The Hemato Encephalic Barrier (HEB) refers to the protective mechanism that restricts the passage of substances from the bloodstream into the central nervous system (CNS) and brain. Also known as the blood-brain barrier (BBB), it is a critical anatomical and physiological barrier that safeguards the brain and spinal cord from potentially harmful molecules.
The HEB is composed of highly specialized cells that line the walls of the blood vessels in the brain, called endothelial cells. These cells are tightly packed, forming a continuous barrier that prevents the free diffusion of molecules into the brain tissue. Additionally, they are connected by tight junctions, which further restrict the movement of substances between the cells.
The primary function of the HEB is to maintain a stable environment within the CNS by actively regulating the transportation of molecules. While some small lipophilic molecules can passively diffuse through the endothelial cells, most substances, including certain medications and toxins, are actively transported across the barrier via specific transport systems.
The HEB plays a crucial role in protecting the brain from potentially harmful substances, such as pathogens, toxins, and large molecules. It also selectively allows the transport of essential molecules, such as glucose and amino acids, into the brain. Moreover, it prevents fluctuations in the composition of the brain's extracellular fluid, ensuring optimal neuronal function.
Disruption of the HEB can occur in certain medical conditions, such as brain inflammation, brain tumors, or during injury. This can lead to increased permeability and the entry of substances that may cause damage to the CNS. Understanding the mechanisms and functions of the HEB is crucial in the development of therapies for various neurological disorders.
