Lecture 8 Cartilage PDF

Lecture 8 Cartilage Presented by: Histology and Cell Biology Department ILOs: List components of cartilage. Describe the microscopic structure and correlated function of cartilage cells. Describe the microscopic structure, functions and sites of different...

Lecture 8 Cartilage Presented by: Histology and Cell Biology Department ILOs: List components of cartilage. Describe the microscopic structure and correlated function of cartilage cells. Describe the microscopic structure, functions and sites of different types of cartilage. Interpret the defective microscopic cartilage structure in various diseases.  Cartilage Is a special type of C.T. Is mesenchymal in origin Is rigid, rubbery with some degree of flexibility. Is well adapted to bear weight. No blood vessels within cartilage (avascular).  Cartilage Is covered by perichondrium (connective tissue covering) Is formed of: 1- Cells: chondrogenic, chondroblast & chondrocytes. 2- Fibers: collagen-II +….. According to type Matrix of 3- Ground substances: GAG + proteoglycan and tissue fluid (75%) cartilage  Types of cartilage: Hyaline cartilage White fibrocartilage (the most common Elastic cartilage type) + +Elastic fibers Type II collagen fibers Type I collagen  I-Hyaline cartilage Is the most common type of cartilage in the Nice to Know Nice to Know body. Sites: - In fetus: is present in fetal skeleton → replaced gradually by bone. - In adult, it is located in: https://images.slideplayer. com/24/7377588/slides/sli de_52.jpg 1. Articular surfaces of bone in joints. 2. Costal cartilage. 3. Respiratory passages 4. Epiphyseal plates of long bone. https://www.google.com.eg/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=2ahUKEwjjqZr1u__hAhX9DGM BHak3BxYQjRx6BAgBEAU&url=https%3A%2F%2Fforum.teropong.id%2F2017%2F09%2F13%2Fpengertian-tulang- rawan-ciri-ciri-fungsi-dan-macam-macam-tulang-rawan-beserta- contohnya%2F&psig=AOvVaw031_z7WYXhycGFMHRXk08S&ust=1556976587174564 Microscopic structure of hyaline cartilage: Nice to Know Perichondrium Perichondrium Cartilage cells Matrix chondrocytes matrix http://www.auburn.edu/academic/classes/zy/hist0509/html /Lec05Bnotes-cart_bone_bloo_files/image003.png https://docplayer.ru/docs-images/63/50460318/images/42-0.jpg  Perichondrium Nice to Know http://undergraduate.vetmed.wsu.edu/i mages/librariesprovider8/VPh308/_blivf 2- Inner chondrogenic 1_wsu_2_068_3.jpg?sfvrsn=c8f31838_4 1- Outer fibrous layer (cellular) layer 1 or 2 rows of cartilage Collagen I, fibroblasts, forming cells blood vessels (Chondrogenic cells & Chondroblasts) Function of perichondrium 1. Supply nourishment to the avascular hyaline cartilage by diffusion (except for articular surface). 2. Growth of cartilage (appositional). 3. Repair & healing of damaged cartilage. 4. Protection. The perichondrium is absent in 2 sites. Where …..?  Cartilage cells Nice to Know 1- Chondrogenic Cells: Origin: embryonic mesenchymal cell. Site: inner chondrogenic layer of the perichondrium. L.M: flat cell ,basophilic cytoplasm. E.M: abundant ribosomes. Fate: they can divide and differentiate into chondroblasts https://www.google.com.eg/url?sa=i&rct=j&q=&esrc=s&source=images&cd =&ved=2ahUKEwi-tPX6zP 10 2-Chondroblasts: Nice to Know Origin: embryonic mesenchymal cell, chondrogenic cells or pericytes. Present in inner chondrogenic layer of perichondrium. L.M.: flat in shape, having central vesicular nucleus & deep basophilic cytoplasm. http://kobiljak.msu.edu/cai/virtual_microscope/Images_534/CB_O E.M.: rER & well-developed Golgi complex (protein bj_02_01_b.jpg secreting cells) Nice to Know Function: They divide & secrete the matrix. Once surrounded by matrix, they become chondrocytes https://d1yboe6750e2cu.cloudfront.net/i/6b52d706a5451f99a506f670d5c0a45937e8b30b  3-Chondrocytes: Origin: chondroblasts L.M: chondrocytes are imprisoned inside spaces called lacunae. Shape: rounded, central & vesicular nucleus, basophilic cytoplasm. Superficially: cells are single inside lacunae. Deeply: cells are in groups of 4-8 in lacunae “ cell nest” https://accessmedicine.mhmedical.com/data/books/1687/mes_c h7_f003.png38411 E.M: (rER- Golgi - mitochondria) protein secreting cells Function: 1- Synthesis & secretion of matrix of cartilage 2- Divide (interstitial growth) Iesgamonares.com  Nice to Know https://encrypted- tbn0.gstatic.com/images?q=tbn:ANd9GcQlKkFJtRlpslhadFeilhBe8g7LtVCrpVrX6ZlAkPEEXsQi4xZp  Matrix of hyaline cartilage Ground Substances Fibers -mainly collagen type II fibrils 75 % Tissue fluid Nice to Know Proteoglycans & Glycosaminoglycans Glycoproteins https://diagnosing-pain-the-msk-game.weebly.com/uploads/6/9/7/6/69766071/6564649_orig.png  Ground Substances: 1. Tissue fluid: forming 75% of cartilage weight & acting as shock absorber. 2. Glycosaminoglycans (GAGs) (Chondroitin sulfate, Keratan sulfate, & Hyaluronic acid (non sulfated)). 3. Proteoglycans: (aggrecan) Core of protein to which many sulfated GAGs are attached. 4. Glycoproteins: as adhesive chondronectin. Nice to Know + collagen type II : thin can NOT be seen by LM. Collagen II: Submicroscopic dimension Same refractive index of ground substance So the matrix appears hyaline (glassy) https://media.springernature.com/original/springer- static/image/chp%3A10.1007%2F978-3-319-41873- 5_7/MediaObjects/333516_1_En_7_Fig1_HTML.gif  Aggrecan molecule Large proteoglycan (protein core attached to it GAG). Negatively charged so attracts water (80% of its weight is water) resisting forces of compression. Collagen –II fibers are added, resisting tensile forces. Staining of the matrix: H&E: basophilic Fine network of collagen type II can’t be seen * Submicroscopic dimension Same refractive index of ground substance So the matrix appears hyaline (glassy) 16 https://d1yboe6750e2cu.cloudfront.net/i/65db127c18a42c69a20ce0c90f26d7d2298d0e8e  II-Elastic cartilage Site: where flexibility and support are needed Ear pinna External auditory canal Eustachian tube Epiglottis http://cal.vet.upenn.edu/projects/histo/Lab3cartilage/Lab3images/s69_hyaline10x.jpg Structure Similar to hyaline cartilage, but matrix contains elastic fibers forming a network that surround the lacunae of chondrocytes. amazonaws.com  III-White fibrocartilage Nice to Know Sites: Intervertebral disc Symphysis pubis Semilunar cartilage of knee joint (meniscus). Near tendon insertion (between tendon& bone)  Structure 1. Bundles of coarse collagenous fibers type I, Nice to Know separated by rows of chondrocytes embedded in basophilic matrix. 2.It is devoid of perichondrium, BUT the associated collagen bundles contain blood vessels. http://www.auburn.edu/academic/classes/zy/hist0509/image/03fibrocartilage.jpg It is tense and resist stretch due to the presence of high content of collagen fibers. All types of cartilage are surrounded by perichondrium EXCEPT: 1.Articular cartilage. 2.White fibrocartilage. https://www.bu.edu/histology/i/03203hoa.jpg  Growth of Cartilage 1- Appositional growth: By differentiation of new chondroblasts in the inner chondrogenic layer, they divide and secrete matrix resulting in addition of new layers to the outer surface of cartilage. Nice to Know https://encrypted- tbn0.gstatic.com/images?q=tbn:ANd9GcROILO6RqeKf3nFEsroF91Gi8uWRHXML8dmSiVsrkOOc4tXGSHg 20  Growth of Cartilage 2- Interstitial growth: By chondrocytes, they divide inside their lacunae and secrete new matrix resulting in growth of cartilage from within. Nice to Know Nice to Know https://encrypted- https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTHdNRN2yu-h3Z36UWC0- tbn0.gstatic.com/images?q=tbn:ANd9GcROILO6RqeKf3nFEsroF91Gi8uWRHXML8dmSiVsrkOOc4tXGSHg hUXkiitfA4ow9iIj6GVi9j4ZC5C0Gt 21  Nutrition Of Cartilage Cartilage is avascular, it takes its oxygen and nutrients from the perichondrial blood vessels by diffusion through the matrix (which is suitable to that by its high content of water 70 -75%). In articular cartilage (which has no perichondrium) it gets its oxygen and nutrients from the synovial fluid of the joints. Also in white fibro-cartilage (no perichondrium) it gets its needs from the blood vessels present in-between the bundles of collagenous fibers. 22  Articular cartilage It is the cartilage that covers articular surfaces of bones. It has NO perichondrium: so, a) Its surface is smooth (for easy movement of the joints). b) Its nutrition is not so good due to absent vessels in perichondrium. (Nutrition occurs through diffusion from Synovial fluid). c) It can not regenerate (due to absent dividing cells in perichondrium). Dr Noha A Makhlouf 23  Articular cartilage Osteoarthritis: Some joints like knee and hip are subjected to persistent Nice to Know wear and tear over the years. This leads to degeneration of the articular cartilage. Friction between the two bony surfaces cause pain. BECAUSE articular cartilage LACKS PERICHONDRIUM, 1. So its nutrition is not so good as other types of hyaline cartilage. 2.it can not regenerate. That’s why osteoarthritis occurs. Osteoarthritis? degeneration of articular cartilage. https://www.google.com.eg/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad= 24  Hyaline cartilage Elastic cartilage Fibrocartilage Perichondrium Present Except articular cartilage Present Absent Arranged single & in groups inside Arranged single or in pairs Arranged in rows between Chondrocytes lacunae inside lacunae bundles Basophilic , Basophilic , Acidophilic contains mainly collagen II. contains elastic & collagen II. due to collagen I Matrix & between cells small amount of basophilic matrix with some collagen II -Fetal skeleton -Ear pinna -Intervertebral discs Location -Articular cartilage -External ear -Semilunar cartilage -Costal cartilage -Eustachian tube -Symphysis pubis -Cartilage of respiratory passages -Epiglottis -Near tendon insertion -Epiphyseal plate of long bone  Suggested Textbooks 1- (Board Review) BRS Cell Biology & Histology (8th edition) p.118-121. 2- The Human Body in Health and Disease (6th edition 2014) p.173-177. 3- Lippincott Illustrated reviews integrated systems (edition 2016) p. 110- 113. 27