Clear, colourless fluid (mainly composed of water)
Where is CSF produced?
Produced by the secretory epithelium of the choroid plexus
How much CSF is produced per day? How much of this is in the CNS?
500-600mls per day 150mls in the CNS
The CSF in the CNS is replaced XXXX times per day?
3-4 times per day
Give a very brief overview of CNS production and circulation?
Produced in ventricles Circulates around the subarachnoid space Reabsorbed into the venous circulation
The CSF is able to supply XXXXX and is able to remove XXXXX
Water/Ions/Amino Acids Metabolites
What are the functions of the CSF?
Protection (Cushions the brain so it floats in the cranial cavity) Homeostatic (pH affects pulmonary ventilation and cerebral blood flow - also contains hormones) Circulation (Medium for transporting nutrients and waste products)
How do you obtain CSF?
What can analysis of CSF tell us?
Helps to diagnose the brain, spinal cord and meninges
Describe what normal CSF contains/looks like?
Clear and colourless Contains a small amount of protein (15-45mg/dl) Contains a small amount of immunoglobulin Contains a small number of cells (1-5/ml)
Describe embryological development of CSF apparatus?
The developing nervous system is made up of a tube called the neural canal. The cavity later develops into the ventricles of the adult brain and the spinal cord canal. From the cells in the walls of the ventricles, the choroid plexus develops. The choroidal cells are specialised secretory cells that secrete the CSF
What produces the choroid fissure?
Developing arteries invaginate into the roof of the ventricle to form the choroid fissure
Where is the choroid plexus of the adult brain found?
In the 3rd, 4th and lateral ventricles
What is the choroid plexus?
A plexus (network) of cells that produce CSF
How many ventricles of the brain are there? What are they?
Four ventricles of the brain They are interconnected cavities where CSF is produced
Describe the structure of the choroid plexus?
Internal capillary Layer of ependymal cells that tight junctions between them Surrounded by CSF
How is CSF secreted?
CSF secretion depends on active transport of ions The movement of polarised ions across the apical and basolateral membranes allows for the secretion of CSF
Describe the movement of ions into the CSF?
Na+ by active transport into CSF from blood This pulls along Cl- Water is pulled along by both ions
Describe the composition of CSF compared to blood?
More Na+ More Cl- Less K+ Less Protein Less Glucose
Describe the relationship between CSF secretion and arterial blood pressure
CSF secretion by the choroid plexus is an active process and is not determined by the arterial blood pressure
Name the ventricles?
Two lateral ventricles 3rd 4th
In which ventricle(s) is CSF first formed?
Choroid Plexus of the lateral ventricles
Describe CSF circulation? (Just through ventricles)
Formed by choroid plexus of lateral ventricles Passes through inter ventricular foraminae into 3rd More CSF added by choroid plexus in room of 3rd Passes into cerebral aqueduct Into fourth ventricle More CSF added by choroid plexus of 4th ventricle
Where does CSF go after it has been in the 4th ventricle?
Circulates in the subarachnoid space Some enters the central canal of the spinal chord Reabsorbed by the arachnoid granulations in the superior saggital sinus
Where is the blood brain barrier?
This is at the endothelial cells in brain capillaries
Function of the blood brain barrier?
This protects the brain from many common bacterial infections and toxins
What is the main obstacle for drug delivery to the CNS?
The blood brain barrier
Describe tumours that can affect the ventricles, choroid plexus and CSF?
- Choroid Plexus Tumours - Colloid Cyst
Describe ventricular haemorrhage?
This is accumulation of blood in the ventricles
What is an epidural haetoma?
Arterial bleed between dura and skull
What is an subdural haemorrhage?
Venous bleed between the dura and the arachnoid
What is a subarachnoid haemorrhage?
Haemorrhage into the subarachnoid space
What is hydrocephalus?
Accumulation of CSF in the ventricles or around the brain (either due to obstruction or overproduction) Causes increase in CSF pressure and ventricular enlargmenet
Describe idiopathic intracranial hypertension?
This is increased CSF pressure for no obvious reason May have headaches and visual field disturbances due to papilloedema
What is papilloedema?
This is swelling of the optic discs due to raised intra-cranial pressure Presents with visual symptoms - blurring, loss of vision, enlarged blind spot
Function of aqueous humour?
This bathes the structures within the eyes Provides oxygen and metabolites Contains bicarbonate to buffer H+ produced by eye structures
Where is aqueous humour produced?
Describe aqueous humour circulation?
Ciliary Body Posterior Chamber Anterior Chamber Drains into the canal of Schlemm