Which statements correctly describe compact bone?
it forms the external walls of a long bone
in flat bones, it is called diploe
it is solid and relatively dense
it contains trabeculae
it is porous
The correct answer and explanation is:
Correct Statements About Compact Bone:
- It forms the external walls of a long bone. ✅
- It is solid and relatively dense. ✅
Explanation:
Compact bone, also known as cortical bone, is one of the two main types of bone tissue in the skeletal system, the other being spongy bone (cancellous bone). Compact bone plays a crucial role in providing structure, strength, and protection to bones.
1. It Forms the External Walls of a Long Bone
Compact bone primarily makes up the outer layer of long bones, such as the femur, humerus, and tibia. This dense layer of bone provides protection and structural integrity to the bone, allowing it to withstand mechanical stress and weight-bearing forces. The diaphysis (shaft) of a long bone is composed mostly of compact bone, which gives it durability and resistance to bending and breaking.
2. It Is Solid and Relatively Dense
Unlike spongy bone, which has a porous structure, compact bone is highly dense. It consists of osteons (Haversian systems), which are cylindrical structures that contain concentric layers of calcified matrix, called lamellae, surrounding a central canal. These central canals contain blood vessels and nerves that supply nutrients to bone cells (osteocytes). This dense organization makes compact bone extremely strong, capable of withstanding significant forces.
Incorrect Statements:
- “In flat bones, it is called diploë.” ❌
- Incorrect. The term diploë refers to the spongy bone found between two layers of compact bone in flat bones, such as the skull.
- “It contains trabeculae.” ❌
- Incorrect. Trabeculae are found in spongy bone, not compact bone. Trabeculae are the thin, web-like bony structures that help reduce bone weight while maintaining strength.
- “It is porous.” ❌
- Incorrect. Compact bone is not porous; it is dense and solid, unlike spongy bone, which has numerous open spaces.