In addition, when dissecting hens, you can see yolk of various sizes. These are immature eggs. The shell of an egg is a calcareous hard shell, called an egg shell. The egg shell plays a protective role. There are about 7000 holes in the egg shell, which can be ventilated. There are two layers of egg membrane close to the egg shell, and the outer layer is thicker.
In the blunt end (big head) of an egg, a small air chamber is often formed between the two membranes to store air for breathing during embryo development. This is the empty part of the boiled egg. Inside the egg membrane is a large amount of egg white (egg white), which consists of water, protein, a small amount of sugar and inorganic salts; The outer layer is thin, which can be called dilute protein, and the inner layer is thick, which is called thick protein.
These substances are nutrients for the development of chicken embryos. Further inside is a spherical yolk (yolk), which is the egg cell. There is a thin membrane on the surface of yolk, called yolk membrane, which is cell membrane. Yolk is generally layered, consisting of yellow yolk and white yolk arranged alternately in concentric circles, with yolk center in the middle and yolk center neck connected to the blastoderm along the long axis of the egg.
Both ends of the yolk are composed of thick protein, which keeps the egg cell in the protein center, plays a buffering role, prevents the egg from shaking, and is beneficial to the hatching of the egg. There is a small white disk on the yolk (that is, a small white dot seen on the yolk), which is composed of the nucleus and a part of cytoplasm. This is the blastoderm.
If it is a fertilized egg, the blastoderm can hatch chicks under suitable conditions. Therefore, it is not accurate to say that an egg is a cell, but it is correct to say that only one cell in an egg is yolk. If it is unfertilized, it is an egg cell, and if it is fertilized, it is a fertilized egg cell.
This is just for the newly born eggs. If the eggs start to hatch and the fertilized eggs need to divide, there will be more than one cell.
Extended data
Although there is a close relationship between birds' eggs and their egg cells, they are two different concepts and cannot be equated.
The reproductive organ that produces egg cells is the ovary of the female bird. There are many immature eggs in the ovary, and the eggs gradually mature in the ovary. When one is mature, one is excluded, leaving the ovary, falling into the body cavity and entering the fallopian tube.
Mature eggs produced by ovaries do not have the structure of protein, shell membrane and eggshell when they leave ovaries, but these structures only exist after the eggs are formed into eggs due to the secretion of the tube wall in the middle and rear sections of fallopian tubes during their movement.
Moreover, egg fertilization is the fusion of sperm and egg in the front of fallopian tube-before the egg is coated with protein, shell and eggshell, not in uterus-after the egg has formed into an egg.
Therefore, protein, shell and eggshell do not belong to the structure of the egg itself (they are wrapped outside the egg, which is the adaptation of birds to its oviparous reproduction mode), and the yolk part hanging in the center of the egg is the egg (when the fertilized egg is formed into an egg and laid, the cleavage has progressed to the early blastocyst stage, and there are not only one cell in the egg, but many cells). Therefore, eggs and egg cells have different connotations, and birds' eggs are not the same as birds' eggs.
Therefore, eggs and egg cells have different connotations, and birds' eggs are not the same as birds' eggs.
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