The brain and spinal cord are surrounded by cerebro-spinal fluid (CSF) contained within the meninges (meningeal membranes).
The meninges consist of three layers: the (outer) dura mater, arachnoid mater and (inner) pia mater.
Cerebro-Spinal Fluid, manufactured by the Choroid Plexuses, circulates within the sub-arachnoid space, i.e between the arachnoid mater and pia mater. It acts as a cushion to protect the brain.
The meningeal membranes are sensitive to stretch, and pain and headache are common symptoms arising from them. The sensory impulses arising in the meninges also cause reflex spasm of neck and paravertebral muscles, which is an important sign of meningeal irritation.
Blood vessels have to pass through the meninges in order to deliver oxygen, glucose and other substances to the brain. These vessels can be ruptured as a result of head injury, or because of weakness associated with an aneurysm (as in sub-arachnoid haemorrhage) or other pathologies, and the consequences can be life threatening.
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The diagram shows a transverse section of the spinal cord and the spinal nerves on each side. It can be seen that the dura and arachnoid cover the cord and the dorsal and ventral roots of each spinal nerve.
The meningeal membranes have three layers- the (outer) dura mater, arachnoid mater and (inner) pia mater
The Dura mater is a very strong fibrous membrane which is the outermost of the three layers of the meninges. On its outside it is in contact and adherent to with the bones of the skull and vertebral column.
The Pia mater is the innermost of the three meninges, and is a fine memebrane found on the surface of the brain and spinal cord. Fine blood vessels run beneath the pia and branches enter the substance of the central nervous system
The arachnoid mater is a fine membrane whose inner surface is in contact with the cerebrospinal fluid, which fills in the sub-arachnoid space.
The sub-arachnoid space contains cerebro-spinal fluid (CSF), and various structures traverse this space including arteries and veins, and elastic bands called arachnoid trabeculae
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The diagram shows the arrangement of the meninges and cerebral veins within the skull
Meninges within the Skull
The basic arrangement of the three layers of meningeal membranes remains true within the skull. However the dura mater covers venous sinuses, which are placed between the skull and the dura (as in the case of the sagittal sinus; or within folds of the dura such as the falx cerebri and tentorium.
Image source: Antranik
Layers of dura are folded to become the falx cerebri and the tentorium, and venous sinuses can be found within folds of the dura or between the dura and the skull
Cerebral veins feed into the sinuses (superior and inferior sagittal sinuses, straight sinus and sigmoid sinus before joining the internal jugular vein.
The subarachnoid space contains the CSF and vessels crossing into the brain from the extradural space.
The meningeal membranes are sensitive to stretch, and pain and headache are common symptoms arising from them. The sensory impulses also cause reflex spasm of head and neck muscles.
Blood vessels have to pass through the meninges in order to deliver blood flow to the brain. These vessels are easily ruptured as a result of head injury, and the consequences are life threatening, as in subarachnoid haemorrhage.
Blood can haemorrhage between the skull and the dura mater following head injury, stretching the meninges and causing pressure on the brain, which can be displaced and compressed.Blood sometimes appears in the CSF between the pia mater and arachnoid membranes as a result of trauma, or because of rupture of an arterial aneurysm, causing symptoms of meningeal irritation.
More on the vascular damage during trauma to the head.