Finger - circulation Flashcards
What two main arteries supply the brain?
Internal carotid (anterior circulation system)
Vertebral artery (posterior circulation system)
These two systems are interconnected at the Circle of Willis.
What forms the anterior circulation and which regions does it supply?
The anterior circulation system arises from the internal carotid artery and supplies the anterior half of the brain including the entire cerebral hemisphere except for the medial part of the occipital lobe and the interior part of the temporal lobe. (students often miss this on test).
What structure do the ventricles arise from?
The remnant of the neural tube. They are a “C” shaped fluid filled structure completely within the brain.
What is the choroid plexus and what does it do?
A pink structure within the lateral ventricle that manufactures the CSF. Fluid flows from the lateral ventricle to the 3rd, to the 4th, where it can escape into the subarachnoid space. Most fluid resides in the subarachnoid space (125 mL grad. cylinders). CSF is vastly overproduced by the choroid plexus (500 mL/day). 20 mL in the ventricles.
The choroid plexus has access to the blood. It basically removes the components of serum desired, and adds these to the CSF.
Obstruction of flow to IV ventricle causes hydrocephalus and compression of brain tissue.
Increased intracranial pressure will manifest what symptoms, clasically? (pediatric patient)
severe headache, nausea, vomiting
What are the types of hydrocephalus, and what causes each?
Obstructive hydrocephalus = noncommunicating (caused by a blockage)
nonobstructive hydrocephalus = communicating (caused by a failure of reabsorption into the plasma)
What forms the posterior circulation and which regions does it supply?
The posterior circulation system, which arises from the vertebral arteries supplies the rest of the brain including the brainstem, cerebellum and some cortex (the medial face of the occipital lobe and inferior temporal lobe).
As the internal carotid artery approaches the ventral surface of the brain, it forms two major terminal branches: the __1___ and the __1___. The anterior cerebral artery enters the____2___ to supply __2____. The middle cerebral artery distributes branches to the __3__ to supply ____3___.
- anterior cerebral artery and the middle cerebral artery
- longitudinal fissure (divides the two halves of the cerebral cortex) to supply the anterior two-thirds of the medial face of the cerebral hemisphere, and the orbital cortex
- distributes branches through the lateral fissure to supply the lateral face of the cerebrum including frontal, parietal and temporal lobes
The vertebral arteries fuse to form the _____ at the level of the _____ (relative to the brain).
Basilar artery; pons
There are fluid-filled spaces inside the brain – the lateral, third, and fourth ventricles. The lateral ventricles include what used to be called the first and second ventricles. The lateral ventricles communicate with the third ventricle via the ______. The _____ connects the third and fourth ventricles. _____ connect the fourth ventricle with the subarachnoid space.
interventricular foramen (one for each lateral ventricle)
cerebral aqueduct
Three apertures (two lateral and one caudal)
_____ is a single layer of cells that lines the ventricles. These cells form a leaky cell layer (no tight junctions), and thus, the CSF in the ventricles exchanges freely with the extracellular fluids in the interstitial space in the brain. This means that substances in the CSF can move freely from the ventricle into the extracellular space in the brain.
Ependyma
CSF is replaced 4x daily. How is it produced, transported, and reabsorbed?
CSF is produced by the chorionic villi. It flows through the sinuses as described previously.
CSF is reabsorbed into the blood by arachnoid granulations (aka arachnoid villi) which line the dural sinuses.
Trace the path a corpuscle might take from the internal carotid artery to the somatosensory cortex. Will this path differ from the foot to the hand region of the cortex?
Internal carotid artery –> middle cerebral artery
**(Since the foot is located more medially on the cerebellar surface, it may instead be supplied by the anterior cerebral which transverses the longitudinal fissure and supplies the medial aspect of most hemispheres. So it would be IC–> anterior cerebral.)
How might blood from the left vertebral artery reach the frontal lobe of the right side in the case of an occlusion of an internal carotid artery?
Frontal lobe would normally be supplied by the anterior cerebral via the internal carotid. With blockage of the left IC, blood would arrive from the left vertebral via:
Left vertebral–> Basilar–>posterior cerebral –> Posterior communicating artery–> Internal Carotid –> (or middle cerebral, depending on variant) –> anterior cerebral
**could also be supplied by the middle cerebral
Draw and label the components of the Circle of Willis
Vertebral, Posterior Inferior Cerebellar Artery (PICA), Anterior Inferior Cerebellar (AICA), Basilar, Superior Cerebellar Artery, Posterior Cerebral Artery, Posterior Communicating Arteries, Internal Carotid, Middle Cerebral, Anterior Cerebral, Anterior communicating
