Cartilage 166945 222689705 2008-06-30T17:08:22Z Emmanuelm 292957 [[WP:UNDO|Undid]] revision 222558336 by [[Special:Contributions/90.197.49.101|90.197.49.101]] ([[User talk:90.197.49.101|talk]]) Nonsense removed [[Image:Cartilage polarised.jpg|thumb|200px|right|[[Histology|Histological]] appearance of hyaline cartilage under partially [[polarization|polarized]] light.]] '''Cartilage''' is a type of dense [[connective tissue]]. It is composed of specialized cells called [[chondrocyte|chondrocytes]] that produce a large amount of extracellular matrix composed of [[collagen]] fibers, abundant [[ground substance]] rich in [[proteoglycan]], and [[elastin]] fibers. Cartilage is classified in three types, '''elastic cartilage''', '''hyaline cartilage''' and '''fibrocartilage''', which differ in the relative amounts of these three main components. Cartilage is found in many places in the body including the articular surface of the [[bone|bones]], the [[rib cage|rib cage]], the [[ear]], the [[nose]], the [[bronchial tubes]] and the [[intervertebral disc]]s. Its mechanical properties are intermediate between [[bone]] and dense connective tissue like [[tendon]]. Unlike other connective tissues, cartilage does not contain blood vessels. The chondrocytes are fed by diffusion, helped by the pumping action generated by compression of the articular cartilage or flexion of the elastic cartilage. Thus, compared to other connective tissues, cartilage grows and repairs more slowly. ==Types of cartilage== ===Hyaline cartilage=== [[Hyaline cartilage]] is a rather hard, translucent material rich in collagen and proteoglycan. It covers the end of [[bone|bones]] to form the smooth articular surface of [[joint|joints]]. It is also found in the [[nose]], the [[larynx]] and between the [[rib|ribs]] and the [[sternum]]. Bones grow via a hyaline cartilage intermediate, a process called [[Endochondral ossification]]. ===Elastic cartilage=== [[Elastic cartilage]] contains large amounts of elastic fibers ([[elastin]]) scattered throughout the matrix. It is stiff yet elastic, and is important to prevent tubular structures from collapsing. Elastic cartilage is found in the [[pinna (anatomy)|pinna]] of the ear, in tubular structures such as the auditory ([[Eustachian tube|Eustachian]]) tubes and in the [[epiglottis]]. ===Fibrocartilage=== [[Fibrocartilage]] is the most common form of cartilage by weight. It is characterized by a dense network of [[Type I collagen]]. It is a white, very tough material that provides high tensile strength and support. It contains more collagen and less proteoglycan than hyaline cartilage. Thus, its properties are closer to those of [[tendon]] than hyaline cartilage. It is present in areas most subject to frequent stress like [[intervertebral discs]], the [[symphysis pubis]] and the attachments of certain tendons and ligaments. ==Growth and development== ===Cartilage in fetal development=== In [[embryogenesis]], the [[skeletal]] system is derived from the [[germ layer#Mesoderm|mesoderm]] germ layer. Chondrification (also known as chondrogenesis) is the process by which cartilage is formed from condensed [[mesenchyme]] tissue, which differentiates into [[chondrocytes]] and begins secreting the molecules that form the extracellular matrix. Early in fetal development, the greater part of the skeleton is cartilaginous. This ''temporary'' cartilage is gradually replaced by bone ([[Endochondral ossification]]), a process that ends at puberty. In contrast, the cartilage in the joints remains unossified during the whole of life and is, therefore, ''permanent''. ===Mineralization=== Adult hyaline articular cartilage is progressively [[mineralization_(biology)|mineralized]] at the junction between cartilage and bone. It is then termed ''articular calcified cartilage''. A mineralization front advances through the base of the hyaline articular cartilage at a rate dependent on cartilage load and shear stress. Intermittent variations in the rate of advance and mineral deposition density of the mineralizing front, lead to multiple "tidemarks" in the articular calcified cartilage. Adult articular calcified cartilage is penetrated by vascular buds, and new bone produced in the vascular space in a process similar to [[endochondral ossification]] at the [[physis]]. A ''cement line'' demarcates articular calcified cartilage from subchondral bone. ===Repair=== Cartilage has limited repair capabilities. Because chondrocytes are bound in [[Lacuna (histology)|lacunae]], they cannot migrate to damaged areas. Also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is usually replaced by fibrocartilage scar tissue. Cartilage can be replaced surgically through [[chondroplasty]]. ==Diseases and treatment== There are several diseases which can affect the cartilage. Chondrodystrophies are a group of diseases characterized by disturbance of growth and subsequent [[ossification]] of cartilage. Some common diseases affecting/involving the cartilage are listed below. *[[Osteoarthritis]]: The cartilage covering bones (articular cartilage) is thinned, eventually completely worn out, resulting in a "bone against bone" joint, reduced motion and pain. Osteoarthritis is very common, affects the joints exposed to high stress and is therefore considered the result of "wear and tear" rather than a true disease. It is treated by [[Arthroplasty]], the replacement of the joint by a synthetic joint made of titanium and teflon. [[Chondroitin sulfate]], a monomer of the polysaccharide portion of [[proteoglycan]], has been shown to reduce the symptoms of osteoarthritis, possibly by increasing the synthesis of the extracellular matrix. *Traumatic rupture or detachment: The cartilage in the [[knee]] is frequently damaged, and can be partially repaired through [[knee cartilage replacement therapy]] *[[Achondroplasia]]: Reduced proliferation of chondrocytes in the epiphyseal plate of long bones during infancy and childhood, resulting in [[dwarfism]]. *[[Costochondritis]]: Inflammation of cartilage in the ribs, causing [[chest pain]]. *[[Spinal disc herniation]] : Asymmetrical compression of an [[intervertebral disc]] ruptures the sac-like disc, causing a [[hernia|herniation]] of its soft content. The hernia compresses the adjacent nerves and causes back pain. *[[Relapsing polychondritis]]: a destruction, probably [[autoimmunity|autoimmune]], of cartilage, especially of the nose and ears, causing disfiguration. Death occurs by [[suffocation]] as the larynx loses its rigidity and collapses. [[Tumor|tumors]] made up of cartilage tissue, either [[benign tumor|benign]] or [[cancer|malignant]], can occur. They usually appear in bone, rarely in pre-existing cartilage. The benign tumors are called [[chondroma]], the malignant ones [[chondrosarcoma]]. Tumors arising from other tissues may also produce a cartilage-like matrix, the best known being [[pleomorphic adenoma]] of the salivary glands. The matrix of cartilage acts as a barrier, preventing the entry of [[lymphocytes]] or diffusion of [[immunoglobulins]]. This property allows for the [[Organ transplant|transplantation]] of cartilage from one individual to another without fear of tissue rejection. [[Bioengineering]] techniques are being developed to generate new cartilage, using a cellular "scaffolding" material and cultured cells to grow artificial cartilage. ==Cartilage in animals== ===Cartilaginous fish=== [[Chondrichthyes|Cartilaginous fish (chondrichthyes)]] like [[Shark|sharks]], [[ray|rays]] and [[skate|skates]] have a skeleton composed entirely of cartilage. [[Shark cartilage]] is a popular but unproven dietary supplement. ===Invertebrate cartilage=== Cartilage tissue can also be found among invertebrates such as [[horseshoe crab]]s, marine [[snail]]s, and [[cephalopod]]s. ==See also== *[[Connective tissue]] *[[Biomechanics]] *[[Shark cartilage]] ==References== ;General references <div class="references-small"> * {{cite book |last=Keller-Peck |first=C.| date=2008 |title=Vertebrate Histology, ZOOL 400| publisher=Boise State University| }} </div> ==External links== *University of Kansas Medical Center [http://www.kumc.edu/instruction/medicine/anatomy/histoweb/cart/cart.htm Cartilage tutorial] *[[Public domain]] [http://www.bartleby.com/107/pages/page279.html text from Gray's anatomy] *[http://www.madsci.org/posts/archives/Mar2003/1048719208.Dv.r.html I've heard 'Ears and nose do not ever stop growing.' Is this false?] *[http://www.cartilagehealth.com Cartilage Health] - Information on Articular Cartilage Injury Prevention, Repair and Rehabilitation {{Bone and cartilage}} [[Category:Skeletal system]] [[Category:Tissues]] [[bg:Хрущял]] [[ca:Teixit cartilaginós]] [[cs:Chrupavka]] [[da:Brusk]] [[de:Knorpel]] [[es:Tejido cartilaginoso]] [[eo:Kartilago]] [[fr:Cartilage]] [[hr:Hrskavica]] [[it:Tessuto cartilagineo]] [[he:סחוס]] [[nl:Kraakbeen]] [[ja:軟骨]] [[no:Brusk]] [[om:Cartilage]] [[pl:Chrząstka]] [[pt:Tecido cartilaginoso]] [[ru:Хрящ]] [[simple:Cartilage]] [[sk:Chrupavka]] [[sr:Хрскавичаво ткиво]] [[sh:Hrskavica]] [[fi:Rustokudos]] [[sv:Brosk]] [[ta:குருத்தெலும்பு]] [[te:మృదులాస్థి]] [[th:กระดูกอ่อน]] [[tr:Kıkırdak doku]] [[uk:Хрящ]] [[yi:קארטילעדזש]] [[zh:软骨]]