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.

**Analysis:** This statement is correct. The hydrostatic pressure in the glomerular capillaries is the primary force that drives the filtration of water and solutes from the blood into the Bowman’s capsule. This pressure is generated by the heart and is higher in the glomerular capillaries compared to other capillaries in the body, facilitating the filtration process.

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

**Analysis:** This statement is also correct. The afferent arteriole, which brings blood into the glomerulus, has a larger diameter compared to the efferent arteriole, which carries blood away from the glomerulus. This difference in diameter helps maintain the high pressure necessary for filtration.

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

**Analysis:** This statement is incorrect. While the fluid collected in the urinary space (filtrate) does contain most of the constituents of blood plasma, it does not contain proteins due to their larger size, which prevents them from passing through the filtration membrane. Therefore, it is not accurate to say it contains all constituents except RBCs.

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

**Analysis:** This statement is also incorrect. The net filtration pressure (NFP) at the glomerulus is typically around 10 mm Hg, not 40 mm Hg. The NFP is calculated by considering the hydrostatic pressure in the glomerular capillaries and the opposing pressures from the Bowman’s capsule and the osmotic pressure of the blood.

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

### Final Answer
The correct answer is that statements I and II are correct.