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A subconjunctival hemorrhage can often occur without any obvious cause or harm to the eye. A strong enough sneeze or cough can cause a blood vessel in the eye to burst. Hyphema is a result of blunt or penetrating trauma to the orbit that increases intraocular pressure, causing tears in the vessels of the ciliary body and iris.
The circle of Willis (also called Willis' circle, loop of Willis, cerebral arterial circle, and Willis polygon) is a circulatory anastomosis that supplies blood to the brain and surrounding structures in reptiles, birds and mammals, including humans. [1] It is named after Thomas Willis (1621–1675), an English physician. [2]
"Anatomy diagram: 13048.000-1". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2014-01-01. The arteries of the base of the brain. Posterior inferior cerebellar artery labeled at bottom. The temporal pole of the cerebrum and a portion of the cerebellar hemisphere have been removed on the right side. Inferior ...
An intracranial aneurysm, also known as a cerebral aneurysm, is a cerebrovascular disorder characterized by a localized dilation or ballooning of a blood vessel in the brain due to a weakness in the vessel wall. These aneurysms can occur in any part of the brain but are most commonly found in the arteries of the cerebral arterial circle. The ...
In serious cases, blood vessels rupture and cause bleeding within the brain (intracranial hemorrhage). [ a ] In more than half of patients with AVM, this is the first symptom. [ 7 ] Symptoms due to bleeding include loss of consciousness , sudden and severe headache, nausea, vomiting , incontinence , and blurred vision , amongst others. [ 4 ]
The brain is supplied with blood by the internal carotid arteries and also by the posterior cerebral arteries; the posterior communicating arteries connects the two systems. This provides redundancies or collaterals in the cerebral circulation so that, if one system is blocked or narrowed, the other can take over.
Cerebral blood flow (CBF) is the blood supply to the brain in a given period of time. [8] In an adult, CBF is typically 750 millilitres per minute or 15.8 ± 5.7% of the cardiac output. [9] This equates to an average perfusion of 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. [10] [11] [12]
Brain ischemia has been linked to a variety of diseases or abnormalities. Individuals with sickle cell anemia, compressed blood vessels, ventricular tachycardia, plaque buildup in the arteries, blood clots, extremely low blood pressure as a result of heart attack, and congenital heart defects have a higher predisposition to brain ischemia in comparison to the average population.