Lecture Notes on Bones and Skeletal System

Introduction to Bones

• Bones are a type of connective tissue.
• Lecture covers: structure of bone, types of bones, and skeletal cartilage.

Skeletal Cartilage

• Characteristics:
  • Contains a lot of water, aids in tension and compression resistance.
  • Contains chondrocytes in lacunae within extracellular matrix.
• Types of Cartilage:
  • Hyaline Cartilage:
    • Most abundant skeletal cartilage.
    • Locations: nose, ribs, larynx, and ends of bones.
  • Elastic Cartilage:
    • Stretchy, found in ears and epiglottis.
  • Fibrocartilage:
    • Highly compressible, found between vertebrae.

Bone Categories

• Axial Bones:
  • Located in head and torso (spine, rib cage, skull).
• Appendicular Bones:
  • Includes limbs (arms, legs), pelvis, and shoulders.

Bone Classifications by Shape

• Long Bones: Longer than wide (e.g., limb bones).
• Short Bones: Cube-like (e.g., ankles, wrists).
• Flat Bones: Thin, often curved (e.g., sternum, shoulder blades).
• Irregular Bones: Complex shapes (e.g., vertebrae, hip bones).

Functions of Bones

• Support and protection (e.g., rib cage protects heart).
• Act as levers for movement.
• Mineral storage (calcium, phosphate).
• Fat storage, hormone production, blood cell formation.

Bone Composition

• Bone as Tissue vs. Organ:
  • Bone tissue is part of the organ, which includes other tissues (nervous, connective, cartilage).
• Gross Anatomy of Bones:
  • Compact Bone: Dense outer layer.
  • Spongy Bone: Honeycomb structure inside.
  • Bone Marrow:
    • Yellow marrow: fat storage.
    • Red marrow: blood cell production.
• Long Bone Structure:
  • Diaphysis: Tubular shaft with compact bone and medullary cavity.
  • Epiphyses: Ends containing spongy bone.
  • Periosteum: Outer membrane with fibrous and osteogenic layers.
  • Endosteum: Covers internal surfaces.
• Bone Markings: Projections, depressions, openings.

Microscopic Anatomy of Bones

• Types of Bone Cells:
  • Osteogenic Cells: Stem cells in periosteum and endosteum.
  • Osteoblasts: Bone matrix secretion and bone growth.
  • Osteocytes: Mature cells maintaining bone matrix.
  • Bone Lining Cells: Maintain matrix on bone surface.
  • Osteoclasts: Break down bone, release minerals.
• Structure of Compact Bone:
  • Osteons: Cylindrical units with central canal.
  • Lamellae: Hollow tubes within osteons.
  • Central Canal: Contains blood vessels and nerve fibers.
  • Canaliculi: Tiny canals connecting lacunae.
  • Interstitial and Circumferential Lamellae: Fill gaps and surround osteons.

Chemical Composition of Bone

• Organic Components:
  • Cells and osteoid (ground substance, collagen fibers).
• Inorganic Components:
  • Hydroxyapatites (calcium phosphate crystals).
• Collaboration of organic and inorganic components ensures bone strength and durability.

Conclusion

• Overview of how bone structure forms the human skeleton.