Dialysis blocks the passage of larger substances (for example, red blood cells, large proteins). This replicates the filtering process that takes place in the kidneys when the blood enters the kidneys and the larger substances are separated from the smaller ones in the glomerulus. The two main types of dialysis, hemodialysis and peritoneal dialysis, remove wastes and excess water from the blood in different ways. Hemodialysis removes wastes and water by circulating blood outside the body through an external filter, called a dialyzer, that contains a semipermeable membrane. The blood flows in one direction and the dialysate flows in the opposite.
Blood–brain barrier more likely, aggravated) by a breakdown in the blood–brain barrier. Cerebral edema is the accumulation of excess water in the extracellular space of the brain, which can result when hypoxia causes the blood–brain barrier to open. Many neurodegenerative diseases including synucleinopathies such as Parkinson's, and tauopathies such as Alzheimer's are thought to result from seeded misfolding from pathological extracellular protein variants known as prions. This prion-like hypothesis is gaining support in numerous studies in vitro and involving in vivo intracerebral injection of brain lysates, extracted protein (tau, alpha-synuclein) and synthetically generated fibers in alpha-synucleinopathies. These proteins are also detectable in