The Brain and Relations Flashcards
Why is the brain deemed a ‘hungry’ organ?
It uses 20% of our metabolic resources
What’s a rough indication of whether an organ or structure has a high metabolic rate?
It will have a more ‘pinky’ appearance which arise due to the presence of lots of capillaries.
What are the covering, protective membranes of the brain?
The 3 meninges
How many single and paired bones do you have in the skull?
6 single bones and 8 paired bones( i.e. that there’s one on the right and one on the left) 6+16=22
How many single and paired bones do you have in the skull?
6 single bones and 8 paired bones( i.e. that there’s one on the right and one on the left) (6+16=22)
Which part of the skull covers the brain?
The cranium or what is otherwise known as the Cranial vault. (This is the round bit on the top of the skull)
How many bones does the cranium/cranial vault consist of and which bones are these?
8 bones. These are the: Unpaired: frontal, occipital, sphenoid, ethmoid bones. and the Paired: parietal, temporal bones.
How can you group bones in the skull?
By whether they are cranial bones or facial bones.
How many facial bones are there and what are they?
14 and they are: Unpaired: mandible, vomer Paired: maxilla, zygomatic, lacrimal, palatine, nasal, inferior conchae
Which Bones contribute to the orbital cavity and how many of them are there in total?
7 bones. They are the frontal bone, sphenoid bone, ethmoid bone, maxilla bone, zygomatic bone, lacrimal and palatine bone.
How do you remember which part of the cerebral cortex is covered by which cranial bone?
They have the same names e.g. the occipital lobe is covered by the occipital bone.
Which bones forms most of the midline of your eye socket?
The ethmoid bone
What is another word for Inferior in regards to position?
Ventral
What are the three paired cranial spaces (fossas) of the floor of the skull?
The Anterior Fossa - where the frontal bone is
The middle fossa - where the temporal bone has been marked on.
The posterior fossa where the occipital bone has been marked.
How do the bones of the skull fit so perfectly around the brain?
Because the shape of the bones is formed by the shape of the brain (not the other way round).
Is the brain bilaterally similar?
Yes
As well as the skull, what is the brain also protected by?
The 3 Meninges or Maters (Mothers)
How many meninges cover the brain?
3
What is the Dura Mater?
A tough connective tissue membrane that protects the Brain
What are the three membranes (meninges) that cover the external surface of the brain (& spinal chord)?
- Outer, Dura Mater
- Middle, Arachnoid Mater
- Inner, Pia Mater
What are characteristics and roles of the Outer/Dura Mater?
Outer, Dura Mater:
- Very tough & fibrous connective tissue, fused to the periosteum (connective tissue of bones) of the skull.
- It suspends the brain - this reduces weight & movement of the brain. This suspension is done via double folds (of the dura mater) extending into the largest fissures, e.g Falx Cerebri (name of double fold in the longitudinal fissure- this fissure is the split between left and right cerebral cortices) & Tentorium Cerebelli (name of double fold between occipital lobe & cerebellum)
- It also encloses & protects Venous Sinuses in these fissures
Why is the Dura Mater fused to the periosteum of the skull?
This is done so the brain doesn’t move when the head moves in order to avoid the brain being bruised especially at sharp movements.
What are characteristics of the Middle / Arachnoid Mater?
•Thinner than Dura Mater.
It wraps over the brain (like ‘clingfilm’) creating a space for larger surface blood vessels + CSF (cerebrospinal fluid) (this is called the sub-arachnoid space - its the space between arachnoid layer and Pia Mater).
(Space seen between Dura Mater and Arachnoid Mater is a processing artefact- so non existent really)
What are the characteristics of the Inner/ Pia Mater?
•Very fine (thinnest mater- you would need a pair of forceps/tweezers to pick it out).
It closely follows the entire brain surface & its capillaries.
It contributes to the blood-brain barrier
What do the Vertebral arteries do wehn they enter the skull through the foramen magnum?
Both arteries (because remember they are paired) come together to form one large artery called the Basilar artery.
The basilar artery then branches out.
What are the branches of the Basilar artery and what do they supply?
The main branches of the Basilar artery are:
posterior cerebral - supplies back end of cerebral cortex - particularly occipital lobe.
various pontine - supply brainstem and cerebellum
cerebellar arteries - supply brainstem and cerebellum
Where do the two arterial supplies which supply blood to the brain (A.K.A the 2 sets of paired arteries; the Internal Carotid Arteries and the Vertebral aretries) join?
They join at the base of the brain in an area called the ‘circle of wilis’.
What is the circle of willis and what is a benefit of it?
See picture attached . The arteries are connected in a circle by smaller arteries labelled (and circled) as communicating arteries. What this means is that blood can flow between them (‘shunting’ can occur).
The benefit of this is, say for example the person is a bit old and has artherosclerosis in the right artery and the blood isnt flowing as quickly as it should do, then blood in the unaffected left artery could be shunted into the right artery and compensate.
What does the anterior communicating artery in the circle of willis link?
The Anterior Communicating Artery links the 2 Anterior Cerebral Arteries
What do the posterior communicating arteries link in the circle of willis?
The 2 Posterior Communicating Arteries link the 2 (left & right) Posterior Cerebral (branches of the Basilar Artery) to the 2 (left & right) Middle Cerebral Arteries
What is a technique for examining whether blood is flowing properly through the brain?
Carotid Angiography- dye is inserted into the carotid artery then an X-ray is taken. It is taken in three stages to examine three different phases - the arterial phase, the capillarial phase and then the venuous phase.
What produces Cerebral Spinal Fluid?
Specialized vascular-epithelial complexes (choroid plexus) (which are inside the Lateral & 3rd Ventricles)
How is the Cerebral Spinal Fluid circulated?
It goes from the lateral ventricles to the third ventricle then through the cerebral aqueduct to the fourth ventricle and finally exists through three holes; the foramen of magendie (middle hole) and the Foramena of Luschka (two of these holes exist at the sides). It then goes into the sub-arachnoid space and into the spinal chord.
What does Hydrocephalus look like in a foetus and why is that?
What does this cause for the child?
CSF accumulates pushing brain & flimsy skull outwards (bones in skull havent ossified (hardened) yet) thus head expands.
This leads to neurological deficits.
What is Papilledema and is it a medical emergency?
Papilledema or papilloedema is optic disc swelling that is caused by increased intracranial pressure due to any cause.
It is a medical emergency!
How are the venous sinuses distributed around the skull?
