Three α chains intertwine into a triple helix, forming a procollagen molecule. 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). Learn vocabulary, terms, and more with flashcards, games, and other study tools. I also engage myself in teaching which enhances my creativity and makes me more expressible. Timely treatment of cartilage damage is therefore essential. Elastic cartilage functions to provide support and maintain the shape of flexible body parts like our ears and larynx. When an embryo is developing, cartilage is the precursor to bone. The cells of the outer layer become fibroblasts and secrete a dense collagenous matrix lined externally by vascular mesenchyme. Newly formed chondroblasts secrete matrix around themselves, creating superficial lacunae beneath the perichondrium. 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. Learn more about the structure and function of cartilage. Like other types of cartilage, it also consists of chondrocytes and ECM. The most common GAG side chains in cartilage are chondroitin sulfate and keratan sulfate. One of the main functions of this type of cartilage is to enable the bones in the joints to move and glide over each other without friction. • Hyaline cartilage is the most widespread type and resembles glass. 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. This article will explain the structure, composition and formation of this structure. It is made up of cells called chondrocytes which are embedded in a matrix of collagen and elastic fibers. Other constituents of cartilage include dissolved salts, non-collagenous proteins, and glycoproteins. 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. It is mostly found in the infant skeleton which replaced by bone during growth. Appositional growth is the result of the continued proliferation of the cells that form the internal, chondrogenic layer of the perichondrium. It is histologically similar to hyaline cartilage but contains many yellow elastic fibers lying in a solid matrix. 2. • There are three types of cartilage: hyaline, fibrous, and elastic cartilage. (adsbygoogle = window.adsbygoogle || []).push({}); Hey, This is Drishti Sharma, pursuing BSc. The length of collagen fibrils and fibers in cartilage is unknown, but even relatively short fibrils can reinforce the matrix by interacting physically and chemically with each other and with other matrix constituents including proteoglycans (Hukins and Aspden 1985), reflecting the fact that the term collagen means ‘glue maker’. It owes its flexibility and toughness to the fibrous tissue and its elasticity to the cartilaginous tissue. Grounded on academic literature and research, validated by experts, and trusted by more than 1 million users. White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions. This causes it to heal very slowly. 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. They are soon separated by a thin septum of the secreted matrix, which thickens and further separates the daughter cells. This cartilage is of three types as. Kenhub. The collagen of articular cartilage is primarily type II (90–95%), with small contributions from types IX and XI. As mentioned before, the ECM is paramount in opposing shear, tensile, and compressive forces normally. Embedded in this are one or two round nuclei with the usual intranuclear network. The cartilage lines the ear lobe, epiglottis and larynx. Required fields are marked *. Cartilage is not hard just like bone. More powerful immune system suppressing agents such as methotrexate and cyclosporine are sometimes used. Collagen type II fibrils are often less than 50 nm in diameter and are too small to be seen by light microscopy. Each cell differentiates into a chondroblast as it secretes a basophilic halo of the matrix, Finally, treatment can also involve surgery or more progressive gene therapy drugs. This can happen through physical mechanical forces, where excessive friction and applied forces wear down the cartilage (e.g. The function of articular cartilage is dependent on the molecular composition of the extracellular matrix (ECM), which consists mainly of proteoglycans and collagen. Mesenchymal cells proliferate and become tightly packed; the shape of their condensation foreshadows that of the future cartilage. Alice Ferng B.S., MD, PhD They consist of translucent protoplasm in which fine interlacing filaments and minute granules are sometimes present. The first type is called hyaline cartilage. Effectively, water is held in place by proteoglycans, which are themselves held in place by the collagen network. This zone is the thickest layer of round chondrocytes, with abundant proteoglycan content. Elastic Cartilage – This type of cartilage provides higher flexibility and thus known as elastic cartilage. It has lots of collagen fibers (Type I and Type II), and it tends to grade into the dense tendon and ligament tissue. Cartilages are made up of specialized cells known as chondrocytes. 2021 Register now RA frequently affects wrists, fingers, hips, knees, feet and ankles on both sides of the body (unlike osteoarthritis). Read more. 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. 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. 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. It works just like a cushion in the joints. Apposition is thought to be most prevalent in mature cartilages, but interstitial growth must persist for long periods in growth-plate cartilage. – Chondrocytes-  These chondrocytes produce large amounts of extracellular matrix composed of collagen fibers, proteoglycan, and elastin fibers. b) Elastic cartilage. Formed by the process of chondrogenesis, the resulting chondrocytes are capable of producing large amounts of collagenous extracellular matrix … In the embryo, bones form first as hyaline cartilage before ossifying as development progresses. It is the only type of cartilage that contains type I collagen in addition to the normal type II. Oftentimes, many of these medications are used in combination. Chondrocytes are responsible for producing large quantities of collagenous extracellular matrix and ground substance that is rich in proteoglycans and elastin fibers. Hyaline cartilage is the most abundant type of cartilage in the body. Look at the eMicroscope of a section of cartilage on the left. Cartilage is a flexible connective tissue that differs from bone in several ways; it is avascular and its microarchitecture is less organized than bone. Medical Anatomy Notes | Human Anatomy Notes. • The main cell types in cartilage are chondrocytes, the ground substance is chondroitin sulfate, and the fibrous sheath is called perichondrium. 3–5 Under electron microscopy, collagen is noted to have a cross-banded fibrillar structure. 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. This smooth, transparent, glassy type of cartilage coats the ends … Elsewhere, many cells become fibroblasts; collagen synthesis predominates and chondroblastic activity appears only in isolated groups or rows of cells that become surrounded by dense bundles of collagen fibers to form white fibrocartilage. “I would honestly say that Kenhub cut my study time in half.” The collagen fibres are hard to see in sections. Reviewer: There are no blood vessels in cartilage to supply the chondrocytes with nutrients. Fibrocartilage. The matrix is mostly comprised of collagen and, in some cases, elastic fibers, embedded in a highly hydrated proteoglycan gel. This type of cartilage contains elastic fiber networks and collagen fibers. In the embryo , it provides support and is a precursor to bone . Cartilage is usually formed in embryonic mesenchyme. 1. 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