There are 4 main types of tissues:
1. Epithelial tissue - performs protective and secretory functions.
2. Nervous tissue - provides a coordinated activity of different systems of organs and the connection of the body with the external environment.
3. Connective tissue - depending on the type, it can perform supporting, protective, hematopoietic, transport, respiratory functions.
4. Muscular tissue is a contractile function.
Cells are tightly adjacent to each other, there is little intercellular substance.
Types of epithelial tissue:
1. Surfacing epithelium (the surface of the cells is smooth, the cells are firmly adjacent to each other) - lines the surface of the skin, mouth, esophagus, alveoli, capsules of nephrons. Carries out integumentary, protective and excretory functions.
2. Glandular epithelium (glandular cells produce secretions) are found in various glands of the body. Functions: excretory (secretion of sweat, tears), secretory (formation of saliva, gastric and intestinal juice, hormones).
3. Ciliar epithelium (consists of cells with numerous cilia) - lines the airways. It has a protective function: cilia delay and remove dust particles.
It is formed by muscular fibers that contain thin filaments that can be excited and contracted.
Types of muscular tissue:
1. Skeletal muscle is a multinucleated cylindrical cells up to 10 cm long, streaked with transverse stripes. It is located in the musculoskeletal system of the body and some internal organs (tongue, pharynx, initial part of the esophagus). Function: arbitrary movements of the body and its parts, facial expressions, speech.
2. Cardiac muscle is responsible for involuntary contractions of the heart muscle to push blood through the chambers of the heart.
3. Smooth muscle (mononuclear cells up to 0.5 mm long with pointed ends) line the walls of the digestive tract, blood and lymph vessels and other internal organs. Functions: involuntary contraction of the walls of the internal hollow organs.