All living organisms, with the exception of algae, are made up of various tissues. Body tissues are collections of cells that are similar in structure, united by a common function. So what are they like?
Plant tissues
There are these types of plant tissues:
- educational;
- main;
- integumentary;
- conductive;
- mechanical.
They all perform their functions. For example, educational ensures the growth of a plant, and all other types of tissues are also formed from it. The covering tissue performs a protective function. In addition, gas exchange occurs through it. Conductive provides transport of substances throughout the plant. Mechanical tissue also plays a protective role. It is present in plants with a stiff stem. The main tissues of the body are responsible for the formation and accumulation of nutrients.
Tissues of the human body
There are many types of animal tissues, which in turn are divided into types.
The animal body is built from four types of tissue:
- epithelial;
- muscular;
- nervous;
- connective.
All typestissues of the human body are divided into types. Let's take a closer look at each one.
Epithelium: varieties and functions
The tissues of living organisms of this type perform mainly a protective function.
Epithelium, first of all, can be divided into single-layer and multilayer. In the first, there is only one row of cells located close to each other. The second one consists of several layers of cells.
According to the shape of the cells, squamous, cubic and cylindrical epithelium are distinguished. Depending on the specific functions performed by the tissue, there are also ciliated, glandular and sensitive, or sensory epithelium.
Different types of epithelial tissue are found in different parts of the body of animals and humans. So, the flat one lines the oral cavity and the esophagus cavity, the cubic one - the renal tubules, the cylindrical one - the stomach and intestines. The ciliated epithelium is located inside the respiratory tract, sensitive (sensory) - in the nasal cavity, glandular - in the glands.
Muscle tissues: characteristics
Muscle tissues of the human body are divided into three types:
- striated muscles;
- smooth muscles;
- cardiac muscles.
The cells of muscle tissue are called myocytes, or fibers. The tissue of this type is able to contract due to the content of contractile proteins in the cells: actin and myosin.
Striated muscles have thin long cylindrical fibers with severalnuclei and a large number of mitochondria that provide the cell with energy. Skeletal muscles are made up of this type of tissue. Their main function is to move the body in space. They can also play a protective role. This applies, for example, to the abdominal muscles, which protect internal organs from damage.
Smooth muscle, unlike striated muscle, cannot be controlled consciously. Such tissues of the human body line some internal organs, such as the intestines, uterus. They also consist of sphincters - circular muscles, which, when narrowed, close the hole. Animals have upper and lower esophageal sphincters, pylorus, several sphincters of the duodenum; sphincters of Oddi, Mirizzi, Lutkens and Helly, located in the organs of the pancreatic system; colonic sphincters and urethral sphincters. In addition, animals and humans also have a sphincter pupil, due to which it narrows and expands. Smooth muscles have spindle-shaped cells containing a single nucleus. Muscles of this type are reduced not as quickly and actively as striated.
Cardiac muscles are similar to both striated and smooth. Like smooth, a person cannot control it consciously. However, it is able to contract as quickly and actively as the striated one. The fibers of the heart tissue are intertwined, forming a strong muscle.
Nervous tissue
It is not divided into species. The cells of this tissue are called neurons. They consist of a body and several processes: one long axon andseveral shorter dendrites. In addition to neurons, neuroglia are also present in the nervous tissue. It consists of small cells with numerous outgrowths. Neuroglia plays a supporting function, provides the cell with energy, and also creates specific conditions for the formation of a nerve impulse.
Connective tissues: varieties, functions, structure
This type of fabric has many types:
- dense fibrous;
- loose fibrous tissue;
- blood;
- lymph;
- bone;
- cartilaginous;
- fatty;
- reticular (mesh) tissue.
Despite the fact that they are all connective tissues, these tissues are quite different in their structure and functions. The main similarity of all these tissues is the presence of a large amount of intercellular substance. Consider the features of the main types of connective tissue.
Reticular tissue features
This is one of the most important connective tissues. Reticular tissue forms the organs of hematopoiesis. It contains cells from which blood cells are formed. Reticular tissue forms the red bone marrow, the main hematopoietic organ of humans and animals, as well as the spleen and lymph nodes.
Reticular tissue has a complex structure. It consists of reticular cells (reticulocytes) and reticular fibers. The cells of this tissue have a light cytoplasm and an oval nucleus. On its surface, it has severalprocesses, with the help of which cells are interconnected and form something like a network. Reticular fibers are also arranged in the form of a lattice, branch and connect to each other. Thus, the network of reticular fibers together with the network of reticulocytes form the stroma of hematopoietic organs.
Reticulocytes can be isolated from the cell network and differentiate into macrophages or hematopoietic cells. Macrophages are special white blood cells that are part of the phagocyte group. They are able to carry out phagocytosis - the capture and absorption of particles, including other cells. The main task of macrophages is to fight pathogenic bacteria, viruses and protozoa.
Bone and cartilage tissue
They perform protective and supporting functions in the body. Their main feature is that the intercellular substance is solid and consists mainly of inorganic substances. As for the cells, they are in the bone tissue of four types: osteoblasts, osteocytes, osteoclasts and osteogenic. All of them differ in structure and function. Osteogenic cells are those from which the other three types of bone cells are formed. Osteoblasts are mainly responsible for the synthesis of organic substances that make up the intercellular substance (collagen, glycosaminoglycans, proteins). Osteocytes are the main tissue cells, they have an oval shape and a small number of organelles. Osteoclasts are large cells with multiple nuclei.
Cartilage is divided intoseveral varieties. These are hyaline, fibrous and elastic cartilage. The main feature of this type of tissue is the presence of a large amount of collagen in the intercellular substance (about 70%). Hyaline cartilage covers the surface of the joints, forms the skeleton of the nose, larynx, trachea, bronchi, is part of the ribs, sternum. Fibrous cartilage can be found in intervertebral discs, as well as in places where tendons attach to bones. Elastic forms the skeleton of the ear.
Blood
She has a huge amount of liquid intercellular substance called plasma. It is 90% water. The remaining 10% are organic (9%) and inorganic (1%) substances. The organic compounds that make up the blood are globulins, albumins and fibrinogen.
The cells in this tissue are called blood cells. They are divided into erythrocytes, platelets and leukocytes. The former perform a transport function: they contain the protein hemoglobin, which is able to carry oxygen. Platelets provide blood clotting, and leukocytes are responsible for protecting the body from pathogens.
