Arachnoid granulations

Arachnoid Granulations

Arachnoid Granulations (pronunciation: /əˈrakˌnoid ˌgran(y)əˈlāSH(ə)n/), also known as Pacchionian bodies or Pacchionian granulations, are small protrusions of the arachnoid mater (the middle layer of the meninges) into the dural sinuses, which allow cerebrospinal fluid (CSF) to exit the subarachnoid space and enter the blood stream.

Etymology

The term "Arachnoid" is derived from the Greek word "Arachne" meaning spider, and "oid" meaning like, due to the web-like appearance of the arachnoid mater. "Granulations" refers to the granular appearance of these structures. They were first described by Italian anatomist Antonio Pacchioni in 1705, hence the alternative name "Pacchionian bodies" or "Pacchionian granulations".

Function

Arachnoid granulations act as one-way valves. Primarily, they are responsible for the transfer of cerebrospinal fluid (CSF) from the subarachnoid space to the venous system. This process plays a crucial role in maintaining the balance of CSF levels, which is essential for the overall homeostasis of the central nervous system.

Clinical Significance

Arachnoid granulations can sometimes be mistaken for dural venous sinuses thrombosis or meningiomas on imaging studies due to their size and location. They are also involved in certain pathological conditions such as idiopathic intracranial hypertension where they are believed to play a role in the impaired CSF absorption.

Related Terms

External links

Medical encyclopedia article on Arachnoid granulations
Wikipedia's article - Arachnoid granulations

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Arachnoid granulations