**Question:** The tensile strength of a bone is due to -

A. Collagen fibers
B. Mineralization
C. Osteons
D. Membrane-bound cells

**Core Concept:** The tensile strength of a bone is primarily determined by the arrangement and quality of its components, particularly collagen fibers and mineralization. Osteons, which are the structural units of bone, contribute to its mechanical strength, but they are not solely responsible for its tensile strength. Membrane-bound cells play a role in bone remodeling and maintenance, but they do not directly determine the bone's tensile strength.

**Why the Correct Answer is Right:** The correct answer is A. Collagen fibers, as they are the primary structural component of bone and provide tensile strength. Collagen fibers are arranged in a specific pattern, known as the "woven" or "cable" pattern, which enhances their tensile strength. Additionally, the mineralization process, which involves the deposition of calcium phosphate crystals, increases the bone's overall hardness and resistance to compressive forces but does not directly contribute to its tensile strength.

**Why Each Wrong Option is Incorrect:**

B. Mineralization is crucial for bone strength but does not solely account for tensile strength. The mineral components enhance the bone's compressive strength but not tensile strength.

C. Osteons are structural units of bone that contribute to its mechanical properties. While osteons do play a role in bone strength, they are not the primary determinant of tensile strength.

D. Membrane-bound cells, such as osteocytes, osteoblasts, and osteoclasts, are essential for bone remodeling and maintenance. Although these cells contribute to bone health, they do not directly determine the bone's tensile strength.

**Clinical Pearl:** The correct answer, collagen fibers, highlights the importance of understanding the structural components of bone and their roles in determining bone strength. This knowledge is essential for understanding bone health, fracture repair, and the effects of various diseases and treatments on bone quality.

**Correct Answer:** A. Collagen fibers