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Arachnoid granulations (also arachnoid villi, and Pacchionian granulations or bodies) are small outpouchings of the arachnoid mater and subarachnoid space into the dural venous sinuses of the brain. The granulations are thought to mediate the draining of cerebrospinal fluid (CSF) from the subarachnoid space into the venous system .
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").
Arachnoid villi are formed around the 35th week of development, with arachnoid granulations noted around the 39th, and continuing developing until 18 months of age. [3] The subcommissural organ secretes SCO-spondin, which forms Reissner's fiber within CSF assisting movement through the cerebral aqueduct. It is present in early intrauterine life ...
The year 1705 was a special time in Pacchioni's life: he was appointed head physician at the ancient Ospedaledi S. Giovanni in Laterano, and published the original description of arachnoid granulations in his Dissertatio Epistolaris de Glandulis Conglobatis Durae Meningis Humanae.
On either side of it are several depressions for the arachnoid granulations, and at its back part, the openings of the parietal foramina when these are present. It is crossed in front by the coronal suture and behind by the lambdoid suture, while the sagittal suture lies in the medial plane between the parietal bones.
The superior sagittal sinus (also known as the superior longitudinal sinus), within the human head, is an unpaired dural venous sinus lying along the attached margin of the falx cerebri.
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 ]
The majority of the CSF is formed in the choroid plexus and flows through the brain along a distinct pathway: moving through the cerebral ventricular system, into the subarachnoid space surrounding the brain, then draining into the systemic blood column via arachnoid granulations of the dural sinuses or to peripheral lymphatics along cranial ...