Structure of the egg: general information

The egg cell is the sex cell of the female, which 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 caviar, 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 structure are 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 of the yolk is covered with a thin and dense yeltic membrane, 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 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 the gases can percolate through the protein layer.

The protein is covered with two subcollapse balls, between which there 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 germ cell that is stored and ripens 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 sexual cell is immobile and until the end of its maturation is in the follicle.

So, the structure of the egg has a similarity with 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 amount of ribosomes, mitochondria, as well as EPS.

Also, throughout the cell, the so-called yolk granules are evenly distributed, which ensure the nutrition of the cell until it enters the uterine wall. Yolk bubbles are filled with nutrients - mostly fats and a small amount of proteins, as well as vitamins and trace elements.

The structure of the female ovum has several other characteristics. 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 in a 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 we compare with the male organism, the process of formation of 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.