The kidneys contain about a million little clusters of looping blood vessels. Each cluster is called a glomerulus. When we talk about more than one glomerulus, we call them glomeruli. Each glomerulus is connected to a small tube called a tubule, and each glomerulus and tubule unit is known as a nephron. The body has about one million nephrons in each kidney.
The glomeruli work to filter the blood, and then waste products and fluid travel through the tubule and become urine. When someone suffers from a glomerular (kidney) disease, it means that their glomeruli are no longer working the way they should.