Blood brain barrier

Blood-brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the central nervous system (CNS). The blood-brain barrier is formed by brain endothelial cells, which are connected by tight junctions.

Structure

The blood-brain barrier consists of several components. These include endothelial cells, basement membrane, pericytes, and astrocyte end-feet. Endothelial cells line the blood vessels and form the primary barrier. The basement membrane provides structural support. Pericytes are embedded in the basement membrane and contribute to the regulation of blood-brain barrier permeability. Astrocyte end-feet envelop the endothelial cells and are involved in the induction and maintenance of the blood-brain barrier.

Function

The primary function of the blood-brain barrier is to protect the brain from harmful substances in the blood, while allowing essential nutrients to reach the brain. It also maintains homeostasis within the CNS by regulating the transport of molecules and ions between the blood and the brain.

Permeability

The blood-brain barrier is selectively permeable, allowing some substances to cross, but not others. Small, lipid-soluble molecules can diffuse across the endothelial cells. Larger molecules, such as glucose and amino acids, require transport proteins to cross the barrier.

Clinical significance

The blood-brain barrier plays a crucial role in many neurological disorders. In conditions such as stroke, multiple sclerosis, and Alzheimer's disease, the integrity of the blood-brain barrier is compromised, leading to increased permeability. This can result in damage to brain tissue and neurological dysfunction. Conversely, the blood-brain barrier can also hinder the delivery of therapeutic drugs to the brain.

Research

Research into the blood-brain barrier is a rapidly expanding field. Current areas of focus include understanding the mechanisms of blood-brain barrier regulation, developing methods to bypass the barrier for drug delivery, and exploring the role of the blood-brain barrier in disease.