Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Collagen fibers cannot be seen in standard histological preparation of hyaline cartilage.
Reason (R) : The ground substance and collagen fibers of hyaline cartilage have same refractive index.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

The word hyaline comes from *hyalos*, meaning "glass".
The glassy, uniform look of the matrix is due to the identical refractive indices of the ground substance and the embedded Type II collagen fibers.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Hyaline cartilage is the most common type of cartilage in the body, providing structural support with flexibility.
It contains a dense network of collagen fibers (mainly Type II) embedded within a highly hydrated gel-like ground substance.
The visibility of these structures under a light microscope depends on optical properties like refractive indices.

Step 2: Detailed Explanation:
Let us analyze the structural and optical properties of hyaline cartilage:
- Refractive Index Match: The ground substance of hyaline cartilage is rich in proteoglycans, glycosaminoglycans, and water.
The Type II collagen fibers embedded within this matrix are extremely fine.
Crucially, these collagen fibers have virtually the same refractive index as the surrounding ground substance.
- Microscopic Appearance: When light passes through a standard histological section of hyaline cartilage, it is not refracted at the interface between the fibers and the matrix.
As a result, the matrix appears glassy and homogeneous (hence the name "hyaline," from the Greek word for glass), and the individual collagen fibers are invisible under a standard light microscope.
Specialized techniques, such as polarized light microscopy or histochemical staining, are required to reveal these underlying fibers.
Therefore, the assertion is correct, the reason is correct, and the reason directly explains the assertion.

Step 3: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A). This corresponds to option (A).