Skeletal system

Question 1

Functions of Bone

Bone Classification
Long Bones: Longer than wide (e.g., femur, humerus).
Short Bones: Cube-shaped (e.g., wrist, ankle bones).
Flat Bones: Thin, flat, and curved (e.g., skull, sternum).
Irregular Bones: Complex shapes (e.g., vertebrae, hip bones).
Sesamoid Bones: Embedded in tendons (e.g., patella).
Bone Structure
Compact Bone: Dense outer layer, strong and rigid.
Spongy Bone: Lightweight, honeycomb structure (trabeculae).
Osteon (Haversian System): Cylindrical structural unit of compact bone.
Lacunae: Small cavities housing osteocytes.
Canaliculi: Tiny channels for cell communication.
Bone Growth and Development
Osteogenesis: Process of bone formation.
Endochondral Ossification: Bone replaces cartilage (e.g., long bones).
Intramembranous Ossification: Bone forms from fibrous tissue (e.g., skull).
Bone Remodelling
Bone Deposition: Osteoblasts build new bone where strength is needed.
Bone Resorption: Osteoclasts break down bone and release minerals.
Wolff’s Law: Bone adapts to mechanical stress.
Hormonal Regulation: Parathyroid hormone controls calcium release.
Key Questions
Which bone cells are responsible for resorption?
→ Osteoclasts
What is the primary function of osteocytes?
→ Maintain bone matrix and signal for repairs.
What type of bone growth increases width?
→ Appositional Growth
What type of ossification forms the skull?
→ Intramembranous Ossification
What does Wolff’s Law state?
→ Bone remodels in response to stress.
Where does blood cell production occur?
→ Red bone marrow
What structure in compact bone contains vessels and nerves?
→ Haversian (Central) Canal
What are the two main components of bone?
→ Collagen fibers and calcium salts

Answer 1

Structural Support: Provides a framework for the body.

Protection: Shields vital organs (e.g., brain, spinal cord).

Movement: Acts as levers for muscles.
Mineral Storage: Stores calcium and phosphate.

Fat Storage: Stores energy in yellow marrow.

Haemopoiesis: Produces blood cells in red marrow.

Question 2

Bone Composition

Answer 2

Collagen Fibers: Provide tensile strength.
Calcium Salts: Provide compressional strength.
Osteoid (Organic Component): Gel-like matrix.
Hydroxyapatite (Inorganic Component): Mineralised matrix.

Question 3

Bone Cells

Answer 3

Osteogenic Cells: Stem cells that differentiate into osteoblasts.
Osteoblasts: Build bone matrix.
Osteocytes: Maintain bone tissue and signal responses.
Osteoclasts: Break down bone tissue (resorption).