State one difference between spongy bone and compact bone.

Explanation

### Step-by-Step Solution:

1. **Definition of Spongy Bone**: Spongy bone, also known as cancellous bone, is characterized by its porous structure. It contains red bone marrow and lacks a regular Haversian system.

2. **Definition of Compact Bone**: Compact bone, on the other hand, is dense and forms the outer layer of the bone. It contains yellow bone marrow and has a well-organized Haversian system.

3. **Key Difference**: The primary difference between spongy bone and compact bone is that spongy bone does not have a regular Haversian system, while compact bone does. This structural difference leads to variations in their functions, such as the way they provide oxygen and nutrition to the bone tissue.

...