Cartilage PDF

Cartilage DR. NAVEEN KUMAR RAKCOMS, RAKMHSU  NaveenTonse Specialized connective tissue Rigid structure -Can withstand the pressure Composed of Cells and matrix (fibers & ground substance) Cell...

Cartilage DR. NAVEEN KUMAR RAKCOMS, RAKMHSU  NaveenTonse Specialized connective tissue Rigid structure -Can withstand the pressure Composed of Cells and matrix (fibers & ground substance) Cells : Chondrocytes and chondroblasts Cartilage Fibers: Collagen -type-II (mostly) or I and/ elastic Ground substance: Proteoglycans (GAG), Glycoproteins & water Present in body where elasticity and rigidity is needed NaveenTonse Importance of cartilage Can be bent and also brought back to original form Provide rigidity & support to soft tissues Provides smooth gliding surface for articulation Enables development and growth of long bones  NaveenTonse Cartilage cells Chondroblasts- Young cartilage cells-secrete cartilage matrix around them. Chondrocytes: Mature cartilage cells - Lie in lacunae present in the matrix  Mesenchymal (Chondrogenic)cells differentiate into chondroblasts  As the cartilage grows- chondroblasts with matrix around get trapped in matrix compartment (lacunae) become matured chondrocytes When cartilage calcifies- chondrocytes die because of deprived of nutrition by diffusion  Ground substance of cartilage Made up of proteoglycans (GAGs), glycoproteins & water Proteoglycans :Chondroitin sulphate & keratan suphate Glycoproteins: Chondronectin (adhesive Gp) & chondrocalcin (calcium – binding protein) Water (tissue fluid)- hydrates the matrix Proteoglycans attracts water molecules form gel gives firm consistency to cartilage Chondronectin: Binds to GAG and collagen fibers- adheres cartilage cells to collagen  NaveenTonse Characteristic features of cartilages Surrounded by Perichondrium (dense irregular CT) Composed of outer fibrous & inner cellular layers Fibrous layer- collagen with fibroblasts Cellular layer- Chondrogenic cells- differentiate to form chondroblasts – secrete matrix Provide nutrient and support to the cartilage Articular cartilage & fibrocartilage are devoid of perichondrium  NaveenTonse Cartilages are Avascular ! Nutrition -by diffusion through ground substance Repair /regeneration is slow No lymphatics… Lack of lymphatics- homogenous cartilage transplantation possible without rejection No nerves- Insensitive  NaveenTonse Understand this Cartilage grows by interstitial & appositional process Appositional process- new cartilage is added to surface (beneath perichondrium)- by chondroblasts increases cartilage width Interstitial process- new cartilage is added internally – by proliferation of chondrocytes increases cartilage size  NaveenTonse Based on the type of fibers present in the matrix 1. Hyaline cartilage- Provides structural support 3 Types of cartilages 2. Elastic cartilage- Confers flexibility 3. White fibrocartilage -Provides tensile strength  Thyroid cartilage Hyaline cartilage:. Cricoid cartilage Found in… Tracheal rings Nose Cartilages of larynx- thyroid, cricoid & lower part of arytenoid Trachea & Bronchi Costal cartilages of ribs Articular cartilage in joints NaveenTonse  NaveenTonse Hyaline cartilage: Functional Significance In young individuals: It presents in Epiphyseal plates allows the bones to grow in length. In adults: Mostly replaced with bone Articular cartilage (hyaline) has no perichondrium In the joint it prevents the friction and allow the smooth movement  NaveenTonse Hyaline cartilage- Structure Surface is covered by perichondrium Glossy matrix- Homogenous, transparent and basophilic - consists of Collagen fibers (type II) Chondrocytes – lie within lacunae Chondrocytes are arranged in Cell-nest form (isogenous groups ) - two or more chondrocytes within a lacunae  NaveenTonse Bluish-white matrix of hyaline cartilage presents: more basophilic -Territorial matrix – surrounds the lacunae less basophilic – Inter-territorial matrix – found between the lacunae Hyalos- transparent stone Refractive index of collagen in the matrix is similar to ground substance -so glossy appearance  NaveenTonse Elastic (yellow fibro) cartilage Highly flexible cartilage Found in Pinna of the (external) ear Epiglottis Part of the auditory tube Cartilages of larynx: Epiglottis, apex of arytenoid, corniculate and cuneiform Arytenoid Corniculate Note!- all above sites are concerned either with the production or reception of sound  NaveenTonse Elastic cartilage- structure Surface is covered by perichondrium Chondroblasts synthesize elastic fibers Matrix contains Elastic fibers with branching & anastomoses few type-II collagen fibers Ground substance is basophilic Chondrocytes are present within the lacunae- mostly singly  NaveenTonse Fibrocartilage (white fibrocartilage) Bear weight & resist compression Found in - secondary cartilaginous joints Intervertebral discs, symphysis Articular disc of temporomandibular joint Glenoidal labrum and acetabular labrum Menisci of the knee joint “White” fibrocartilage- structure ‘White’- because of abundant collagen and less ground substance in its matrix Has no perichondrium* Matrix contains thick bundles of collagen fibers (type1) - arranged in interlacing bundles Chondrocytes are fewer in number and seen as a single row between adjacent bundles  NaveenTonse Osteoarthritis Due to degeneration of articular cartilage Since no perichondrium- no regeneration capacity Degeneration causes- Difficulty in walking (hip & knee joint if involved) Involvement joint of hand- Painful  NaveenTonse Self learning Identify the photomicrographs marked A,B C A B C List the histological differences between them Mention their occurrence (where it is found) Sample MCQ: Which of the following is responsible for high water content in cartilage? a. Proteoglycan b. Collagen fibers c. Perichondrium d. Chondrocytes e. Glycoprotein NaveenTonse In the nutshell…..