The human body has many organ systems, each of which needs constant replenishment of nutrients and the diversion of metabolic products. To this end, blood, which is the main transport medium, copes. In this context, it is natural to ask what tissues are devoid of blood vessels. How they are called and how their nutrition is carried out should be considered in more detail.
Articular cartilage nutrition
When considering the question of which tissues are devoid of blood vessels, two obvious answer options should be recalled. The first is cartilage, the second is derivatives of the epidermis of the skin. Cartilage hyaline tissue is an example of connective tissue that forms a protective shock-absorbing shell for joints. In the remaining cartilages of the body, for example, in the larynx, auricles, fibrous rings and valves of the heart, blood vessels are present. But in the cartilage that protects the joints, they are not. Articular cartilage nutrition is achieved through synovial fluid and substances dissolved in it. Also, blood vessels are completely absent in the cornea of the eye, the nutrition of which is provided by tear fluid.
Derivatives of the epidermis
All skin epidermis derivatives known in biology are not provided with blood. Such tissues are devoid of blood vessels, which the epidermis itself does not have. It is a dying cell that does not need to be provided with nutrients. Hair, unlike nails and epidermis, has signs of life. Their nutrition is provided by the hair bulb.
Epithelial tissue
Despite indirect communication with the blood supply system, epithelial tissue does not have its arteries and veins. This answers the question of which tissues are devoid of blood vessels. Why? It is necessary to understand in more detail. Any epithelium is a collection of cells located on the basement membrane. The latter is a semipermeable structure through which nutrients dissolved in the intercellular fluid pass freely. The blood vessels themselves do not penetrate the basement membrane, which consists of fibrillar proteins.
Epithelial tissue nutrition is achieved through simple diffusion and active transport of substances from the intercellular fluid. There they enter through capillary fenestra and freely pass through the basement membrane, reaching the epithelial cells. At the same time, nutrients in large part are spent on meeting the needs of the germ layer of the epithelium. The farther from it, the less nutrition the epithelial tissue receives. However, this is sufficient for its functioning.
When asked which tissues are deprived of blood vessels in humans, it should be answered that they are epithelial, since they are associated only with intercellular fluid. From it, the epithelium receives nutrition, and metabolic products can be dumped into the opening cavity, and not into the blood. A special situation is observed in the case of intestinal epithelium, which, in addition to excretion, is able to absorb substances from the intestine.
So, which tissues are devoid of blood vessels? Answer: all epithelial, limited from the vessels by the basement membrane, but indirectly communicating with the circulatory system. Therefore, normally all nutrients from the intestine also enter the intercellular space and later diffuse into the blood.