Bone Structure Lecture Notes

Introduction to Bone as an Organ

• Bones are considered organs.
  • Contain osseous tissue, nervous tissue, cartilage, fibrous connective tissue, muscle cells, and epithelial cells.

Levels of Bone Study

1. Gross Anatomical Level
   • Observations with the unaided eye.
2. Microscopic and Chemical Levels
   • Focus of the chapter.

Types of Bone

• Compact Bone
  • Dense outer layer, smooth and solid.
  • Forms outer boundary.
• Spongy Bone
  • Honeycomb structure, trabeculae.
  • Contains marrow, lighter, resists tension.

Structure of Bones

Short, Irregular, and Flat Bones

• Diploë: Thin plates of spongy bone covered by compact bone.
• Membranes
  • Periosteum: Surrounds outside of compact bone, attachment point for tendons/ligaments.
  • Endosteum: Lines inner chambers, nourishes bone.
• Bone Marrow: Scattered throughout spongy bone.

Long Bones

• Diaphysis: Shaft, tubular structure, contains medullary cavity with yellow marrow.
• Epiphysis: Rounded ends, spongy bone, covered with articular cartilage.
• Epiphyseal Line/Plate
  • Plate: Hyaline cartilage for growth in youth.
  • Line: Remnant in adults.

Internal Bone Structure

• Medullary Cavity
  • Contains yellow marrow (triglycerides storage).
• Periosteum
  • Dense, fibrous, surrounds bone.
  • Contains nerve fibers and blood vessels.
• Endosteum
  • Lines inner surfaces, supports bone nourishment.
  • Contains osteogenic cells for bone repair.

Vascular Nature of Bone

• High vascularity.
• Contains blood vessels for nourishment and growth.

Bone Markings

• Sites of muscle, ligament, tendon attachment, joint formation, and passageways for vessels/nerves.
• Types of Markings
  • Projections: Outward bulges for muscle pull.
  • Depressions: Bowl/groove for passages or joints.
  • Openings: Holes/canals for vessels/nerves.

Specific Bone Markings

• Projections for Attachment
  • Tuberosities: Large, rounded projections.
  • Trochanters: Large, blunt processes.
  • Crests and Lines: Narrow ridges.
• Joint Formations
  • Heads and Facets: Expansion and smooth surfaces.
  • Condyles: Rounded articular projections.
  • Ramus: Arm-like bone bars.
• Depressions and Openings
  • Grooves, Fissures, Foramina, Notches, Meatuses, Fossae, Sinuses: Various bone cavities and passages.

Conclusion

• Understanding bone structure is critical for comprehending its function as an organ and its role in the body.