Cartilage is a type of dense connective tissue. Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix composed of collagen fibers, abundant ground substance rich in proteoglycan, and elastin fibers. Chondrocytes (from Greek chondros cartilage + kytos cell are the only cells found in Cartilage. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Ground substance is a term for the non-collagenous components of Extracellular matrix. Proteoglycans represent a special class of Glycoproteins that are heavily glycosylated. Elastin is a Protein in Connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting 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 bones, the rib cage, the ear, the nose, the bronchial tubes and the intervertebral discs. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce The human rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic (chest cavity and supports the pectoral The ear is the sense organ that detects Sounds The Vertebrate ear shows a common biology from Fish to Humans with variations Anatomically a nose is a protuberance in Vertebrates that houses the Nostrils or nares which admit and expel air for respiration in conjunction with the A bronchus (plural bronchi, adjective bronchial) is a caliber of airway in the Respiratory tract that conducts air into the Lungs No Gas Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine. Its mechanical properties are intermediate between bone and dense connective tissue like tendon. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce A tendon (or sinew) is a tough band of Fibrous connective tissue that usually connects Muscle to Bone and is capable of withstanding tension
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.
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Types of cartilage
Hyaline cartilage
Hyaline cartilage is a rather hard, translucent material rich in collagen and proteoglycan. Hyaline cartilage (aka “Gristle" consists of a slimy mass of a firm consistency but of considerable elasticity and pearly bluish color It covers the end of bones to form the smooth articular surface of joints. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce A joint is the location at which two or more Bones make contact It is also found in the nose, the larynx and between the ribs and the sternum. Anatomically a nose is a protuberance in Vertebrates that houses the Nostrils or nares which admit and expel air for respiration in conjunction with the The larynx (plural larynges) colloquially known as the voicebox, is an organ in the Neck of Mammals involved in protection of the In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage. The sternum (from Greek στέρνον sternon, "chest" or breastbone) is a long flat Bone located in the center of the thorax (chest Bones grow via a hyaline cartilage intermediate, a process called Endochondral ossification. Endochondral ossification is one of the two processes during Fetal development of the mammalian skeletal system in which Bone tissue is
Elastic cartilage
Elastic cartilage contains large amounts of elastic fibers (elastin) scattered throughout the matrix. Elastic cartilage or yellow cartilage is a type of Cartilage present in the Outer ear, Larynx, and Epiglottis. Elastin is a Protein in Connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting It is stiff yet elastic, and is important to prevent tubular structures from collapsing. Elastic cartilage is found in the pinna of the ear, in tubular structures such as the auditory (Eustachian) tubes and in the epiglottis. The pinna ( Latin for Feather) is the visible part of the Ear that resides outside of the head (this may also be referred to as the auricle or The Eustachian tube (or auditory tube) is a tube that links the Pharynx to the Middle ear. The epiglottis is a lid-like flap of Elastic cartilage tissue covered with a Mucous membrane, attached to the root of the Tongue.
Fibrocartilage
Fibrocartilage is the most common form of cartilage by weight. White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions to the former of these constituents it owes its flexibility and toughness It is characterized by a dense network of Type I collagen. Type-I collagen is the most abundant collagen of the human body 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. A tendon (or sinew) is a tough band of Fibrous connective tissue that usually connects Muscle to Bone and is capable of withstanding tension It is present in areas most subject to frequent stress like intervertebral discs, the symphysis pubis and the attachments of certain tendons and ligaments. Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine. The pubic symphysis is the midline cartilaginous Joint (secondary cartilaginous uniting the superior rami of the left and right pubic bones.
Growth and development
Cartilage in fetal development
In embryogenesis, the skeletal system is derived from the mesoderm germ layer. Embryogenesis is the process by which the Embryo is formed and develops In Biology, the skeleton is a strong and often a rigid framework that supports the body of an animal holding it upright and giving it shape and strength (Also skeletal A germ layer is a collection of cells formed during animal Embryogenesis. 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. Mesenchyme refers to loosely organized connective tissue present in the embryo regardless of origin Chondrocytes (from Greek chondros cartilage + kytos cell are the only cells found in Cartilage.
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. Endochondral ossification is one of the two processes during Fetal development of the mammalian skeletal system in which Bone tissue is 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 mineralized at the junction between cartilage and bone. For other uses see Mineralization In biology mineralization refers to the process where a substance is converted from an organic substance to an 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. Endochondral ossification is one of the two processes during Fetal development of the mammalian skeletal system in which Bone tissue is Physis (grc φύσις is a Greek theological, philosophical, and scientific term usually translated into English as " Nature " A cement line demarcates articular calcified cartilage from subchondral bone.
Repair
Cartilage has limited repair capabilities. Because chondrocytes are bound in lacunae, they cannot migrate to damaged areas. In Histology, a lacuna is a small space containing an Osteocyte in bone or Chondrocyte in cartilage 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. Chondroplasty refers to Surgery of the Cartilage, the most common being corrective surgery of the cartilage of the Knee.
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. Ossification is the process of Bone formation in which connective tissues such as Cartilage are turned to bone or bone-like tissue 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 ( OA, also known as degenerative Arthritis, degenerative joint disease) is a clinical syndrome in which low-grade inflammation 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. Arthroplasty (literally "formation of Joint " is an operative procedure of orthopaedic surgery performed in which the arthritic or dysfunctional joint surface 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. Chondroitin sulfate is a sulfated Glycosaminoglycan (GAG composed of a chain of alternating sugars ( N-acetylgalactosamine and Glucuronic acid) Proteoglycans represent a special class of Glycoproteins that are heavily glycosylated.
- 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. The knee is the lower extremity Joint connecting the Femur, Patella, and the Tibia. Articular cartilage, most notably that which is found in the knee joint is generally characterized by very low friction high wear resistance and poor regenerative qualities Achondroplasia is a type of Autosomal dominant Genetic disorder that is a common cause of Dwarfism. Dwarfism ( is a medical condition in humans characterized by extreme small size
- Costochondritis: Inflammation of cartilage in the ribs, causing chest pain. Tietze's syndrome is a benign Inflammation of one or more of the Costal cartilages It was first described in 1921 by the German surgeon Alexander Tietze In Medicine, chest pain is a Symptom of a number of serious conditions and is generally considered a Medical emergency.
- Spinal disc herniation : Asymmetrical compression of an intervertebral disc ruptures the sac-like disc, causing a herniation of its soft content. Intervertebral discs (or intervertebral fibrocartilage) lie between adjacent vertebrae in the spine. A hernia is a protrusion of a tissue, structure or part of an organ through the muscular tissue or the membrane by which it is normally contained The hernia compresses the adjacent nerves and causes back pain.
- Relapsing polychondritis: a destruction, probably autoimmune, of cartilage, especially of the nose and ears, causing disfiguration. Relapsing polychondritis is a condition where cartilage deteriorates Autoimmunity is the failure of an organism to recognize its own constituent parts as self, which results in an immune response against its own cells and tissues Death occurs by suffocation as the larynx loses its rigidity and collapses.
tumors made up of cartilage tissue, either benign or malignant, can occur. See also Cancer A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells (termed neoplastic A benign tumor is a Tumor that lacks all three of the Malignant properties of a Cancer. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled They usually appear in bone, rarely in pre-existing cartilage. The benign tumors are called chondroma, the malignant ones chondrosarcoma. A Chondroma is a benign cartilaginous Tumor, which is encapsulated with a lobular growing pattern A chondrosarcoma is a type of Cancer of the Bone. Chondrosarcoma is a cartilage-based tumor and is in a category of cancers called Sarcomas About 25% Tumors arising from other tissues may also produce a cartilage-like matrix, the best known being pleomorphic adenoma of the salivary glands. Pleomorphic Adenoma is a benign neoplastic tumor of the salivary glands
The matrix of cartilage acts as a barrier, preventing the entry of lymphocytes or diffusion of immunoglobulins. A lymphocyte is a type of White blood cell in the Vertebrate Immune system. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily This property allows for the 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. Bioengineering (also known as Biological Engineering is the application of Engineering principles to address challenges in the fields of Biology and Medicine
Cartilage in animals
Cartilaginous fish
Cartilaginous fish (chondrichthyes) like sharks, rays and skates have a skeleton composed entirely of cartilage. Chondrichthyes or cartilaginous fishes are jawed Fish with paired fins paired nostrils scales two-chambered hearts and skeletons made of Cartilage rather Sharks ( Superorder Selachimorpha) are a type of Fish with a full cartilaginous Skeleton and a highly streamlined body Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays Shark cartilage is a popular but unproven dietary supplement. Shark Cartilage, the tough material that a sharks' skeleton is composed of is dried and powdered to create this popular Dietary supplement.
Invertebrate cartilage
Cartilage tissue can also be found among invertebrates such as horseshoe crabs, marine snails, and cephalopods. The horseshoe crab or Atlantic horseshoe crab ( Limulus polyphemus) is a marine Chelicerate Arthropod. The word snail is a Common name that can be used for almost all members of the Molluscan class Gastropoda which have coiled shells in the The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by
See also
References
- General references
- Keller-Peck, C. Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, Muscle, and Nervous tissue) Biomechanics is the application of mechanical principles on living organisms Shark Cartilage, the tough material that a sharks' skeleton is composed of is dried and powdered to create this popular Dietary supplement. (2008). Vertebrate Histology, ZOOL 400. Boise State University.
External links
- University of Kansas Medical Center Cartilage tutorial
- Public domain text from Gray's anatomy
- I've heard 'Ears and nose do not ever stop growing.' Is this false?
- Cartilage Health - Information on Articular Cartilage Injury Prevention, Repair and Rehabilitation
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