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66-404: Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body. Examples include the rings of the trachea, such as the cricoid cartilage and carina . Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix , abundant ground substance that is rich in proteoglycan and elastin fibers. Cartilage

132-420: A cricoidectomy can be performed in which part or all of the cricoid cartilage is removed. This is commonly done to relieve blockages within the trachea. Fractures of the cricoid cartilage can be seen after manual strangulation also known as throttling. Stress concentration In solid mechanics , a stress concentration (also called a stress raiser or a stress riser or notch sensitivity )

198-549: A base material for such a purpose. These gels have exhibited great promises in terms of biocompatibility, wear resistance, shock absorption , friction coefficient, flexibility , and lubrication, and thus are considered superior to polyethylene-based cartilages. A two-year implantation of the PVA hydrogels as artificial meniscus in rabbits showed that the gels remain intact without degradation, fracture, or loss of properties. Several diseases can affect cartilage. Chondrodystrophies are

264-414: 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 transplantation of cartilage from one individual to another without fear of tissue rejection. Cartilage does not absorb X-rays under normal in vivo conditions, but

330-461: A disc of cartilage is placed in an impervious, fluid-filled container and covered with a porous plate that restricts the flow of interstitial fluid to the vertical direction. This test can be used to measure the aggregate modulus of cartilage, which is typically in the range of 0.5 to 0.9 MPa for articular cartilage, and the Young’s Modulus, which is typically 0.45 to 0.80 MPa. The aggregate modulus

396-432: A discontinuity under typically tensile loads can be expressed as a non-dimensional stress concentration factor K t {\displaystyle K_{t}} , which is the ratio of the highest stress to the nominal far field stress. For a circular hole in an infinite plate, K t = 3 {\displaystyle K_{t}=3} . The stress concentration factor should not be confused with

462-451: A dye can be injected into the synovial membrane that will cause the X-rays to be absorbed by the dye. The resulting void on the radiographic film between the bone and meniscus represents the cartilage. For in vitro X-ray scans, the outer soft tissue is most likely removed, so the cartilage and air boundary are enough to contrast the presence of cartilage due to the refraction of

528-448: A group of diseases, characterized by the disturbance of growth and subsequent ossification of cartilage. Some common diseases that affect the cartilage are listed below. Tumors made up of cartilage tissue, either benign or 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

594-425: A high collagen content, called cartilage-like matrix, and collagen lacking a highly cellularized core, called osteoid-like matrix. The cartilage-like matrix surrounds the osteoid-like matrix. The amount of the acellular fibrous region is variable. The model organisms used in the study of cartilage in sabellid polychaetes are Potamilla species and Myxicola infundibulum . Vascular plants , particularly seeds , and

660-507: A larger number of mineral deposits, which has a similarly undesired stiffening effect. Osteoarthritis has more extreme effects and can entirely wear down cartilage, causing direct bone-to-bone contact. Lubricin , a glycoprotein abundant in cartilage and synovial fluid , plays a major role in bio-lubrication and wear protection of cartilage. Cartilage has limited repair capabilities: Because chondrocytes are bound in lacunae , they cannot migrate to damaged areas. Therefore, cartilage damage

726-445: A low amount of extra cellular matrix containing collagen. The odontophore contains muscle cells along with the chondrocytes in the case of Lymnaea and other mollusks that graze vegetation. The sabellid polychaetes , or feather duster worms, have cartilage tissue with cellular and matrix specialization supporting their tentacles. They present two distinct extracellular matrix regions. These regions are an acellular fibrous region with

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792-478: A patient under general anesthesia prior to surgery, the anesthesiologist will press on the cricoid cartilage to compress the esophagus behind it so as to prevent gastric reflux from occurring: this is known as the Sellick manoeuvre . The Sellick Manoeuvre is typically only applied during a Rapid Sequence Induction (RSI), an induction technique reserved for those at high risk of aspiration. The Sellick maneuver

858-414: A slow decrease to equilibrium. Typically, the permeability of articular cartilage is in the range of 10^-15 to 10^-16 m^4/Ns. However, permeability is sensitive to loading conditions and testing location. For example, permeability varies throughout articular cartilage and tends to be highest near the joint surface and lowest near the bone (or “deep zone”). Permeability also decreases under increased loading of

924-438: A small sample size at a time when high tidal volumes, head-down positioning, and barbiturate anesthesia were the rule. Cricoid pressure may frequently be applied incorrectly. Cricoid pressure may frequently displace the esophagus laterally, instead of compressing it as described by Sellick. Several studies demonstrate some degree of glottic compression reduction in tidal volume and increase in peak pressures. Based on

990-417: Is a confined compression test, which can be used in either a 'creep' or 'relaxation' mode. In creep mode, the tissue displacement is measured as a function of time under a constant load, and in relaxation mode, the force is measured as a function of time under constant displacement. In creep mode, the tissue displacement is measured as a function of time under a constant load. During this mode, the deformation of

1056-461: Is a location in an object where the stress is significantly greater than the surrounding region. Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of stress. This arises from such details as holes , grooves , notches and fillets . Stress concentrations may also occur from accidental damage such as nicks and scratches. The degree of concentration of

1122-474: Is a vesicular cell-rich cartilage due to the large, spherical and vacuolated chondrocytes with no homologies in other arthropods. Other type of cartilage found in L. polyphemus is the endosternite cartilage, a fibrous-hyaline cartilage with chondrocytes of typical morphology in a fibrous component, much more fibrous than vertebrate hyaline cartilage, with mucopolysaccharides immunoreactive against chondroitin sulfate antibodies. There are homologous tissues to

1188-399: Is adding a fillet to internal corners. Another example is in a threaded component, where the force flow line is bent as it passes from shank portion to threaded portion; as a result, stress concentration takes place. To reduce this, a small undercut is made between the shank and threaded portions Functionally Graded Materials : Using materials with properties that vary gradually can reduce

1254-410: Is aggrecan, which, as its name suggests, forms large aggregates with hyaluronan and with itself. These aggregates are negatively charged and hold water in the tissue. The collagen, mostly collagen type II, constrains the proteoglycans. The ECM responds to tensile and compressive forces that are experienced by the cartilage. Cartilage growth thus refers to the matrix deposition, but can also refer to both

1320-415: Is classified into three types — elastic cartilage , hyaline cartilage , and fibrocartilage — which differ in their relative amounts of collagen and proteoglycan. As cartilage does not contain blood vessels or nerves , it is insensitive. However, some fibrocartilage such as the meniscus of the knee has partial blood supply. Nutrition is supplied to the chondrocytes by diffusion . The compression of

1386-441: Is difficult to heal. Also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Over the last years, surgeons and scientists have elaborated a series of cartilage repair procedures that help to postpone the need for joint replacement. A tear of the meniscus of the knee cartilage can often be surgically trimmed to reduce problems. Complete healing of cartilage after injury or repair procedures

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1452-705: Is generally presumed that the material used is consistent and homogeneous throughout. In practice, however, material inconsistencies such as internal cracks, blowholes, cavities in welds, air holes in metal parts, and non-metallic or foreign inclusions can occur. These defects act as discontinuities within the component, disrupting the uniform distribution of stress and thereby leading to stress concentration. Contact Stress : Mechanical components are frequently subjected to forces that are concentrated at specific points or small areas. This localized application of force can result in disproportionately high pressures at these points, causing stress concentration. Typical instances include

1518-403: Is hindered by cartilage-specific inflammation caused by the involvement of M1/M2 macrophages , mast cells , and their intercellular interactions. Biological engineering techniques are being developed to generate new cartilage, using a cellular "scaffolding" material and cultured cells to grow artificial cartilage. Extensive researches have been conducted on freeze-thawed PVA hydrogels as

1584-432: Is rich in proteoglycans (which dispel and reabsorb water to soften impacts) and thin collagen oriented parallel to the joint surface which have excellent shear resistant properties. Osteoarthritis and natural aging both have negative effects on cartilage as a whole as well as the proper function of the materials gradient within. The earliest changes are often in the superficial zone, the softest and most lubricating part of

1650-450: Is the process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondroblasts and begins secreting the molecules ( aggrecan and collagen type II) that form the extracellular matrix. In all vertebrates, cartilage is the main skeletal tissue in early ontogenetic stages; in osteichthyans, many cartilaginous elements subsequently ossify through endochondral and perichondral ossification. Following

1716-486: Is the ratio of the highest stress σ max {\displaystyle \sigma _{\max }} to a nominal stress σ nom {\displaystyle \sigma _{\text{nom}}} of the gross cross-section and defined as Note that the dimensionless stress concentration factor is a function of the geometry shape and independent of its size. These factors can be found in typical engineering reference materials. E. Kirsch derived

1782-490: Is “a measure of the stiffness of the tissue at equilibrium when all fluid flow has ceased”, and Young’s modulus is a measure of how much a material strains (changes length) under a given stress. The confined compression test can also be used to measure permeability, which is defined as the resistance to fluid flow through a material. Higher permeability allows for fluid to flow out of a material’s matrix more rapidly, while lower permeability leads to an initial rapid fluid flow and

1848-475: The X-ray . Cartilaginous fish ( Chondrichthyes ) or sharks , rays and chimaeras have a skeleton composed entirely of cartilage. Cartilage tissue can also be found among some arthropods such as horseshoe crabs , some mollusks such as marine snails and cephalopods , and some annelids like sabellid polychaetes. The most studied cartilage in arthropods is the branchial cartilage of Limulus polyphemus . It

1914-424: The knee and hip have been studied extensively at macro, micro, and nano-scales. These mechanical properties include the response of cartilage in frictional, compressive, shear and tensile loading. Cartilage is resilient and displays viscoelastic properties. Since cartilage has interstitial fluid that is free-moving, it makes the material difficult to test. One of the tests commonly used to overcome this obstacle

1980-415: The stress intensity factor , which is used to define the effect of a crack on the stresses in the region around a crack tip. For ductile materials, large loads can cause localised plastic deformation or yielding that will typically occur first at a stress concentration allowing a redistribution of stress and enabling the component to continue to carry load. Brittle materials will typically fail at

2046-441: The voice box and functions as an attachment site for muscles, cartilages, and ligaments involved in opening and closing the airway and in producing speech. The cricoid cartilage is the only laryngeal cartilage to form a complete circle around the airway. It is smaller yet thicker and tougher than the thyroid cartilage above. It articulates superiorly with the thyroid cartilage , and the paired arytenoid cartilage . Inferiorly,

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2112-458: The articular cartilage or flexion of the elastic cartilage generates fluid flow, which assists the diffusion of nutrients to the chondrocytes. Compared to other connective tissues, cartilage has a very slow turnover of its extracellular matrix and is documented to repair at only a very slow rate relative to other tissues. In embryogenesis , the skeletal system is derived from the mesoderm germ layer. Chondrification (also known as chondrogenesis)

2178-453: The attachment of the cricothyroid muscle. It is made of hyaline cartilage , and so can become calcified or even ossified , particularly in old age. The function of the cricoid cartilage is to provide attachments for the cricothyroid muscle , posterior cricoarytenoid muscle and lateral cricoarytenoid muscle muscles, cartilages, and ligaments involved in opening and closing the airway and in speech production . When intubating

2244-476: The cricoid cartilage. It measures 2-3 cm superoposteriorly. The cricoid lamina exhibits a midline vertical ridge posteriorly; the ridge creates posterior concavities to either side. It is anatomically related to the thyroid gland; although the thyroid isthmus is inferior to it, the two lobes of the thyroid extend superiorly on each side of the cricoid as far as the thyroid cartilage above. The thyroid cartilage and cricoid cartilage are connected medially by

2310-437: The cricoid lamina of that side. The superior margin of the cricoid arch is rather elliptical in outline; the inferior margin is nearly horizontal and circular in outline. The cricoid arch is palpable inferior to the laryngeal prominence , with an interval containing a depression (beneath which is the conus elasticus ) between the two. The cricoid lamina is the roughly quadrilateral broader and flatter posterior portion of

2376-421: The current literature, the widespread recommendation that cricoid pressure be applied during every rapid sequence intubation is quickly falling out of favor. Gastric reflux could cause aspiration if this is not done considering the general anesthesia can cause relaxation of the gastroesophageal sphincter allowing stomach contents to ascend through the esophagus into the trachea. A medical procedure known as

2442-474: The design phase, there are multiple approaches to estimating stress concentration factors. Several catalogs of stress concentration factors have been published. Perhaps most famous is Stress Concentration Design Factors by Peterson, first published in 1953. Finite element methods are commonly used in design today. Other methods include the boundary element method and meshfree methods . Stress concentrations can be mitigated through techniques that smoothen

2508-471: The effective crack tip radius and thus reduce the stress concentration. Hole Reinforcement : Adding higher strength material around the hole, usually in the form of bonded rings or doublers. Composite reinforcements can reduce the SCF. Shape Optimization : Adjusting the hole shape, often transitioning from circular to elliptical, to minimize stress gradients. This must be checked for feasibility. One example

2574-412: The endosternite cartilage in other arthropods. The embryos of Limulus polyphemus express ColA and hyaluronan in the gill cartilage and the endosternite, which indicates that these tissues are fibrillar-collagen-based cartilage. The endosternite cartilage forms close to Hh-expressing ventral nerve cords and expresses ColA and SoxE, a Sox9 analog. This is also seen in gill cartilage tissue. In cephalopods,

2640-416: The equations for the elastic stress distribution around a hole . The maximum stress felt near a hole or notch occurs in the area of lowest radius of curvature . In an elliptical hole of length 2 a {\displaystyle 2a} and width 2 b {\displaystyle 2b} , under a far-field stress σ 0 {\displaystyle \sigma _{0}} ,

2706-490: The expression SoxD and SoxE, analogs of the vertebrate Sox5/6 and Sox9, in the developing cartilage. The cartilage growth pattern is the same as in vertebrate cartilage. In gastropods, the interest lies in the odontophore , a cartilaginous structure that supports the radula. The most studied species regarding this particular tissue is Busycotypus canaliculatus . The odontophore is a vesicular cell rich cartilage, consisting of vacuolated cells containing myoglobin, surrounded by

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2772-464: The flow of stress around a discontinuity: Material Removal : Introducing auxiliary holes in the high stress region to create a more gradual transition. The size and position of these holes must be optimized. Known as crack tip blunting, a counter-intuitive example of reducing one of the worst types of stress concentrations, a crack , is to drill a large hole at the end of the crack. The drilled hole, with its relatively large size, serves to increase

2838-417: The flow of stress. Geometric discontinuities cause an object to experience a localised increase in stress. Examples of shapes that cause stress concentrations are sharp internal corners, holes, and sudden changes in the cross-sectional area of the object as well as unintentional damage such as nicks, scratches and cracks. High local stresses can cause objects to fail more quickly, so engineers typically design

2904-526: The geometry to minimize stress concentrations. Material discontinuities, such as inclusions in metals, may also concentrate the stress. Inclusions on the surface of a component may be broken from machining during manufacture leading to microcracks that grow in service from cyclic loading. Internally, the failure of the interfaces around inclusions during loading may lead to static failure by microvoid coalescence . The stress concentration factor , K t {\displaystyle K_{t}} ,

2970-448: The growth and remodeling of the extracellular matrix. Due to the great stress on the patellofemoral joint during resisted knee extension, the articular cartilage of the patella is among the thickest in the human body. The ECM of articular cartilage is classified into three regions: the pericellular matrix, the territorial matrix, and the interterritorial matrix. The mechanical properties of articular cartilage in load-bearing joints such as

3036-407: The initial chondrification that occurs during embryogenesis, cartilage growth consists mostly of the maturing of immature cartilage to a more mature state. The division of cells within cartilage occurs very slowly, and thus growth in cartilage is usually not based on an increase in size or mass of the cartilage itself. It has been identified that non-coding RNAs (e.g. miRNAs and long non-coding RNAs) as

3102-443: The interactions at the points of contact in meshing gear teeth, the interfaces between cams and followers , and the contact zones in ball bearings . Thermal Stress : Thermal stress occurs when different parts of a structure expand or contract at different rates due to variations in temperature. This differential in thermal expansion and contraction generates internal stresses, which can lead to areas of stress concentration within

3168-403: The median cricothyroid ligament , and postero-laterally by the cricothyroid joints. The cricoid is joined with the first tracheal ring inferiorly by the cricotracheal ligament . The cricothyroid muscle attaches to the anterior and lateral external aspects of the cricoid arch. The cricopharyngeus part of inferior pharyngeal constrictor muscle attaches onto the cricoid arch posterior to

3234-677: The millions of loading cycles experienced by human joins over a lifetime, would eventually lead to failure. For example, the elastic modulus of human bone is roughly 20 GPa while the softer regions of cartilage can be about 0.5 to 0.9 MPa. When there is a smooth gradient of materials properties, however, stresses are distributed evenly across the interface, which puts less wear on each individual part. The body solves this problem with stiffer, higher modulus layers near bone, with high concentrations of mineral deposits such as hydroxyapatite. Collagen fibers (which provide mechanical stiffness in cartilage) in this region are anchored directly to bones, reducing

3300-404: The models used for the studies of cartilage are Octopus vulgaris and Sepia officinalis . The cephalopod cranial cartilage is the invertebrate cartilage that shows more resemblance to the vertebrate hyaline cartilage. The growth is thought to take place throughout the movement of cells from the periphery to the center. The chondrocytes present different morphologies related to their position in

3366-418: The most important epigenetic modulators can affect the chondrogenesis. This also justifies the non-coding RNAs' contribution in various cartilage-dependent pathological conditions such as arthritis, and so on. The articular cartilage function is dependent on the molecular composition of the extracellular matrix (ECM). The ECM consists mainly of proteoglycan and collagens . The main proteoglycan in cartilage

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3432-418: The possible deformation. Moving closer to soft tissue into the region known as the tidemark, the density of chondrocytes increases and collagen fibers are rearranged to optimize for stress dissipation and low friction. The outermost layer near the articular surface is known as the superficial zone, which primarily serves as a lubrication region. Here cartilage is characterized by a dense extracellular matrix and

3498-483: The radius of curvature approaches zero, such as at the tip of a sharp crack, the maximum stress approaches infinity and a stress concentration factor cannot therefore be used for a crack. Instead, the stress intensity factor which defines the scaling of the stress field around a crack tip, is used. Stress concentration can arise due to various factors. The following are the main causes of stress concentration: Material Defects : When designing mechanical components, it

3564-451: The stems of some mushrooms, are sometimes called "cartilaginous", although they contain no cartilage. Cricoid cartilage The cricoid cartilage / ˌ k r aɪ k ɔɪ d ˈ k ɑː r t ɪ l ɪ dʒ / , or simply cricoid (from the Greek krikoeides meaning "ring-shaped") or cricoid ring , is the only complete ring of cartilage around the trachea . It forms the back part of

3630-410: The stress at the ends of the major axes is given by Inglis' equation: where ρ {\displaystyle \rho } is the radius of curvature of the elliptical hole. For circular holes in an infinite plate where a = b {\displaystyle a=b} , the stress concentration factor is K t = 3 {\displaystyle K_{t}=3} . As

3696-443: The stress concentration. However, repeated low level loading may cause a fatigue crack to initiate and slowly grow at a stress concentration leading to the failure of even ductile materials. Fatigue cracks always start at stress raisers, so removing such defects increases the fatigue strength . Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to

3762-624: The structure. Geometric Discontinuities : Features such as steps on a shaft, shoulders, and other abrupt changes in the cross-sectional area of components are often necessary for mounting elements like gears and bearings or for assembly considerations. While these features are essential for the functionality of the device, they introduce sharp transitions in geometry that become hotspots for stress concentration. Additionally, design elements like oil holes, grooves, keyways, splines, and screw threads also introduce discontinuities that further exacerbate stress concentration. Rough Surface : Imperfections on

3828-549: The surface of components, such as machining scratches, stamp marks, or inspection marks, can interrupt the smooth flow of stress across the surface, leading to localized increases in stress. These imperfections, although often small, can significantly impact the durability and performance of mechanical components by initiating stress concentration. There are experimental methods for measuring stress concentration factors including photoelastic stress analysis , thermoelastic stress analysis, brittle coatings or strain gauges . During

3894-410: The tissue has two main regions. In the first region, the displacement is rapid due to the initial flow of fluid out of the cartilage, and in the second region, the displacement slows down to an eventual constant equilibrium value. Under the commonly used loading conditions, the equilibrium displacement can take hours to reach. In both the creep mode and the relaxation mode of a confined compression test,

3960-435: The tissue. Indentation testing is an additional type of test commonly used to characterize cartilage. Indentation testing involves using an indentor (usually <0.8 mm) to measure the displacement of the tissue under constant load. Similar to confined compression testing, it may take hours to reach equilibrium displacement. This method of testing can be used to measure the aggregate modulus, Poisson's ratio, and permeability of

4026-413: The tissue. Degradation of this layer can put additional stresses on deeper layers which are not designed to support the same deformations. Another common effect of aging is increased crosslinking of collagen fibers. This leads to stiffer cartilage as a whole, which again can lead to early failure as stiffer tissue is more susceptible to fatigue based failure. Aging in calcified regions also generally leads to

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4092-629: The tissue. Initially, there was a misconception that due to its predominantly water-based composition, cartilage had a Poisson's ratio of 0.5 and should be modeled as an incompressible material. However, subsequent research has disproven this belief. The Poisson’s ratio of articular cartilage has been measured to be around 0.4 or lower in humans and ranges from 0.46–0.5 in bovine subjects. The mechanical properties of articular cartilage are largely anisotropic, test-dependent, and can be age-dependent. These properties also depend on collagen-proteoglycan interactions and therefore can increase/decrease depending on

4158-419: The tissue. The embryos of S. officinalis express ColAa, ColAb, and hyaluronan in the cranial cartilages and other regions of chondrogenesis. This implies that the cartilage is fibrillar-collagen-based. The S. officinalis embryo expresses hh, whose presence causes ColAa and ColAb expression and is also able to maintain proliferating cells undiferentiated. It has been observed that this species presents

4224-586: The total content of water, collagen, glycoproteins, etc. For example, increased glucosaminoglycan content leads to an increase in compressive stiffness, and increased water content leads to a lower aggregate modulus. In addition to its role in load-bearing joints, cartilage serves a crucial function as a gradient material between softer tissues and bone. Mechanical gradients are crucial for your body’s function, and for complex artificial structures including joint implants. Interfaces with mismatched material properties lead to areas of high stress concentration which, over

4290-519: The trachea attaches onto it. It occurs at the level of the C6 vertebra . The posterior part of the cricoid cartilage ( cricoid lamina ) is somewhat broader than the anterior and lateral part ( cricoid arch ). Its shape is said to resemble a signet ring . The cricoid arch is the curved and vertically narrow anterior portion of the cricoid cartilage. Anteriorly, it measures 5-7 mm superoinferiorly; it becomes wider on eithers side towards its transition into

4356-406: Was considered the standard of care during rapid sequence induction for many years. The American Heart Association still advocates the use of cricoid pressure during resuscitation using a BVM , and during emergent oral endotracheal intubation. However, recent research increasingly suggests that cricoid pressure may not be as advantageous as once thought. The initial article by Sellick was based on

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