Lecture Notes: Microscopic Structure of Bones

Introduction

• Discussion: Microscopic structure of bones
• Previous video: Introduction to the skeletal system
• Important Cells:
  • Osteocytes: Main bone cells
  • Osteoblasts: Build bone
  • Osteoclasts: Cut down bone (similar origin to macrophages)

Bone Composition

• Matrix: Consists of Type 1 Collagen
• Minerals: Primarily calcium (forms hydroxyapatite crystals)
• Collagen: Starts as pre-pro-collagen, becomes pro-collagen, then collagen
  • Post-translational modification is crucial
  • Disruption leads to diseases (pathology)

Haversian System

• Bone Layers: Known as lamellae
• Osteons: Organized structure of matrix and minerals
  • Haversian Canal: Longitudinal, contains blood vessels
  • Volkmann's Canal: Horizontal, connects Haversian canals
• Lacunae: Houses osteocytes
• Canaliculi: Small canals connecting lacunae

Bone Nourishment

• Bones are vascular (unlike cartilage)
  • Contains blood, lymph vessels, and nerves

Vitamin D and Calcium Homeostasis

• Essential for calcium regulation
• Active form requires:
  • Sunlight
  • Liver
  • Gut
  • Skin
  • Kidney
• Process:
  • Liver and skin add hydroxyl groups
  • Kidney produces 1,25-dihydroxyvitamin D (calcitriol)

Parathyroid Hormone (PTH) and Calcitonin

• PTH: Raises calcium in blood, lowers phosphate
  • Acts on gut, bone, kidney
• Calcitonin: Lowers calcium and phosphate
• Vitamin D: Increases both calcium and phosphate

Bone Remodeling

• Continuous process involving osteoclasts and osteoblasts
• Affected by hormones and mineral balance

Additional Information

• Mention of online courses related to medicine and physiology
• Encouragement to subscribe and engage with content