Dr. Amam Ali Amam PhD: Periodontal Disease

1. Cartilage Dr. Amam Ali AmamPhD: Periodontal Disease

2. Cartilage, Definition • Is a special form of connective tissue in which the firm consistency of the extra-cellular matrix allows the tissue to bear mechanical stresses. • Is a semi-rigid form.

3. Cartilage Cartilage is characterized by: an extracellular matrix enriched with glycosaminoglycans and proteoglycans, macromolecules that interact with collagen and elastic fibers.

4. Cartilage, Functions 1-Bearing mechanical stresses. 2-Support soft tissue. 3- Shock-absorbing and sliding area for joints and facilitates bone movements. (Because it is smooth surfaced and resilient) 4- Developmental and growth of long bones before and after birth.

5. Cartilage is a connective tissue • We have to study : • 1- cells • 2- fibers • 3- ground substance

6. Cartilage consist of: 1- Cells Called Chondrocytes 2- Extracellular matrix 2- Ground substance 1-Fibers 1- Hyaluronic acid. 1- Collagen. 2- Proteoglycans. 2- Elastic . 3- Small amount of several glycoproteins

7. Chondrocyte • It is derived from chondroblast, which resembles fibroblast • It synthesizes and secretes the extracellular matrix . • It is interacted in the matrix that it’s secretes it! • Histological: it is seen in cavities called lacunae.

8. 3 Types of cartilage Variations in the composition of these matrix components produce three types of cartilage adapted to local biomechanical needs. 1-Hyaline cartilage. 2- Fibro cartilage. 3- Elastic cartilage. Articular cartilage.

9. 1-Hyaline cartilage. • It is the most common type & the best studied of the three forms. • Small aggregation of chondrocytes embedded in an amorphous matrix of ground substance reinforced by collagen fibers ( II )

10. 1-Hyaline cartilage, cont... • Location:1- in the articular surfaces of the movable joints.2- in the walls of larger respiratory passage (nose, larynx, trachea, bronchi).3- the ventral ends of the ribs

11. 40 % of the dry weigh of Hyaline Cartilage consist of : 1- collagen embedded in a firm 2- hydrated gel of Proteoglycans. 3-structural Glycoproteins

12. Hyaline cartilage

13. Hyaline cartilage

14. Cartilage matrix

16. 2- Fibro cartilage. • Is a tissue intermediate between dense connective tissue and hyaline cartilage. • Is a combination of dense supporting tissue and cartilage. • Presents in regions of the body subjected to pulling forces. • Is characterized by a matrix containing a dense network of coarse type I collagen fibers. • It contains chondrocytes (singly or groups).

18. 2- Fibro cartilage, cont... • It is found at :- intervertebral discs.- the symphysis pubica.- the knee joint.- the mandibular joint.- the sternoclavicular Joint.- the shoulder Joint.- Ligaments and the connections of some tendons of bone.

19. Fibrocartilage

22. 3- Elastic cartilage. • Elastic Cartilage, characterized by its great pliability, contains significant amounts of the protein elastin in the matrix. The more pliable and distensible elastic cartilage possesses, in addition to collagen type II, an abundance of elastic fibers within its matrix.

23. 3- Elastic cartilage, cont... • Elastic Cartilage is found in:- The auricle of the ear.- The walls of the external auditory canal.- The auditory (Eustachian) tube.- The epiglottis.- The larynx.Elastic Cartilage possesses a perichondrium (like hyaline cartilage) .

24. Elastic cartilage

25. Articular cartilage • Covers the surface of the bones of movable joints. • Is devoid of perichondrium. • Is sustained by the diffusion of oxygen and nutrients from the synovial fluid.

26. Perichondrium At the periphery of mature cartilage is a zone of condensed supporting tissue called perichondrium containing chondroblasts with cartilage – forming potential .

27. Perichondrium • Is a sheath of dense connective tissue that surrounds cartilage in most places, forming an interface between the cartilage and the tissue supported by the cartilage. • Most cartilage is devoid of blood vessels

28. Perichondrium • All cartilage is covered by a layer of dense connective tissue (perichondrium) • (except in the articular cartilage of joints & fibro cartilage). • It’s essential for the growth & maintenance of cartilage. • It’s rich in collagen type I fibers & contains numerous fibroblasts. • contains nerves lymphatic vessels.

29. Cartilage Properties • Nutrition • Growing • Regenerating • Degenerative • Histogenesis

30. Cartilage Properties • In all 3 forms, Cartilage is avascular (no vascular). Nutrition: is nourished by the diffusion of nutrients from capillaries in adjacent connective tissue (perichondrium) or by synovial fluid from joint cavities. • Cartilage has no lymphatic vessels or nerves. Growth : 1- Interstitial growth 2- Appositional growth

31. The Growth of Cartilage • 1- Interstitial growth: • Resulting from the mitotic • division of preexisting • Chondrocytes. • Less important process. • important in increasing the length of long bones • occurs during the early phase of cartilage formation. • 2- Appositional growth • Resulting from the • differentiation of • perichondrial cells. • Grows in girth only by • opposition.

32. Histogenesis A- mesenchyme. B- Mitotic Proliferation of mesenchyme. C- Chondroblasts. D- rise to isogenous group.

33. Perichondrium & Hyaline cartilage

34. Degenerative changes • Hyaline cartilage is more susceptible to degenerative aging processes ( in contrast of other tissues). • Calcification of the matrix, preceded by an increase in the size & volume of the chondrocytes and followed by their death.

35. Poor Regeneration of Cartilage Tissue • Except in young children, damage cartilage regenerates with difficulty & often incompletely by activity of the perichondrium, which invades the injured area and generates new cartilage

36. Fibrocartilage, young animal