The function of articular cartilage is dependent on the molecular composition of the extracellular matrix (ECM), which consists mainly of proteoglycans and collagen. This zone is also the only zone where articular cartilage progenitor cells have been identified. Oftentimes, many of these medications are used in combination. This smooth, transparent, glassy type of cartilage coats the ends … Apposition is thought to be most prevalent in mature cartilages, but interstitial growth must persist for long periods in growth-plate cartilage. Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours. “I would honestly say that Kenhub cut my study time in half.” Start studying Cartilage: Types, Functions, Locations, Slides. Each type has varying amounts of elastin and collagen. This type of cartilage contains elastic fiber networks and collagen fibers. There are several diseases and processes that can affect cartilage. (adsbygoogle = window.adsbygoogle || []).push({}); Cartilage proteoglycans are similar to those found in general, i.e. Cartilage – Introduction, Structure, Formation And Types Of Cartilage, Collagen type II is found in the notochord, the nucleus pulposus of an intervertebral disc, the vitreous body. It is histologically similar to hyaline cartilage but contains many yellow elastic fibers lying in a solid matrix. The matrix is mostly comprised of collagen and, in some cases, elastic fibers, embedded in a highly hydrated proteoglycan gel. Hyaline cartilage has widely dispersed fine collagen fibres (type II), which strengthen it. It is covered externally by a fibrous membrane, called the perichondrium, except at the articular ends of bones; it also occurs under the skin (for instance, ears and nose). Articular cartilage is specifically the smooth, white tissue covering the ends of bones where they come together to form joints. Treatment involves arthroplasty and chondroitin sulfate or glucosamine sulfate supplements. When a chondroblast divides, its descendants temporarily occupy the same chondroitin. Additionally, a glycoprotein known as lubricin that is abundant in the superficial layer of cartilage and synovial fluid plays a major role in bio-lubrication and wear protection of cartilage. Rheumatoid arthritis (RA) is a disease process where the body’s immune system attacks synovial cells, and therefore the lining of joint capsules, which is a tough membrane that encloses joints. Copyright © Last reviewed: August 31, 2020 Structure of Hyaline Cartilage The calcified zone of the articular cartilage serves to bind the articular cartilage to the bone tissue by anchoring the collagen fibrils of the deep zone of the cartilage to the subchondral bone. More typical of cartilage is collagen type II, which forms very thin fibrils dispersed between the proteoglycan molecules so that they do not clump together to form larger fibers. Articular cartilage is found only in diarthroidal joints (synovial joints), and is comprised of hyaline cartilage – a particularly smooth type of cartilage which allows for easy articulation, increased weight distribution, and shock absorption. This forms 90% of collagen in the body; functions to resist tension and stretching; found in the dermis, tendons, ligaments, fibrocartilage, bones, and fascia Type II Collagen Is the main fiber type in hyaline and elastic cartilage and functions to resist tensile strain that occurs when cartilage is compressed T Chondrocytes are responsible for producing large quantities of collagenous extracellular matrix and ground substance that is rich in proteoglycans and elastin fibers. The cells of the outer layer become fibroblasts and secrete a dense collagenous matrix lined externally by vascular mesenchyme. The collagen network varies in different types of cartilage and with age. It contains no nerves or blood vessels, and its structure is relatively simple. As mentioned previously, the main proteoglycan in cartilage is aggrecan, which forms large aggregates with hyaluronan and are negatively charged to hold water in the tissue. Cartilage is a connective tissue found in various parts of the adult skeleton including all joints between bones and structures which is deformable as well as strong e.g. “The knee is the largest joint in the body, and relies on two knee cartilage types to function effectively: fibrocartilage and articular cartilage. It is harder and stronger than prior tissue types. Other constituents of cartilage include dissolved salts, non-collagenous proteins, and glycoproteins. In the embryo, bones form first as hyaline cartilage before ossifying as development progresses. (adsbygoogle = window.adsbygoogle || []).push({}); Hey, This is Drishti Sharma, pursuing BSc. It has lots of collagen fibers (Type I and Type II), and it tends to grade into the dense tendon and ligament tissue. non-specialized, connective tissue. Cartilage is not innervated and therefore relies on diffusion to obtain nutrients. While osteoarthritis is a disease that affects the whole joint, one of the most affected tissues is the articular cartilage, which is thinned or completely worn away. Since osteoarthritis affects the joints exposed to the highest stress (knees, elbows, and hips), this condition is considered less of a disease and is rather regarded as a result of “wear and tear”. Cartilage is a flexible connective tissue that differs from bone in several ways; it is avascular and its microarchitecture is less organized than bone. Cartilage is a strong, flexible type of connective tissue found within a body. So this is called articular cartilage. Treatment often involves various anti-inflammatory medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin or ibuprofen, or other COX inhibitors for symptomatic relief. • Due to the lack of blood vessels, cartilage cannot heal itself. Functions of Cartilage Cartilage is the only tissue that never stops growing! – Chondrocytes-  These chondrocytes produce large amounts of extracellular matrix composed of collagen fibers, proteoglycan, and elastin fibers. Consequently, the ECM functions to respond to the tensile, shear, and compressive forces that are experienced by cartilage during mechanical use such as normal gait or weight-bearing movements. Like other types of cartilage, it also consists of chondrocytes and ECM. The main cell types in cartilage are chondrocytes, the ground substance is chondroitin sulfate, and the fibrous sheath is called perichondriu… Your email address will not be published. In all cases, developing cartilage is surrounded by condensed mesenchyme, which differentiates into a bilaminar perichondrium. It is a progressive and chronic autoimmune disease that triggers inflammation and results in damage to joint tissue, nearby bone and other organs, therefore indirectly affecting cartilage. Examples of tubes include the cricoid cartilage and carina of the trachea, the torus tubarius at the opening of the auditory tube, and the auricle/pinna of the ear. Timely treatment of cartilage damage is therefore essential. The collagen of articular cartilage is primarily type II (90–95%), with small contributions from types IX and XI. Elastic Cartilage – This type of cartilage provides higher flexibility and thus known as elastic cartilage. These are relatively soft and elastic or flexible. Collagen type II fibrils are often less than 50 nm in diameter and are too small to be seen by light microscopy. There are three types of cartilage: Elastic cartilage (yellow cartilage) – the most springy and supple type of cartilage. Each cell differentiates into a chondroblast as it secretes a basophilic halo of the matrix, (adsbygoogle = window.adsbygoogle || []).push({}); Cartilage grows by interstitial and appositional mechanisms. Articular cartilage is a physiologically non-self-renewing avascular tissue with a singular cell type, the chondrocyte, which functions as the load-bearing surface of the arthrodial joint. An essential feature of the cartilage is that it has no blood vessels. Starting from the subchondral bone, there is a tidemark that is deep to the basal layer and separates true articular cartilage from the deeper cartilage, which is a remnant of cartilage anlage from longitudinal growth during childhood. • Hyaline cartilage is the most widespread type and resembles glass. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. So, you can find hyaline cartilage in the larynx and trachea in the throat portion of the body, and then also in all of the joints where the surfaces of bones are articulating each other. Cartilage is not innervated and therefore relies on diffusion to obtain nutrients. c) fibrocartilage. Achondroplasia is an autosomal dominant disease usually related to a mutation in the FGFR3 gene, which causes abnormal endochondral ossification to convert cartilage to bone, and results in dwarfism. Cartilage function is more than structural, and has different functions in the life cycle. While more rigid and less flexible than muscle, cartilage is not as stiff as bone. Fibrocartilage is found in the pubic symphysis, the annulus fibrosus of intervertebral discs, menisci, and the temporal-mandibular joint. Read more. Embryonic cartilage either remains as cartilage or provides a substructure for endochondral ossification, meaning it also functions as a template for the rapid growth and … Costochondritis is a cause of chest pain resulting from inflammation of cartilage connecting the ribs to the sternum. More powerful immune system suppressing agents such as methotrexate and cyclosporine are sometimes used. The main cell types in cartilage are chondrocytes, the ground substance is chondroitin sulfate, and the fibrous sheath is called perichondrium. This layer has type II collagen that is oriented in parallel to the joint. 1. Elastic cartilage has the most ECM; hyaline a middle amount; and fibrous cartilage has the least amount of ECM. Tumors made up of cartilage tissue can also occur, but can be either benign or malignant in nature. It is composed of a dense network of collagen fibers embedded in a gelatinous ground substance. Therefore, when this ECM is affected, it can lead to damage or injury. The collagen (mainly type II), acts to constrain the proteoglycans and helps it hold its structure. Benign tumors are called chondromas, and the malignant tumors are called chondrosarcomas. Finally, treatment can also involve surgery or more progressive gene therapy drugs. When an embryo is developing, cartilage is the precursor to bone. Articular cartilage damage worsens over time and, if left untreated, leads to arthritis of the entire joint. Formed by the process of chondrogenesis, the resulting chondrocytes are capable of producing large amounts of collagenous extracellular matrix and ground substance, which together form cartilage itself. Mesenchymal cells proliferate and become tightly packed; the shape of their condensation foreshadows that of the future cartilage. Understanding knee cartilage types “Knee injuries are an area of focus for me, so I get questions about cartilage all the time,” says sports medicine surgeon Dr. Jack Skendzel. Introduction to the musculoskeletal system, chondrocytes are bound in lacunae and cannot migrate to damaged areas, cartilage does not have a blood supply so deposition of new ECM is very slow, damaged hyaline cartilage is often replaced by fibrocartilage scar tissue with different biomechanical properties, Articular cartilage of the elbow (sagittal view) - Paul Kim. The chondroblasts that are caught in the matrix are called chondrocytes, and are the main type of specialized cells found in cartilage. Hyaline cartilage is the most abundant type of cartilage in the body. On account of being avascular (lacking blood supply), articular cartilage can get damaged due to the normal wear and tear that occurs with age or an injury. Learn vocabulary, terms, and more with flashcards, games, and other study tools. RA frequently affects wrists, fingers, hips, knees, feet and ankles on both sides of the body (unlike osteoarthritis). Read more. I also engage myself in teaching which enhances my creativity and makes me more expressible. Cartilage is a pliant, load-bearing connective tissue, covered by a fibrous perichondrium except at its junctions with bones and over the articular surfaces of synovial joints. from IGNOU and have completed a Diploma in Medical Laboratory Technology from Young Women Christian Association (YWCA) institute. At some sites, continued secretion of matrix separates the cells, producing typical hyaline cartilage. Learn more about the structure and function of cartilage. A preponderance of fixed negative charges on the surface of GAGs strongly attracts polarized water molecules, causing wet cartilage to swell until restricted by tension in the collagen network, or by external loading. The cartilage lines the ear lobe, epiglottis and larynx. They give elastic cartilage great flexibility so it can withstand repeated bending. They consist of translucent protoplasm in which fine interlacing filaments and minute granules are sometimes present. Chondrogenesis is the process by which cartilage is formed from condensed mesenchymal cells expressing collagen I, III and V. This process also involves differentiation of chondroprogenitor cells secreting molecules (aggrecan and type II, IX and XI collagen) that form the extracellular matrix. The remodeling of cartilage is predominantly affected by changes and rearrangements of the collagen matrix, which responds to tensile and compressive forces experienced by the cartilage. These cells have generally straight outlines where they are in contact with each other, with the rest of their circumference rounded. Matrix Healthy articular cartilage allows joints to move and glide over each other with very little friction, but is subject to damage and injury, as well as normal wear and tear. Cartilage is a robust and viscoelastic connective tissue that can be found in joints between bones, the rib cage, intervertebral discs, the ear, and the nose. Relatively little is known about the factors that determine the overall shape of cartilage structures. Cartilage is an avascular, supporting and articular skeletal tissue consisting of cells in an extracellular matrix that may or may not mineralise depending on cartilage type, species or group of organisms; many invertebrates have cartilage but it never mineralises. Finally, there is most superficial layer, also known as the tangential zone. It is made up of cells called chondrocytes which are embedded in a matrix of collagen and elastic fibers. The most common proteoglycan molecule, aggrecan, form huge molecular aggregates with other proteoglycans and with hyaluronan. Required fields are marked *. the elbows, knees, and ankles, ends of the ribs, Between the vertebrae in the spine, ears, and nose, Bronchial tubes or airways. These fibers form bundles that appear dark under a microscope. Large proteoglycan molecules have numerous side chains of glycosaminoglycans (GAGs), carbohydrates with remarkable water-binding properties. composed of a delicate network of fine type II collagen fibrils, type IX collagen, and proteoglycan core protein. It works just like a cushion in the joints. RA progresses normally from various small to larger joints of the body, and damage to hands and feet is more likely to develop before damage to larger joints such as the hips or knees. These properties allow cartilage to serve as a support structure for holding tubes open or for proper locomotion. Cartilage is a group of tissues produced by chondrocytes that is characterized by a relative lack of vascularity and consists of cells surrounded by a specialized extracellular matrix composed predominantly of type II collagen and proteoglycan, often in the form of proteoglycan aggregate. Your email address will not be published. As mentioned before, the ECM is paramount in opposing shear, tensile, and compressive forces normally. 3. 3–5 Under electron microscopy, collagen is noted to have a cross-banded fibrillar structure. Cartilage is not hard just like bone. • There are three types of cartilage: hyaline, fibrous, and elastic cartilage. –  There are two types of which are the following: – Chondroblast – It is a type of cell that develops into a chondrocyte or cartilage cell. It is the only type of cartilage that contains type I collagen in addition to the normal type II. Brian K. Hall, in Bones and Cartilage (Second Edition), 2015. Cartilage is a resilient and smooth elastic tissue, rubber-like padding that covers and protects the ends of long bones at the joints and nerves. The continuing division produces isogenous groups. The collagen fibres are hard to see in sections. Damage or injury can also happen through pathologic states, where ossification or breakdown of cartilage occurs due to dysfunction of cartilage-specific cells or synovial cells, or imbalances in the microenvironment surrounding the cartilage. This causes it to heal very slowly. Skeletal system – Introduction & functions of skeletal system. There are no blood vessels in cartilage to supply the chondrocytes with nutrients. Hyaline cartilage, the most abundant type of cartilage, plays a supportive role and assists in movement. 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