Bone Structure and Composition Quiz

Bone Structure

Bone is the primary structural element of the human skeletal system, providing mechanical support, shielding vital organs, and acting as a reservoir for minerals such as calcium and phosphorus. It is composed primarily of collagen fibers and inorganic salts, specifically hydroxyapatite crystals made up of mainly calcium and phosphate ions. The structure of bone varies based on its function, with two main architectural subtypes: cortical and trabecular bones.

Periosteum

The periosteum is a thin layer of connective tissue covering all bones except the flat ones like the skull. It provides innervation, circulation, and nutrition to the outer third of bone segments. Periosteal blood vessels reach the Haversian canal via endosteum-lined Volkmann canals, which are channels traversing the osteon.

Compact Bone

Compact or cortical bone is the outer, dense layer of bone that makes up around 80% of adult bone mass. It is resistant to bending, torsion, and compression, and has a minimal role in metabolism. Compact bone is found mostly in the shaft of long bones, such as the femur and tibia, as well as the outer shell of trabecular bone.

Central Medullary Cavity

The central medullary cavity is the inner, hollow region within compact bone, where yellow marrow is stored. Yellow marrow consists mostly of fat cells and fewer immune cells than red marrow.

Bone Structure

Bone is a specialized connective tissue comprised chiefly of type I collagen fibers and inorganic salts. Type I collagen forms the soft framework for bone, while the inorganic salts harden the framework through crystal formation. Osteoblasts, the primary cellular component of bone, produce and arrange the organic matrix, initiating mineralization and controlling neighboring bone cell activities. Once the osteoid is mineralized, precursor cells become mature osteocytes, surrounded by lacunae.

Bone Marrow

Bone marrow exists in both the central medullary cavity and the inner portions of cancellous bones, which are meshlike structures. Red marrow, found in long bones' epiphyses and metaphysis regions, produces blood cells during hematopoiesis. White marrow, present in other areas, stores fat and has fewer immune cells compared to red marrow.