L6 - Blood supply

• The internal carotid artery enters the skull through the carotid canal
• The internal carotid is a branch of the common carotid artery
• The vertebral arteries branch off from the subclavian. There is a right and left vertebral artery. They pass through the openings in the cerebral vertebrae called the transverse foramen
• The common carotid artery branches directly off of the aorta and splits into the external and internal carotid arteries
• The vertebral arteries enters the skull through the foramen magnum
• Each internal carotid artery enters the skull through the carotid canal in the temporal bone and runs medially in the petrous part of the temporal bone and emerges into the cranial cavity (does to 90 degree bends)

  
• The internal carotid arteries pierce the dura lateral to the optic nerve and enters the subarachnoid space. Gives off a branch called the ophthalmic artery to supply the eye
• Branches of the internal carotid artery (ICA) are given off only after it enters the subarachnoid space. The branches are

  • ophthalmic artery (supplies the eye and travels with the optic nerve)
  • posterior communicating artery
  • anterior choroidal artery
  • terminal branches: anterior cerebral artery (ACA) and middle cerebral artery (MCA)
• Two anterior cerebral arteries are connected by an anterior communicating artery
• Each vertebral artery traverses transverse foramina of C6-C1 vertebra. It passes through the foramen magnum and enters the subarachnoid space. Branches are given off only in the subarachnoid space
• The right and left vertebral arteries join to form a single basilar artery (BA) which lies in the median grove of the pons
• Right and left anterior spinal arteries (ASA) arise from respective arteries to join to form a single anterior spinal artery
• Posterior spinal arteries (PSA) arise from vertebral arteries
• Terminal branches of the basilar artery are the posterior cerebral arteries (PCA)
• Label the vertebral and basilar arteries

  A) vertebral arteries

  B) posterior spinal arteries

  C) anterior spinal artery

  D) basilar artery

  E) posterior cerebral arteries

  
• Label the cerebral arterial circle (circle of willis)

  A) anterior cerebral

  B) anterior communicating

  C) middle cerebral

  D) internal carotid

  E) posterior communicating

  F) posterior cerebral

  G) basilar

  H) vertebral

  
• The middle cerebral is not a part of the circle of willis
• The anterior cerebral artery enters the longitudinal fissure and curves posteriorly around the corpus callosum. It supplies the medial surfaces of frontal and parietal loves, olfactory bulb, corpus callosum and superolateral surface of frontal and parietal lobes

  
• The middle cerebral artery is a terminal branch of the internal carotid artery. It enters the lateral fissure. Supplies the lateral surfaces of frontal, parietal, and temporal lobes

  
• The posterior cerebral artery is a terminal branch of the basilar artery. It curves dorsolaterally around midbrain. It supplies medial and inferior surfaces of temporal and occipital lobes

  
• The sensory map is located on the postcentral gyrus of the parietal lobe
• The motor map is located on the precentral gyrus of the frontal lobe
• The cerebral arterial circle (circle of willis) allows for collateral circulation
• What are the two types of strokes?

  • hemorrhagic stroke (hemorrhage/blood leaks into brain tissue)
  • ischemic stroke (clot stops blood supply to an area of the brain)
• The spinal cord is supplied by an anterior spinal artery and a pair of posterior spinal arteries, and reinforced by anterior and posterior radicular arteries (radicular arteries travel along spinal nerve roots)
• The middle meningeal artery is within the dura and supplies the dura. It comes into the skull through the foramen spinosum. It is a branch of the external carotid artery, more specifically the maxillary artery

  
• A fracture of the pterion can tear the middle meningeal artery leading to an epidural hematoma. This is where blood accumulates between the skull and the dura mater causing compression of the brain. Results in a lens-shaped image on MRI.

  
• Label the type of hematoma

  A) epidural hematoma

  
• An aneurysm is a bulge in a blood vessel wall from weakening of the vessel wall. This dilated area can burst leading to a hemorrhagic stroke.
• If there is an aneurysm in a cerebral artery in the subarachnoid space, it can result in a subarachnoid hematoma. Blood will flow into the sulci of the brain and in the cerebrospinal fluid. Symptoms include:

  • thunderclap headache
  • nausea, vomiting, LOC
  • neck stiffness
  • visual changes

  
• Label the type of hematoma

  A) subarachnoid hematoma

  
• A subdural hematoma is from sudden acceleration-deceleration (someone falling and hitting their head). Veins traveling from the subarachnoid space to the superior sagittal sinus can be torn from the shear forces. Blood will pool in the subdural space between the dura and arachnoid. Bleeding may be slower because veins have lower pressure. Subdural hematomas have a crescent-shape on MRI (because the dura is still attached to the skull)

  
• Label the type of hematoma

  A) subdural hematoma

  
• There are only two veins that drains all the venous blood from the brain - the two internal jugular veins
• Certain areas of the brain do not have a blood-brain barrier (e.g., parts of the hypothalamus) to allow chemicals and hormones to pass