Cartilage (PDF)

Cartilage Lecturer mr saisha  Cartilage Cartilage is a specialized form of firm and resilient connective tissue that can bear stresses without permanent distortion. It serves as a precursor or model for the embryonic development and subsequent growth of many long bo...

Cartilage Lecturer mr saisha  Cartilage Cartilage is a specialized form of firm and resilient connective tissue that can bear stresses without permanent distortion. It serves as a precursor or model for the embryonic development and subsequent growth of many long bones. Structure of the Cartilage It consists of cells chondroblasts chondrocytes extracelluar matrix, has high concentrations of GAGs and proteoglycans, which interact with collagen and elastic fibers. Cartilage composition Cells Chondrocytes: located within matrix; lacunae Chondroblasts: located at periphery; secrete extracellular matrix Fibers Collagen and elastic fibers Ground substance Rich in glycosaminoglycans and proteoglycans CHONDROBLAST Progenitor of chondrocytes Lines border between perichondrium and matrix Secretes type II collagen and other ECM components Chondroblasts build CHONDROCYTE Mature cartilage cell Reside in a space called the lacuna Clear areas = Golgi and lipid droplets Cells of the cartilage Chondrocytes completely fill their lacunae RER and euchromatic nuclei Synthetically active, secrete matrix  MATRIX Provides the rigidity, elasticity, & resilience FIBERS Collagenous and elastic GROUND SUBSTANCE Glycosaminoglycans (chondroitin sulfates, keratin sulfate, hyaluronic acid) Proteoglycans: GAGs + core protein Water Basophilic Territorial matrix – high conc of sulfated proteoglycans  CARTILAGE GROWTH Appositional Increasing in WIDTH; chondroblasts deposit matrix on surface of pre-existing cartilage Interstitial Increasing in LENGTH; chondrocytes divide and secrete matrix from w/in lacunae Growth of cartilage Appositional “Growth from outside” Chrondroblasts in perichondrium (external covering of cartilage) secrete matrix Interstitial “Growth from within” Chondrocytes within divide and secrete new matrix Cartilage stops growing in late teens (chrondrocytes stop dividing) Regenerates poorly in adults Cartilage composition Perichondrium Perichondrium is a layer of dense irregular connective tissue. It is essential for the growth and maintenance of cartilage. Dense irregularly arranged connective tissue (type I collagen) Ensheaths the cartilage Houses the blood vessels that nourish chondrocytes Features of Cartilage Avascular; Nutrients diffusion from perichondrium or synovial fluid; No innervation; No lymphatic vessels; Chondrocytes have low metabolic activity TYPES OF CARTILAGE HYALINE ELASTIC FIBROUS Types of Cartilage Hyaline cartilage: most common, much type II collagen Elastic cartilage: elastic fibers Fibrocatilage: dense network of type I collagen Hyaline Cartilage FUNCTION Support tissue and organs Model for bone development MATRIX Type II collagen (thin fibrils) Chondroitin sulfate, keratin sulfate, hyaluronic acid Water LOCATION Tracheal rings, nasal septum, larynx, articular surfaces of joints, ends of the ribs Hyaline Cartilage Chondrocytes present in groups of 4 to 8 cells Cell nests ( isogenous aggregates) Teritorial matrix lacunar capsule :- deeply stained matrix interstitial matrix ELASTIC CARTILAGE FUNCTION Support with flexibility MATRIX Normal components of hyaline matrix plus ELASTIC fibers LOCATION External ear, external auditory canal, epiglottis, laryngeal cartilage (corniculate and cuneiform) STAINS Elastic fibers stain BLACK with Weigert stain Elastic Cartilage Yellow cartilage Covered by perichondrium NOTE: Elastic cartilage is located in sites associated with production and or reception of sound.  Fibrocartilage FUNCTION Support with great tensile strength MATRIX Type I collagen - Oriented parallel to stress plane LOCATION Intervertebral disks, pubic symphysis Fibrocartilage White fibrocartilage Looks like dense fibrous tissue Chondrocytes occur singly in the lacunar No distinct surrounding perichondrium NB; Fibrocartilage is associated with structures in the midline of the body.  Types of cartilage: 3 1. Hyaline cartilage: flexible and resilient Chondrocytes appear spherical Lacuna – cavity in matrix holding chondrocyte Collagen the only fiber 2. Elastic cartilage: highly bendable Matrix with elastic as well as collagen fibers Epiglottis, larynx and outer ear 3. Fibrocartilage: resists compression and tension Rows of thick collagen fibers alternating with rows of chondrocytes (in matrix) Knee menisci and annunulus fibrosis of intervertebral discs Applied Anatomy Hyaline cartilage is susceptible to calcification during aging Oesteoarthritis, a chronic condition during aging affect hyaline cartilage in joints Cartilage inability to full repair due to its avascularity Tumours of the cartilage Chondromas chondrosarcomas