Workshop_Cartilage_and_Cartilage_Formation (1).pptx

Workshop Cartilage and Cartilage Formation Fall 2023 Dr. Mhawi Piont Solution Session ID: amir1 https://www.surveymonkey.com/r/T 75P6TD •• If you have technical difficulties during the session that you cannot solve in a few minutes, please email [email protected] at the time of the difficulty to...

Workshop Cartilage and Cartilage Formation Fall 2023 Dr. Mhawi Piont Solution Session ID: amir1 https://www.surveymonkey.com/r/T 75P6TD •• If you have technical difficulties during the session that you cannot solve in a few minutes, please email [email protected] at the time of the difficulty to have your situation logged. Ensure that you clearly indicate your course and the specific activity you are having difficulty with if you would like this to be effective." •• For assistance with any technical or connectivity issues, students can always message [email protected] Cartilage General Features • Avascular • Consists of • Chondrocytes • Extracellular matrix (ECM; 95%) chondrocytes • ECM contains large amount of proteoglycan aggregates • Permits diffusion of material from blood vessels in the surrounding connective tissue to chondrocytes ECM https://www.surveymonkey.com/r/T 75P6TD Types of Cartilage Hyaline cartilage chondrocyte Elastic Cartilage Fibrocartilage Elastic fibers Chondrocytes Chondrocytes chondroc yte Elastic fibers ECM EC M - ECM contains: - Type II collagen fibrils - Ground substance (Proteoglycan aggregates + glycoproteins) - ECM secreted by the chondrocytes - ECM of hyaline cartilage + elastic fibers and lamellae - ECM secreted by the chondroblastes and chondrocytes Type I collagen Type I collagen - ECM of hyaline cartilage + type I collagen fibrils - Contains chondrocytes and fibroblasts - Most of the ECM Hyaline Cartilage Isogen ous groups • Chondrocytes • Differentiate from chondroblasts • Chondrocytes divide and form isogenous groups • Each chondrocyte occupies a space called lacuna • Lacunae are found throughout the matrix • During the fetal life serves as precursor for long bones • During the postnatal life found in: • Articular surfaces • Epiphyseal growth plate • Responsible for the lengthening of bones during the growth period (will be revisited in bone and bone formation workshop • The wall of the trachea and bronchi lacuna ECM of Hyaline Cartilage • Contains three components: 1- Type II collagen fibrils • Not bundled • Fibrils arranged in a 3-dimensional pattern 2- Proteoglycans • Contain 2 types of GAGs: • Chondroitin sulfate • Keratan sulfate • Chondroitin & keratan joined to form proteoglycan monomer • (called AGGRECAN) 3- Multi-adhesive glycoproteins • Influence the interaction between chondrocytes and other ECM molecules • Anchorin CII: functions as collagen receptor on chondrocytes • Have clinical value as markers of cartilage turnover and degeneration Chondroitin sulfate (GAG) Keratan sulfate (GAG) Aggrecan proteoglycan monomer • ECM exhibits metachromasia • It means matrix does not stain homogeneously • Due to different concentrations of proteoglycans Metachromasia represented by 3 different regions in matrix: 1- Capsular or pericellular matrix 3 2 1 - Highest concentration of sulfated proteoglycans - Found in immediate vicinity of chondrocytes - Stains intensively with basic dyes 2- Territorial matrix - Surrounds the isogenous group of chondrocytes - Stains less intensively - Lower conc. of sulfate proteoglycans 3- Interterritorial matrix - Occupies the spaces between groups of chondrocytes. - Weak basophilia - Lowest conc. of proteoglycans • Proteoglycan content diminishes as cartilage ages perichondrium Perichondrium Outer fibrous layer • Firmly attached irregular Inner chondrogenic layer dense connective tissue (yellow arrows) • Contains blood vessels, nerves, and lymphatic vessels chondroblast • Surrounds both hyaline and chondrocyte elastic cartilage • Source of new cartilage cells • When cartilage is growing has 2 layers: • Outer fibrous layer • Inner chondrogenic layer • Gives rise to chondroblasts • Chondroblasts differentiate into chondrocytes Hyaline cartilage Elastic cartilage 8 Fibrocartilage • A mixture of dense connective tissue and hyaline cartilage • No perichondrium • Consists of: • Chondrocytes chondrocytes fibroblasts • Produce type II collagen • Fibroblasts • Produce type I collagen • Predominates • Found between the groups of chondrocytes • Found in: • Intervertebral disc • Pubic symphysis • Attachment of ligament to articular cartilage Bundles of type I collagen Photomicrograph of fibrocartilage. Note the rows of chondrocytes separated by type I collagen fibers. Picrosirius-hematoxylin stain. What’s wrong with the intervertebral disc in the left image? Annulus fibrosus develops fissures (thick black arrow) between the lamilae of the fibrous cartilage Intervertebral Disc articular hyaline cartilage annulus fibrosus (AF) nucleus pulposus (NP) ellylike content of the nucleus pulposus enters the fissures (disc herniation) and annulus fibrosus (AF) may presses the spinal nerve causing pain articular hyaline cartilage - Annulus fibrosus: Made of concentric fibrocartilage - nucleus pulposus: Contains viscous fluid rich in hyaluronan an type II collagen fibrils Chondrogenesis (Chondrification) Stage A: • Cells of hyaline cartilage arise from highly vascular tissue called mesenchyme tissue • Mesenchyme cells are stellate (has cytoplasmic processes) • Connected to each other by gap junctions Stage B: • Mesenchyme cells lose their processes, junctions, and become round • Continue to divide and form avascular aggregate called blastema Blastema • Blastema is surrounded by mesenchyme cells Stage C: • Blastema cells differentiate to chondroblasts • Chondroblasts move apart as matrix is produced by them • Chondroblasts called chondrocytes when completely surrounded by matrix Stage D: • Chondrocytes divide and form isogenous groups • Mesenchymal tissue around the growing cartilage makes perichondrium mesenchym Blaste e ma Mesenchyme cells Cartilage Growth • Two kinds of growth will resume: • Appositional • Process that forms new cartilage at surface of preexisting cartilage • Interstitial growth • Process that forms new cartilage within the cartilage mass Cartilage Growth APPOSITIONAL GROWTH chondrogenic cells Perichondrium differentiate into chondroblasts Chondrogenic cell chondroblast • • • • New chondrogenic cells derived from inner layer of perichondrium Chondrogenic cells differentiate into chondroblasts New chondroblasts secrete matrix on the outer preexisting matrix New matrix increases the cartilage mass New chondroblasts secrete matrix Growing cartilage Perichondrium Cartilage Growth INTERSTITIAL GROWTH: • New cartilage cells produced by division of chondrocytes in lacunae • Chondrocytes retain the ability to divide • Daughter cells occupy same lacuna until they make enough matrix to separate from each other •Overall growth of cartilage results from interstitial and appositional growth chondrogenic cells differentiate into chondroblasts New chondroblasts Secrete matrix Articular Cartilage is Irreparable if Injured, Why? • Perichondrium of hyaline cartilage at the articular surfaces is absent at the following sites: 1. Where cartilage makes direct contact with bone (dashed arrows) 2. At the articular (free) surface (solid arrows) articular cartilage bone • NO SOURCE OF NEW CARTILAGE CELLS Q1. Four samples of cartilaginous tissues are presented in the accompanying collage of light micrographs. Which of these cartilaginous tissues is/are part of the bronchial wall? A. B. C. D. E. Cartilage 1 Cartilage 2 Cartilage 3 Cartilage 4 Cartilages 2 and 3 1 2 3 4 :50 Q2. Four samples of cartilaginous tissues are presented in the accompanying collage of light micrographs. Which of these cartilaginous tissues is/are part of the epiglottis? A. B. C. D. E. Cartilage 1 Cartilage 2 Cartilage 3 Cartilage 4 Cartilages 2 and 3 1 2 3 4 :50 Q3. Four samples of cartilaginous tissues are presented in the accompanying collage of light micrographs. Which of these cartilaginous tissues serve(s) as a model for long bones of the fetal skeleton? A. B. C. D. E. Cartilage 1 Cartilage 2 Cartilage 3 Cartilage 4 Cartilages 2 and 3 1 2 3 4 :50 Q4. In the accompanying collage of light micrographs of cartilaginous tissues, which numbered type would be involved in the lengthening of bones during the growth period? A. B. C. D. E. Type 1 Type 2 Type 3 Type 4 Types 2 and 3 1 2 3 4 :50 s question is based on Osteoarthritis vedio Q5. Which of the following are the main components of healthy articular cartilage? A. Type I collagen, heparan sulfate, and chondroitin sulfate B. Type II collagen, chondroitin sulfate, and keratan sulfate C. Type II collagen, dermatan sulfate, and keratan sulfate D. Type I collagen, chondroitin sulfate, and keratan sulfate E. Hyaluronic acid, heparan sulfate, and dermatan sulfate :50 Q6. Which of the following characterizes osteoarthritic hyaline cartilage? A. Chondrocytes are stimulated to synthesize metalloproteinase B. Type II collagen replaced by type III C. The matrix arround the chondrocytes (pericellular matrix) becomes more basophilic D. The chondrogenic cells of the surrounding perichondrium differentiate into fibroblasts :50 Q7. In the accompanying collage of light micrographs of cartilaginous tissues, which feature makes cartilages 1 and 4 different from cartilages 2 and 3? A. Presence of isogenous group B. Absence of ECM C. Presence of perichondrium D. Absence of blood vessels E. Presence of type II collagen fibrils 1 2 3 4 :50 Q8. Formation of long bones (e.g., femur) depends on the presence of a hyaline cartilage model. During the fetal life the hyaline cartilage model undergoes a gradual growth until it takes the shpe of the future long bone. An autopsy of growing hyaline cartilage (shown in the image) is obtained from 10-week-old fetus who died from unkown cause. By which mechanism(s) hyaline cartilage model grows to acquire the shape of the future long bone? A. By interstitial growth B. By deposition of mineralized ECM C. By deposition of type I collagen fibrils D. By appositional growth E. By all of the abovementioned mechanisms This question may have two right answers :50 Q9. SR, is a 22-year-old man, presents to the emergency department after he injured his knee articular cartilage in a very competetive ice hockey game. The treating sergeon told SR “your knee injury will take quite some time to heal but, unfrotunately, will never get back to normal”. A similar uninjured articular cartilage is stained with hematoxylin and esosin (shown in the image) and examined under the light microscope. What makes SR’s articular hyaline cartilage incapable of full recovery? A. Articular cartilage contains less chondrocytes B. Articular cartilage lacks perichondrium C. Type I collagen fibrils predominates ECM of the articular cartilage D. Articular cartilage is avascular This question may have two right answers :50 Q10. In the vertebral column herniation of the intervertebral disc is best described by which of the following? A. Crack within the hyaline cartilage that covers the articular surfaces of the adjacent vertebrae B. Overgrowth of the perichondrium surrounding the disc C. Development of a fissure in the annulus fibrosus through which a Jellylike content of the nucleus pulposus can pass D. Extension of the annulus fibrosus between the adjacent vertebrae :50