Functions and types of tissues (biology)

The body of many living organisms consists of tissues. Exceptions are all single-celled, as well as some multicellular, for example, lower plants, which include algae, as well as lichens. In this article we will look at the types of tissues. Biology is studying this topic, namely its section - histology. The name of this industry comes from the Greek words "cloth" and "knowledge". There are many kinds of fabrics. Biology studies both plant and animal. They have significant differences. Fabrics, types of tissue biology has been studying for a long time. For the first time they were described even by such ancient scientists as Aristotle and Avicenna. Fabrics, types of tissues, biology continues to study further - in the XIX century they were studied by such famous scientists as Moldingauer, Mirbel, Hartig and others. With their participation, new types of cell sets were discovered, their functions were studied.

Kinds of fabrics - biology

First of all, it should be noted that the tissues that are characteristic of plants are not characteristic of animals. Therefore, the types of tissue biology can be divided into two large groups: plant and animal. Both unite a large number of varieties. We will consider them further.

Types of animal tissues

Let's start with what is closer to us. Since we belong to the kingdom of animals, our body consists precisely of tissues, the varieties of which will now be described. Types of animal tissues can be combined into four large groups: epithelial, muscular, connective and nervous. The first three are divided into many varieties. Only the last group is represented by only one type. Next, consider all types of tissues, structure and functions that are characteristic of them, in order.

Nerve tissue

Since it happens to be only one species, let's start with it. The cells of this tissue are called neurons. Each of them consists of a body, an axon and dendrites. The latter are the processes by which the electrical impulse is transferred from cell to cell. Axon in a neuron alone is a long process, there are several dendrites, they are smaller than the first one. In the body of the cell is the nucleus. In addition, the so-called Nissla bodies are located in the cytoplasm - an analog of the endoplasmic reticulum, mitochondria, which produce energy, as well as neurotransmitters that participate in the impulse from one cell to another. Depending on their functions, neurons are divided into several types. The first type is sensory, or afferent. They carry out an impulse from the senses to the brain. The second type of neuron is associative, or switching. They analyze the information that came from the senses, and develop a reciprocal impulse. Such types of neurons are found in the brain and spinal cord. The latter variety is motor, or afferent. They conduct an impulse from associative neurons to organs. Also in the nerve tissue there is an intercellular substance. It performs very important functions, namely, it provides a fixed arrangement of neurons in space, participates in the removal of unnecessary substances from the cell.

Epithelial

These are such types of tissues, the cells of which are closely fitting to each other. They can have a variety of shapes, but they are always close. All the different types of tissues of this group have a similarity in the fact that the intercellular substance in them is small. It is mainly represented as a liquid, in some cases it may not be. These are the types of body tissues that provide it with protection, and also perform a secretory function. This group unites several varieties. It is flat, cylindrical, cubic, sensory, ciliate and glandular epithelium. From the name of each one can understand, from the cells of what form they are composed. Different types of epithelial tissues differ in their location in the body. So, flat lining the cavity of the upper organs of the digestive tract - the oral cavity and esophagus. Cylindrical epithelium is located in the stomach and intestines. Cubic can be found in the renal tubule. The sensory lining the nasal cavity, on it there are special villi, providing the perception of odors. Cells of ciliated epithelium, as it is clear from its name, have cytoplasmic cilia. This type of tissue lining the airways, which are located below the nasal cavity. The cilia, which each cell has, perform a purifying function - they to some extent filter the air that passes through the organs covered by this kind of epithelium. And the last variety of this group of tissues is glandular epithelium. Its cells perform a secretory function. They are found in the glands, as well as in the cavity of certain organs, such as the stomach. Cells of this kind of epithelium produce hormones, earwax, gastric juice, milk, sebum and many other substances.

Muscular tissues

This group is divided into three types. The muscle is smooth, striated and cardiac. All muscle tissues are similar in that they consist of long cells - fibers, they contain a very large number of mitochondria, since they need a lot of energy to carry out movements. Smooth muscle tissue lining the cavity of the internal organs. We can not control the contraction of such muscles ourselves, as they are innervated by the autonomic nervous system. Cells of cross-striated muscle tissue differ in that they contain more mitochondria than in the first. This is because they need more energy. The striated muscle is able to contract much faster than the smooth muscle. It consists of skeletal muscles. They are innervated by the somatic nervous system, so we can consciously control them. Muscular cardiac tissue combines some characteristics of the first two. It is capable of actively and rapidly contracting, as cross-striated, but innervated by the autonomic nervous system, as well as smooth.

Connective tissue types and their functions

All tissues of this group are characterized by a large amount of intercellular substance. In some cases, it appears in the liquid aggregate state, in some cases in the liquid state, sometimes in the form of an amorphous mass. There are seven types to this group. It is dense and loose fibrous, bone, cartilaginous, reticular, fatty, blood. The first variety is dominated by fibers. It is located around the internal organs. Its functions consist in giving them elasticity and their protection. In a loose fibrous fabric, the amorphous mass predominates over the fibers themselves. It completely fills the gaps between the internal organs, while the dense fibrous forms only the peculiar shells around the latter. It also plays a protective role. Bone and cartilaginous tissues form a skeleton. It performs in the body a supporting function and is partially protective. In cells and the intercellular substance of bone tissue, inorganic substances predominate , mainly phosphates and calcium compounds. The exchange of these substances between the skeleton and blood regulates such hormones as calcitonin and parathyreotropin. The former maintains the normal state of the bones by participating in the conversion of phosphorus and calcium ions into organic compounds stored in the skeleton. And the second, on the contrary, with a shortage of these ions in the blood provokes their getting from the tissues of the skeleton.

Blood contains a lot of liquid intercellular substance, it is called plasma. Her cells are quite distinctive. They are divided into three types: platelets, erythrocytes and leukocytes. The first are responsible for blood clotting. During this process, a small blood clot forms, which prevents further blood loss. Erythrocytes are responsible for transporting oxygen through the body and providing them with all tissues and organs. They may contain aglyutinogens, which exist in two species - A and B. In blood plasma, the content of alpha or beta agglutinins is possible. They are antibodies to aglutinogens. For these substances, the blood group is determined. In the first group, there are no aglyutinogens on red blood cells, and there are aglutinins of two kinds in the plasma at once. The second group has aglyutinogen A and aglutinin beta. The third is B and alpha. In the fourth plasma, there are no aglutinins, but on the red blood cells there are aglutinogens, and A, and B. If A occurs with alpha or B with beta, the so-called agglutination reaction occurs, resulting in erythrocytes perishing and clots forming. This can happen if you transfuse the blood of an inappropriate group. Taking into account that only red blood cells are used for transfusion (plasma is screened out at one of the stages of donor blood treatment), then the person with the first group can only be transfused with the blood of his own group, the second - the blood of the first and second group, the third - of the first and third groups, With the fourth - any group.

Also on the red blood cells there can be antigens D, which determines the Rhesus factor, if they are present, the last positive, if there is none, negative. Lymphocytes are responsible for immunity. They are divided into two main groups: B-lymphocytes and T-lymphocytes. The first are produced in the bone marrow, the latter in the thymus (gland located behind the breastbone). T-lymphocytes are divided into T-inducers, T-helpers and T-suppressors. Reticular connective tissue consists of a large amount of intercellular substance and stem cells. Blood cells are formed from them. This tissue forms the basis of the bone marrow and other organs of hematopoiesis. Also there is a fatty tissue, the cells of which contain lipids. It performs a spare, heat-insulating and sometimes protective function.

How are plants arranged?

These organisms, like animals, consist of aggregates of cells and intercellular substance. We describe the types of plant tissues further. All of them are divided into several large groups. These are educational, covering, conducting, mechanical and basic. Types of plant tissues are numerous, as several groups belong to each group.

Educational

These include apical, lateral, intercalary and wounded. Their main function is to ensure the growth of the plant. They consist of small cells that actively divide, and then differentiate, forming any other kind of tissue. The apical are on the tips of the stems and roots, the lateral ones are inside the stem, under the coverslips, the intercalary - in the interstice bases, the wound ones - at the site of the injury.

Covering

They are characterized by thick cell walls consisting of cellulose. They play a protective role. There are three types: epidermis, crust, cork. The first covers all parts of the plant. It can have a protective wax coating, it also contains hairs, stomata, cuticle, pores. The crust differs in that it has no pores, for all other characteristics it is similar to the epidermis. Cork - this is the dead coverslips, which form the bark of trees.

Conductive

These tissues come in two varieties: xylem and phloem. Their functions are transport of substances dissolved in water from the root to other organs and vice versa. Xylem is formed from the vessels formed by dead cells with solid membranes, there are no transverse membranes. They transport the liquid upward. Floema - sieve tubes - living cells in which there are no nuclei. Transverse membranes have large pores. With the help of this variety of plant tissues, substances dissolved in water are transported downward.

Mechanical

They are also of two types: collenchyma and sclerenchyma. Their main task is to ensure the strength of all organs. Collenchyma is represented by living cells with stiffened membranes, which fit tightly to each other. Sclerenchyma consists of elongated dead cells with solid membranes.

Basic

As their name implies, they form the basis of all the organs of the plant. They are assimilative and spare. The first are in the leaves and the green part of the stem. In their cells there are chloroplasts, which are responsible for photosynthesis. Organic substances accumulate in the accumulating tissue, in most cases it is starch.