Lecture Notes: Microscopic Structure of Bones

Introduction

• Topic: Microscopic structure of bones
• Previous video covered skeletal system and bone structures
• Essential to watch the previous video for better understanding

Main Cells of Bones

• Osteocytes: Main cells of the bones
• Osteoblasts: Build up bone
• Osteoclasts: Cut down bone
• Origin: Mesodermal
• Homeostasis maintained by balance between bone formation (osteoblasts) and bone destruction (osteoclasts)

Composition of Bones

• Bones are composed of matrix and minerals
• Type 1 Collagen: Main component of the matrix
• Calcium: Main mineral, forms hydroxyapatite crystals
• Collagen synthesis involves:
  • Rough endoplasmic reticulum
  • Pre-pro-collagen → Pro-collagen → Collagen
  • Post-translational modification
• Disruption in collagen synthesis leads to diseases

Haversian System

• Osteones: Form concentric lamellae
• Haversian System composed of:
  • Haversian Canal (longitudinal)
  • Volkmann's Canal (horizontal)
  • Purpose: Contain blood vessels, lymph vessels, and nerves for bone nourishment
  • Canaliculi: Small canals connecting lacunae, facilitate communication
• Bones are vascular, unlike avascular cartilage

Bone Remodeling

• Osteoclasts: Function like macrophages, phagocytic, share mesodermal origin
• Remodeling involves breaking down (osteoclasts) and rebuilding (osteoblasts)
• Factors affecting remodeling: Hormones, calcium, phosphate homeostasis

Role of Vitamin D

• Activation Process:
  • Requires sunlight, liver, gut, skin, kidney
  • Active form: 1,25-dihydroxyvitamin D (Calcitriol)
• Function: Calcium homeostasis
• Relation to Parathyroid Hormone (PTH):
  • PTH raises blood calcium, lowers phosphate
  • Vitamin D raises both calcium and phosphate
  • Calcitonin: Lowers calcium and phosphate

Conclusion

• Bone health relies on balance of osteoblasts and osteoclasts
• Vitamin D and PTH play crucial roles in maintaining calcium and phosphate levels
• For further learning, courses available on medicosisperfectionist.com

Additional Notes

• For more details, refer to the antibiotics, kidney physiology, and neuropharmacology courses available online
• Contact and support options provided

These notes provide a summary and structure to help understand the key concepts of bone microscopic structure and related physiological mechanisms.