The human body, like all living things, consists of independent structural and functional units - cells. They, in turn, are united by common features (origin, morphology, functions) into tissues, from which all our organs, vessels, blood and lymph are built. A special part of them is made up of epithelium, because it predominates in the body and performs the integumentary and secretory functions. So, on its basis the skin and serous membranes are constructed, it forms the structure of all the glands of internal and external secretion. And most importantly, it lays all internal organs and vessels (flat epithelium). That is, it is borderline, one way or another, between the body and the environment. This tissue is constructed from epithelial cells that are firmly connected to each other by means of various methods of intercellular contacts: gluing and closure belts, as well as special finger-like protrusions of the membrane-interdigitations. Also they are held together by the so-called. Cementing substance containing in a large amount hyaluronic acid. Thus, whole layers are formed, which are usually attached to the basement membrane, and their nutrition is provided by an even more inferior loose fibrous connective tissue with vessels and nerves. All ions and energy substrates pass into the epithelial cells through diffusion through thin-walled capillaries.
Classification and functions
According to the morphology and features of the structure, it is customary to distinguish between the epithelium of flat, cubic, cylindrical, multilayer, ciliary (ciliary) and glandular.
In turn, all the subtypes, except the latter, form a common cover-type group, since they separate the environment of the organism from the surrounding one and metabolize between them by absorption and excretion. Also the epithelium, flat including, protects all underlying layers from various damages: mechanical, chemical, physical, etc. In this regard, it has the highest regenerative capacity in comparison with other tissues of the body. Especially great is its importance for the skin and respiratory tract, as they directly touch the external environment. Also, the epithelium flat and glandular lining the organs of the gastrointestinal tract and the genitourinary system, protecting against adhesion and the introduction of pathogenic bacteria, as well as poisons and toxins.
Role in diagnosis
As the cells are constantly updated, the dead ones are exfoliated and carried away by the current of the urine or are absorbed by the macrophages in the blood. In connection with this, and the epithelium is flat, the norm of which in the general urine analysis is 1-2 in the field of view of the microscope, has some diagnostic significance. And if in men it is rarely determined, then women almost always. The reason is different in the structure of the outflow tracts: in the strong sex, the epithelium flat enters the urine from the lower third of the urethra, and in the weak one, also from the vagina. In the presence of inflammation in the urinary tract, its amount can increase dramatically, but the transitional epithelium, which is normally absent in analyzes, is of greater diagnostic value.