Lecture Notes: Difference Between Compact and Spongy Bone

Overview

• Bones provide structural support and aid in body movement.
• Two types of bone tissue: compact and spongy bone.

Key Differences

• Compact Bone

  • Hard outer layers of bone
  • Also called cortical bone
  • Lacks spaces between lamellae
  • Contains yellow bone marrow (stores fat)
  • Composed of osteons
  • Strong and dense
  • Provides structural support
  • Found in the outer surface of long bones
  • Withstands up to 5000 pounds

• Spongy Bone

  • Inner porous layers of bone
  • Also called cancellous or trabecular bone
  • Contains spaces between lamellae
  • Contains red bone marrow (produces blood cells)
  • Composed of trabeculae
  • Less dense, lighter
  • Found in the middle of long bones and at bone ends
  • Cannot withstand high weights

Compact Bone Features

• Hard outer shell, strongest and densest bones.
• Contains passages for blood vessels and nerves.
• Covered by periosteum; inner surface covered by endosteum.
• Marrow cavity located in the shaft of long bones (diaphyses).
• Bone structure composed of hydroxyapatite (rich in calcium and phosphorous).
• Flexibility provided by collagen fibers.
• Structure made of osteons surrounding tiny central canals (Haversian canal).
• Osteogenic cells secrete bone matrix forming lamellae (osteocytes in lacuna).
• Canaliculi provide nutrients to osteocytes and connect lacunae.
• Provides structural support, protects organs, shapes the body, and stores minerals.

Spongy Bone Features

• Located in the middle of bones; less dense.
• Composed of mineral bars (trabeculae) forming latticework.
• Spaces filled with red bone marrow and blood vessels.
• Major component of ribs, shoulder blades, flat bones of the skull, and short flat bones.
• High metabolic activity.
• Transformation into compact bone by osteoblast activity.

Similarities

• Both types made of osseous tissue (connective tissue).
• Involved in body movement.
• Contain calcium.

Detailed Comparison

• Definition: Compact bone is non-cancellous; Spongy bone is osseous tissue with trabeculae.
• Alternative Names: Compact is cortical; Spongy is cancellous/trabecular.
• Composition: Compact has osteons; Spongy has trabeculae.
• Lamellae Spaces: Absent in compact; Present in spongy.
• Marrow Cavity: Present in compact; Absent in spongy.
• Calcium Content: High in compact; Low in spongy.
• Skeleton Weight Contribution: 80% compact; 20% spongy.
• Bone Shape: Cylindrical compact; Cuboidal spongy.
• Bone Marrow: Yellow in compact; Red in spongy.
• Bone Types: Compact in long bones; Spongy in short bones.
• Structure: Hard compact; Soft and porous spongy.
• Location: Inner surface compact; Outer layers spongy.
• Strength: High in compact; Low in spongy.
• Function: Structural support compact; Buffer for compact spongy.

Conclusion

• Compact and spongy bones serve different roles in the body based on their structure and function.
• The main difference lies in their density, composition, and function in the skeletal system.