Reproduction or reproduction of offspring into the world is one of the most important destinations of all living things on our planet. Genetic material is transmitted from parents to offspring, which allows for a rather long time not to interrupt your family. Today we will talk more about the continuation of the human race. Consider concepts such as spermatogenesis and ovogenesis. Where does the breeding process begin? Of course, with the penetration of the male cell into the female. Where do they come from? We are interested in the process of gametogenesis. Ovogenesis is a sequential process of the formation of a female reproductive cell. Spermatogenesis is the formation of a male reproductive cell. Today we will analyze what are the similarities and what are the differences between these processes.
Egg
We have already mentioned that ovogenesis is the process of reproduction of the female reproductive cell, which has the name "egg". We offer a little talk about why it is needed and what function it performs. Briefly consider the structure of the egg.
As mentioned earlier, an egg is a reproductive cell that has a rounded shape. It necessarily contains all the necessary nutrients, because its main function is to ensure the development of the body from the moment of fertilization. Like any other cell, the egg in the center contains the nucleus. Around the nucleus with a haploid set of chromosomes is the cytoplasm. The egg also has an upper protective layer - a radiant crown. This shell got its name because it consists of a large number of small villi.
Near the nucleus, as a result of meiosis, another small body is formed, this formation is a cell of very tiny sizes. In total, a newborn girl has approximately one million eggs in stock. But over time, many of them die. Until the time of puberty, only about 300 thousand remain, and approximately 400 of them undergo ovulation. Where does everyone else go? They just die, never having time to ripen.
We propose to discuss the process itself under the name "ovogenesis". This is the maturation of those same female germ cells. Let's get started right now.
Ovogenesis
Ovogenesis is the formation of female germ cells. It is immediately worthwhile to clarify that in mammals it begins even before birth, that is, in utero. Before we list and characterize all stages of ovogenesis, we outline the main purpose of this process. So the functions are:
- a haploid set of chromosomes should form in the nucleus of the egg;
- zygote satisfaction in the availability of nutrients.
We can immediately note that the process of ovogenesis is not very different from spermatogenesis, you yourself will notice later.
So, the stages of ovogenesis are distinguished as follows:
- reproduction;
- height;
- maturation.
The very first stage takes place in the womb. The girl already has a large number of primary germ cells, which at this stage can be called: embryos or embryos. These future eggs are very actively dividing, so the accumulation of ovogony occurs. They accumulate in the cortical layer. It is ovogony that accumulates all the necessary nutrients, namely:
What is the difference between ovogony and germ cells? They become larger in size. Their similarity lies in the fact that the genetic composition is the same.
If we briefly consider the second phase, we will see that it also occurs before the birth of the girl. Now ovocytes form first-order oocytes. The size during division is significantly reduced, but oocytes quickly gain their mass. Further, the future eggs are waiting for a long preservation in the form of prophase oocytes. Now there are about two million of them, and only about 400 oocytes will receive further development.
The last stage occurs after a large amount of time (approximately 11-12 years, and sometimes more). At this phase, one of the preserved oocytes suddenly begins its further development. The result will be the arrival of menstruation.
Sperm
We learned that in ovogenesis, a female reproductive cell called an egg is formed. Now we turn to spermatogenesis and the male reproductive cell. So, to continue the human race, you need a pair of eggs, which can fertilize it. Sperm - this is that necessary half.
There can be many millions of sperm in the male body, unlike the eggs in the female body. They consist of:
- from the head;
- cervix;
- middle part;
- filamentous tail.
When the sperm reaches the ovum, the tail needed for movement disappears. Further, the female reproductive cell passes only the sperm head into itself, since it carries genetic material. As you know, the egg shell is quite strong, so there is an acrosome on the sperm head. It contains a special substance that can dissolve the shell. The size of one male reproductive cell is only 0.05 mm, so in order to see it, you need a powerful microscope.
Spermatogenesis
Spermatogenesis and ovogenesis are fairly similar processes. In the first, the following stages are distinguished:
- reproduction;
- height;
- maturation;
- formation.
At the breeding stage, more than a thousand spermatogonia are formed by dividing each about ten times. During division, they absorb nutrients.
In the process of growth, they greatly increase in size. It is at the growth stage that spermatogonia transform into first-order spermatocytes.
At the ripening stage, 2 divisions occur:
- meiosis (as a result, we have second-order spermatocytes);
- mitosis (spermatid forms).
During the formation of spermatids, they come into contact with the processes of the cell, and sperm are formed. When they finish their formation, they gain mobility.
Similarities
It is worth noting immediately the first similarity of ovogenesis and spermatogenesis - both processes are necessary for the formation, maturation and growth of germ cells, male or female. Although there are many similarities in the processes, some differences can be revealed.
Another common feature is the almost identical stages of the process (spermatogenesis has one more stage). General stages:
- reproduction;
- height;
- maturation.
We considered the features of these stages in detail above. We proceed to the differences.
Differences
To begin with, during ovogenesis and spermatogenesis we have different results, ovogenesis corresponds to such a result as the formation of a female reproductive cell, and spermatogenesis - to a male one. As you already noticed, in the process of sperm formation there is one more step than during the formation of an egg. The former also undergo a formation stage, while ovogenesis does not need this stage.
The process of ovogenesis begins in girls in the womb, and spermatogenesis begins in boys who have reached 12 years of age. This is another difference.
The last difference is more male germ cells compared to female. This can be explained as follows: only one sperm from the order of 200 million gets to the egg.