In capillaries, the key task of blood circulation is solved: there is an exchange of various substances and gases between blood and tissue fluid. These processes are possible because the capillary walls are represented by a single layer of cells that are not tightly adjacent to each other (endothelium). Such a structure, favorable for metabolic processes, made the capillaries incapable of actively changing their inner diameter.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.