According to biology, tissue is a special structure that ensures the functioning of any organism as a whole. What structural features do you need to have in order to perform such an important function?
What is tissue: biology will give an answer
According to the definition, tissue is a group of cells similar in structure and function. Not all living organisms are formed by such structures. So, viruses are non-cellular forms of life, and all bacteria are unicellular.
Groups of specialized cells allow all physiological processes to be carried out more efficiently. That is why highly organized living objects are made up of organs. This fact is proved by biology. Tissue is just a structure consisting of cells and forming organs.
Plant tissue
What does the fabric consist of? Plant biology shows that not only from cells. Between them there is an intercellular substance that performs the function of a connecting link. Plant tissues are practically devoid of it.
They are represented by the following types:
1. Coverslip:
- peel - living tissue with special structures - stomata, used for gas exchange;
- cork - a dead tissue in which lentils metabolize.
2. The main - stores nutrients, implements the process of photosynthesis, forms the basis of organs.
3. Mechanical - performs a supporting function.
4. Conducting - provides upward (water from the root) and downward (organic matter from the leaves) current of substances.
5. Educational - during division, restores the cells of any affected tissue, performing regeneration.
Animal tissue
A distinctive feature of this group of cells is the presence of a large amount of intercellular substance.
In animals, the following tissues are classified:
1. Epithelial - performs a protective function. It also forms glands and metabolizes. How is epithelial tissue formed? Its biology is simple: small, tight-fitting cells of various shapes.
2. Connective - consists of large cells and a large amount of intercellular substance. It is the basis of the whole organism. Its varieties are blood, bone, cartilage and adipose tissue.
3. Muscular - represented by individual fibers capable of contracting - myofibrils. Thanks to them, it is possible to move the body in space and the movement of individual organs.
4. Nervous - connects the body with the environment, determines the presence of conditioned and congenital reflexes. It consists of cells called neurons, and their processes - axons and dendrites. It is through them that information is transmitted from receptors of sensory systems to the brain, and from there to the working organs.
The relationship of structure and function
But most importantly, as biology claims, tissue is a group of cells whose functions are determined by their structure.
For example, small, closely spaced epithelial cells, almost devoid of intercellular substance, look like a shield. With such structural features, the function is obvious - protection. Connective tissue is arranged in a completely different way. Since it creates the basis of all organs, it should be a lot. This explains the presence of large cells and a large amount of intercellular substance. Especially a lot of it in the blood. This substance is known to everyone under the name plasma. It contains shaped elements. Red blood cells - red blood cells - transport oxygen from the lungs to the organs and carbon dioxide in the opposite direction. Platelets are blood platelets that provide blood coagulation. White blood cells are colorless cells. They form immunity, helping the body resist infectious diseases.
Tissues and evolution
What is tissue, biology did not immediately recognize. After all, only with the invention of the light microscope a surprising microscopic image of cells and, with it, tissues was revealed to a person.
Lower plants, which include algae, do not have tissues. And even their multicellular representatives consisted of separate non-specialized cells that were not functionally interconnected. Further, with a change in climatic conditions, the first plant natives on land appeared on Earth. According to biology, tissue is a necessary condition for their survival in new conditions. In mosses and grouse, first appeared the mechanical tissues necessary for their spatial arrangement. And after - and conductive. Such development has led to the formation of these organs: root and shoot.
The most primitive multicellular animals also do not have real tissues. We are talking about a representative of the type Intestinal freshwater hydra. Her body is formed by specialized cells: epithelial, muscle, genital, skin-muscular, glandular, etc. But they do not form clusters, but are scattered throughout the body.
Thus, the appearance of tissues was the beginning of a complication of the structure of living organisms, allowing better adapt to any conditions.