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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").
Arachnoiditis is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the central nervous system. The outermost layer of the meninges is the dura mater (Latin for hard) and adheres to inner surface of the skull and vertebrae. [ 1 ]
Medical condition Subarachnoid hemorrhage Other names Subarachnoid haemorrhage CT scan of the brain showing subarachnoid hemorrhage as a white area in the center (marked by the arrow) and stretching into the sulci to either side Pronunciation / ˌ s ʌ b ə ˈ r æ k n ɔɪ d ˈ h ɛ m ər ɪ dʒ / Specialty Neurosurgery, Neurology Symptoms Severe headache of rapid onset, vomiting, decreased ...
The outermost membrane, the dura mater, is a thick durable membrane, which is attached to both the arachnoid membrane and the skull. In bacterial meningitis, bacteria reach the meninges by one of two main routes: through the bloodstream (hematogenous spread) or through direct contact between the meninges and either the nasal cavity or the skin.
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.
CSF returns to the vascular system by entering the dural venous sinuses via arachnoid granulations. [2] These are outpouchings of the arachnoid mater into the venous sinuses around the brain, with valves to ensure one-way drainage. [2] This occurs because of a pressure difference between the arachnoid mater and venous sinuses. [3]
Cerebrospinal fluid is produced by the choroid plexus in the ventricles of the brain and contained by the dura and arachnoid layers of the meninges. [23] [42] [64] The brain floats in CSF, which also transports nutrients to the brain and spinal cord. As holes form in the spinal dura mater, CSF leaks out into the surrounding space.
The middle element of the meninges is the arachnoid mater, or arachnoid membrane, so named because of its resemblance to a spider web. It cushions the central nervous system. This thin, transparent membrane is composed of fibrous tissue and, like the pia mater, has an outer layer of tightly packed flat cells, forming the arachnoid barrier. [8]