Vävnadsbarriären

Vävnadsbarriären refers to the protective layers that limit the movement of substances into and out of specific tissues and organs within the body. These barriers are crucial for maintaining tissue homeostasis and preventing the entry of harmful agents. The most well-known example is the blood-brain barrier, which controls the passage of molecules from the bloodstream into the central nervous system. This barrier is formed by specialized endothelial cells with tight junctions, surrounded by astrocytes and pericytes. Another significant barrier is the epithelial barrier, found in the skin, intestines, and lungs, which prevents the invasion of pathogens and restricts the absorption of unwanted substances while allowing necessary nutrient transport. The placental barrier regulates the exchange of nutrients and waste products between the mother and the fetus. In general, these barriers are characterized by cellular structures like tight junctions, desmosomes, and a basement membrane, as well as the presence of efflux pumps and specific transporters that selectively mediate the passage of molecules. Dysfunction of these tissue barriers can lead to various diseases and pathological conditions.