When they talk about this type of fabric, I remember infirst of all, the skin, although epithelial tissue is basically a kind of “border guard”. It separates the organs from each other, it is contained in the mucous. Epithelial tissue is heterogeneous, the structure and functions of which are interconnected in a special way for each of the types of this tissue. What kinds of speech? Read on.
A characteristic common feature of all kinds is cells,which fit snugly together, are often arranged in layers, which is explained by the barrier function of epithelial tissue. Also, all types of epithelial tissue are united by the fact that they are always separated from neighboring structures by connective tissue - this formation is called the basement membrane.
In general, the epithelium is simple (in one layer) and layered (in several). Accordingly, the epithelial tissue structure can be very different.
A simple epithelium may be slightly flattened byform. This type is called squamous. It lines the lungs, blood vessels, cavities of the heart. Also, these cells are located in the upper layers of the skin and oral mucosa.
It is not difficult to guess the shape of the cubic cellsepithelium. Such cells are found in the glands, ducts of the glands and the renal tubules. In addition, they constitute the primordial epithelium in the ovaries of women and male testes.
Prismatic epithelium is simple and layered.Cells have the form of oblong columns. The nuclei in such cells are “hidden” closer to the basement membrane and away from the surface. Well, in the stomach, whose surface they line, it is very rational - the environment is too aggressive there. Some of these cells are part of the sensory organs - smell, taste and hearing.
Ciliated prismatic epithelium has outgrowthsspecial forms that are able to promote what is next to them with fast wave-like movements. They "live" in the nose and ... in the fallopian tubes in women, which allows them to move the egg to the uterus.
Железистым эпителием называют призматический, containing secreting cells. Sometimes there are more secreting cells than columnar cells. Where do the cells that create the secret come from? These are cells of epithelial tissue that have passed the path of specialization. And “specialists” they can be very different. Engaged in the production of enzymes, hormones, milk, mucus, sweat, earwax and saliva. Of course, all these substances are unable to produce single-celled glands, this is the case of glands consisting of many epithelial cells. And unicellular cells are called goblet cells. Initially they were called enterocytes, because most of these cells are in the small intestine. But then it turned out that they are present in the conjunctiva of the eye, in the respiratory system, and in the ducts of the glands.
Where processes of friction are great and likelyinjury, the body builds a complex epithelium - the one that always consists of several layers. We are talking about the skin and oral mucosa. On the surface of the skin are cells in which a lot of keratin protein, keratin in the mouth is small in the cells, so the skin and the oral mucosa are significantly different to the touch.
Epithelial tissue function is very different. The list below is not completely complete.
Protective function. The epithelium prevents mechanical damage, chemical burns, puts a barrier against infection and protects the underlying cells from water loss.
Sensation function: specialized cells of epithelial tissue form sensory organs.
Secretory function: described in detail in the section on the glandular epithelium.
Absorbent: in the small intestine, nutrients are absorbed through the epithelium.
Excretion: sweat glands secrete unwanted substances, also the epithelium in the kidneys is able to participate in filtration, and in reabsorption too.
Diffusion: through the thin epithelium in the respiratory system into the body and from it penetrate gases.
Cleaning function: in the airways, the epithelium cleans the air of dust.
Friction reduction: The vascular epithelium reduces friction between the vessel wall and blood cells.
As you can see, there are many functions, because there are many types. You can read more about this in good histology textbooks.
