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The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that regulates the transfer of solutes and chemicals between the circulatory system and the central nervous system, thus protecting the brain from harmful or unwanted substances in the blood. [1]
Nervous tissue, also called neural tissue, is the main tissue component of the nervous system.The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system (PNS) comprising the branching peripheral nerves.
The nervous system consists of nervous tissue which, at a cellular level, is defined by the presence of a special type of cell, called the neuron. Neurons have special structures that allow them to send signals rapidly and precisely to other cells.
Cerebrospinal fluid (CSF) is a clear, colorless transcellular body fluid found within the meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricles of the brain. CSF is mostly produced by specialized ependymal cells in the choroid plexuses of the ventricles of the brain, and absorbed in the arachnoid granulations .
These are nervous tissue cells with simple columnar shape, much like that of some mucosal epithelial cells. [2] Early monociliated ependymal cells are differentiated to multiciliated ependymal cells for their function in circulating cerebrospinal fluid.
The brain, although protected by the blood–brain barrier, can be affected by infections including viruses, bacteria and fungi. Infection may be of the meninges ( meningitis ), the brain matter ( encephalitis ), or within the brain matter (such as a cerebral abscess ).
Neuroinflammation is widely regarded as chronic, as opposed to acute, inflammation of the central nervous system. [5] Acute inflammation usually follows injury to the central nervous system immediately, and is characterized by inflammatory molecules, endothelial cell activation, platelet deposition, and tissue edema. [6]
Brain cells make up the functional tissue of the brain. The rest of the brain tissue is the structural stroma that includes connective tissue such as the meninges, blood vessels, and ducts. The two main types of cells in the brain are neurons, also known as nerve cells, and glial cells, also known as neuroglia. [1]