Classification of cartilage.pptx

cartilage histology presentation

1. Classification of cartilage Aditi Biswas-1056

2. About cartilage Cartilage is a tough and flexible form of connective tissue It is different from connective tissue mainly in the nature of ground substance It is characterised by ECM , high GAG’s ,proteoglycans concentration(HS, CS, KS), hyaluronic acid. Proteoglycans make the matrix basophilic Cartilage has very little vasculature and nerves supply. In case of extensive damage, perichondrium produces a scar of dense connective tissue instead of new cartilage. The poor repair capacity of cartilage or regeneration is due to its avascular in nature

3. Perichondrium Cartilage is covered externally by a dense connective tissue sheath known as perichondrium except articular cartilage and fibro cartilage. Has two layers- outer fibrous layer (vascular) and inner chondrogenic layer (cellular) Perichondrium is essential for growth and maintenance of cartilage Among these fibroblasts, inner layer of perichondrium are progenitor cells for chondroblasts Perichondrium consists type I collagen and fibroblast ( more acidophilic)

4. 3 types of cartilage

5. Hyaline cartilage hyalos means glass in latin Semi-transparent in fresh state Most common form of cartilage Location: articular surfaces of movable joints , respiratory passages ( nose, larynx, trachea, bronchi), ventral ends of ribs ,epiphyseal plates of long bones In embryo, hyaline cartilage forms temporary skeleton that is replaced by bone Osteo-arthritis occurs during ageing which involves gradual loss or changed physical properties of hyaline cartilage that lines articular ends of bones on joints

6. Cells They are derived from undifferentiated mesenchymal cells, these have cytoplasmic processes. Young cells(elliptical shaped) are small known as chondroblasts are present at the periphery, they multiply to chondrocytes Older and mature cells are known as chondrocytes Chondrocytes are bigger in size and are found in spaces called as lacunae They are found either groups of 2-4 cells together known as cell nest or individual cells They are responsible for production of fibres and ground substance of the cartilage . Old mature cells are incapable of multiplication

7. Chondrocyte Occupy in lacunae R esponsible for the synthesis of collagen fibers and ground substances Isogenous groups of chondrocyte Nucleus is euchromatic initially Mitochondria, Golgi apparatus, endoplasmic reticulum are prominent . As cartilage cells matures, nuclei become heterochromatic and cells organelles become less prominent

8. Ground substance Type II collagen fibers Collagen- stability & strength Fibers constitute about the 40% of dry weight of cartilage 150 Keratan sulphate and chondroitin sulphate side chains attach to ACAN ( aggrecan) or cartilage specific proteoglycan core protein . This aggregate attaches (non-covalently) to the hyaluronic acid backbone via Linker protein This structure then binds to collagen fibre II Semi rigid nature of cartilage is due to water bound to negatively charged sulphated GAG chains extending from proteoglycan core proteins Another important component of matrix is chondronectin which is a multi adhesive protein that binds specifically to GAG’s, collagen II and integrins

9. Highest concentration present around the lacuna Matrix around the cells is brighter and deep blue in colour than other areas, this matrix is known as capsule / territorial matrix. (newly formed) Two groups of cells are separated by a lightly coloured matrix known inter-territorial matrix Due to devoid of capillaries, chondrocytes respire under low oxygen conditions So hyaline cartilage metabolize glucose mainly by anaerobic glycolysis to produce lactic acid as end product Chondrocyte synthesis of sulphated GAG’s and secretion of proteoglycans is accelerated by hormones and growth factors Major regulator of hyaline cartilage growth is pituitary derived growth hormone

10. Examples

11. Function of hyaline cartilage Articular cartilage provides smooth surface for movement at joints Though it is flexible, it provides support because of its firmness Firmness of the cartilage keeps the lumen of trachea and bronchi patent It facts as the base for formation of skeletal bones in the embryological growth period. Epiphyseal plates of long bones

12. Elastic cartilage Yellow fibrocartilage Perichondrium present Characterized by the presence of elastic fibers in abundance which branch and anastomose Chondrocytes are larger than those of hyaline cartilage Chondrocytes are found singly or group two in lacuna. Though the matrix of hyaline cartilage calcifies in old age, the matrix of elastic cartilage doesn't calcify with age Function : It provides shape and support to the organ with elasticity

13. Examples Auricle or pinna Epiglottis Tip of artenoids Corniculate & cuneiform cartilage of larynx External auditory meatus

14. Fibrocartilage White Fibrocartilage Perichondrium is characteristically absent Has thick bundles of collagen fibers (type I) lesser proteoglycans make it more acidophilic Minimal amount of ground substance, few cells Chondrocytes are seen between fibers in single or in narrow rows Function : Fibrocartilage is capable of resisting compressive and shear forces

15. Peripheral annulus fibrosus which is rich in type I collagen Central nucleus pulposus which is gel like matrix and is rich in hyaluronic acid

16. Examples Pubic Symphysis Manubriosternal joint Intervertebral discs Glenoidal labrum of shoulder joint Acetabular labrum of hip joint,

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