Functions and Composition of Bones

Study Notes

Functions of the Skeleton

Supports locomotion and bodily functions.
Protects soft tissues and vital organs.
Provides an environment for bone marrow.
Serves as a reservoir for minerals.

Bone Composition

Bone consists of 30% organic components, allowing maintenance and adaptability to microtrauma.
- Includes collagen type I (osteoid), osteoblasts, osteoclasts, periosteum, blood vessels, and nerves.
70% inorganic components in bone structure.
- Primarily calcium phosphate deposits and hydroxyapatite.

Types of Bones

Flat bones: e.g., sternum, scapula.
Long bones: e.g., femur, tibia, radius, ulna.
Small irregular bones: e.g., bones of the wrist and foot.

Structure of Long Bones

Composed of three main regions:
- Diaphysis: the cylindrical shaft.
- Metaphysis: flares out from the diaphysis.
- Epiphysis: the end part; separated from metaphysis by the epiphyseal line where growth occurs.

Types of Bone Tissue

Lamellar Bone:
- Organized structure enhancing function and load resistance.
- Features concentric sheets of collagen with mineral deposits, forming hollow cylinders.
- Cortical bone: densely packed outer layer for strength.
- Cancellous bone: loosely organized inner layer in a lattice form (not woven).
Woven Bone:
- Disorganized arrangement, formed rapidly during childhood or fracture healing.

Bone Mechanics

Inorganic components resist compression; they are stiff and brittle.
Organic components provide elasticity, resisting tension and shear forces.

Types of Fractures

Trauma Fracture: caused by excessive force overpowering bone structure.
Stress Fractures: arise from repetitive low-magnitude forces leading to microdamage.
Pathological Fractures: occur due to weakened bone from diseases.

Stress Fractures

Result from overuse or sudden activity increase causing microfractures.
Common in lower extremities and associated with specific sports like tennis and running.
X-ray may show delayed changes; CT or MRI usually needed for diagnosis.
Treatment primarily involves rest, sometimes requiring casting.

Pathological Fractures

Caused by conditions altering bone's mechanical properties, such as:
- Primary bone tumors.
- Metastatic tumors.
- Osteomalacia: compromised mineralization.
- Osteoporosis: reduced bone mineral density.

Phases of Fracture Healing

Hematoma Phase:
- Occurs immediately post-injury; blood vessels are damaged leading to hematoma formation.
- Hematoma serves as a scaffold for healing, and osteoclasts begin to resorb damaged bone.
Reparative Phase:
- Cells from the periosteum migrate into the hematoma, creating substrates.
- Chondroblasts produce hyaline cartilage; osteoblasts synthesize woven bone—collectively known as soft callus.
- The soft callus transitions through endochondral ossification to mature bone.
Remodeling Phase:
- The soft callus matures under mechanical stress into hard callus.
- Wolf’s Law dictates bone remodeling in response to physical stress, with osteoclasts and osteoblasts working to strengthen the area.
- Encouragement to bear weight aids in stimulating callus formation and maturation.

Description

This quiz explores the essential functions of the skeleton, including support for locomotion, protection of vital organs, and mineral storage. It also delves into the composition of bones, types of bones, and the structure of long bones. Test your knowledge on these fundamental concepts in anatomy.