Meninges Flashcards
Meninges
3 layers of protective tissue that cover the brain
The 3 meninges layers:
- Dura mater
- Arachnoid Mater
- Pia mater
(Outermost to innermost)
Dura Mater
Thickest, outermost layer, protective, impermeable
- Periosteal Layer
- Meningeal Layer
Periosteal Layer
- Attached to inner surface of skull (outer)
- Adheres tightly to the inner skull
- Continuous with periosteum on outside of skull bones and sutures
- Not continuous with dura mater of spinal cord
Meningeal Layer
Protective layer covering brain (inner)
- penetrate spaces in cerebral hemispheres
- continuous with dura mater of spinal cord and epineurium of cranial nerve
Meningeal layers has two partitions:
- Falx Cerebri
2. Tentorium Cerebelli
Arachnoid mater
Middle layer, impermeable, connects dura
- separated from Pia mater by subarachnoid space that’s filled with CSF
Pia Mater
Delicate, permeable, innermost, testing on brain surface
- vascular membrane that adheres closely to the brain
- arteries carry sheath of Pia as enter parenchyma
- fuses with ependymal choroid plexus
Venous sinus
Large, low pressure blood vessel return path of cerebral venous blood
Falx Cerebri
Sickle-shaped fold that separates cerebral hemispheres
- superior convex border forms floor of superior Sagittal sinus
- inferior border houses inferior sagittal sinus
Tentorium Cerebelli
Fits between the cerebellum and the occipital lobes
- separates posterior cranial fossa from rest of cranial vault
- arches upward along median line to become continuous with Falx cerebri to form straight venous sinus
Falx Cerebri & Tentorium Cerebelli function:
Restrict brain displacement associated with acceleration and deceleration
- hold the brain in place so it doesn’t move
- they are part of the meningeal layer
Epidural space + hemorrhage/hematoma:
Location: tight space between the dura mater and the skull
Cause: rupture of the middle (meningeal) artery during head trauma
Symptoms: no symptoms at first, there’s a lucid interval. But within a few hours, the hematoma compresses the brain and causes an increase in intracranial pressure. This results on herniation and death, unless surgery.
Subdural space + Hemorrhage/hematoma
Location: between the dura mater and the loosely adherent arachnoid mater
Cause: rupture of the bridging veins that pass through en-route to Durham sinuses. Vulnerable to shear injury.
Acute Hematoma
Occurs with high velocity impact
Chronic Hematoma
In elderly. Brain atrophy allows brain to move freely in cranial vault making bridging veins more susceptible to injury. Slow bleeding over weeks/months allows brain to accommodate so symptoms are often vague (headache, cognitive impairment, unsteady gait)
Subarachnoid space
Separates arachnoid mater from Pia mater
- cerebral arteries and veins lie in this space and send off branches into the brain
- the branches that go into the brain are aneurysm sites that may hemorrhage
Trabeculae
Delicate threads that connect arachnoid to Pia
Arachnoid granulations
The site where CSF diffuse into the venous sinuses
Headaches
Brain doesn’t have any pain receptors, so pain that causes headache comes from trigeminal and 3 cervical nerve innervating the meninges and vasculature
Dura above tentorium
Innervating by trigeminal; forehead and face
Dura below tentorium
Innervating by C1-3; back of head and neck
Space occupying lesions
Raise intracranial pressure; irritation, stretching of dura
Timor located above tentorium:
Front of head
