AEMCA Practice Exam

How is the filtration process in the kidneys described?

1. Selective and active

2. Non-selective and passive

3. Selective and passive

4. Active and regulated

The correct answer is: Non-selective and passive

The filtration process in the kidneys is primarily a non-selective and passive one. This means that as blood flows through the kidneys, specifically in the glomeruli, substances such as water, electrolytes, and small molecules are filtered out of the blood without the need for energy expenditure. The process relies on hydrostatic pressure, allowing these substances to pass through the glomerular membrane into the Bowman’s capsule. This passive filtration is driven by the difference in pressure, and it allows for a wide range of solutes to enter the renal tubules. While some filtration processes later along in the nephron may involve selective reabsorption or secretion, the initial filtration at the glomerulus does not selectively choose which molecules to filter based on their properties, hence it is termed as non-selective. The other processes that occur in the nephron, such as reabsorption and secretion, can be selective, active, or regulated, but they occur after this initial passive filtration step. Therefore, this context confirms that option B aptly describes the filtration process in the kidneys.