An egg is a female sex cell that contains 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 fish roe, a chicken egg, etc. Each type of animal has its own characteristics.
The structure of the egg
Probably the most striking example of this structure are the eggs of birds and reptiles, which in many respects have a similar structure. An egg is a huge egg, which is easy to learn without special equipment.
Poultry egg 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 a lot of fats, proteins, vitamins, pigments and trace elements of the egg. Its main purpose is nutrition of the embryo.
On top of the yolk is covered with a thin and dense yolk shell, on the surface of which you can notice a small light spot - this is a blastodisc, in place of which there was an egg cell before fertilization.
Next is egg white, which is divided into four 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 leak through the protein layer.
The protein is covered with two subshell balls, between which there is 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 characteristic features of each individual species.
The structure of the human egg
The female egg is a reproductive cell that is stored and matures in the follicles of the ovary. As with all animals, the human germ cell is designed to transmit a set of chromosomes during reproduction.
Unlike somatic, germ cells are formed by meiosis, therefore, they contain only a haploid (23 in humans) chromosomes. The structural features of the human egg will be described below.
The first distinguishing feature is the size. If a normal somatic cell rarely exceeds 20 microns, then the diameter of a female egg is about 100 microns. This germ cell is motionless and is located in the follicle until the end of its maturation.
So, the structure of the egg cell is similar to other cells of the body - it consists of a nucleus, a cytoplasm and is limited by a plasma membrane. As already mentioned, the nucleus is haploid. The cytoplasm contains a huge number of ribosomes, mitochondria, as well as EPS.
Also, the so-called yolk granules are evenly distributed throughout the cell, which provide nutrition to the cell until it is introduced into the uterine wall. The yolk vesicles are filled with nutrients - mainly fats and a small amount of protein, as well as vitamins and minerals.
The structure of the egg of a woman has some more features. For example, the outer ball of the cytoplasm contains special secretory granules. When the sperm penetrates inside, the contents of the granules are released and act on the egg shell - as a result of this, it changes its structure so that no more sperm can penetrate through it.
An interesting fact is that the number of eggs in a woman is laid even in the embryonic period of development. It is during the development of the ovaries that the fetus already forms a certain number of follicles and eggs. When compared with the male body, the process of sperm formation, starting from puberty, is ongoing.
As you can see, the structure of the egg is quite specific and fully corresponds to its functions.