Week 1 - H - CSF/Aqueous humour production&circulation (physiology 1) Flashcards
What is the clear colourless liquid most composed of water in the brain?
This is cerebrospinal fluid (CSF)
What produces CSF?
The secretory epithelium of the choroid plexus produces CSF
Once CSF is produced by the choroid plexus, what is its circulation?
Produced in choroid plexus which exists in each of the brains ventricles It then circulates in the subarachnoid space before being absorbed into venous circulation
What are the three main functions of CSF? (mechanical, homeostatic, circulatory - explain them)
Mechanical protection: shock-absorbing medium that protects brain tissue. Brain “floats” inside the cranial cavity
Homeostatic function: pH of CSF affects pulmonary ventilation and cerebral blood flow. Transports hormones.
Circulation: medium for minor exchange of nutrients and waste products between blood and brain tissue
How is clinical CSF analysis obtained?
Obtained via lumbar puncture as CSF exists in the sub arachnoid space surrounding the spinal cord
At three weeks of embryology, what is the first well defined nerual structure to form?
The neural tube
What does the neural tube give rise to?
The anteriro part gives rise to the brain and its ventricles
The posterior (caudal) part gives rise to the spinal cord
What forms the choroid plexus cells?
Cells in the walls of the ventricles
In development of the choroid plexus, arteries invaginate into the pia matter and ependyma giving rise to what?
This gives rise to the chorid fissure
The involuted ependymal cells along with the vessels enlarge into villi and form the choroid plexus, responsible for CSF production WHat are the 4 ventircles of the adult braiin in which the chorid plexus is formed? What do the ependymal cells line?
2 lateral ventricles, and the third and fourth ventricle
Ependymal cells line the CSF filled ventircles
The choroid plexus scerete CSF through the capillaries in the walls of the ventircles and through the ependymal lining of the ventricles into the ventricle itself The production of CSF in the choroid plexuses is an active secretory process, and not directly dependent on the arterial blood pressure. What does the secretion of fluid depend on?
The secretion of fluid by the choroid plexus depends on the active Na+-transport across the cells into the CSF.
What connects each of the ventricles?
The lateral ventricles are connected to the thrid ventricle by the interventricular foramen
The third ventricle is connected to the fourth by the cerebral aqueduct
What is another name for the interventricular foramen?
The foramen of Monroe
The cerebral aqueduct (sylvian aqueduct) connects the 3rd and 4th ventricle What nucleus lies inferior to the cerebral aqueduct?
The trochlear nerve nucleus
Found in the midbrain
The trochlear nucleus and which other cranial nerve nucleus is found in the midbrain of the brainstem?
The oculomotor nucleus
What connects the fourth ventricle to the subarachnoid space?
The medial and lateral apertures
What are the 2 lateral apertures known as?
Foramina of Luschka
Medial aperture known as the Foramina of Magendie
Choroid plexus exist in each of the four ventricles, describe the flow of the CSF now?
Choroid plexus in the lateral ventricles produce CSF then flow through the interventricular foramen (of Monroe) into the third ventricle
Flows through the cerebral aqueduct (Sylvian aqueduct) into the fourth ventricle
which then have medial (Magendie) and lateral (Luschka) apertures which connect the flow to the subarachnoid space
How does the CSF in the subarachnoid space enter the dural venous sinuses? What is the volume of CSF produced and absorbed every day?
Enters via arachnoid villi
500ml
Where is the dural venous sinus located?
Located superior to the sagittal suture hence known as the superior saggital sinus (SSS)
The blood supply to the majority of the brain is restricted by a tight barrier WHat is this barrier known as?
The blood brain barrier
Endothelial cells in brain capillaries are the site of the BBB, a barrier between blood and brain What is the blood brain barrier composed of?
Composed of Capillary endothelium, basal membrane and perivascular astrocytes
Different tumours can arise in the ventricules causing a rasied ICP What is a tumour(growth) often found at the interventricular foramen?
Colloid cyst
What is the accumulation of blood in the ventricles usually due to? This is known as a ventricular haemorrhage
Can have a Epidural haemotoma (arertial connection between skull and dura)
Subdural haematoma - (venous connection between dura and arachnoid)
Subarachnoid haemorrhage
accumulation of CSF in the ventricular system or around the brain (either due to obstruction or overproduction) subsequent enlargement of one or more ventricles and increase in CSF pressure What is this known as?
This is known as hydropcephalus
What is optic disc swelling that is caused by increased intracranial pressure?
Papilloedema
Ciliary processes in the ciliary body filter blood into what substance that is released into the posterior chamber of the eye?
Aqueous humour
The aqueous humour then flows into the anterior chamber and then drains to the scleral venous sinus through what canal surrounded by what? What is the scleral venous sinus also known as?
Drains into the scleral venous sinus through the trabecular meshwork
Scleral venous sinus is also known as the canal of Schlemm
What vein does the scleral venous sinus connect to that drains the blood into the bloodstream?
The anterior ciliary veins
Where in the eye is the canal of schelmm located? (it is also known as the iridocroneal angle/junction)
It is located at the corneal limbus
