Which of the following statements about the glomerular filtration is CORRECT ?
I. The hydrostatic pressure of blood in glomerular capillaries allows filtration.
II. The diameter of the efferent arteriole is lesser than the diameter of the afferent arteriole.
III. The fluid collected in the urinary space contains all constitution of blood except RBCs.
IV. The net filtration pressure at the glomerulus is around 40 mm Hg.

Options

A. I and III
B. II and IV
C. I and II
D. III and IV

Answer

To determine which statements about glomerular filtration are correct, let's analyze each statement step by step.

### Step 1: Analyze Statement I
**Statement I:** The hydrostatic pressure of blood in glomerular capillaries allows filtration.

- **Explanation:** The hydrostatic pressure in the glomerular capillaries is indeed the primary force that drives the filtration of blood into the Bowman’s capsule. This pressure is generated by the blood flow from the afferent arteriole into the glomerulus. Therefore, this statement is **correct**.

### Step 2: Analyze Statement II
**Statement II:** The diameter of the efferent arteriole is lesser than the diameter of the afferent arteriole.

- **Explanation:** The afferent arteriole has a larger diameter compared to the efferent arteriole. This difference in diameter creates a pressure gradient that facilitates filtration. Therefore, this statement is also **correct**.

### Step 3: Analyze Statement III
**Statement III:** The fluid collected in the urinary space contains all constituents of blood except RBCs.

- **Explanation:** The fluid that enters the Bowman’s capsule (glomerular filtrate) does not contain red blood cells (RBCs), white blood cells (WBCs), or plasma proteins because their sizes are too large to pass through the filtration slits. Thus, this statement is **incorrect** because it does not mention WBCs and plasma proteins.

### Step 4: Analyze Statement IV
**Statement IV:** The net filtration pressure at the glomerulus is around 40 mm Hg.

- **Explanation:** The net filtration pressure is calculated by considering the hydrostatic pressure and the opposing pressures (osmotic and capsular pressures). The typical value for net filtration pressure is around 10 to 25 mm Hg, not 40 mm Hg. Therefore, this statement is **incorrect**.

### Conclusion
Based on the analysis:
- **Correct Statements:** I and II
- **Incorrect Statements:** III and IV

Thus, the correct answer is that statements I and II are correct regarding glomerular filtration.

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