Choroidal plexuses: anatomy, functions and pathologies
Spinal fluid is essential for the functioning and hygiene of the central nervous system, especially the brain. This substance is produced in the four structures we know as “choroid plexuses”, located in the brain’s ventricles.
In this article we will describe the anatomy and main functions of the choroidal plexuses . We will also mention the pathologies most frequently associated with these regions of the central nervous system.
Anatomy of the choroidal plexuses
The choroid plexuses are located in the ventricular system of the brain; there is one plexus in each of the four ventricles. Their nucleus is made up of connective tissue, capillaries and lymphoid cells, and is surrounded by a layer of epithelial cells. The production of cerebrospinal fluid , the main function of the choroidal plexuses, depends on the epithelium.
In addition, this structure separates and connects the central nervous system and the circulatory system, which explains the involvement of the choroidal plexuses in the transport of nutrients and hormones to the brain and in the elimination of waste substances.
The ventricles are four interconnected brain cavities. After being generated in the choroid plexuses, which are found in practically all regions of the ventricular system, the cerebrospinal fluid circulates through the brain via the ventricles until it reaches the spinal cord.
Functions of this structure
The number of functions attributed to the choroid plexuses has increased in recent years; they have been found to be not only relevant because of their ability to make spinal fluid and protect neurons, but also to play additional roles that could lead to therapeutic benefits as research advances in the future.
1. Production of cerebrospinal fluid
The cerebrospinal fluid performs 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 defences, regulates homeostasis (extracellular balance) and helps remove waste substances from the brain.
2. Formation of the blood-brain barrier
The epithelial tissue of the choroidal plexuses composes a part of the blood-brain barrier, which separates blood and extracellular fluid from the central nervous system but allows the exchange of nutrients and waste. It also has a defensive function, preventing the entry of certain toxins.
3. Maintenance of extracellular homeostasis
The extracellular balance of the brain and spinal cord is maintained in part by the choroidal plexuses, which modulate the interaction between the central nervous system and the immune system.
4. Tissue and neuron regeneration
The choroid plexuses secrete neuroprotective compounds that favour the healing of neuronal damage; this effect has been mainly related to traumatic injuries. Moreover, in these structures a certain degree of neurogenesis (production of new neurons from progenitor cells) has been detected even in adulthood.
5. Brain detoxification
The choroid 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, their connection with the circulatory system facilitates the transfer of residual substances into the blood to allow their elimination.
6. Other functions
In addition to the processes we have described, in recent years research has begun on the role of the choroid plexuses in other functions: the
the production of polypeptides that nourish neurons, the transfer of information to the sympathetic nervous system…
Pathologies of the choroid plexuses
Since the choroid plexuses, and in particular the cerebrospinal fluid they produce, perform fundamental functions for the organism, alterations in the anatomy and functionality of these structures can favour the appearance of various pathologies.
There are also a large number of factors that occasionally cause alterations in the choroidal plexuses. The relationship of these structures with Alzheimer’s disease , strokes and head injuries is especially relevant.
In people with Alzheimer’s disease, the ependymal cells of the choroid plexuses atrophy, causing decreased production of cerebrospinal fluid, increased oxidative stress, and increased accumulation of toxins in the brain.
On the other hand, and although it often has no serious consequences, the appearance of cysts in the choroid plexuses during fetal development can cause tumours and has been associated with aneuploidies (alterations in the number of chromosomes in the cells) such as Edwards syndrome, which is fatal for most babies.
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- 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.
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