Lesson 2: Coverings & Spaces of the CNS Flashcards
What type of cells create CSF?
Specialized ependymal cells
Where is CSF produced?
In the choroid plexus
How does CSF get from the lateral ventricles to the 3rd ventricle?
The interventricular foramen of Monroe
How does CSF get from the 3rd ventricle to the 4th?
The cerebral aqueduct
How does CSF get from the 4th ventricle to the subarachnoid space? What happens to a small amount?
The foramina of Luschka and the foramen of Magendie. A small amount exits into the central canal of the spine
What is the choroid plexus made of? What are its three layers?
It is made of a network of infolded vascular capillaries. It is covered by pia mater and connective tissue, which are then lined by an epithelium layer
What are the four parts of the lateral ventricles? What separates them?
A body, and three horns: anterior, posterior, inferior. The septum pellucidum is located between the anterior ventricular horns
What structures are above and below the lateral ventricles?
Above: corpus callosum
Below: thalamus
Where is the third ventricle located? What is at its floor?
Between the two thalami, with the hypothalamic nuclei at its floor
Where is the cerebral aqueduct located? Which ventricles does it connect?
It separates the tectum and the tegmentum in the midbrain. It connects the 3rd and 4th ventricle
Where is the fourth ventricle located?
Roof: cerebellum
Floor: pons and medulla
How are the connections between the fourth ventricle and the subarachnoid space located? What are their names?
Laterally: the foramina of Luschka (2)
Medially: foramen of Magendie (1)
Where is the subarachnoid space located? What is inside of it - both for irrigation and waste removal?
Between the arachnoid membrane and pia mater. It houses cisterns, and all the smaller blood vessels for the brain
What is a perivascular space?
Site for possible diffusion of metabolic solutes from the CSF into extracellular fluid (cysts)
What are arachnoid granulations? Where are they located?
They absorb CSF. They are part of the arachnoid membrane that sticks into the dura mater. They are located dorsally bilaterally along the superior sagittal sinus, which they empty CSF into
What is required for the emptying of arachnoid granulations?
A pressure difference - the sinus pressure must be below the pressure of the ventricles, otherwise the arachnoid villi close
What are the four causes of lesions in the ventricular system?
Excess fluid production
Tumours actually blocking the space
Blockage of the cerebral aqueduct
Diminished absorption
What is the most common type of lesion of the ventricular system after brain injury?
Diminished absorption of CSF
What are meninges? What are they made of?
The layers over the brain after the skull. Made of connective tissue
What is connective tissue made of?
Fibrous sheets made by fibroblasts
What are the three meninges layers of the brain?
Outermost: dura mater
Middle: arachnoid mater
Innermost: pia mater
What are the two dura mater layers?
Periosteal and meningeal
What qualities are specific to the dura mater?
Is has a rich vascular supply and sensory innervation
It is dense
Is has two layers
What is the periosteal dura mater?
Lines the skull internally
What is the falx cerebri?
Where the meningeal dura mater extends into the longitudinal fissure to separate the cerebrum’s hemispheres
What is the tentorium cerebelli?
Horizontal infolding of the meningeal dura mater that separates the cerebellum and the cerebrum
What is the falx cerebelli?
Meningeal dura mater that separates the cerebellum into two hemispheres below the tentorium cerebelli
What occurs in the space where the periosteal and meningeal dura mater layers separate?
The sinuses
What is the subdural space? What does it contain?
Between the visceral (innermost) dura mater layer and the arachnoid mater. It contains a few cerebral veins
What is the arachnoid mater like? Where is it located
Between the subdural space and the pia mater. It is like plastic wrap
What is the structure of the pia mater? What feature is unique to it?
It is a single cell layer directly on brain tissue that follows all infoldings. It is permeable, and thus allows for the passage of small vessels into the brain tissue
What is the anterior cranial fossa located over?
The frontal lobe
The nasal cavity and orbits
What is the posterior cranial fossa contain?
The cerebellum
What is the foramen magnum?
The hole through which the spinal cord exits the skull
Where is the sphenoid bone located?
Behind the eye
Where is the zygomatic arch located? What does it connect?
Over the temple. It connects the zygomatic bone (cheekbone) to the temporal bone
Where is the pterion located?
It attaches the parietal bone and the sphenoid bone
Where is the external acoustic meatus?
Behind and below the zygomatic arch, directly below the temporal bone
Where is the styloid process?
Anterior to the mastoid process, below the ear
Where is the mastoid process?
Posterior to the styloid process, below the ear
Where is the internal acoustic meatus?
The interior part of the eardrum
Where is the foramen rotundum? What exits from it?
It is in the floor of the middle cranial fossa. It is the exit point of the maxillary nerve (a branch of the trigeminal nerve)
Where is the foramen ovale? What exits from it - both a nerve and an artery
It is in the floor of the middle cranial fossa. It provides passage for the mandibular nerve (from the trigeminal nerve) and the accessory meningeal artery
Where is the carotid canal? What enters through it?
Anteromedial to the styloid process. It allows the internal carotid artery in
Where is the foramen spinosum? What artery enters through it?
It is posterior-lateral to the foramen ovale. It allows through the middle meningeal artery and the meningeal branch of the mandibular nerve
Where is the jugular foramen located? What nerves pass through it, and what venous structures?
It is immediately inferior to the internal acoustic meatus. The glossopharyngeal, vagus and accessory nerve all pass through it. The internal jugular vein also does.
What arteries supply the brain? (4)
Left and right internal carotid arteries and vertebral arteries
What venous sinuses drain the venous blood from the brain?
Left and right internal jugular veins
What is an arteriovenous malformation?
A blood vessel abnormality, where the blood flows directly from arteries to veins without a pressure-reducing capillary bed
What is a sign of oculomotor nerve damage? Why does this occur?
Since the oculomotor nerve carries info to constrict the pupil - the pupil is thus constantly dilated (big)
What is an aneurysm, and what is its consequence?
A large defect in the blood vessel. It causes pressure on brain tissue and the adjacent blood vessels
Where does the brain swell to if it swells sideways?
Against the falx cerebri
Where does the brain swell if it swells downward? What can is push that can be deadly?
To the anterior portion of the tentorium cerebelli. It can push the tonsil of the cerebellum through the foramen magnum, which puts pressure on the medulla
