The concept of tissues

We have already noted that the cell in the body is not an independent unit, therefore the history of the formation of complex organisms are formed complex cells and non-cellular elements of a body with similar functions and structure; they are formed from certain rudiments of the body. Such complexes cells and non-cellular elements make up the fabric of our body. Taken to distinguish between the 4 main groups of tissues.

epithelial tissue
Fig. 4. Epithelial tissue.
and mono - layer cubic epithelium;
b - multi-layer flat epithelium.

Epithelial or the edge of the fabric. They are located on the surface of the body, forming the skin, mucous membranes lining the digestive canal, respiratory tract and other organs. Thus, these fabrics are in the places where the body is in contact with the external environment - air, food, water, etc. Cells of epithelial tissue are closely adjoined to each other, like soldiers in close formation, they form the reservoirs are located in the shared unstructured vinyl; cell layers can represent one or more layers (Fig. 4). The epithelium meet the protective role, protecting the body from being hit by harmful substances and bacteria, preventing the evaporation of water, which is so rich fabric of our body. As epithelium take the edge position, they would participate in the exchange between the organism and the environment: for example, through the mucous membranes penetrate into the internal environment of the body is water and nutrients; through the skin (since then) and mucous membranes are from the body unnecessary substances, waste products. This group tissues applies glandular epithelial - cells produce and secrete different juices of our body. Glandular epithelium forms of cancer, such as salivary, gastric, intestinal, tearful, and others.
Connective tissue. While epithelial tissue are located on the border of the body with its surrounding environment is connective tissue are the internal environment of the body and therefore they are called fabrics internal environment. This group brings together numerous and very different in appearance tissue, such as bone, blood, loose connective tissue, etc. However, in spite of the difference, they all have common features in the structure and functions: first, for the whole of this group is typical that the cells do not adjoin densely to each other, as in epithelia, and are often placed at significant distances and the space between them is filled intermediate or intercellular living matter; secondly, these fabrics play an important role in metabolism and perform supporting and protective role. For example, the blood carries nutrients and oxygen to cells her fight with microbes, protecting the body from disease. The bones of the skull, thorax, spine to provide support for the authorities and protect them from damage, at the same time, they play an important role in the exchange of salts. Adipose tissue consists of cells containing in the cytoplasm of the drops of fat, it is unique depot breeding material and at the same time forms the "strip" between the bodies. Those or other kinds of connective tissue involved in the formation of all organs and play in their structure an important role. Below we take a closer look at the structure of the bone, cartilage tissue, blood and lymph.
Muscle tissue. The common feature of these materials is the ability to cut items that they form. These properties provide the ability to move. There are two types of muscular tissue: smooth and striated. The main element of smooth muscle is a muscle cell. In its cytoplasm contains special filamentary structure of myofibrils, enabling the reduction. Cells of this fabric are closely adjoined to each other, forming layers. Muscles, consisting of her, are in the internal organs (stomach, intestines, etc.,) and in the blood vessels. Their peculiarity is that they are reduced regardless of the will, that is, not by conscious control. For example, we cannot be forced to shrink the stomach faster or slower.
Striated muscle tissue consists of fibres with a length of 12 see, as seen under the microscope in this fiber is easy to detect many cores. In addition, the muscle fiber as the cells of smooth muscle, penetrated in the longitudinal direction of the myofibrils, providing contractile activity of the muscle fibers. However, unlike the smooth muscles of myofibrils here consist of two substances, different refracting light. These substances are evenly take turns; areas of myofibrils the same building are located on the same level within fibres; therefore, when viewed under a microscope and marked cross striation fiber thin lines (darker through areas heavily refracting light, more light - due to poorly refractive areas). Unlike smooth muscle tissue work striated muscles is controlled and operated by consciousness. This tissue forms all the muscles of our body and is a part of some internal organs, such as language, pharynx.
Nervous tissue. On the description of this fabric here we will not be stopped. About it will be discussed in Chapter four.