Structure of the bird's egg: a scheme, features

Oocytes (eggs) are, as a rule, the embryonic form of an animal or an ovum. The study of them deals with oology - a special section of zoology.

general information

Their sizes can be different. For example, in a mouse the egg size is about 0.06 millimeters, but the diameter of the embryonic form of an African ostrich can reach 15-18 centimeters. The form can also be different. But usually eggs have a spherical or oval shape. In some living beings, they can also be elongated, elongated, as, for example, in mule fish, myxin or insects. Depending on the degree of distribution and the amount of nutrients within the egg, the size and other characteristics are determined. Accumulation of yolk (this substance) is carried out either as a continuous mass, or in the form of granules. Depending on this, experts divide oocytes into different types. The fertilization process is carried out in the upper part of the oviduct. As the oocyte passes through the canal, crushing occurs. This process is a discoidal incomplete process. Due to the fact that the beginning of the crushing takes place already in the oviduct, in birds the deferred egg can stay at one of the stages of crushing (as, for example, in a dove) or gastrulation (like a chicken).

Bird's Egg

Females of all species of feathered fauna representatives lay oocytes. Different species carry eggs of different shapes. This is due to the place where the masonry will be located. For example, if the nest is arranged in holes or holes, the eggs will be round. In birds, whose masonry is located on rocky protrusions, the oocytes will be oblong. Usually, the larger the bird, the bigger the size of the egg. But in this rule there are exceptions. Thus, for example, brood species, the offspring of which are adapted at once to independent feeding, carry eggs, the size of which is larger (compared with the female body) than those whose chicks appear helpless. The ratio of oocyte weight to body weight in small species is often greater than that of larger species. It is believed that the largest egg is laid by the African ostrich. Regarding the body weight of this feathered representative, its oocyte is 1% of body weight. But the weight of the hummingbird egg is 6% of the bird's weight.

Some peculiarities of the bird's egg structure

In birds, living in mountainous areas, oocytes have "ribs", like ribs of stiffness. They are necessary to preserve the integrity of the eggs, so that they do not break up when the birds land in a nest that has a small area. It should be noted, among other things, that this fin is capable of withstanding pressures of the order of 40 kg / sq. Cm, and the side where it is absent is not more than 2 kg / sq. See the surface of eggs is rough or smooth, shiny or matte. Color can be completely anything: from pure white to green and dark purple. The surface of eggs of some species is covered with specks, in some cases forming a corolla around the blunt edge. Color will depend on the image and place of nesting. Thus, in many secretly laying eggs and domestic feathered eggshells, it has a white color. In those who leave the masonry on the ground, the coloring becomes identical to the surrounding conditions: it merges with pebbles or a plant rag that lines the nest. The egg receives its color even in the ancestral ways of the female. For example, biliverdin (pigment) in conjunction with zinc imparts a blue or green color to the surface of the egg. Due to protoporphyrin, a red or brown color, or spots of such shades, is obtained. Next, consider in more detail the internal structure of the egg of the bird.

Oocyte device

The structure of the bird's egg is appropriate for the purpose. It contains everything necessary for the formation and development of a young organism. The embryo in the egg is fed by the compounds that are contained in the yolk. This mass is presented in two forms - in white and yellow. They are arranged in concentric alternating layers. Yolk is in the vitelline membrane. It is surrounded by protein. In the early stages of development of the egg shell, birds perform a nutritional function. The protein, in addition, protects the new organism from contact with the shell. The contents of the oocyte itself are surrounded by two subcultured layers: external and internal. Considering the structure of the bird's egg, it is necessary to say a few words about the shell itself. It consists mainly of calcium carbonate. At the blunt edge of the oocyte after masonry, an air chamber gradually forms.

Yolk

Considering the structure of the bird's egg, the scheme of which is given below, it should be said that the deuteroplasm (yolk) is an integral component of the inner contents of the oocyte. In the yolk mass are collected all the necessary substances that provide nutrition and normal development of the body. Deutoplasm is found in the egg cell not only of birds, but also of other animals (and in humans) and represents a cluster of plates or grains that merge in some cases into a continuous mass. The amount of yolk, as well as its distribution, can be different. With a small volume of deuteroplasm, the grain or plate is distributed evenly over the cytoplasm. In this case, they talk about "isoletsitalnyh" eggs. With a large amount of yolk, the components accumulate either in the central region of the cytoplasm - near the nucleus or in the vegetative part of the oocyte. In the first case, they speak of centrolecital, and in the second case, telolecital eggs. In accordance with the volume and degree of distribution of yolk mass, the type of oocyte fragmentation is also established. Chemically, the structure of the egg of the bird provides for three types of deutoplasm. Yolk can be carbohydrate, fatty or protein. But, as a rule, in most individuals, the yolk components include, in addition to these compounds, minerals, pigments, ribonucleic acid, thus having a complex chemical structure. So, for example, in the finished chicken oocyte oocyte in the yolk contains neutral fat 23%, protein 16%, 1.5% cholesterol, phospholipids 11% and mineral compounds 3%. In the accumulation and synthesis of the yolk component, various organoids take part: mitochondria, endoplasmic reticulum, Golgi complex. Synthesis of the protein component of the yolk structure in many animals occurs outside the ovary. By means of pinocytosis, the protein component penetrates into the developing egg.

Other elements of the oocyte structure

All shells prevent spreading, drying and damage to the egg. But they do not provide the necessary moisture to the growing body. It is formed by extraembryonic organs. In particular, they include an aqueous (or amniotic) shell. At the expense of it, the cavity of the amnion is confined, which is filled with liquid, where, in fact, the organism develops. Together with the water, two more layers are formed: vascular and serous (or allantois). In birds and reptiles, this layer is the organ of excretion and respiration. From the egg to the blunt and sharp edges of the egg go off khalazy - protein twisted dense strands. They provide a stable position of the core, preventing displacement from the middle position.

Shell

Studying the structure of the bird's egg, we should elaborate on the layers surrounding the nucleus. The hardest outer layer is the shell. It is sufficiently dense and performs the function of protection against mechanical damage and negative influence of the external environment. Under the shell there are shell shells. At the blunt end they diverge and form an air chamber. It contains oxygen, which is necessary for the breathing of a new organism.

Trophic oocytes

There is a type of eggs, which in the masonry serve as food for the offspring. As a rule, they are unfertile, and their appearance is practically the same as usual. They are laid by the females of some ants and uterus termites until the colony begins to produce enough food. Unfertilized oocytes of meat-egg and egg chicken are in some cases mistakenly called trophic, because they are used not by the birds themselves, but by humans and sometimes by domestic animals.