Choroidal plexuses: anatomy, functions and pathologies

Cerebrospinal fluid is essential for the functioning and hygiene of the central nervous system, especially the brain. This substance is produced in the four structures that we know as "choroid plexuses", located in the cerebral ventricles.

In this article we will describe the anatomy and the main functions of the choroidal plexus . We will also mention the pathologies that are most frequently associated with these regions of the central nervous system.

• Related article: "Parts of the human brain (and functions)"

Anatomy of the choroidal plexus

The choroid plexuses are located in the ventricular system of the brain; there is a plexus in each of the four ventricles. Its nucleus is formed by connective tissue, capillaries and lymphoid cells, and is surrounded by a layer of epithelial cells. The production of cerebrospinal fluid depends on the epithelium , main function of the choroid plexus.

In addition, this structure separates and connects the central nervous system and the circulatory system, which explains the involvement of the choroid plexus in the transport of nutrients and hormones to the brain and in the elimination of residual substances.

The ventricles are four interconnected brain cavities. After being generated in the choroid plexuses, which are found in virtually all regions of the ventricular system, the cerebrospinal fluid circulates through the brain through the ventricles until reaching the spinal cord.

Functions of this structure

The number of functions attributed to the Choroid plexus has increased in recent years; It has been discovered that they are not only relevant for their ability to manufacture cerebrospinal fluid and protect neurons, but also fulfill additional roles that could bring therapeutic benefits when the research advances in the future.

1. Production of cerebrospinal fluid

Cerebrospinal fluid fulfills several key functions in the central nervous system: cushions the blows received by the brain and allows it to maintain its density, participates in immune defenses, regulates homeostasis (extracellular balance) and helps eliminate waste substances from the brain.

2. Formation of the blood-brain barrier

The epithelial tissue of the choroid plexus composes a part of the blood-brain barrier, which separates blood and extracellular fluid from the central nervous system but it allows the exchange of nutrients and waste. It also has a defensive function, by preventing the entry of certain toxins.

3. Maintenance of extracellular homeostasis

The extracellular balance of the brain and spinal cord is maintained in part thanks to the choroidal plexuses, which modulate the interaction between the central nervous system and the immune system.

4. Regeneration of tissues and neurons

Choroid plexuses secrete neuroprotective compounds that favor the healing of neuronal damage; This effect has been related mainly to traumatic injuries. Also in these structures a certain degree of neurogenesis has been detected (production of new neurons from progenitor cells) even in adulthood.

• Related article: "Neurogenesis: how are new neurons created?"

5. Detoxification of the brain

The choroidal plexuses contribute to the detoxification of the brain in two ways: on the one hand, the cerebrospinal fluid they produce fulfills this function, and on the other hand its connection with the circulatory system facilitates the transfer of residual substances to the blood to allow its elimination.

6. Other functions

In addition to the processes we have described, in recent years we have begun to investigate the role of the choroid plexus in other functions:

, the production of polypeptides that nourish neurons, the transfer of information to the sympathetic nervous system ...

Pathologies of the choroidal plexus

Since the choroid plexuses, and in particular the cerebrospinal fluid that they produce, fulfill fundamental functions for the organism, alterations in the anatomy and functionality of these structures may favor the appearance of various pathologies.

There is also a large number of factors that occasionally cause alterations in the choroid plexuses. The relationship of these structures with Alzheimer's disease , cerebrovascular accidents and traumatic brain injuries is especially relevant.

In people with Alzheimer's disease atrophy occurs in the ependymal cells of the choroid plexuses; This decreases the production of cerebrospinal fluid, increases oxidative stress and accumulates toxins in the brain to a greater extent.

On the other hand, and although it frequently does not have serious consequences, appearance of cysts in the choroid plexus during fetal development It can cause tumors and has been associated with aneuploidies (alterations in the number of chromosomes of cells) such as Edwards syndrome, which is deadly for most babies.

Bibliographic references:

• Borlongan, C.V., Skinner, S.J.M., Vasconcellos, A., Elliott, R.B. & Emerich, D. F. (2007). The choroid plexus: A novel graft source for neural transplantation. In Davis, C. D. & Sanberg, P. R. (Eds.), "Cell Therapy, Stem Cells and Brain Repair." New York: Humana Press.

• Emerich, D. F., Vasconvellos, A., Elliott, R.B., Skinner, S.J.M. & Borlongan, C.V. (2004). The choroid plexus: Function, pathology and therapeutic potential of its transplantation. Expert Opinion on Biological Therapy, 4 (8): 1191-201.

• Straziel, N. & Ghersi-Egea, J. F. (2000). Choroid plexus in the central nervous system: biology and physiopathology. Journal of Neuropathology and Experimental Neurology, 59 (7): 561-74.