Blood Supply to the Head and Neck

What percentage of arterial blood supply goes to the brain

20%

What does the brain need a constant supply of

oxygenated blood

glucose as a primary energy source

What percentage of body weight does the brain take up

2%

What are the 5 gross divisions of the aorrta

aortic arch

aortic root

ascending aorta

descending aorta

abdominal aorta

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Label this image

What does the brachiocephalic artery supply

supplies the right upper side of the body

At which level does the braciocephalic artery divide

sternoclavicular articulation

around T1 vertebral level

Which structures does the braciocephalic artery divide into

right common carotid artery

right subclavian artery

What does the right common carotid artery supply

supplies right side of the neck and right anterior cerberal circulation

What does the left common carotid artery supply

supplies arterial blood to the left side of the neck and left side of the cerebral circulation

When the common carotid arteries bifurcate, what do they give rise to

internal and external carotid artery

Describe th origins of the left and right common carotid artery

right- brachiocephalic artery

left- arch of aorta

Describe the course of the left and right common carotid artery

-symmetrical course in the neck

Describe the position of the ICA between individuals

variable position between individuals

How can we tell the difference between the ICA and ECA

ICA doesn’t have any branches in the neck unlike the ECA

ICA has a dilation/bulge at its start (as a result of the carotid sinus)

ECA courses through the neck more superficially

Function of the carotid sinus

-contains baroreceptors

-involved in homeostatic control of blood pressure

Which extracranial structures are supplied by the external carotid artery

supplies the neck, face, scalp, mouth and jaw tissues

Which structures does the ECA supply intracranially

middle meningeal artery

accessory meningeal artery

What are the 6 branches of the ECA

superior thyroid

lingual

facial

ascending pharyngeal

occipital

posterior auricular

What are the terminal branches of the ECA

-superficial temporal

-maxillary

What are the 2 sources of blood supply to the intracranial compartment

left and right internal carotid arteries

left and right vertebral arteries

How do the internal carotid arteries enter the skull

via the carotid canal

What are the ICAs responsible for

anterior circulation of the brain

How do the vertebral arteries enter the skull

via the foramen magnum

What are the vertebral arteries responsible for

psoterior circulation of the brain

How are the ICAs and vertebral arteries connected

-connected by the circle of willis

What is the circle of willis

circular arterial anastomosis (connection between 2 blood vessels)

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The circle of willis

Location of the circle of willis

-located within the subarachnoid space

-sits below the brain, forming the floor on which the brain rests on

Importance of the circle of willis

-provides alternative routes of blood flow if an artery is blocked (collateral circulatinon) which ensures the brain remains perfused

What are the 2 functional circulations of the circle of willis

anterior and posterior circulation

Anterior circulation of the circle of willis

middle cerebral artery

anterior cerebral artery

anterior communicating artery

CHECK AND CHANGE ANSWERS

Posterior circualtion of the circle of willis

posterior cerebral arteries

posterior communicating arteries

CHECK AND CHANGE ANSWERS

Where does the carotid bifurcation occur

upper border of the thyroid cartilage (more reliable)

C4 (less reliable, varies between individuals)

What are the 4 main anatomical segments of the ICA

cervical

petrous

cavernous

cerebral

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Why does the ICA have several bends/curves

-they allow energy dissipation which slows down blood flow and reduce transmission of high arterial pressure to delicate cerebral arteries

What is the petrosphenoidal fissure

-narrow gap situated between the greater wing of sphenoid bone and the petrous portion of the temporal bone.

-skull base landmark

Label this image, what does it show

shows the passage of the ICA near the petrosphenoidal fissure

What are the branches of the ICA

3 major branches:

-middle cerebral artery

-anterior cerbral artery

-posterior communicating artery

2 smaller branches:

-ophthalmic artery

-anterior choroidal artery

What does the anterior cerebral artery supply

arterial blood supply to the inner medial (towards the midline) surfaces of the frontal and pariteal lobes

Why is the anterior cerebral artery known as the artery of the leg

supplies the parts of the pre central gyrus (primary motor cortex) and post central gyrus (primary sensory cortex) which are responsible for motor and sensory function of the legs

Where in the brain does the middle cerebral artery supply

lateral aspects of the frontal, parietal and occipital cortex

What are lateral striate arteries and what is their significance

-they are small branches from the MCA that go deep into the brain

-they supply basal ganglia (brain structures involved in motor control)

Arterial territory of the MCA

Where do most strokes occur

-occur in MCA territory

What does the posterior cerebral artery supply

-goes around the midbrain and supplies the midbrain, thalamus, temporal and occipital lobes

Which artery is the posterior cerebral artery a branch of

the basilar artery

Which arteries do the vertebral arteries arise from

subclavian arteries

Explain why the vertebral arteries are considered to have a tortuous course

-don’t travel straight from the subclavian arteries to the brain

-have a twisted, winding course

What are the branches coming off the vertebral arteries

largest branch- posterior inferior cerebellar artery

other branches- spinal arteries

Function of the basilar artery

supplies most of the brainstem

Location of the basilar artery

overlies the pons

Formation of the basilar artery

-formed by union of left and right vertebral arteries at the ponto-medullary junction

What does the basilar artery bifurcate into

2 posterior cerebral arteries

Function fo the venous system of the brain

drains blood and cerebrospinal fluid

How is the venous system of the brain organised

organised into superficial and deep veins which drain into dural venous sinuses

Location of the cavernous sinus

lies either side of the sella turcica

Function of the cavernous sinus

drains the superior and inferior ophthalmic veins from the superior orbital fissure

drains the superficial middle cerebral vein and sphenoparietal sinuses

Which structures run through the cavenous sinus

-internal carotid artery

-cranial nerves III, IV, V1, V2 and VI

What is the infratemporal fossa

irregularly shaped, complex space in the skull

located below the zygomatic arch, behind the maxilla,

acting as a crucial pathway for nerves and vessels connecting the cranial cavity to the face

Label this image, what does it show

shows the veins of the infratemporal fossa

What is a stroke

clinical syndrome of abrupt loss of focal brain function lasting over 24 hours (or causing death) due to either spontaneous haemorrhage or inadequate blood supply to part of the brain (thrombosis, embolism)

What si transient ischaemic attack

-focal disturbance of brain function (specific part of the brain stops working leading to problems with the region of the body that part of the brain is responsible for)

-sudden onset

-assumed to be of vascular origin

-resolves completely in 24 hours