Structure of the egg: general information
The egg cell is the sex cell of the female, whichcontains a haploid set of chromosomes. Its main purpose is the transfer of genetic information during fertilization. The structure of the egg in nature can be very diverse. For example, an egg is a caviar of fish, a chicken egg, etc. Each kind of animal has its own characteristics.
Structure of the ovum of birds
Perhaps the most striking example of this structureare the eggs of birds and reptiles, which in many respects have a similar structure. Egg is a huge egg, which is easy to learn without special equipment.
The egg of the bird consists of yolk, protein and shell. Each of these constituent parts has its own characteristics. The yolk is a dense, yellowish, rounded structure located in the center of the egg. It contains many fats, proteins, vitamins, pigments and trace elements of the egg. Its main purpose is to feed the fetus.
On top, the yolk is covered with a thin and dense yolkshell, on the surface of which you can see a small light spot - a blastodisk, in place of which was the core of the egg before fertilization.
Next comes the egg white, which is divided intofour balls. It contains a lot of proteins, vitamins and nutrients. In addition, there is lysozyme - a special enzyme that has an antibacterial effect. Only gases can percolate through the protein layer.
The protein is covered with two subcollapse balls, betweenwhich remains a small gap. The eggshell is a very dense protective shell of the egg, which consists mainly of calcium carbonate. Egg shells can have different thicknesses and colors - these are the characteristics of each individual species.
Structure of the human ovum
A female egg is a sex cell thatstored and matures in the ovary follicles. Like all animals, the human sex cell is designed to transmit a set of chromosomes during reproduction.
Unlike somatic, sex cells are formed by meiosis, therefore they contain only a haploid set (in humans it is 23) a set of chromosomes. Features of the structure of the human ovum will be described below.
The first distinguishing feature is the size. If the normal somatic cell rarely exceeds 20 μm, the diameter of the female egg is approximately 100 μm. This germ cell is immobile and until the end of its maturation is in the follicle.
So, the structure of the egg has a similarity withother cells of the body - it consists of a nucleus, cytoplasm and is limited by the plasma membrane. As already mentioned, the nucleus is haploid. The cytoplasm contains a large number of ribosomes, mitochondria, as well as EPS.
Also throughout the cell are evenly distributed socalled yolk granules, which provide nutrition to the cells until it is introduced into the uterine wall. The yolk bubbles are filled with nutrients - basically they are fats and a small amount of proteins, as well as vitamins and microelements.
The structure of the female ovum has and still somefeatures. For example, in the outer sphere of the cytoplasm, there are special secretory granules. When penetrating the sperm, the contents of the granules are released and act on the egg shell - as a result, it changes its structure so that no more spermatozoa can penetrate through it.
It is also interesting that the number of oocytes ina woman is laid in the embryonic period of development. It is during the development of the ovaries that a certain number of follicles and oocytes are already formed in the fetus. If compared with the male body, the process of forming spermatozoa, beginning with the period of puberty, goes on constantly.
As you can see, the structure of the egg is quite specific and fully corresponds to the functions it performs.