In all connective tissues, except....the cells secrete fibres of structural proteins called collagen or elastin.

Options

A. Blood
B. Bone
C. Cartilage
D. Areolar tissue

Explanation

To solve the question, we need to identify the connective tissue type that does not secrete fibers of structural proteins like collagen or elastin. Here’s the step-by-step solution:

### Step 1: Understand the Types of Connective Tissues
Connective tissues are a diverse group of tissues that support, bind, or separate other tissues and organs. They can be classified into various types, including loose connective tissue, dense connective tissue, adipose tissue, cartilage, bone, and blood.

### Step 2: Identify the Function of Connective Tissue Cells
Most connective tissue cells, such as fibroblasts, chondrocytes, and osteocytes, are responsible for producing fibers of structural proteins. Collagen provides strength and elasticity, while elastin allows tissues to return to their original shape after stretching.

### Step 3: Analyze the Options
The question implies that there is one type of connective tissue where the cells do not secrete collagen or elastin. Among the types of connective tissues, blood is unique because it is a fluid connective tissue and does not have a matrix composed of fibers like collagen or elastin.

### Step 4: Conclusion
Based on the analysis, the connective tissue that does not secrete fibers of structural proteins like collagen or elastin is **blood**.

### Final Answer
In all connective tissues, except **blood**, the cells secrete fibers of structural proteins called collagen or elastin.

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