Choroid plexus is the name for a plexus of veins located in the cavity system of the brain. The plexus is important for the production of cerebrospinal fluid.
What is the choroid plexus?
The choroid plexus is a branching plexus of veins in the ventricle (cavity system) of the human brain. It is also known as the choroid plexus or choroid plexus. The brain has four ventricles, each of which is equipped with such a plexus of veins. They are also called villous bulges and are responsible for the production of cerebrospinal fluid (CSF). This so-called cerebrospinal fluid is a colorless clear fluid that resembles the tissue fluid of the brain. Most of the CSF is produced by blood ultrafiltration.
Anatomy and structure
The choroid plexus is composed of an invagination of the pia mater (soft meninges). This is covered by ependymal cells and has blood vessels. The ependymal cells originate in the neural epithelium. The neural epithelium first produces neuroblasts. This is followed by glioblasts and finally ependymal cells. The ependyma lines the neural tube and the central canal. As the human brain develops, the end brain grows much faster than the diencephalon. As a result, the soft meninges of both cerebral hemispheres overlap, resulting in a meningeal duplication called the tela choroidea. This refers to a connective tissue plate that spans between the diencephalon and the hemispheres. At the lateral edges, vascular villi are formed by the pia mater for the plexus of the lateral ventricle. It also covers the roof of the third ventricle. In this region, two rows of vascular villi penetrate against the ventricular lumen and establish the plexus proper. The plexus of the IV ventricle also results from a duplication of the soft meninges. In this process, the inferior surface of the cerebellum attaches to the surface of the rhombencephalon. Two layers form the choroid plexus. These are the lamina epithelialis (plexus epithelium) and the lamina propria (tela choroidea). The squamous epithelium is composed of the ependymal cells, which are special glial cells. It usually has a cubic shape, but can also be cylindrical or flat. The apical cell poles are equipped with 30 to 60 kinocilia per cell. In addition, a distinct microvillus set is present. On the surface of the squamous epithelium are macrophages, also known as Kolmer cells. The tela choroidea forms a special form of the soft meninges. Thus, it has a large number of collagen fibers and is traversed by capillaries. The choroid plexus is located on the inner side of the subcortex, the pars centralis of the lateral ventricles and in the roof of ventricles III and IV. At the terminal portion of the IV ventricle, a portion of the choroid plexus projects from the luschkae foramen, also called the apertura lateralis. This area is named Bochdalek’s flower basket because of its shape. Via the interventriculae foramen, there is a connection between the choroid plexus of the III ventricle as well as that of the lateral ventricles.
Function and Tasks
Among the most important tasks of the choroid plexus is the production of cerebrospinal fluid. For this purpose, it transports sodium ions via sodium-potassium ATPase (sodium-potassium pump) of the plasma membrane of the plexus epithelial cells. Water and chloride ions connect through ion and chloride channels. Apart from ions, the choroid plexus also secretes various nucleosides, vitamin C, vitamin B12, glucose, transthyretin and leptin. Another function of the choroid plexus is to form the blood-liquor barrier. Parts of the blood-liquor barrier include the endothelial basement membrane, the plexus epithelial cells, which have their own basement membrane, and the fenestrated endothelium. While larger peptides and molecules cannot pass through the fenestrated regions of the endothelium, smaller particles can pass through the barrier. Also important is the reabsorption and detoxification of the cerebrospinal fluid. For example, medical agents such as barbiturates as well as leukotrienes, bile salts, and bilirubin are directed toward the tela choroidea by the MDR 1 (multi-drug resistance transporter 1) detoxification system.In addition, transporters for glutamate and organic cations and anions are present.
Diseases
Various diseases can occur at the choroid plexus. Choroid plexus cysts, which appear in the region of the choroid plexus in unborn children, are considered harmless. They have an oval or round shape and are visible on both sides. They usually reach a size of 0.3 to 2.0 millimeters. If there are no other special features, the plexus cysts are not considered to be in need of treatment because they have no disease value. In most cases, the cysts disappear on their own and do not negatively affect the child’s health. A rarely occurring brain tumor is plexus papilloma. It originates in the covering layer of the choroid plexus. This type of tumor accounts for only 0.4 to 0.6 percent of all brain tumors. Children and adolescents are particularly affected by the disease. The benign tumor is characterized by increased intracranial pressure, which is accompanied by nausea, vomiting and headaches. Sometimes the formation of a plexus papilloma is associated with various syndromes such as Li-Fraumeni syndrome or Aicardi syndrome. Among the most severe diseases of the choroid plexus is choroid plexus carcinoma, which is a malignant brain tumor. The tumor is believed to be formed by the epithelium of the choroid plexus. Obstructions to cerebrospinal fluid flow result in increased intracranial pressure, which in turn causes nausea, vomiting, and headaches. Treatment is considered difficult.
