Blood Supply to the Brain Flashcards
What is the importance if arterial blood supply to the brain?
- Needs a constant supply of blood to obtain oxygen and nutrient
- Uses glucose as its primary energy source (only uses glucose for respiration)
- 2% of the body weight and 20% of cardiac output from the heart
What are the divisions of the aorta?
When the blood exits the heart the first part of the aorta it goes into is the aortic base, then will go into the accenting aorta, then arch of aorta, then descending aorta and last part of the aorta would be the abdominal aorta
* Aorta has 3 branches (sometimes 4 in some people)
○ Most left=left subclavian artery
○ Most right=brachiocephalic artery which branches to form the right common carotid artery and the right subclavian artery.
○ In the middle of these 2 there is the left common carotid artery
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How is blood supplied to the head and neck?
- Brachiocephalic artery provides blood to the right side of the body
- Brachiocephalic artery then divides into the right subclavian artery and the right common carotid artery at the level of the sternoclavicular articulation/join
- Heart gives itself blood thought the aortic root (coronary arteries)
- Arch of aorta rests at T4-T5
- Arch of aorta branches are not always the same for everyone
- Some people may have more than 3 branches
- Subclavian strikes give rise to vertebral arteries
- Vertebral arteries provide blood to head and neck
- Vertebral artery in the Foramen transversaria
- Subclavian artery a travels under the subclavius muscle under the clavicle
What are the carotid arteries and what are the 3 sections?
- Symmetrical pathway of travel between the left and right common carotid arteries in the neck
- Common carotid arteries end by bifurcation into the internal carotid artery and the external carotid artery
- Bifurcates at the level of the superior border of the thyroid cartilage (C4)
Tell me about the external carotid artery and its distribution.
- More superficial than the internal carotid artery
- Terminal branches
○ Superficial temporal
○ Maxillary - Six branches
○ Superior thyroid
○ Lingual
○ Facial
○ Ascending
○ Pharyngeal
○ Occipital
○ Posterior auricular - Can get the arterial pulse point from the superficial temporal branches
- Terminal branches
How is blood supplied to the intracranial compartment?
- There are two separate but convergent arterial sources as follows:
○ The left & right internal carotids
○ The left and right vertebral arteries- These arterial systems connect to form an arterial anastomosis
What is arterial anastomosis and what is its importance?
- Terminal branches of the internal carotid artery branches form an anastomotic circle, called the Circle of Willis
- Connects separate arteries that supplies the brain
Tell me about the internal carotid artery.
- Internal carotid artery is position deeper than the external carotid artery, doesn’t give branches in the neck and has dilatation at its start.
- Gives many branches that supply the neck and face
- Internal carotid artery has the carotid sinus (bulge)
- Internal carotid doesn’t branch in the neck
- They move superiorly within the carotid sheath, and enter the brain via the carotid canal of the temporal bone. They do not supply any branches to the face or neck.
What us the distribution if the internal carotid artery?
- Divisible into 4 segments
○ Cervical
○ Petrous
○ Cavernous
○ Cerebral- Has 6 right angle bends to decrease the blood flow
What are the internal carotid artery branches?
- Terminates by giving rise to 3 major branches, 2 smaller branches and changing its name
- 3 major branches: middle cerebral artery, anterior cerebral artery and posterior communicating artery
- 2 smaller branches: ophthalmic artery and anterior choroidal artery
Tell be about the anterior cerebral artery.
- Branch of the internal carotid artery
- Also known as the artery of the leg because it supplies blood to the part of the brain that controls the leg
- Supplies the medial surface and adjacent convexity if the cortex (frontal and partial lobes)
- Joined by anterior communicating artery
Tell be about the middle cerebral artery.
- Direct continuation of the internal carotid artery (has 60-80% of the blood flow from the internal carotid artery)
- Supplies 2/3rds of the convexity of the cortex
- Lateral aspects if the frontal cortex, paraxial cortex and occipital cortex
- Lateral striate arteries supply basal ganglia
- Storkes mostly occur in the middle cerebral artery
Tell be about the posterior communicating artery.
- Bifurcation of basilar artery (25% get main supply form the internal carotid artery)
- Goes around the midbrain
- Supplies the midbrain, thalamus, temporal and occipital lobes
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Tell be about the vertebral arteries.
- Arise from the subclavian arteries
- Tortuous course
- Largest branch-posterior inferior cerebellar artery
Other branches-spinal artery
Tell be about the basilar artery.
- Formed by union of left and right vertebral arteries at the ponto-medullary junction
- Overlies the pons
- Supplies most of the brainstem
- Superior & Anterior inferior cerebellar arteries
- Bifurcates into 2 PCA’s
Tell be about the venous drainage in the head.
- The venous system of the brain drains blood and cerebrospinal fluid
- It is organised into:
○ Superficial Veins
○ Deep Veins - the confluence of sinuses splits into two transverse sinuses which drain into the sigmoid sinus before draining into the internal Jugular veins
- It is organised into:
What is the infratemporal fossa?
- Lies either side of the sella turcica
- Drains the sup and inf. Opthalmic veins from the superior orbital fissure as well as the superficial middle cerebral vein and sphenoparietal sinuses
- The int. Carotid as well as CN III, IV, V1, V2 and VI run through this venous structure
- Maxillary vein
- Middle meningeal vein(s)
- Pterygoid venous plexus
○ Key
§ 1- Superior ophthalmic vein
§ 2- anterior intercavernous sinus
§ 3- inferior ophthalmic vein
§ 4- pterygoid plexus
○ 5- middle meningeal vein
