Bone_Histology_Presentation by Dr.Rumaisa PT

THIS slide contains all the basic knowledge of bone tissues regarding histology containing all the types of bone cells spongy and compact bone Haversian system etc

1. Bone Histology Based on Histology by Laiq Hussain & Standard References By Dr. rumaisa pt

2. Introduction Bone = specialized connective tissue Functions: support, protection, locomotion, mineral storage, blood cell formation Highly vascular & metabolically active Dynamic tissue: undergoes continuous remodeling

3. Classification of Bones By shape: Long, Short, Flat, Irregular, Sesamoid By structure: Compact (cortical) bone, Spongy (cancellous/trabecular) bone

4. Microscopic Types of Bone Immature (Woven) Bone: Random collagen arrangement, more osteocytes, less mineralized Mature (Lamellar) Bone: Organized lamellae, stronger, more mineralized

5. Components of Bone Tissue Cells: Osteoprogenitor cells, Osteoblasts, Osteocytes, Osteoclasts Extracellular Matrix: Organic part (osteoid), Inorganic part (hydroxyapatite crystals)

6. Osteoprogenitor Cells Derived from mesenchymal stem cells Location: periosteum, endosteum Differentiate into osteoblasts Active in growth & fracture repair

7. Osteoblasts Bone-forming cells located on bone surfaces Secrete osteoid (organic matrix) Initiate mineralization Become osteocytes when embedded in matrix

8. Osteocytes Mature bone cells in lacunae Processes extend into canaliculi for nutrient exchange Maintain bone matrix Act as mechanosensors

9. Osteoclasts Large, multinucleated cells Derived from monocyte/macrophage lineage Located in Howship’s lacunae Resorb bone & release calcium Ruffled border: site of enzymatic degradation

10. Bone Matrix Organic (35%): Type I collagen, proteoglycans, glycoproteins Inorganic (65%): Hydroxyapatite crystals (Ca, P, Mg, Na) Hardness from minerals, tensile strength from collagen

11. Compact Bone Structure Organized into osteons (Haversian systems) Osteon: central Haversian canal, concentric lamellae, osteocytes in lacunae, canaliculi Volkmann’s canals connect Haversian canals

12. Spongy Bone Trabecular network with marrow spaces Lined by endosteum Trabeculae resist stress Found in epiphyses, vertebrae, flat bones

13. Periosteum and Endosteum Periosteum: Outer fibrous + inner osteogenic layer Endosteum: Thin osteogenic layer lining marrow cavity & trabeculae

14. Bone Formation (Ossification) Intramembranous: mesenchymal → osteoblasts (skull, clavicle) Endochondral: replaces cartilage model (long bones)

15. Remodeling of Bone Resorption by osteoclasts, deposition by osteoblasts Controlled by mechanical stress & hormones (PTH, calcitonin, vitamin D) Maintains strength & calcium homeostasis

16. Clinical Correlation Osteoporosis: decreased bone mass Rickets/Osteomalacia: defective mineralization (Vit D deficiency) Osteopetrosis: defective osteoclasts → brittle bones Fracture healing: hematoma, callus, remodeling

17. Summary Bone = specialized connective tissue with 4 cell types Matrix = organic + inorganic Compact vs. spongy bone structure Ossification: intramembranous & endochondral Bone undergoes continuous remodeling

18. References Laiq Hussain, Histology: A Text and Atlas Junqueira’s Basic Histology, 16th Ed. Wheater’s Functional Histology, 6th Ed.