Dialysis vs Ultrafiltration
Kidneys are one of the most vital organs in our bodies. Lot of harmful byproducts is generated in our everyday metabolic processes. These harmful byproducts should be immediately removed from our bodies. This process is known as excretion. While some of the byproducts are excreted via exhalation through lungs, sweating (via skin), etc kidney is the organ that is differentiated specifically into this function. Not only waste material, but all the excess substances like water, glucose, vitamins etc, should also be removed to establish the balanced environment inside. This function is also done by the kidneys. The process of producing urine primarily takes place in nephrons, in the kidneys. Each kidney has millions of nephrons. The natural urine formation in a nephron can be divided into three steps as ultrafiltration, reabsorption, and secretion.
Ultrafiltration is the process where the blood is filtered into the nephron at the Bowman’s capsule. Glomerulus is the capillary network bringing blood with waste material into the Bowman’s capsule. Then blood is filtered under high pressure, and most of the substances in blood (except globular proteins, red blood cells, white blood cells and platelets) go into the nephron. The high pressure for this filtration has resulted due to the size difference in the incoming and outgoing capillary to the Bowman’s capsule. The afferent arteriole brings blood in, and efferent arteriole takes blood out. The diameter of the efferent arteriole is less than the afferent arteriole, increasing the blood pressure and causing it to be filtered. The filtration takes place through the membranes of the capillaries and the inner membrane of the Bowman’s capsule. This phenomenon, where a filtration is taking place under high hydrostatic pressure through a semipermeable membrane is known as ultrafiltration. Not only in kidneys, this can be simulated in external environments, to separate substances from a mixture. This can be used in industries, to purify solution mixtures and concentrate them. While filtering by ultrafiltration, high molecular weight substances are retained in the filter, and others will pass through.
Dialysis is a process to treat patients with kidney failures. In them, urine formation is not sufficiently taking place due to the incapability in filtering. So through dialysis, their waste products and excess substances can be removed. This is an artificial way of replacing the kidney functions. Dialysis is often used for various other external methods to separate inorganic ions such as chloride or sodium, or small organic molecules from high molecular weight species, such as proteins. The process happens mainly through diffusion, where substances travel from high concentration to low concentration according to an electrochemical gradient. A dialysate flow is on the opposite direction to the blood / fluid flow. While flowing in counter directions, substances travel from one media to another.
What is the difference between Dialysis and Ultrafiltration?
• Dialysis is an artificial method to imitate the ultrafiltration function happens in kidneys.
• In dialysis, the movement of substances from high concentration to low concentration takes place through an electrochemical gradient. In ultrafiltration, the substances travel due to a pressure gradient.
• The rate of ultrafiltration depends on the porosity of the membrane and the speed of blood flow (or the pressure created by the blood flow). The dialysis rate depends on the dialysate flow rate.