CSF Aqueous and Vitreous fluid Flashcards
Where is CSF produced?
On the roof of the choroid plexus, by secretory epithelium
How much CSF is produced a day?
150 mls
Replaced between 3/4 times a day.
What are the main functions of the CSF?
Mechanical protection
Circulation
Homeostatic function
How does the CSF offer mechanical protection?
Brain is surrounded by and sits within the CSF.
What is the circulatory function of the CSF?
Is a minor exchange medium for water, amino acids, ions and removes metabolites.
What is the homeostatic function of CSF?
The pH of the CSF affects the pulmonary ventilation and the cerebral blood flow.
Also transports hormones
What us the make up of CSF?
Very little proteins and little to no immunoglobulins
Na+ Cl- HCO3- in higher concentration than the blood.
In what ventricles can a choroid plexus be found?
3rd
4th
Lateral
At three weeks what does the nervous system appear as?
A neural canal
What forms the ventricles of the brain?
The cavity within the neural canal.
The cavity is also the precursor for the central spinal chord canal.
How is the choroid plexus formed?
Developing arteries are invaginated into the roof of the ventricle. Form villi to increase surface area.
What is CSF secretion dependant on?
The active transport of Na+ from the basolateral membrane (blood) through the apical membrane (CSF) into the ventricle.
Why is important that the NA + is actively transported?
It creates the electrical gradient which Cl- follows.
Water also follows by osmosis.
How does CSF exit the ventricles and enter the subarachnoid space?
Leaves from the 4th ventricle via apertures.
What apertures within the 4th ventricle allow CSF to enter the subarachnoid space?
Single median aperture
Paired lateral aperture
How is CSF returned to the venous blood?
Leaves via the arachnoid granulations into the superior sagittal sinus.
How is the Blood Brain Barrier able to prevent bacteria and toxins from entering the CSF?
Tightly bound epithelial cells have too small a junction.
What three tumours affect the ventricles?
Colloid cyst
Ependymomas
Choroid plexus tumour
What kind of haemorrhages can relating to the CSF?
Epidural - Arterial bleed between skull and the dura
Subdural - Venous between dura and arachnoid
Subarachnoid
What is hydrocephalus?
Accumulation of CSF within ventricles or around the brain
Increase in CSF pressure
Due to overproduction or drainage blockage.
What is idiopathic intracranial hypertension?
Increased CSF pressure without the imaging related to hydrocephalus.
What are the symptoms of someone with idiopathic intracranial hypertension?
Headache
Visual disturbance - papilloedema
What is papilloedema?
Optic disc swelling due to in increased ICP
What are the symptom of someone with papilloedema?
Enlarged blind spot
Blurred vision
Loss of vision
Where is aqueous humour produced?
Within the ciliary body.
Where is aqueous humour drained?
Removed by the scleral venous sinus via the canal of schlemm.
Why is the HCO3- important in aqueous humour?
Acts as a buffer to the H+ produced by the cornea as a result of anaerobic glycolysis.
What two epithelial cells make up the ciliary body ?
Non pigmented - lies of the Apical side
Pigmented -lies adjacent to the non pigmented but is the basolateral side.
What does aqueous humour provide?
O2 HCO3- and metabolites
Why is carbonic anhydrase important in the production of aqueous humour?
CA is the enzyme that produces H+ and HCO3-, these are required to help create the electrochemical gradient needed for the active transports on Na+ and the subsequent transport of Cl-.
How does water enter the aqueous humour?
Follows the Na+ and Cl- via osmosis, aquaporins accommodate the movement through the membranes.
