Feb 22 2009
Kidney Circulation
Blood enters the kidney by the renal artery, a thick branch from the descending aorta. In the hilar, is divided into several branches which are distributed by the kidneys and the lobes are forming numerous branching afferent arterioles that form the glomerular ball. These are the walls of these capillaries that act as the Ultra Filters, allowing the passage of small particles. The blood that comes out through the efferent arteriole circulates through the blood vessels of the kidney (the real kidney capillaries that provide oxygen and the nutrients required for their function). These capillaries are grouped to form the renal vein, which in turn, poured into the inferior vena cava.
Given the role of the kidneys to eliminate waste products through urine, it is not surprising that these organs are receiving greater amounts of blood per gram of weight. One way to express the renal blood flow is to consider the renal fraction or fraction of cardiac output passing through the kidneys. For example, a subject of some 60 kg of weight, cardiac output is about 6 liters / minute, assuming 20% renal fraction (1.6 liters / min) of this volume. Dividing this volume by the weight of both kidneys, obtained a blood flow of 420 ml/min/100 g of tissue, flow substantially greater than the liver or muscle at rest.
The regulation of blood flow in the glomeruli is accomplished by three formations: the bearing polar cells of the macula densa and Goormaghtigh. The bearing consists of a polar wall thickening of the afferent arteriole before it enters the renal glomerulus. The arteriole loses its elastic membrane, the endothelium becomes discontinuio of the tunica media and is available in two layers, formed by secretory cells, these secretory cells produce erythropoietin and angiotensin. Goormaghtigh cells are arranged in the angle between the afferent arterioles and efectente and gather in small columns. Are highly related to the cells bearing polar. Between the two formations is the macula densa (macula densa or Zimmerman) that is in contact with the distal tubule and the afferent arteriole just before it enters the glomerulus. These three formations bearing polar cells of the macula densa and Goormaghtigh forming apparatus yuxtaglomerular. which is what regulates the flow of blood in the glomerulus.