Bone Histology Quiz

Bone Histology

• Bone is a highly specialized type of connective tissue (CT).
• Its matrix is calcified, making it hard and strong enough to support the body.
• Like all CT, bone is composed of cells, fibers, and a hard matrix.
• Bone is classified anatomically as long (e.g., humerus, femur), short (e.g., carpal, tarsal bones), flat (e.g., skull, ribs), and irregular (e.g., vertebrae).
• Bone functions include support, protection, movement, mineral storage, and blood cell formation.

Learning Objectives

• Classify bone anatomically and histologically.
• Identify the location of compact and spongy bone in the human body.
• Understand the microscopic structure of bone.

Histological Classification

• Compact Bone: Dense, solid, and lacks visible spaces.
• Forms the shaft of long bones and the outer layer of other bone types.
  • Composed of lamellae (layers) without visible cavities.
• Cancellous (Spongy) Bone: Irregular arrangement of branching, anastomosing bony trabeculae (thin plates).
  • Located within the interior of flat bones, short bones, irregular bones, and the epiphyses of long bones.
  • Contains bone marrow cavities.

Bone Structure

• Bone Cells:

  • Osteogenic cells (osteoprogenitor cells): Stem cells that differentiate into osteoblasts.
  • Osteoblasts: Bone-forming cells that synthesize osteoid tissue.
  • Osteocytes: Mature bone cells, maintaining the bone matrix.
  • Osteoclasts: Multinucleated cells that resorb bone. Located in Howship's lacunae. They accomplish resorption by secreting enzymes and releasing hydrogen ions.

• Ground Substance: Organic components like collagen (Type I) and proteoglycans, which are 35% of this bone tissue but without water.

• Hydroxyapatite Crystals: Inorganic component (Ca phosphate and hydroxide), making up 65% of this bone tissue (with water, total amount is almost 100%). They are deposited on collagen fibers to harden the matrix.

Compact Bone Histology

• Periosteum: Outer fibrous layer.
• External Circumferential Lamellae: Layers immediately beneath the periosteum.
• Haversian System (Osteon): Fundamental unit of compact bone. Concentric layers (lamellae) surrounding a central (Haversian) canal, that contains blood vessels, nerves, and loose connective tissue(CT). Haversian canals communicate with other channels via Volkmann's canals.
• Interstitial Lamellae: Irregularly arranged lamellae between Haversian systems.
• Internal Circumferential Lamellae: Layers lining the medullary cavity.
• Endosteum: Single layer of osteoblasts lining the marrow cavity.

Spongy Bone Histology

• Composed of irregular branching, anastomosing bony trabeculae (thin plates) separated by spaces that contain bone marrow.
• Each trabeculum is formed of irregularly arranged lamellae enclosing osteocytes.
• Spongy bone lacks osteons.

Test your knowledge on bone histology with this quiz. Explore the classifications of bone types, their functions, and the microscopic structures of compact and spongy bone. Perfect for students of anatomy and physiology.