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Leptomeningeal collaterals lie within the leptomeninges, the two deep layers of the meninges called the pia mater and the arachnoid mater. [4] Their diameter has been measured at approximately 300 micrometers, [ 5 ] but there is variability between individuals in the size, quantity and location of these vessels, and between either hemisphere ...
The arachnoid mater covering the brain is referred to as the arachnoidea encephali, and the portion covering the spinal cord as the arachnoidea spinalis. The arachnoid and pia mater are sometimes considered as a single structure, the leptomeninx, or the plural version, leptomeninges (lepto, from the Greek root meaning "thin" or "slender").
Pia mater is medieval Latin meaning "tender mother". [1] The other two meningeal membranes are the dura mater and the arachnoid mater. Both the pia and arachnoid mater are derivatives of the neural crest while the dura is derived from embryonic mesoderm. The pia mater is a thin fibrous tissue that is permeable to water and small solutes.
The arachnoid is attached to the dura mater, while the pia mater is attached to the central nervous system tissue. When the dura mater and the arachnoid separate through injury or illness, the space between them is the subdural space. There is a subpial space underneath the pia mater that separates it from the glia limitans.
Although the pia mater adheres to the surface of the brain, closely following the contours of its gyri and sulci, the arachnoid mater only covers its superficial surface, bridging across the gyri. This leaves wider spaces between the pia and arachnoid and the cavities are known as the subarachnoid cisterns. [citation needed]
A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrounding the brain. It usually results from rips in bridging veins that cross the subdural space.
Between the arachnoid mater and the pia mater is the subarachnoid space and subarachnoid cisterns, which contain the cerebrospinal fluid. [11] The outermost membrane of the cerebral cortex is the basement membrane of the pia mater called the glia limitans and is an important part of the blood–brain barrier. [12]
The dura mater is the outermost layer, and it forms a tough protective coating. Between the dura mater and the surrounding bone of the vertebrae is a space called the epidural space. The epidural space is filled with adipose tissue, and it contains a network of blood vessels. The arachnoid mater is the middle protective layer. Its name comes ...