The transfer of fluid from the glomerulus to Bowman’s capsule results from active transport transfers large molecules as easily as small ones is very selective as to which subprotein-sized molecules are transferred is mainly a consequence of blood pressure in the capillaries of the glomerulus
The Correct Answer and Explanation is:
The correct statement is: The transfer of fluid from the glomerulus to Bowman’s capsule is mainly a consequence of blood pressure in the capillaries of the glomerulus.
Explanation:
The process of filtration in the kidneys primarily occurs in the glomerulus, which is a network of capillaries located in the nephron. This filtration process allows the transfer of fluid (called the filtrate) from the blood in the glomerular capillaries into Bowman’s capsule, which is the first part of the nephron. The mechanism driving this transfer is blood pressure in the glomerular capillaries.
- Blood Pressure and Filtration: The glomerular capillaries have a high blood pressure due to their unique anatomical structure. The afferent arteriole, which brings blood into the glomerulus, is wider than the efferent arteriole, which carries blood out. This difference in diameter creates a pressure gradient, causing fluid and small solutes to pass through the porous walls of the glomerular capillaries into the Bowman’s capsule. This process is passive and driven by the high blood pressure, not by active transport.
- Selective Filtration: The filtration barrier between the glomerular capillaries and Bowman’s capsule is very selective. It allows small molecules like water, glucose, salts, and urea to pass through, but larger molecules, like proteins and blood cells, are usually retained in the blood. The filtration membrane has three layers: the endothelium of the glomerular capillaries, the basement membrane, and the podocytes of Bowman’s capsule. These layers prevent large molecules from passing while permitting small molecules to filter through.
- Active Transport: Active transport plays a role in later stages of renal function, such as reabsorption in the proximal convoluted tubule. However, filtration itself, as described here, is largely a passive process driven by blood pressure.
Therefore, while the process is selective, it is primarily blood pressure that drives the movement of fluid from the glomerulus into Bowman’s capsule. Active transport is not involved in this initial filtration process.
