Mohana Ruban

Vayva Elkins

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CIRCLE OF WILLIS - the blood supply to the brain enters through internal carotid arteries and vertebral arteries , eventually give raise to circle of willis

The major artery carrying oxygenated blood away from heart is the  aorta.the very first branches gives off the aorta supply with nutrition and oxygen.the next branches gives raise to  the Common carotid arteries. Which further branches into Internal carotid arteries.The external carotid arteries supply blood to the tissues on the surface of cranium. The bases of the common carotid arteries contain  stretch receptors that immediately respond to the  drop in blood pressure upon standing. The Orthostatic reflex  is a reaction to this change in body position , so that blood pressure is maintained against the increasing effect of gravity(Orthostatic means "standing up"). Heart rate increases - a reflex of the sympathetic division of the autonomic nervous system  and this raises blood pressure.
      
    The internal carotid artery enter the cranium through Carotid canal of the temporal bone. A second set of vessels that supply  the CNS  are the vertebral arteries .
which are protected as they pass through the neck region by the transverse foramina of the cervical vertebrae. The vertebral arteries  enter the cranium through foramen magnum of occipital bone. Branches of the right and left vertebral arteries merge into the anterior spinal artery supplying  the anterior aspects of the spinal cord , found along the anterior median fissure.the two vertebral arteries then merge into the basilar artery , which gives raises to the branches of the brain stem and cerebellum.

    The right and left internal carotid arteries and branches of the basilar artery all become the circle of willis, a confluence of arteries that can maintain perfusion of the brain even if narrowing or a  blockage limits through one part.

CIRCLE OF WILLIS - the blood supply to the brain enters through internal carotid arteries and vertebral arteries , eventually give raise to circle of willis

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