary germ cells. At the same time, their diploid set of chromosomes is preserved. This causes an increase in their number. The process of formation of male and female gametes has its own significant differences. Thus, from one primary spermatozoon four full-fledged cells are formed, capable of fertilization. In female gametes, only one egg acquires this ability.
The structure of the egg
What is a female gamete? It is always a stationary cell containing a sufficient supply of nutrients necessary for the development of the future organism. It has a round or spherical shape. The egg is reliably protected by several membranes: vitelline, transparent and outer. Its cytoplasm is a real storehouse of yolk inclusions.
Features of male reproductive cells
Now let's figure out what a male gamete is. Sperm are always much smaller in size compared to eggs. This is due to the fact that male gametes contain only genetic information. Why are they deprived of nutrients? The fact is that the basis of the future organism is precisely the egg, which has them in sufficient quantity.
Gametes of plants and animals: similarities and differences
Male gametes of animals are mobile. Sperm consists of three parts: head, neck and tail. The first of them contains the core. Its chromosome set is haploid, or single. This structural feature is typical of all germ cells. The head of the sperm also contains an acrosome, or apical body. produces a special enzyme that is capable of dissolving the protective membranes of the egg. The neck contains centrioles and mitochondria. They produce the energy needed to move the tail.
Male plant gametes are called sperm. In the higher seed representatives of this kingdom they are located in the anthers of the stamens. They move with the help of wind, insects or humans. The process of their transfer to the stigma of the pistil is called pollination.
What is a plant gamete and where is it located? If we are talking about an egg, then, just like in plants, it is a stationary oval-shaped cell. It is located in the lower expanded part of the pistil of flowers. For gamete fusion to occur, two sperm move towards the female gamete as the germ tube grows. As a result of their fertilization, a seed is formed.
In higher spore plants, sex cells mature in specialized organs - gametangia. These organisms have a clear alternation of generations in their life cycle.
Let's consider this process using mosses as an example. Its sexual generation is represented by a green “mat”. It consists of individual leafy plants. Gametophytes are formed on them, in which sex cells mature. As a result of the fertilization process, which requires water, an asexual generation grows - the sporophyte. It looks like a box on a dry stem. Asexual reproduction cells called spores mature in it. They enter the soil and again give rise to a gametophyte. This is how the phases of the life cycle replace each other.
Result of fertilization
The fertilized egg is called a zygote. Her chromosome set is already diploid, or double. In animals, fertilization can be external or internal. In the first case, it occurs outside the female’s body. This method is typical for fish and amphibians. With the help of a male, he introduces sperm into the female’s body. The development of the fetus also occurs there, so this method is more progressive.
In plants, the most complex process of gamete fusion is observed in flowering plants. It is called double because the female gamete and the central germ cell are connected to the sperm. As a result, an embryo, a reserve nutrient called endosperm, and a peel are formed. And all together - a seed.
The zygote begins to fragment. In this case, an embryo is formed. At first it consists of one layer. It's called blastula. Next, the laying of tissues and future organs begins. During this period it is called gastrula. The formation of the embryo continues with the laying of three germ layers, from which certain organs and their systems develop.
So, in our article we looked at what a gamete and a zygote are. These structures are carriers of hereditary information and give rise to a new organism.
Medicine is rich in a wide variety of terms. Some of them are simple and understandable to ordinary people. Others require some explanation. This article will tell you about what a sperm is. You will learn about the structural features of this cell. You can also find out outside the man's body. It is worth explaining the main functions of the gamete.
What is a spermatozoon?
This cell is present in the body of males of different species. However, the gamete is most often studied in humans. If you have a question about what a sperm is, then this article will tell you about it.
A sperm is a reproductive cell, without which procreation is impossible. It is formed in the testicles of a man and is released during ejaculation. Sperm production is influenced by many factors. This is the work of a man’s hormonal system, his lifestyle, emotional and physical state. The structure of the gamete is very interesting. What is a spermatozoon? This is a cell that has a head, a main body and a tail. Gametes have a fairly high speed. This is what allows fertilization to occur. Those cells that do not have one of the parts or move incorrectly are often called sperm. It is worth saying that it is the sperm that determines the gender of the unborn child. This fact depends on the content of certain chromosomes in the gamete. The set may contain an X or Y chromosome. Accordingly, at conception a female or male fetus is formed.
Cell structure
As you already know, a sperm consists of a head, body and tail. These parts, in turn, have their own characteristics. Let's look at them.
- Head. This part contains the nucleus, which has a specific set of chromosomes. It is very important for fertilization. In addition, there is an acrosome. This substance is not involved in the process of zygote formation. However, it allows you to dissolve the shell of the egg and penetrate inside. The centrosome is an important detail that allows you to organize the correct movement of the tail.
- Body. There are no parts important for fertilization. However, the sperm body contains a cytoskeleton. It is this part that helps the cell move forward and achieve its goal.
- Ponytail. This part does not carry chromosomes. But it is worth saying that without it, the male gamete simply will not be able to advance. The functioning of the tail is regulated by the centrosome, which is located in the head of the cell. There is one peculiarity. If male cells do not have tails, then fertilization can occur in vitro.
The correct structure of the sperm is very important for fertilization. That is why doctors pay special attention to this point.
Main tasks
You already know. What is this small cell of the male body needed for? The main feature of a gamete is that it can exist outside the host's body. Moreover, in a favorable environment, sperm live up to ten days.
The main task of the male gamete is fertilization. It can occur naturally or artificially. The cells enter the body of the fairer sex and cross the cervical canal. It is worth noting that one cell will not be enough. Although a single sperm and egg fuse during conception, many similar cells are needed to move the male gamete.
After crossing the female genital organs, the sperm enters the egg. Then continuous division begins. The zygote moves through the fallopian tubes and enters the uterus. Here the already formed substance is called the fertilized egg.
Possible problems
Male sperm does not always have the correct structure. Often representatives of the stronger sex have to face problems. Pathologies are detected after an analysis called a spermogram.
Thus, some cells may have an incorrect structure or impaired movement. Sometimes partial damage to the head or tail of the sperm occurs. In medicine, there are certain standards that male gametes must comply with. In case of violations and pathologies, corrections are made. Treatment allows you to restore the health of sperm and improve the reproductive function of a man.
Summing up
Now you know what a sperm is. This cell is the smallest in the male body, but it performs very important functions. Also, the gamete has its own individual characteristics. It is the sperm that allows a man to continue his race and reproduce. It is worth noting that the structure and functions of this cell are studied in the school curriculum. Every person, especially a man, should know what a sperm is. Check the quality of your reproductive cells. Good luck!
Gametes (from the Greek words gamete - wife, gametes - husband) are sexual, or reproductive, cells of animals and plants, which, when fused, ensure the development of a new individual and the transmission of hereditary characteristics from parents to descendants. Gametes are haploid, that is, they contain a single set of chromosomes. When they merge, i.e. during fertilization, or the sexual process, a zygote with a double (diploid) set of chromosomes appears. This is how the genetic material of the parent individuals is combined and the full set of chromosomes is restored.
Animals that reproduce sexually (see Reproduction) produce male gametes, sperm, and female gametes, ova, or eggs.
In many protozoa, male and female gametes are the same size and shape, and both are motile (isogamy).
For fertilization to occur, the gametes need to find each other. It is also necessary to provide the zygote with a sufficient supply of nutrients and protective membranes. These functions were divided in the process of evolution between male and female gametes. Therefore, in most animals, male gametes are small and mobile, while female gametes are larger, contain a lot of nutrients and are not able to move (anisogamy, or oogamy). The largest eggs are in animals whose embryonic development occurs in the external environment, and not in the maternal body, and lasts for a long time - days, weeks (birds, reptiles, amphibians, fish, cephalopods).
Spermatozoa consist of a head, neck and tail, which provides them with mobility. The head contains a nucleus with tightly packed chromosomes, and the neck contains mitochondria, which supply energy for metabolism and tail movement. Male gametes of aquatic organisms sometimes have flagella, which ensure their mobility. In some organisms (roundworms, many arthropods), male gametes move in an amoeba-like manner, using pseudopodia.
In most animals, except higher mammals, the cytoplasm of the eggs contains a large amount of yolk.
The process of formation of gametes is called gametogenesis, sperm - spermatogenesis, and eggs - oogenesis. In multicellular animals, gametes develop in the sex glands - gonads (in males - testes, in females - ovaries). The formation of gametes in lower animals occurs through mitosis, and in most animals through meiosis. Gametes are produced in excess quantities because not all sperm reach the egg and not all fertilized eggs (zygotes) can develop into adults.
In plants, depending on the structure of the gametes, different types of the sexual process are distinguished (see Sex, Fertilization). In hetero- and especially mogamous plants, significantly more male gametes are formed than female ones, which increases the likelihood of fertilization.
A cell located in the male reproductive system that serves to fertilize a female gamete is called a sperm. From ancient Greek it is translated as seed and life. This terminology is used to characterize micro gametes that are unusually mobile. They are characterized by a type of sexual process in which the fusion of germ cells that differ sharply from each other occurs.
Sex cell
Spermatozoa are smaller in size than the female egg, since they do not have as much cytoplasmic fluid in their structure. But a huge number of them are produced in the male body.
The very meaning of spermatozoon is important to distinguish from the word sperm, since the latter has a watery quality, which includes the male gametes themselves. In addition, semen contains a certain concentration of epithelial cells coming from the urethral canal.
History of discovery
Discoverer The first to describe the male gamete was the Dutch scientist Antonie van Leeuwenhoek. The discovery dates back to 1677. As the microscopist himself reported in his treatises, his friend Johann Hamm told him about sperm. Formally, he is the discoverer, but it was Leeuwenhoek who examined and made sketches in detail of spermatozoa.
What is a spermatozoon and what does it represent? The sperm is a specific cell, the structure of which gives it the ability to perform the function intended by nature to overcome the female genital tract, subsequently penetrating the female egg, introducing the genetic material contained in it.
In the process of fusion of a sperm with an egg, fertilization occurs and the formation of a zygote. is about 55 microns in length, making it the smallest cell in the human body. The upper part, called the head of the sperm, is 5.0 µm in length and 3.5 µm in width. The middle part and special tail are about 4.5 and 45 microns in length, respectively.
Such small sizes are due to the fact that the male gamete needs to move as quickly as possible along the female paths to the egg. In the process of maturation of the male gamete, a decrease in size occurs due to the transformation and compaction of the nucleus, and the cytoplasmic fluid is released to a greater extent. This way, only the most necessary parts of the sperm remain.
The male gamete contains X and Y chromosomes. Those containing the Y chromosome are called androspermia, and the X chromosome is gynospermium. Fertilization of the egg occurs with only one sperm, and the probability that it will be andro or gynospermium is equal, which in turn does not provide clear guarantees to guess the future sex of the baby .
Components
The head of the sperm in the male human body is presented in the form of an ellipse, compressed on both sides. One side has a small dent, which gives rise to talk about the spoon-shaped head of the male gamete.
The head contains a number of cellular structures, which include:
Cell functions - The nucleus is an important component that carries the necessary chromosome set. This type of nucleus is called haploid. After the process of fusion of the male and female reproductive cells has occurred, a zygote is formed, with a diploid set of chromosomes, and it contains maternal and paternal chromosomes.
Important! It is noteworthy that during the process of strong accumulation, the chromatin in the sperm nucleus is not active and ribonucleic acid is not formed in the nucleus. - Acrosome - performs the function of a lysosome, but slightly modified. The acrosome contains specific lytic enzymes that can break down the membrane membrane of the egg. The modified lysosome occupies most of the head of the sperm and is equal in size to the nucleus. The acrosome is located in front of the nucleus, and for this reason it is also called the cap. In the process of contact with the egg, enzymes are released from the modified lysosome, dissolving the required area of the egg shell. One of the most basic enzymes in the acrosome is acrosin, but besides it there are about 15 more.
- The centrosome, the center responsible for the movement of the tail of the male gamete, is formed from special microtubules.
In addition, the sperm is distinguished between the middle part and the neck. Next is the tail. The entire middle part of the male gamete has a tail cytoskeleton, but in the middle part around the tail, there is a mitochondrion. It is one large mitochondrion in the form of a spiral, wrapping around the cytoskeleton of the tail. It is this mitochondrion that allows the flagellum to move through the synthesis of adenosine triphosphoric acid.
The tail is located immediately behind the middle part and has a fine structure. The process of movement of human sperm is ensured by the tail, or flagellum. When making a movement, the male gamete moves, making revolutions around its axis. The movement speed can reach up to 30 cm in 60 minutes.
In the human body, after sexual intercourse, sperm reach the ampulla of the female fallopian (uterine) tube within several hours. This is where the process of fertilization occurs. While in the male body, sperm are in standby mode, not showing their activity, and the movements of their tails are barely noticeable. The removal of sperm along with the seminal fluid occurs due to the compression of the muscle fibers of the ducts and the beating of the ciliary parts of the cells located in the ducts.
Male gametes begin to show their activity after the process of ejaculation has occurred. The reason for their activation is a special prostatic fluid containing enzymes.
Important! Along the reproductive tract of the female body, sperm move only against the flow of fluid
In order for the fertilization process to be successful, no less than 10 million sperm must enter the fallopian tubes of the female body. During the movement, of the total number of sperm, only a few thousand will remain, reaching the ampulla of the female fallopian tube.
The speed of sperm movement is 2-5 millimeters per 60 seconds. This type of movement and speed allows it to reach the anterior third of the oviduct within 6-10 hours.
How long do sperm live?
After the maturation process has ended (about 65 days), the male gamete can remain in the body for up to 30 days. In seminal fluid, the ability to survive depends on environmental factors (light, room temperature, humidity) for up to one day. In the vaginal cavity, gametes die within several hours. But in the cervix, directly in the uterus and fallopian tubes, viability can last up to 72 hours.
Under pathological conditions in a man’s body, the number of sperm in the seminal fluid may change. It also happens that mature germ cells are absent during a special analysis, a spermogram.
Male gametes can be killed by high temperature, ultraviolet radiation, acidic environment, and salts of heavy metals. In addition, radiation, alcoholic beverages, nicotine, narcotic substances, antimicrobial drugs and potent medical substances have an unfavorable effect on male gametes.
Male gametes, called spermatozoa in the purple, are spherical or ovoid mononuclear cells. As for the Florideaceae, the question of the presence or absence of a membrane in spermatozoa has not been fully clarified. It is only known that at the moment they settle on the female plant they are already surrounded by a thin shell.
Male gametes in such gymnosperms are motile spermatozoa, which, with the help of numerous flagella, easily reach the female gametophyte and penetrate the archegonium.
Male gametes are mobile and have positive chemotaxis, causing them to move towards the chemical secretion secreted by female gametes.
Male gametes are found inside pollen grains and are transferred to the female reproductive organs in a process called pollination.
Any male gamete has the potential to fuse with any female gamete.
During pollination, male gametes are delivered through the pollen tube to the female gametes, avoiding the accidents to which free-floating gametes of lower plants are exposed. As a result, not only does the possibility of gamete fusion significantly increase, but also the conditions for the development of the embryo improve - due to its protected position inside the plant (Fig. In angiosperms, the ovary, inside which the ovule is located, usually develops into a fruit. In contrast, the seed of gymnosperms is not enclosed inside the megasporophyll, but located outside, on its surface.
During fertilization, a male gamete fuses with a female gamete to form a fertilized female gamete, called a zygote. As we found out, male and female gametes have different types, which contain either dominant or recessive alleles of genes responsible for certain traits. Exactly what type of male gamete (sperm) turned out to be and what type of female gamete (egg) turned out to be when a particular zygote is formed is a classic problem from probability theory. The zygote will contain the total chromosome set of fused gametes; its gene structure will turn out to be one or the other depending from the types of gametes that participated in the act of fertilization. Now it is this gene structure that is the genotype of the individual that will develop from this zygote through repeated cell divisions.
At the same time, male gametes swim vigorously for several hours, collecting under culture conditions in the darkest part of the vessel. Eventually they too become flaccid and attach to the substrate. Male and female gametes in scytosiphon are formed on different thalli. Zygotes begin to germinate 1 - 2 days after formation.
In animals and humans, male gametes are called sperm, and female gametes are called eggs. Gametes contain a haploid (single) set of chromosomes. In evolutionary modeling, the category of sex of an individual is not used. The object of modeling is panmictic populations of asexual organisms, that is, populations in which there is no prohibition on the crossing of any two individuals. Heterogeneity in natural populations plays the role of a natural limitation on crossing - neither a pair of two males nor a pair of two females can produce offspring.
