WHERE AM I?

1. WHERE AM I? Online Anatomy Module 1 INTRO & TERMS CELL EPITHELIUM CARTILAGE MUSCLE NERVOUS SYSTEM AXIAL SKELETON APPENDICULAR SKELETON MUSCLES EMBRYOLOGY

2. SKELETON & DISTINCT CARTILAGE ‘SKELETONS’ Ear cartilage Nasal cartilage Cartilage participates as pieces that develop, and stay attached to the skeleton Xiphoid process an extension to the breast-bone Other cartilages act as separate skeletal elements in their own right: supporting the larynx (voice-box) [feel its firmness on yourself] and the trachea (windpipe) & bronchi

3. CARTILAGE & ITS SITES Ears Cartilage is a firm, but flexible, pressure-resisting tissue, needed to support and connect other tissues and structures Nose Airway Ends of ribs Spine disks Joints

4. CARTILAGES: Technical names Auricular cartilage Ears Nasal/septal cartilage Nose Laryngeal & tracheal cartilages Airway Ends of ribs Costal cartilages Spine disks Intervertebral disks Joints Articular cartilages

5. CARTILAGE PG H2O Cartilage cells introduceto the tissue resistance to pressure & an ability to recover shape , principally by aggregated proteoglycans able avidly to bind water. The PGs themselves are held in place by a meshwork of fine collagen fibrils (tiny fibers). Chondrocytes make a Matrix of Collagen II fibrilmeshwork trapping aggregated ProteoglycansPGs L - Link protein L L L aggregating backbone ofHYALURONAN L PGs bind PG

6. CARTILAGE vertebral endplate Cartilage cells introduceto the tissue resistance to pressure & an ability to recover shape, principally by aggregated proteoglycans able avidly to bind water. The PGs themselves are held in place by a meshwork of fine collagen fibrils. Fibrocartilage is dense fibrous tissue with chondrocytes & their PGs substituted for fibroblasts Intervertebral disk is under pressure, but has tensile strength to resist bursting and pull fibrocartilage of annulus fibrosus nucleus pulposus

7. CARTILAGE Fibrocartilage is dense fibrous tissue with chondrocytes & their PGs substituted for fibroblasts Intervertebral disk is under pressure, but has tensile strength to resist bursting and pull fibrocartilage of annulus fibrosus Fibril orientation differs from one fibrous layer to the next nucleus pulposus

8. CARTILAGE Intervertebral disk is under pressure, but usually has enough tensile strength to resist bursting and pull, however fibrocartilage of annulus fibrosus nucleus pulposus Herniated/ruptured disk pressing on nerve leaving spinal canal, e.g., causing sciatica

9. JOINT/ARTICULAR CARTILAGE resilient, thin, lubricated, attached, living, nourished, modifiable, vulnerable Bone Joint capsule Muscle

10. JOINT TERMS SYNOVIUM Joint capsule j c o a i v n i t t . y Joint cartilageabsorbs and spreads load Spongy subchondral bone absorbs and directs load to shaft { loose connective tissue lining cells

11. SKELETON & CARTILAGE Cartilage provides some flexibility & recovery of shape at critical places Cartilage participates as pieces that develop, and stay attached to the skeleton Other cartilage develops with bones (indeed, it precedes the bone), then remains at the ends to make the joint surface or articular cartilage Facial and skull vault/dome bones form with negligible cartilage present

12. SKELETAL DEVELOPMENT Skeletal piece of hyaline cartilage Grows by internal expansion and from the surface Cell enlargement/hypertrophy Matrix calcification Calcified cartilage can be resorbed like bone, and be attached to bone selective erosion into mineralized cartilage

13. LATER ENDOCHONDRAL OSSIFICATION Articular cartilage Growth/epiphyseal plate Secondary ossificationcenters Shaft bonegrows by deposition on the outside, with mild resorption on the inside surface, plus osteonal remodelling in the interior + - Bone would belarger thanin theprevious view

14. JOINT CARTILAGE Chondrocytes in holes/lacunae Matrix Spongy subchondral bone layer of mineralizedcartilage for attachment to bone

15. PG H2O JOINT CARTILAGE Chondrocytes make a Matrix of Collagen II fibrilmeshwork trapping aggregated ProteoglycansPGs L - Link protein L L L aggregating backbone ofHYALURONAN L PGs bind PG

16. H2O SO4 SO4 SO4 coo H2O PROTEOGLYCAN STRUCTURE & H2O-BINDING Sugar side-chains of repeating pairs (disaccharides) } -XL- GA-GU- GA-GU- GA-GU- GA-GU- Core protein Side chains bear-bindingcharged groups which mutually repel, but cannot disperse because ofO2 bonds& anchorage to thecore protein

17. ARTICULAR CARTILAGE NUTRITION NutritionSYNOVIAL FLUIDLubrication Why via synovial fluid? #1 Load-bearing surface, therefore vessels would not survive Nutrition from marrow blocked by mineralized-cartilage layer

18. JOINT/ARTICULAR CARTILAGE Resilient - Meshwork loaded with H2O-trapping huge molecules Lubricated - Synovial fluid & its special molecules Attached - Via mineralized lowest layer to subchondral bone Living - Matrix allows diffusion to chondrocytes in lacunae Nourished - From synovial vessels via synovial fluid Modifiable- Cells continue to make & selectively destroy ECM

19. JOINT CARTILAGE VULNERABILITIES Thin and easily worn away(osteoarthrosis) Relies on very indirect nutrition A few cells look after extensive matrix Has nearby a loose CT (synovium) in which damaging defensive responses occur, e.g., to crystals (gout), virus? (rheumatoid arthritis) Inflammatory synovial cells release damaging enzymes into synovial fluid, or cytokine signals turning on chondrocyte ECM destruction Large ECM molecules (PGs & Collagen) easily cleaved by enzymes into useless shorter pieces

20. CARTILAGE TYPES Precursor to bony skeleton stays on asArticular cartilage HYALINE CARTILAGE Laryngeal pieces Airway skeleton ELASTIC CARTILAGE Tracheal rings like hyaline, but reinforced with elastic fibers a few ‘vocal’ Laryngeal pieces Auricle(“ear’) joins bones, e.g., vertebrae, & tendons to bone FIBROCARTILAGE more like dense fibrous tissue

21. CARTILAGES: Technical names Auricular cartilage elastic Ears Nasal/septal cartilage Nose Laryngeal & tracheal cartilages Airway Ends of ribs Costal cartilages Spine disks Intervertebral disks fibrocartilage Joints Articular cartilages The rest are hyaline, as is most of the embryonic skeleton

22. TYPICAL PIECE* OF CARTILAGE PERICHONDRIUM ( dense irregular CT) vessels Chondrocytes * Fibrocartilage does not occur as discrete pieces

23. CARTILAGE GROWTH PERICHONDRIUM Chondroblasts Appositional growth by surface cell division & differentiation Chondrocytes Interstitial growth by interior cell division & matrix depostion

24. JOINT COMPONENTS SYNOVIUM JOINT CAPSULE Joint cartilageabsorbs and spreads load LIGAMENT Spongy bone with struts/ trabeculae Periosteum Fibrous Osteoblastic

25. JOINT CAPSULE & SYNOVIUM SYNOVIUM JOINT CAPSULE JOINT SPACE Synovium lines the joint capsule, but it itself has a lining or surface

26. EASY SLIDING BOUNDARY LUBRICANT FIRM ELASTIC SUBSTRATE FLUID FILM FIRM ELASTIC SUBSTRATE

27. Hydrophilic side attaches to cartilage Bond to Hydrophobic side lowers surface energy for NON-STICK surface EASY SLIDING: Synovial Joint Attached, polar PHOSPHOLIPID molecules Articular layer or Disc Articular layer WATER + HYALURONAN + PROTEINS

28. SYNOVIOCYTE ROLES SYNOVIAL FLUID ‘FIBROBLAST’ synthesizes hyaluronan & glycoproteins ‘MACROPHAGE’ phagocytoses debris in the joint space SUB-INTIMA for inflammatory defensive responses

29. ECM MOLECULAR INTERACTIONS - Pathology 2 Unwanted degradation by bystander inclusion in cytokine signaling pathways of defensive cells IL-1 Lymphocytes of inner joint synovium MF IL-1 Joint cartilage cells also respond to the signal: enzymes enzyme inhibitors proteoglycans Articular chondrocytes = an inappropriate response causing cartilage matrix destruction - ARTHRITIS

30. JOINT PANNUS SYNOVIUM PANNUS is a overgrowth of inflamed synovium onto & eating into the articular cartilage Joint cartilage PTERYGIUM is a similar, but less inflamed growth of conjunctiva onto the eye’s cornea

31. SKELETAL DEVELOPMENT Skeletal piece of hyaline cartilage Grows by internal expansion and from the surface Cell enlargement/hypertrophy Matrix calcification Calcified cartilage can be resorbed like bone, and be attached to bone selective erosion into mineralized cartilage

32. EARLY ENDOCHONDRAL OSSIFICATION } EPIPHYSIS perichondrium } periosteum Bony collarprovides support as mineralized cartilage is eaten away DIAPHYSIS/SHAFT primary ossification front

33. LATER ENDOCHONDRAL OSSIFICATION Articular cartilage Growth/epiphyseal plate Secondary ossificationcenters Shaft bonegrows by deposition on the outside, with mild resorption on the inside surface, plus osteonal remodelling in the interior + - Bone would belarger thanin theprevious view

34. ZONES/LAYERS OF THE GROWTH PLATE } RESTING } PROLIFERATION } HYPERYTROPHY } CALCIFICATION } OSSIFICATION Expansion Matching erosion Osteoclasts stop the trabeculae from forever extending new boneoncalcified cartilage

35. Cartilage is replaced by bone. There is no transformation of cartilage into bone

36. Caution how you exit. BACK on your browser is needed Unfortunately there is no way that you can directly reach other topics listed here by clicking on them. You get there by going back to the Paramedical Anatomy menu WHERE AM I? Online Anatomy Module 1 You are at the End ORIENTATION CELL EPITHELIUM CARTILAGE MUSCLE NERVOUS SYSTEM AXIAL SKELETON APPENDICULAR SKELETON MUSCLES EMBRYOLOGY