Glomeruli are the components that carry out the primary filtering action of the kidney. They connect on one side to the blood vessels that enter the kidney, and on the other side to fluid-collecting structures called tubules. The glomeruli accept the blood from the arteries and pass the filtered wastes and any extra water present into the tubules, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
Scientists use the term nephron to refer to a single glomerulus and its associated tubule. Each human kidney contains approximately 1 million individual nephrons. The National Institute of Diabetes and Digestive and Kidney Diseases states that in healthy kidneys, the glomeruli filter wastes, while retaining proteins and red blood cells in the blood stream. However, sometimes disease can alter this process, allowing protein or red blood cells to pass through the glomeruli and into the tubules.
Springfield Technical Community College explains that the rate at which the glomeruli filter blood is an important factor in the way the body functions and overall health. This rate is called the glomeruli filter rate, or GFR. Humans generally have a GFR of 125 milliliters per minute. Over the course of 24 hours, this translates to about 180 liters. As the human body only contains about 5 liters of blood, this means that the total volume of blood in the body is filtered over 50 times per day.