Introduction

Three separate processes contribute to the formation of urine within the nephron of the kidney. These are filtration, reabsorption and secretion. We shall be considering the first of these, filtration.

Filtration occurs in the glomerulus of the nephron. The glomerulus is a capillary bed within the nephron, and filtration of fluid out of the glomerulus occurs both as a result of the structure of the nephron, and of Starling's forces. The glomerulus is part of the vascular structure of the nephron. It is a dense capillary bed – or capillary tuft – that emerges from an afferent arteriole, and returns to an efferent arteriole.