Bone Tissue and Long Bones Summary

Bone Tissue & Long Bones

Macroscopic Structure of Long Bones

  • Diaphysis: The shaft of a long bone, mainly composed of compact bone.
  • Epiphyses: The ends of the bone, containing spongy bone and red bone marrow; there are two epiphyses.
  • Yellow Bone Marrow: Located in the medullary cavity; stores fat.
  • Red Bone Marrow: Found within some bones, responsible for blood cell production.
  • Periosteum: A fibrous membrane covering the outer surface of the bone, containing blood vessels and nerves.
  • Articular Cartilage: Covers the joint surfaces, providing a smooth interface for movement.

Functional Classification of Bones

  • Total of 206 bones in the human body:
    • Types: long, flat, short, irregular, sesamoid.
    • Long Bones: Characterized as longer than they are wide; they support weight and allow movement.

Composition of Bone

  • Connective Tissue: Provides shape, support, and structure to the body.
  • Living Components: Cells such as osteocytes, osteoblasts, and osteoclasts.
  • Non-Living Components: The bone's matrix, composed of organic and inorganic materials.
Organic Matrix
  • Contains sugars and proteins, primarily collagen fibers.
  • Contributes to flexibility and tensile strength, enabling bones to resist stretching and twisting.
Inorganic Matrix
  • Composed of mineral salts, mainly calcium phosphates.
  • Provides hardness to bones, allowing them to resist compression.

Microscopic Structure of Bone

Compact Bone Structure
  • Osteons (Haversian System): The structural unit of compact bone.
    • Components:
    • Central Canal: Contains blood vessels and nerve fibers.
    • Lamellae: Rings of bony matrix that provide structure and flexibility.
    • Lacunae: Small spaces in the matrix that house osteocytes.
    • Canaliculi: Hairlike canals connecting lacunae and the central canal, allowing communication between osteocytes.
  • Each osteon functions as a weight-bearing pillar, providing strength to the bone.
Spongy Bone Structure
  • Trabeculae: Irregular plates of bone that form a network within spongy bone.
  • No osteons are present; cells (osteocytes) are located within lacunae.
  • Canaliculi connect the cells to capillaries in the surrounding endosteum.
  • Provides support and houses red bone marrow.

Bone Cells

  • Osteocytes: Mature bone cells that maintain the bone matrix.
  • Osteoblasts: Immature cells responsible for bone matrix formation.
  • Osteoclasts: Cells that break down and reabsorb bone tissue.
  • Bone Stem Cells: Give rise to new bone cells.

Nutrient Supply in Bone

  • Nutrients for osteocytes in spongy bone diffuse through canaliculi, sourced from capillaries in the endosteum surrounding trabeculae.

Conclusion and Activities

  • Review your knowledge by completing the "Microscopic Structure of Bone" worksheet.
  • Watch related videos on bone remodeling for visual learning.
  • Pre-read from Chapter 8.5 of the Human Perspectives textbook to reinforce concepts learned about bone.