**Question:** All of the following statements are true for **metaphysis of bone** except:

A. The cortex is thicker than the spongiosa.
B. The spongiosa is an osteoid tissue.
C. The spongiosa has a lower mineralization than the cortex.
D. The spongiosa is composed of osteocytes only.

**Correct Answer: B.**

**Core Concept:** The **metaphysis** is the region of the long bones where the growth occurs and is divided into two layers: the outer layer of compact bone (cortex) and the inner layer of trabecular bone (spongiosa). Both layers have different functions and properties.

**Why the Correct Answer is Right:**

The correct answer (B) states that the **spongiosa** is an osteoid tissue. Osteoid tissue is a precursor to mature bone and is produced by osteoblasts, while spongiosa is the term for the inner layer of trabecular bone in the metaphysis. Osteoid tissue is found in the process of bone formation, not in the mature structure of the spongiosa.

**Why Each Wrong Option is Incorrect:**

A) The cortex is thicker than the spongiosa: This is incorrect because the spongiosa, despite being thinner, is the larger layer of the two.

C) The spongiosa has a lower mineralization than the cortex: This statement is partially correct, as the mineralization of the cortex is indeed higher due to its role in providing strength and protection.

D) The spongiosa is composed of osteocytes only: This is incorrect because osteocytes are the mature bone cells found in both the cortex and spongiosa. In the spongiosa, there are also osteoblasts and osteoclasts involved in bone remodeling and resorption.

**Clinical Pearl:** Understanding the properties of bone layers is crucial for understanding bone health, trauma, and diseases like osteoporosis that affect the mineralization and thickness of these layers.