Histology of Cartilage.pptx

Cartilage is a connective tissue structure that is composed of a collagen and proteoglycan-rich matrix and a single cell type: the chondrocyte. Cartilage is unique among connective tissues in that it lacks blood vessels and nerves and receives its nutrition solely by diffusion

1. Histology of Cartilage Dr. Mathew Joseph MBBS, MD(AIIMS), BCC(Palliative Medicine) Ass istant Professor Department of Anatomy Amala Institute of Medical Sciences, Thrissur

2. C artilage Modified connective tissue Forms skeletal basis of some parts of body Matrix is firm giving it the characteristic consistency Resists compression Avascular (nutrients diffuse through matrix) Perichondrium is rich in blood vessels

3. Dense irregularly arranged fibrous tissue Ensheaths the cartilage Composed of cells & matrix Matrix consists of fibres & ground substance Houses the blood vessels that nourish chondrocytes Present in most of the hyaline & elastic cartilage Absent in fibrocartilage Fibrous layer Cellular layer Perichondrium

4. C hondroblast Mesenchymal (embryologically) Progenitor of chondrocytes Lines border between perichondrium and matrix Produce the intercellular matrix and collagen fibres Cells which become imprisoned within this matrix become chondrocytes.

5. Chondrocyte Mature cartilage cell Reside in a space called the lacuna Isogenous cell group Basophilic Clear areas = Golgi and lipid droplets

6. Chondrocyte Chondrocytes completely fill their lacunae RER and euchromatic nuclei Synthetically active, secrete matrix Synthesize type II collagen, proteoglycans and chondronectin. Cartilage matrix RER N

7. M atrix Provides the rigidity, elasticity, & resilience FIBERS - Collagenous and elastic GROUND SUBSTANCE Glycosaminoglycans (chondroitin sulfates & keratan sulfate) Proteoglycans Water Basophilic Territorial matrix Interterritorial matrix Territorial matrix surrounds lacuna (space in which chondrocyte lives)

8. Cartilage Growth Interstitial Newly formed cartilage grows by multiplication of cells throughout its substance. Appositional Addition of new cartilage over the surface of existing cartilage.

9. Cartilage Types H yaline E lastic F ibrous

10. Cartilage Locations

11. Hyaline Cartilage Sites: Tracheal rings, nasal septum, larynx, costal cartilage & articular surfaces of joints Cartilage cells: Present singly or in groups of 2 or 4 cells inside lacunae Cartilage Matrix: Collagen type II Ground substance: Homogenous, clearly basophilic Functions: supportive

12. Hundreds of Eyes staring back at you

13. Identification Points - Hyaline cartilage: 1. Has encapsulated cartilage cells, forming cell nests (2-4 chondrocytes) and ground substance appears homogenous . 2. Refractive index of collagen II is same as that of matrix, so they are not seen separately. 3. Perichondrium covers hyaline cartilage except at articular surfaces. 4. It is avascular . 5. T rachea, B ronchial tree, L arynx

14. Elastic Cartilage Sites: Auricle, E xt auditory meatus, A uditory tube, E piglottis, A pices of A rytenoid cartilage Cartilage cells: L arger, N umerous, P acked more closely Cartilage Matrix: E lastic fibres, C ollagen type II Ground substance: Rich in elastic fibres Functions: S upportive with resilience Elastic fibers stain with orcein.

15. Identification Points - Elastic cartilage : 1. Encapsulated cartilage cells are present singly. 2. Ground substance contain elastic fibres and collagen fibers. 3. M atrix is non- ho mogeneous . 4. Elastic fibres are better seen with orcein stain. 5 . Example Epiglottis, Cartilage of external ear, corniculate and apices of arytenoid.

16. Fibrocartilage Sites: IVD , A rytenoid cartilage (except apices), P ubic symphysis, MSJ , A rticular disc of TM J . Cartilage cells: F ewer, S maller, scattered singly or in rows Cartilage Matrix: C ollagen type I & II Ground substance: A cidophilic Functions: S upportive with tensile strength Intervertebral disc

17. Identification Points - Fibrocartilage : 1 Encapsulated chondrocytes are ovoid , surrounded by concentrically striated matrix.
2 Chondrocytes lie in rows or layers , between rows there are bundles of collagen fibres - Type 1 .
3 Perichondrium is absent.
4 Example intervertebral disc, symphysis pubis, intra articular disc.

18. Osteoarthritis

19. Achondroplasia

20. Thank You

21. bonE Modified connective tissue Highly vascular mineralized connective tissue consisting of cells and dense intercellular organic matrix impregnated with inorganic salts. Provide support & protection to the vital organs Forms skeletal framework

22. Articular cartilage Spongy bone Marrow cavity Compact bone (location of haversian systems) Periosteum

23. Composition Cells: Osteogenic cells Osteoblasts Osteocytes Osteoclasts Fibers: collagen type I Ground Substance: Proteoglycans & glycoproteins

24. The matrix of bone is a mixture of organic (collagen) and inorganic (calcium phosphate) 90% of bone is matrix, with the remaining 10% made of osteocytes.

25. Microscopic Anatomy of Bone Figure 5.3

26. Lamellar arrangement Slide 5.11a Lamellae Rings around the central canal Sites of lacunae Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings Figure 5.3

27. Slide 5.11b Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system Figure 5.3 Lamellar arrangement

28. compact bone The morphofunctional unit of the bone is osteon, or Haversian system. Lamellar pattern of compact bone: Haversian system Interstitial lamellae Circumferential lamellae

29. T.S. through compact bone ‘ Haversian Systems’

30. Dark spots are called ‘ lacunae ’ and would contain osteocytes in living bone Central canal containing an artery, vein, lymph vessel and nerves

31. What happens when excessive bending force compresses the bone…! compression force

32. Clinical application Scurvy Rickets Osteomalacia Osteoporosis Osteogenesis imperfecta Pseudoachondroplasia

33. Save your bones

34. Take home message Aerobic exercises Low impact, weight bearing exercises Resistance exercises

35. References 1. diFiore’s Atlas of Histology with functional Correlations, 12 th Edition. 2. Essentials of Anatomy for Dentistry Students,1 st Edition. 3. Textbook of Histology, 3 rd Edition.

36. MCQ Fibrous cartilage is present in: Auricle Nose Tracheal rings Intervertebral discs

37. Label the following A B C Don’t confuse this picture with the Liver Lobule!

38. MCQ Elastic cartilage is present in: Apices of arytenoid cartilage Epiphysis Tracheal rings Temporomandibular joints

39. MCQ Hyaline cartilage is present in: Tracheal rings External auditory meatus Semilunar cartilages of knee joint Intervertebral discs

40. MCQ The blood vessels and nerves go inside the compact bone through: 1. Haversian canal 2. Volkman’s canal 3. Canaliculi 4. Interstitial lamellae