Long ducts of collecting tubules extend from

Options

A. cortex to inner part of medulla
B. medulla to outer cortex
C. medulla to inner cortex
D. cortex to outer part of medulla.

Explanation

### Step-by-Step Solution:

1. **Understanding the Structure of the Kidney**:
- The kidney is a vital organ responsible for excretion and filtration of blood. It has several parts, including the cortex and medulla.

2. **Identifying the Collecting Tubules**:
- The collecting tubules are structures within the kidney that collect urine from the nephrons, which are the functional units of the kidney.

3. **Locating the Ducts**:
- The long ducts of the collecting tubules extend from the outer region of the kidney, known as the cortex, and travel towards the inner region, known as the medulla.

4. **Conclusion**:
- Therefore, the long ducts of the collecting tubules extend from the cortex to the inner part of the medulla.

5. **Final Answer**:
- The correct answer is: "The long ducts of collecting tubules extend from the cortex to the inner part of the medulla."