Contortion (sometimes contortionism ) is a performance art in which performers called contortionists showcase their skills of extreme physical flexibility. Contortion acts often accompany acrobatics , circus acts, street performers and other live performing arts. Contortion acts are typically performed in front of a live audience. An act will showcase one or more artists performing a choreographed set of moves or poses, often to music, which require extreme flexibility . The physical flexibility required to perform such acts greatly exceeds that of the general population. It is the dramatic feats of seemingly inhuman flexibility that captivate audiences.
110-459: Many factors affect the flexibility of performers including age, genetics, stature, and adherence to rigorous physical training routines. Most contortionists are generally categorized as "frontbenders" or "backbenders", depending on the direction in which their spine is most flexible. Relatively few performers are equally adept at both. Skills performed by contortionists include: A medical publication from 2008 suggests that long-term damage to
220-450: A chitin support. The silk gel is part of the protein portion and is mainly composed of glycine and alanine . It is not an ordered structure. The acidic proteins play a role in the configuration of the sheets. The chitin is highly ordered and is the framework of the matrix. The main elements of the overall are: In bone, mineralization starts from a heterogeneous solution having calcium and phosphate ions. The mineral nucleates, inside
330-439: A composite material , mineral function as a highly strong and highly wear- and erosion-resistant surface layer. While the soft organic scaffolds provide a tough load-bearing base to accommodate excessive strains. Ice temptation/ Freeze casting is a new method that uses the physics of ice formation to develop a layered-hybrid material. Specifically, ceramic suspensions are directionally frozen under conditions designed to promote
440-578: A finite element model analysis to investigate the behaviour of the interface. A model has shown that during tension, the back stress that is induced during the plastic stretch of the material plays a big role in the hardening of the mineralized tissue. As well, the nanoscale asperities that is on the tablet surfaces provide resistance to interlamellar sliding and so strengthen the material. A surface topology study has shown that progressive tablet locking and hardening, which are needed for spreading large deformations over large volumes, occurred because of
550-628: A hernia . Spinal stenosis is a narrowing of the spinal canal which can occur in any region of the spine though less commonly in the thoracic region. The stenosis can constrict the spinal canal giving rise to a neurological deficit . Pain at the coccyx (tailbone) is known as coccydynia . Spinal cord injury is damage to the spinal cord that causes changes in its function, either temporary or permanent. Spinal cord injuries can be divided into categories: complete transection, hemisection, central spinal cord lesions, posterior spinal cord lesions, and anterior spinal cord lesions. Scalloping vertebrae
660-412: A central cavity, the central canal . Adjacent to each vertebra emerge spinal nerves . The spinal nerves provide sympathetic nervous supply to the body, with nerves emerging forming the sympathetic trunk and the splanchnic nerves . The spinal canal follows the different curves of the column; it is large and triangular in those parts of the column that enjoy the greatest freedom of movement, such as
770-449: A curve, convex forward, that begins at the axis (second cervical vertebra) at the apex of the odontoid process or dens and ends at the middle of the second thoracic vertebra; it is the least marked of all the curves. This inward curve is known as a lordotic curve. The thoracic curve, concave forward, begins at the middle of the second and ends at the middle of the twelfth thoracic vertebra. Its most prominent point behind corresponds to
880-457: A group. In the past, contortionists were associated almost exclusively with circuses and fairs. More recently they have also been found performing in nightclubs , amusement parks , in magazine advertisements, at trade shows, on television variety shows , in music videos , and as warmup acts or in the background at music concerts. The Ross Sisters were American contortionists most famous for their musical rendition of 'Solid Potato Salad' in
990-408: A larger variety of material chemistries can be used to simulate the same properties in engineering applications. However, the success of biomimetics lies in fully grasping the performance and mechanics of these biological hard tissues before swapping the natural components with artificial materials for engineering design. Mineralized tissues combine stiffness, low weight, strength and toughness due to
1100-452: A layer-by-layer assembly to make multilayered composites like nacre. Some examples of efforts in this direction include alternating layers of hard and soft components of TiN/Pt with an ion beam system. The composites made by this sequential deposition technique do not have a segmented layered microstructure. Thus, sequential adsorption has been proposed to overcome this limitation and consists of repeatedly adsorbing electrolytes and rinsing
1210-413: A neural arch, while the haemal arch is found underneath the centrum in the caudal (tail) vertebrae of fish , most reptiles , some birds, some dinosaurs and some mammals with long tails. The vertebral processes can either give the structure rigidity, help them articulate with ribs, or serve as muscle attachment points. Common types are transverse process, diapophyses, parapophyses, and zygapophyses (both
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#17328811005071320-535: A region can vary but overall the number remains the same. In a human vertebral column, there are normally 33 vertebrae. The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs , and the lower nine are fused in adults, five in the sacrum and four in the coccyx , or tailbone . The articulating vertebrae are named according to their region of the spine. From top to bottom, there are 7 cervical vertebrae , 12 thoracic vertebrae and 5 lumbar vertebrae . The number of those in
1430-456: A region can vary but overall the number remains the same. The number of those in the cervical region, however, is only rarely changed. The vertebrae of the cervical, thoracic, and lumbar spines are independent bones and generally quite similar. The vertebrae of the sacrum and coccyx are usually fused and unable to move independently. Two special vertebrae are the atlas and axis , on which the head rests. A typical vertebra consists of two parts:
1540-399: A remnant of the notochord. Reptiles often retain the primitive intercentra, which are present as small crescent-shaped bony elements lying between the bodies of adjacent vertebrae; similar structures are often found in the caudal vertebrae of mammals. In the tail, these are attached to chevron-shaped bones called haemal arches , which attach below the base of the spine, and help to support
1650-438: A result of lifting the head and the lumbar curvature forms as a result of walking. The vertebral column surrounds the spinal cord which travels within the spinal canal , formed from a central hole within each vertebra . The spinal cord is part of the central nervous system that supplies nerves and receives information from the peripheral nervous system within the body. The spinal cord consists of grey and white matter and
1760-419: A scale of several hundred nanometres. The second are the elementary components of mineralized tissues at a scale of tens of nanometres. The components are the mineral crystals of hydroxyapatite , cylindrical collagen molecules, organic molecules such as lipids and proteins, and finally water. The hierarchical structure common to all mineralized tissues is the key to their mechanical performance. The mineral
1870-452: A thin silicon film. The interfaces are etched by reactive ion etching and then filled with photoresist . There are three films deposited consecutively. Although the MEMS technology is expensive and more time-consuming, there is a high degree of control over the morphology and large numbers of specimens can be made. The method of self-assembly tries to reproduce not only the properties, but also
1980-453: A two layered system, one of which is nacre. Nacre constitutes the inner layer while the other, outer, layer is made from calcite . The latter is hard and thus prevents any penetration through the shell, but is subject to brittle failure. On the other hand, nacre is softer and can uphold inelastic deformations, which makes it tougher than the hard outer shell. The mineral found in nacre is aragonite , CaCO 3 , and it occupies 95% vol. Nacre
2090-496: Is 3000 times tougher than aragonite and this has to do with the other component in nacre, the one that takes up 5% vol., which is the softer organic biopolymers. Furthermore, the nacreous layer also contains some strands of weaker material called growth lines that can deflect cracks. The Microscale can be imagined by a three-dimensional brick and mortar wall. The bricks would be 0.5 μm thick layers of microscopic aragonite polygonal tablets approximately 5-8 μm in diameter. What holds
2200-404: Is a complex biological material. The types of mechanisms that operate at different structural length scales are yet to be properly defined. Five hierarchical structures of bone are presented below. Compact bone and spongy bone are on a scale of several millimetres to 1 or more centimetres. There are two hierarchical structures on the microscale. The first, at a scale of 100 μm to 1 mm,
2310-406: Is a notochord remnant). The dorsal portion of the vertebral column houses the spinal canal , an elongated cavity formed by alignment of the vertebral neural arches that encloses and protects the spinal cord , with spinal nerves exiting via the intervertebral foramina to innervate each body segments . There are around 50,000 species of animals that have a vertebral column. The human spine
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#17328811005072420-413: Is classed as a spinal disease or dorsopathy and includes the following abnormal curvatures: Individual vertebrae of the human vertebral column can be felt and used as surface anatomy , with reference points are taken from the middle of the vertebral body. This provides anatomical landmarks that can be used to guide procedures such as a lumbar puncture and also as vertical reference points to describe
2530-416: Is curved in several places, a result of human bipedal evolution . These curves increase the vertebral column's strength, flexibility, and ability to absorb shock, stabilising the body in upright position. When the load on the spine is increased, the curvatures increase in depth (become more curved) to accommodate the extra weight. They then spring back when the weight is removed. The upper cervical spine has
2640-652: Is dislocated without medical examination such as an X-ray . However, as long as the joint socket is the right shape, most extreme bends can be achieved without dislocating the joint. Actual dislocations are rarely used during athletic contortion acts since they make the joint more unstable and prone to injury, and a dislocated limb cannot lift itself or support any weight. The primary origins of contortion take place in Asian traditions. In China and Mongolia , traditional Buddhist Cham dances would incorporate contortion into their movement. The success of these dances then encouraged
2750-543: Is extremely strong but brittle and the soft "mortar" layer between the bricks generates limited deformation, thereby allowing for the relief of locally high stresses while also providing ductility without too much loss in strength. Additive manufacturing encompasses a family of technologies that draw on computer designs to build structures layer by layer. Recently, a lot of bioinspired materials with elegant hierarchical motifs have been built with features ranging in size from tens of micrometers to one submicrometer. Therefore,
2860-412: Is inevitable in order to properly reconstruct them artificially. Even if questions remain in some aspects and the mechanism of mineralization of many mineralized tissues need yet to be determined, there are some ideas about those of mollusc shell, bone and sea urchin. The main structural elements involved in the mollusk shell formation process are: a hydrophobic silk gel, aspartic acid rich protein, and
2970-411: Is inside the compact bone where cylindrical units called osteons and small struts can be distinguished. The second hierarchical structure, the ultrastructure, at a scale of 5 to 10 μm, is the actual structure of the osteons and small struts. There are also two hierarchical structures on the nanoscale. The first being the structure inside the ultrastructure that are fibrils and extrafibrillar space, at
3080-400: Is involved in the toughening properties of mineralized tissues. The interaction in the organic-inorganic interface is important to understand these toughening properties. At the interface, a very large force (>6-5 nN) is needed to pull the protein molecules away from the aragonite mineral in nacre, despite the fact that the molecular interactions are non-bonded. Some studies perform
3190-459: Is its inability to form a segmented layered microstructure. Segmentation is an important property of nacre used for crack deflection of the ceramic phase without fracturing it. As a consequence, this technique does not mimic microstructural characteristics of nacre beyond the layered organic/inorganic layered structure and requires further investigation. The various studies have increased progress towards understanding mineralized tissues. However, it
3300-467: Is one of the most-studied examples, as the general structure of human vertebrae is fairly typical ( homologous ) of that found in other mammals , reptiles and birds . The shape of the vertebral body does, however, vary somewhat between different groups of living species. Individual vertebrae are named according to their corresponding body region ( neck , thorax , abdomen , pelvis or tail ). In clinical medicine , features on vertebrae (particularly
3410-432: Is shallow, and by the laminae and transverse processes in the thoracic region, where it is deep and broad; these grooves lodge the deep muscles of the back. Lateral to the spinous processes are the articular processes, and still more laterally the transverse processes. In the thoracic region, the transverse processes stand backward, on a plane considerably behind that of the same processes in the cervical and lumbar regions. In
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3520-433: Is still unclear which micro/nanostructural features are essential to the material performance of these tissues. Also constitutive laws along various loading paths of the materials are currently unavailable. For nacre, the role of some nanograins and mineral bridges requires further studies to be fully defined. Successful biomimicking of mollusk shells will depend will on gaining further knowledge of all these factors, especially
3630-423: Is that the highly oriented stiff components give the materials great mechanical strength and stiffness , while the soft matrix “glues” the stiff components and transfer the stress to them. Moreover, the controlled plastic deformation of the soft matrix during fracture provides an additional toughening mechanism. Such a common strategy was perfected by nature itself over millions of years of evolution, giving us
3740-470: Is the core part of the axial skeleton in vertebrate animals . The vertebral column is the defining and eponymous characteristic of the vertebrate endoskeleton , where the notochord (an elastic collagen -wrapped glycoprotein rod) found in all chordates has been replaced by a segmented series of mineralized irregular bones (or sometimes, cartilages ) called vertebrae , separated by fibrocartilaginous intervertebral discs (the center of which
3850-412: Is the increase in the concavity of the posterior vertebral body. It can be seen on lateral X-ray and sagittal views of CT and MRI scans. Its concavity is due to the increased pressure exerting on the vertebrae due to a mass. Internal spinal mass such as spinal astrocytoma , ependymoma , schwannoma , neurofibroma , and achondroplasia causes vertebrae scalloping. Excessive or abnormal spinal curvature
3960-452: Is the inorganic component of mineralized tissues. This constituent is what makes the tissues harder and stiffer. Hydroxyapatite , calcium carbonate , silica , calcium oxalate , whitlockite , and monosodium urate are examples of minerals found in biological tissues. In mollusc shells, these minerals are carried to the site of mineralization in vesicles within specialized cells. Although they are in an amorphous mineral phase while inside
4070-516: The Arabian (breed) can have one less vertebrae and pair of ribs. This anomaly disappears in foals that are the product of an Arabian and another breed of horse. Vertebrae are defined by their location in the vertebral column. Cervical vertebrae are those in the neck area. With the exception of the two sloth genera ( Choloepus and Bradypus ) and the manatee genus, ( Trichechus ), all mammals have seven cervical vertebrae. In other vertebrates,
4180-585: The Chinese tradition , contortion is typically performed as a feat of acrobatics , used to dazzle the audience with the unusual shapes built before them. According to Chinese historical records, early contortionism originated in China during Western Zhou Dynasty (1045-771 BC), which matured in Sui Dynasty (581–618). Spine (anatomy) The vertebral column , also known as the spinal column , spine or backbone ,
4290-432: The crack of materials only can happen and propagate on the microscopic scale, which wouldn't lead to the fracture of the whole structure. However, the time-consuming of manufacturing the hierarchical mechanical materials, especially on the nano- and micro-scale limited the further application of this technique in large-scale manufacturing. Layer-by-layer deposition is a technique that as suggested by its name consists of
4400-433: The intervertebral discs . The notochord disappears in the sclerotome (vertebral body) segments but persists in the region of the intervertebral discs as the nucleus pulposus . The nucleus pulposus and the fibers of the anulus fibrosus make up the intervertebral disc. The primary curves (thoracic and sacral curvatures) form during fetal development. The secondary curves develop after birth. The cervical curvature forms as
4510-438: The macroscopic scales are used to imitate these week interfaces with layered composite ceramic tablets that are held together by weak interface “glue”. Hence, these large scale models can overcome the brittleness of ceramics. Since other mechanisms like tablet locking and damage spreading also play a role in the toughness of nacre, other models assemblies inspired by the waviness of microstructure of nacre have also been devised on
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4620-412: The paraxial mesoderm that lies at the sides of the neural tube and they contain the precursors of spinal bone, the vertebrae ribs and some of the skull, as well as muscle, ligaments and skin. Somitogenesis and the subsequent distribution of somites is controlled by a clock and wavefront model acting in cells of the paraxial mesoderm. Soon after their formation, sclerotomes , which give rise to some of
4730-436: The sacrum and coccyx are fused without a central foramen. The vertebral arch is formed by a ventral pair of pedicles and a dorsal pair of laminae , and supports seven processes , four articular , two transverse and one spinous , the latter also being known as the neural spine. The transverse and spinous processes and their associated ligaments serve as important attachment sites for back and paraspinal muscles and
4840-435: The spinal canal , a body cavity that contains the spinal cord . Because the vertebral column will outgrow the spinal cord during child development , by adulthood the spinal cord often ends at the upper lumbar spine (at around L1/L2 level), the lower ( caudal ) end of the spinal canal is occupied by a ponytail -like bundle of spinal nerves descriptively called cauda equina (from Latin " horse's tail " ), and
4950-411: The spinal cord and the notochord . This column of tissue has a segmented appearance, with alternating areas of dense and less dense areas. As the sclerotome develops, it condenses further eventually developing into the vertebral body . Development of the appropriate shapes of the vertebral bodies is regulated by HOX genes . The less dense tissue that separates the sclerotome segments develop into
5060-420: The spinous process ) can be used as surface landmarks to guide medical procedures such as lumbar punctures and spinal anesthesia . There are also many different spinal diseases in humans that can affect both the bony vertebrae and the intervertebral discs, with kyphosis / scoliosis , ankylosing spondylitis , degenerative discs and spina bifida being recognizable examples. The number of vertebrae in
5170-438: The thoracolumbar fasciae . The spinous processes of the cervical and lumbar regions can be felt through the skin, and are important surface landmarks in clinical medicine . The four articular processes for two pairs of plane facet joints above and below each vertebra, articulating with those of the adjacent vertebrae and are joined by a thin portion of the neural arch called the pars interarticularis . The orientation of
5280-409: The vertebral body (or centrum ), which is ventral (or anterior , in the standard anatomical position ) and withstands axial structural load ; and the vertebral arch (also known as neural arch ), which is dorsal (or posterior ) and provides articulations and anchorages for ribs and core skeletal muscles . Together, these enclose the vertebral foramen , the series of which align to form
5390-449: The vesicles , the mineral destabilizes as it passes out of the cell and crystallizes. In bone, studies have shown that calcium phosphate nucleates within the hole area of the collagen fibrils and then grows in these zones until it occupies the maximum space. The organic part of mineralized tissues is made of proteins. In bone for example, the organic layer is the protein collagen. The degree of mineral in mineralized tissues varies and
5500-450: The 1944 movie Broadway Rhythm . In addition, contortion photos and digital movie clips are traded by fans on the Internet, and several web sites provide original photos of contortion acts for a monthly fee, or sell videotapes of performances through the mail. Some loose-jointed people are able to pop a joint out of its socket without pain, thereby making it difficult to determine if a joint
5610-454: The act to expand into other forms of performance. Contortion also found similarities and expressions in the Hindu doctrine of yoga . Throughout daily meditation , yoga practitioners work to assume many similar poses to those in the performance-based contortion. The recognition of these similarities in various practices and thoughts brought contortion into more clear and explicit light. For those in
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#17328811005075720-425: The adjacent vertebra to a degree less than a dislocation. Spondylolysis , also known as a pars defect, is a defect or fracture at the pars interarticularis of the vertebral arch. Spinal disc herniation , more commonly called a "slipped disc", is the result of a tear in the outer ring ( anulus fibrosus ) of the intervertebral disc , which lets some of the soft gel-like material, the nucleus pulposus , bulge out in
5830-416: The bone of the skull, the vertebrae and ribs, migrate, leaving the remainder of the somite now termed a dermamyotome behind. This then splits to give the myotomes which will form the muscles and dermatomes which will form the skin of the back. Sclerotomes become subdivided into an anterior and a posterior compartment. This subdivision plays a key role in the definitive patterning of vertebrae that form when
5940-427: The bony vertebral body. In most ray-finned fishes , including all teleosts , these two structures are fused with, and embedded within, a solid piece of bone superficially resembling the vertebral body of mammals. In living amphibians , there is simply a cylindrical piece of bone below the vertebral arch, with no trace of the separate elements present in the early tetrapods. In cartilaginous fish , such as sharks ,
6050-418: The bricks together are the mortars and in the case of nacre, it is the 20-30 nm organic material that plays this role. Even though these tablets are usually illustrated as flat sheets, different microscopy techniques have shown that they are wavy in nature with amplitudes as large as half of the tablet's thickness. This waviness plays an important role in the fracture of nacre as it will progressively lock
6160-506: The centrum. Centra with flat ends are acoelous , like those in mammals. These flat ends of the centra are especially good at supporting and distributing compressive forces. Amphicoelous vertebra have centra with both ends concave. This shape is common in fish, where most motion is limited. Amphicoelous centra often are integrated with a full notochord . Procoelous vertebrae are anteriorly concave and posteriorly convex. They are found in frogs and modern reptiles. Opisthocoelous vertebrae are
6270-423: The cervical and lumbar regions, and is small and rounded in the thoracic region, where motion is more limited. The spinal cord terminates in the conus medullaris and cauda equina . Spina bifida is a congenital disorder in which there is a defective closure of the vertebral arch. Sometimes the spinal meninges and also the spinal cord can protrude through this, and this is called spina bifida cystica . Where
6380-464: The cervical and upper part of the thoracic regions and gradually increasing in size to the last lumbar. They transmit the special spinal nerves and are situated between the transverse processes in the cervical region and in front of them, in the thoracic and lumbar regions. There are different ligaments involved in the holding together of the vertebrae in the column, and in the column's movement. The anterior and posterior longitudinal ligaments extend
6490-511: The cervical region, however, is only rarely changed, while that in the coccygeal region varies most. Excluding rare deviations, the total number of vertebrae ranges from 32 to 35. In about 10% of people, both the total number of pre-sacral vertebrae and the number of vertebrae in individual parts of the spine can vary. The most frequent deviations are: 11 (rarely 13) thoracic vertebrae, 4 or 6 lumbar vertebrae, 3 or 5 coccygeal vertebrae (rarely up to 7). There are numerous ligaments extending
6600-430: The cervical region, the transverse processes are placed in front of the articular processes, lateral to the pedicles and between the intervertebral foramina. In the thoracic region they are posterior to the pedicles, intervertebral foramina, and articular processes. In the lumbar region they are in front of the articular processes, but behind the intervertebral foramina. The sides of the vertebral column are separated from
6710-421: The child begins to walk. When viewed from in front, the width of the bodies of the vertebrae is seen to increase from the second cervical to the first thoracic; there is then a slight diminution in the next three vertebrae. Below this, there is again a gradual and progressive increase in width as low as the sacrovertebral angle. From this point there is a rapid diminution, to the apex of the coccyx. From behind,
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#17328811005076820-429: The condition does not involve this protrusion it is known as spina bifida occulta . Sometimes all of the vertebral arches may remain incomplete. Another, though rare, congenital disease is Klippel–Feil syndrome , which is the fusion of any two of the cervical vertebrae. Spondylolisthesis is the forward displacement of a vertebra and retrolisthesis is a posterior displacement of one vertebral body with respect to
6930-402: The cranial zygapophyses and the caudal zygapophyses). The centrum of the vertebra can be classified based on the fusion of its elements. In temnospondyls , bones such as the spinous process , the pleurocentrum and the intercentrum are separate ossifications. Fused elements, however, classify a vertebra as having holospondyly. A vertebra can also be described in terms of the shape of the ends of
7040-403: The curvatures of the vertebral column. The articulating vertebrae are named according to their region of the spine. Vertebrae in these regions are essentially alike, with minor variation. These regions are called the cervical spine, thoracic spine, lumbar spine, sacrum, and coccyx. There are seven cervical vertebrae, twelve thoracic vertebrae, and five lumbar vertebrae. The number of vertebrae in
7150-437: The dermal skeleton of early agnathans . The dermal skeleton is just surface dentin and basal bone, which is sometimes overlaid by enameloid. It is thought that the dermal skeleton eventually became scales, which are homologous to teeth. Teeth were first seen in chondrichthyans and were made from all three components of the dermal skeleton, namely dentin, basal bone and enameloid. The mineralization mechanism of mammalian tissue
7260-447: The facet joints restricts the range of motion between the vertebrae. Underneath each pedicle is a small hole (enclosed by the pedicle of the vertebral below) called intervertebral foramen , which transmit the corresponding spinal nerve and dorsal root ganglion that exit the spinal canal. From top to bottom, the vertebrae are: For some medical purposes, adjacent vertebral regions may be considered together: The vertebral column
7370-602: The formation of lamellar ice crystals , which expel the ceramic particles as they grow. After sublimation of the water, this results in a layered homogeneous ceramic scaffold that, architecturally, is a negative replica of the ice. The scaffold can then be filled with a second soft phase so as to create a hard–soft layered composite. This strategy is also widely applied to build other kinds of bioinspired materials, like extremely strong and tough hydrogels , metal/ceramic, and polymer/ceramic hybrid biomimetic materials with fine lamellar or brick-and-mortar architectures. The "brick" layer
7480-426: The hole area of the collagen fibrils, as thin layers of calcium phosphate , which then grow to occupy the maximum space available there. The mechanisms of mineral deposition within the organic portion of the bone are still under investigation. Three possible suggestions are that nucleation is either due to the precipitation of calcium phosphate solution, caused by the removal of biological inhibitors or occurs because of
7590-410: The inspiration for building the next generation of structural materials. There are several techniques used to mimic these tissues. Some of the current techniques are described here. The large scale model of materials is based on the fact that crack deflection is an important toughening mechanism of nacre. This deflection happens because of the weak interfaces between the aragonite tiles. Systems on
7700-502: The interaction of calcium-binding proteins. The sea urchin embryo has been used extensively in developmental biology studies. The larvae form a sophisticated endoskeleton that is made of two spicules . Each of the spicules is a single crystal of mineral calcite . The latter is a result of the transformation of amorphous CaCO 3 to a more stable form. Therefore, there are two mineral phases in larval spicule formation. The mineral-protein interface with its underlying adhesion forces
7810-581: The large scale. All hard materials in animals are achieved by the biomineralization process - dedicated cells deposit minerals to a soft polymeric (protein) matrix to strengthen, harden and/or stiffen it. Thus, biomimetic mineralization is an obvious and effective process for building synthetic materials with superior mechanical properties. The general strategy is started with organic scaffolds with ion-binding sites that promote heterogeneous nucleation. Then localized mineralization can be achieved by controlled ion supersaturation on these ion-binding sites. In such
7920-449: The length of the column, which include the anterior and posterior longitudinal ligaments at the front and back of the vertebral bodies , the ligamentum flavum in deep to the laminae , the interspinous and supraspinous ligaments between spinous processes , and the intertransverse ligaments between the transverse processes . The vertebrae in the human vertebral column is divided into different body regions , which correspond to
8030-432: The length of the vertebral column along the front and back of the vertebral bodies. The interspinous ligaments connect the adjoining spinous processes of the vertebrae. The supraspinous ligament extends the length of the spine running along the back of the spinous processes, from the sacrum to the seventh cervical vertebra . From there it is continuous with the nuchal ligament . The striking segmented pattern of
8140-403: The locations of other parts of human anatomy, such as the positions of organs . The general structure of vertebrae in other animals is largely the same as in humans. Individual vertebrae are composed of a centrum (body), arches protruding from the top and bottom of the centrum, and various processes projecting from the centrum and/or arches. An arch extending from the top of the centrum is called
8250-408: The lumbar region, by narrower intervals in the neck, and are closely approximated in the middle of the thoracic region. Occasionally one of these processes deviates a little from the median line — which can sometimes be indicative of a fracture or a displacement of the spine. On either side of the spinous processes is the vertebral groove formed by the laminae in the cervical and lumbar regions, where it
8360-457: The macroscale, the shell, its two layers ( nacre and calcite ), and weaker strands inside nacre represent three hierarchical structures. On the microscale, the stacked tablet layers and the wavy interface between them are two other hierarchical structures. Lastly, on the nanoscale, the connecting organic material between the tablets as well as the grains from which they are made of is the final sixth hierarchical structure in nacre. Like nacre and
8470-405: The mechanisms involved in vertebral segmentation are conserved across vertebrates. In humans the first four somites are incorporated in the base of the occipital bone of the skull and the next 33 somites will form the vertebrae, ribs, muscles, ligaments and skin. The remaining posterior somites degenerate. During the fourth week of embryogenesis , the sclerotomes shift their position to surround
8580-417: The mineral hydroxyapatite or one analogous to it. Imaging techniques such as infrared spectroscopy are used to provide information on the type of mineral phase and changes in mineral and matrix composition involved in the disease. Also, clastic cells are cells that cause mineralized tissue resorption . If there is an unbalance of clastic cell, this will disrupt resorptive activity and cause diseases. One of
8690-442: The minerals they contain. The secret to this underlying strength is in the organized layering of the tissue. Due to this layering, loads and stresses are transferred throughout several length-scales, from macro to micro to nano, which results in the dissipation of energy within the arrangement. These scales or hierarchical structures are therefore able to distribute damage and resist cracking. Two types of biological tissues have been
8800-771: The musculature. These latter bones are probably homologous with the ventral ribs of fish. The number of vertebrae in the spines of reptiles is highly variable, and may be several hundred in some species of snake . Mineralized tissue Mineralized tissues are biological tissues that incorporate minerals into soft matrices. Typically these tissues form a protective shield or structural support. Bone, mollusc shells , deep sea sponge Euplectella species, radiolarians , diatoms , antler bone, tendon , cartilage , tooth enamel and dentin are some examples of mineralized tissues. These tissues have been finely tuned to enhance their mechanical capabilities over millions of years of evolution. Thus, mineralized tissues have been
8910-423: The next vertebral body fits. Even these patterns are only generalisations, however, and there may be variation in form of the vertebrae along the length of the spine even within a single species. Some unusual variations include the saddle-shaped sockets between the cervical vertebrae of birds and the presence of a narrow hollow canal running down the centre of the vertebral bodies of geckos and tuataras , containing
9020-405: The number of cervical vertebrae can range from a single vertebra in amphibians to as many as 25 in swans or 76 in the extinct plesiosaur Elasmosaurus . The dorsal vertebrae range from the bottom of the neck to the top of the pelvis . Dorsal vertebrae attached to the ribs are called thoracic vertebrae, while those without ribs are called lumbar vertebrae. The sacral vertebrae are those in
9130-446: The opposite, possessing anterior convexity and posterior concavity. They are found in salamanders, and in some non-avian dinosaurs. Heterocoelous vertebrae have saddle -shaped articular surfaces. This type of configuration is seen in turtles that retract their necks, and birds, because it permits extensive lateral and vertical flexion motion without stretching the nerve cord too extensively or wringing it about its long axis. In horses,
9240-431: The organic component in nacre is known to restrict the growth of aragonite. Some of the regulatory proteins in mineralized tissues are osteonectin , osteopontin , osteocalcin , bone sialoprotein and dentin phosphophoryn . In nacre, the organic component is porous, which allows the formation of mineral bridges responsible for the growth and order of the nacreous tablets. Understanding the formation of biological tissues
9350-420: The organic component occupies a smaller volume as tissue hardness increases. However, without this organic portion, the biological material would be brittle and break easily. Hence, the organic component of mineralized tissues increases their toughness . Moreover, many proteins are regulators in the mineralization process. They act in the nucleation or inhibition of hydroxyapatite formation. For example,
9460-429: The organism. For example, kidney stones contain mineralized tissues that are developed through pathologic processes. Hence, biomineralization is an important process to understand how these diseases occur. The evolution of mineralized tissues has been puzzling for more than a century. It has been hypothesized that the first mechanism of animal tissue mineralization began either in the oral skeleton of conodont or
9570-498: The other mineralized tissues, bone has a hierarchical structure that is also formed by the self-assembly of smaller components. The mineral in bone (known as bone mineral ) is hydroxyapatite with a lot of carbonate ions, while the organic portion is made mostly of collagen and some other proteins. The hierarchical structural of bone spans across to a three tiered hierarchy of the collagen molecule itself. Different sources report different numbers of hierarchical level in bone, which
9680-423: The pelvic region, and range from one in amphibians, to two in most birds and modern reptiles, or up to three to five in mammals. When multiple sacral vertebrae are fused into a single structure, it is called the sacrum. The synsacrum is a similar fused structure found in birds that is composed of the sacral, lumbar, and some of the thoracic and caudal vertebra, as well as the pelvic girdle . Caudal vertebrae compose
9790-418: The posterior part of one somite fuses to the anterior part of the consecutive somite during a process termed resegmentation. Disruption of the somitogenesis process in humans results in diseases such as congenital scoliosis. So far, the human homologues of three genes associated to the mouse segmentation clock, (MESP2, DLL3 and LFNG), have been shown to be mutated in cases of congenital scoliosis, suggesting that
9900-417: The posterior surface by the articular processes in the cervical and thoracic regions and by the transverse processes in the lumbar region. In the thoracic region, the sides of the bodies of the vertebrae are marked in the back by the facets for articulation with the heads of the ribs. More posteriorly are the intervertebral foramina, formed by the juxtaposition of the vertebral notches, oval in shape, smallest in
10010-490: The presence of minerals (the inorganic part) in soft protein networks and tissues (the organic part). There are approximately 60 different minerals generated through biological processes, but the most common ones are calcium carbonate found in mollusk shells and hydroxyapatite present in teeth and bones. Although one might think that the mineral content of these tissues can make them fragile, studies have shown that mineralized tissues are 1,000 to 10,000 times tougher than
10120-410: The processing of bioceramics . In this process, raw materials readily available in nature are used to achieve stringent control of nucleation and growth. This nucleation occurs on a synthetic surface with some success. The technique occurs at low temperature and in an aqueous environment. Self-assembling films form templates that effect the nucleation of ceramic phases. The downside with this technique
10230-474: The role of the mineralized tissues involved. Natural structural materials comprising hard and soft phases arranged in elegant hierarchical multiscale architectures, usually exhibit a combination of superior mechanical properties . For instance, many natural mechanical materials ( Bone , Nacre , Teeth , Silk , and Bamboo ) are lightweight, strong, flexible, tough, fracture-resistant, and self-repair. The general underlying mechanism behind such advanced materials
10340-542: The sacrovertebral articulation, and ends at the point of the coccyx ; its concavity is directed downward and forward as a kyphotic curve. The thoracic and sacral kyphotic curves are termed primary curves, because they are present in the fetus . The cervical and lumbar curves are compensatory , or secondary , and are developed after birth. The cervical curve forms when the infant is able to hold up its head (at three or four months) and sit upright (at nine months). The lumbar curve forms later from twelve to eighteen months, when
10450-401: The spine is established during embryogenesis when somites are rhythmically added to the posterior of the embryo. Somite formation begins around the third week when the embryo begins gastrulation and continues until all somites are formed. Their number varies between species: there are 42 to 44 somites in the human embryo and around 52 in the chick embryo. The somites are spheres, formed from
10560-631: The spine, is common in long-term contortion practitioners. A study of five practitioners using magnetic resonance imaging (MRI) by Peoples et al. documented limbus vertebrae , intervertebral disc bulges , and disc degeneration . Three of the five practitioners also reported back pain . Contortion acts are highly variable; many incorporate elements of humor, drama, shock, sensuality, or a blend of styles. Contortion may be incorporated into other types of performance, such as dance and theater. A contortionist may perform alone or may have one or two assistants, or up to four contortionists may perform together as
10670-446: The spinous process of the seventh thoracic vertebra. This curve is known as a kyphotic curve. The lumbar curve is more marked in the female than in the male; it begins at the middle of the last thoracic vertebra, and ends at the sacrovertebral angle. It is convex anteriorly, the convexity of the lower three vertebrae being much greater than that of the upper two. This curve is described as a lordotic curve. The sacral curve begins at
10780-418: The studies involving mineralized tissues in dentistry is on the mineral phase of dentin in order to understand its alteration with aging. These alterations lead to “transparent” dentin, which is also called sclerotic. It was shown that a ‘‘dissolution and reprecipitation’’ mechanism reigns the formation of transparent dentin. The causes and cures of these conditions can possibly be found from further studies on
10890-419: The subject of many studies since there is a lot to learn from nature as seen from the growing field of biomimetics . The remarkable structural organization and engineering properties makes these tissues desirable candidates for duplication by artificial means. Mineralized tissues inspire miniaturization, adaptability and multifunctionality. While natural materials are made up of a limited number of components,
11000-406: The tablets when they are pulled apart and induce hardening. The 30 nm thick interface between the tablets that connects them together and the aragonite grains detected by scanning electron microscopy from which the tablets themselves are made of together represent another structural level. The organic material “gluing” the tablets together is made of proteins and chitin . To summarize, on
11110-457: The tablets, which results in multilayers. Thin film deposition focuses on reproducing the cross-lamellar microstructure of conch instead of mimicking the layered structure of nacre using micro-electro mechanical systems (MEMS) . Among mollusk shells, the conch shell has the highest degree of structural organization. The mineral aragonite and organic matrix are replaced by polysilicon and photoresist . The MEMS technology repeatedly deposits
11220-416: The tail, and the final few can be fused into the pygostyle in birds, or into the coccygeal or tail bone in chimpanzees (and humans ). The vertebrae of lobe-finned fishes consist of three discrete bony elements. The vertebral arch surrounds the spinal cord, and is of broadly similar form to that found in most other vertebrates. Just beneath the arch lies a small plate-like pleurocentrum, which protects
11330-415: The tail. The general structure of human vertebrae is fairly typical of that found in other mammals , reptiles , and birds ( amniotes ). The shape of the vertebral body does, however, vary somewhat between different groups. In humans and other mammals, it typically has flat upper and lower surfaces, while in reptiles the anterior surface commonly has a concave socket into which the expanded convex face of
11440-569: The target of extensive investigation, namely nacre from mollusk shells and bone, which are both high performance natural composites. Many mechanical and imaging techniques such as nanoindentation and atomic force microscopy are used to characterize these tissues. Although the degree of efficiency of biological hard tissues are yet unmatched by any man-made ceramic composites, some promising new techniques to synthesize them are currently under development. Not all mineralized tissues develop through normal physiologic processes and are beneficial to
11550-463: The upper surface of the notochord , and below that, a larger arch-shaped intercentrum to protect the lower border. Both of these structures are embedded within a single cylindrical mass of cartilage. A similar arrangement was found in the primitive Labyrinthodonts , but in the evolutionary line that led to reptiles (and hence, also to mammals and birds), the intercentrum became partially or wholly replaced by an enlarged pleurocentrum, which in turn became
11660-449: The vertebrae consist of two cartilaginous tubes. The upper tube is formed from the vertebral arches, but also includes additional cartilaginous structures filling in the gaps between the vertebrae, and so enclosing the spinal cord in an essentially continuous sheath. The lower tube surrounds the notochord, and has a complex structure, often including multiple layers of calcification . Lampreys have vertebral arches, but nothing resembling
11770-409: The vertebral bodies found in all higher vertebrates . Even the arches are discontinuous, consisting of separate pieces of arch-shaped cartilage around the spinal cord in most parts of the body, changing to long strips of cartilage above and below in the tail region. Hagfishes lack a true vertebral column, and are therefore not properly considered vertebrates, but a few tiny neural arches are present in
11880-475: The vertebral column presents in the median line the spinous processes. In the cervical region (with the exception of the second and seventh vertebrae), these are short, horizontal, and bifid. In the upper part of the thoracic region they are directed obliquely downward; in the middle they are almost vertical, and in the lower part they are nearly horizontal. In the lumbar region they are nearly horizontal. The spinous processes are separated by considerable intervals in
11990-405: The waviness of the tablets. In vertebrates , mineralized tissues not only develop through normal physiological processes, but can also be involved in pathological processes. Some diseased areas that include the appearance of mineralized tissues include atherosclerotic plaques, tumoral calcinosis , juvenile dermatomyositis , kidney and salivary stones . All physiologic deposits contain
12100-775: Was later elaborated in actinopterygians and sarcopterygians during bony fish evolution. It is expected that genetic analysis of agnathans will provide more insight into the evolution of mineralized tissues and clarify evidence from early fossil records. Hierarchical structures are distinct features seen throughout different length scales. To understand how the hierarchical structure of mineralized tissues contributes to their remarkable properties, those for nacre and bone are described below. Hierarchical structures are characteristic of biology and are seen in all structural materials in biology such as bone and nacre from seashells Nacre has several hierarchical structural levels. Some mollusc shells protect themselves from predators by using
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