Arachnoid villi are small protrusions that project from the arachnoid membrane into the dural sinuses of the brain. The spelling of "arachnoid villi" can be explained using IPA phonetic transcription: /əˈræk.nɔɪd ˈvɪ.li/. The first syllable is pronounced as "uh-rak-noid," with the stress on the second syllable. The second word, "villi," is pronounced "vil-eye" with the stress on the first syllable. This important medical term is commonly used in the field of neuroscience and is crucial for understanding brain physiology and the circulatory system.
Arachnoid villi are small, finger-like projections found on the arachnoid membrane, which is one of the three layers that make up the meninges - the protective covering of the brain and spinal cord. These villi play a crucial role in cerebrospinal fluid (CSF) circulation and absorption.
The arachnoid membrane is located between the pia mater, which covers the brain, and the dura mater, the outermost layer of the meninges. The arachnoid villi are composed of a collection of specialized cells and blood vessels bundled together.
Their main function is to facilitate the movement of CSF from the subarachnoid space, which is the space between the arachnoid and pia mater, into the bloodstream. CSF is a clear fluid that surrounds and protects the brain and spinal cord, acting as a shock absorber.
The arachnoid villi contain tiny openings called arachnoid granulations, and it is through these granulations that CSF passes into the bloodstream. They act as one-way valves, allowing the CSF to exit the subarachnoid space and enter the venous sinuses of the brain, from where it can be filtered and reabsorbed into the bloodstream.
By regulating the flow and absorption of CSF, the arachnoid villi play a vital role in maintaining the balance and pressure within the cranial cavity, preventing the buildup of excess fluid and ensuring optimal brain function.
Pacchionian hodies.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "arachnoid" has its roots in the Greek word "arakhnē", which means spider. It refers to the delicate, spiderweb-like appearance of the arachnoid membrane, one of the three membranes that surround the brain and spinal cord.
The term "villi" comes from the Latin word "villus", which means hair or thread. Villi are small, finger-like projections found in various parts of the body, such as the small intestine, acting to increase surface area for absorption or secretion.
Therefore, "arachnoid villi" can be understood as a combination of the Greek word for spider-like appearance and the Latin word for finger-like projections, describing the appearance and structure of certain tissue in the brain that helps to absorb cerebrospinal fluid into the bloodstream.