Explain the terms ultrafiltration and selective absorption.
Ultrafiltration
The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent (outgoing) arteriole is narrower than the afferent (incoming) arteriole. This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called ultrafiltration. During ultrafiltration almost all the liquid part of the blood comes out of the glomerulus and passes into the funnel-shaped cavity of the Bowman’s capsule. The fluid entering the renal tubule is called the glomerular filtrate. The glomerular filtrate consists of water, urea, salts, glucose, and other plasma solutes. The thicker part of the blood left behind in the glomerulus after ultrafiltration.
Selective absorption
The glomerular filtrate entering the renal tubule is not urine. It is an extremely dilute solution containing a lot of useful materials including glucose and some salts such as those of sodium. As the filtrate passes down the tubule, much of the water is reabsorbed together with the useful substances. But their reabsorption is only to the extent that the normal concentration of the blood is not disturbed.
Ultrafiltration
The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent (outgoing) arteriole is narrower than the afferent (incoming) arteriole. This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called ultrafiltration. During ultrafiltration almost all the liquid part of the blood comes out of the glomerulus and passes into the funnel-shaped cavity of the Bowman’s capsule. The fluid entering the renal tubule is called the glomerular filtrate. The glomerular filtrate consists of water, urea, salts, glucose, and other plasma solutes. The thicker part of the blood left behind in the glomerulus after ultrafiltration.
Selective absorption
The glomerular filtrate entering the renal tubule is not urine. It is an extremely dilute solution containing a lot of useful materials including glucose and some salts such as those of sodium. As the filtrate passes down the tubule, much of the water is reabsorbed together with the useful substances. But their reabsorption is only to the extent that the normal concentration of the blood is not disturbed.
