Week 1 - H - CSF/Aqueous humour production&circulation (physiology 1)

Question 1

What is the clear colourless liquid most composed of water in the brain?

Answer 1

This is cerebrospinal fluid (CSF)

Question 2

What produces CSF?

Answer 2

The secretory epithelium of the choroid plexus produces CSF

Question 3

Once CSF is produced by the choroid plexus, what is its circulation?

Answer 3

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

Question 4

What are the three main functions of CSF? (mechanical, homeostatic, circulatory - explain them)

Answer 4

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

Question 5

How is clinical CSF analysis obtained?

Answer 5

Obtained via lumbar puncture as CSF exists in the sub arachnoid space surrounding the spinal cord

Question 6

At three weeks of embryology, what is the first well defined nerual structure to form?

Answer 6

The neural tube

Question 7

What does the neural tube give rise to?

Answer 7

The anteriro part gives rise to the brain and its ventricles

The posterior (caudal) part gives rise to the spinal cord

Question 8

What forms the choroid plexus cells?

Answer 8

Cells in the walls of the ventricles

Question 9

In development of the choroid plexus, arteries invaginate into the pia matter and ependyma giving rise to what?

Answer 9

This gives rise to the chorid fissure

Question 10

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?

Answer 10

2 lateral ventricles, and the third and fourth ventricle

Ependymal cells line the CSF filled ventircles

Question 11

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?

Answer 11

The secretion of fluid by the choroid plexus depends on the active Na+-transport across the cells into the CSF.

Question 12

What connects each of the ventricles?

Answer 12

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

Question 13

What is another name for the interventricular foramen?

Answer 13

The foramen of Monroe

Question 14

The cerebral aqueduct (sylvian aqueduct) connects the 3rd and 4th ventricle What nucleus lies inferior to the cerebral aqueduct?

Answer 14

The trochlear nerve nucleus

Found in the midbrain

Question 15

The trochlear nucleus and which other cranial nerve nucleus is found in the midbrain of the brainstem?

Answer 15

The oculomotor nucleus

Question 16

What connects the fourth ventricle to the subarachnoid space?

Answer 16

The medial and lateral apertures

Question 17

What are the 2 lateral apertures known as?

Answer 17

Foramina of Luschka

Medial aperture known as the Foramina of Magendie

Question 18

Choroid plexus exist in each of the four ventricles, describe the flow of the CSF now?

Answer 18

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

Question 19

How does the CSF in the subarachnoid space enter the dural venous sinuses? What is the volume of CSF produced and absorbed every day?

Answer 19

Enters via arachnoid villi

500ml

Question 20

Where is the dural venous sinus located?

Answer 20

Located superior to the sagittal suture hence known as the superior saggital sinus (SSS)

Question 21

The blood supply to the majority of the brain is restricted by a tight barrier WHat is this barrier known as?

Answer 21

The blood brain barrier

Question 22

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?

Answer 22

Composed of Capillary endothelium, basal membrane and perivascular astrocytes

Question 23

Different tumours can arise in the ventricules causing a rasied ICP What is a tumour(growth) often found at the interventricular foramen?

Answer 23

Colloid cyst

Question 24

What is the accumulation of blood in the ventricles usually due to? This is known as a ventricular haemorrhage

Answer 24

Can have a Epidural haemotoma (arertial connection between skull and dura)

Subdural haematoma - (venous connection between dura and arachnoid)

Subarachnoid haemorrhage

Question 25

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?

Answer 25

This is known as hydropcephalus

Question 26

What is optic disc swelling that is caused by increased intracranial pressure?

Answer 26

Papilloedema

Question 27

Ciliary processes in the ciliary body filter blood into what substance that is released into the posterior chamber of the eye?

Answer 27

Aqueous humour

Question 28

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?

Answer 28

Drains into the scleral venous sinus through the trabecular meshwork

Scleral venous sinus is also known as the canal of Schlemm

Question 29

What vein does the scleral venous sinus connect to that drains the blood into the bloodstream?

Answer 29

The anterior ciliary veins

Question 30

Where in the eye is the canal of schelmm located? (it is also known as the iridocroneal angle/junction)

Answer 30

It is located at the corneal limbus