A joint or articulation (or articular surface ) is the connection made between bones , ossicles , or other hard structures in the body which link an animal's skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee , elbow , and shoulder , are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement (only during birth) in order to protect the brain and the sense organs . The connection between a tooth and the jawbone is also called a joint, and is described as a fibrous joint known as a gomphosis . Joints are classified both structurally and functionally.
34-412: The ghost knifefishes are a family, Apteronotidae , of ray-finned fishes in the order Gymnotiformes . These fish are native to Panama and South America . They inhabit a wide range of freshwater habitats, but more than half the species in the family are found deep in rivers (typically deeper than 5 m or 16 ft) where there is little or no light. The Apteronotidae should not be confused with
68-439: A balanced diet, and avoiding excessive strain, is critical for maintaining joint health, preventing disorders, and improving overall quality of life. The number of joints depends on if sesamoids are included, age of the human and the definition of joints. However, the number of sesamoids is the same in most people with variations being rare. Joints are mainly classified structurally and functionally. Structural classification
102-459: A free-swimming larval stage. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism . In most cases this involves protogyny , fish starting life as females and converting to males at some stage, triggered by some internal or external factor. Protandry , where a fish converts from male to female, is much less common than protogyny. Most families use external rather than internal fertilization . Of
136-442: A single joint. Arthritis is the leading cause of disability in people over the age of 55. There are many different forms of arthritis, each of which has a different cause. The most common form of arthritis, osteoarthritis (also known as degenerative joint disease), occurs following trauma to the joint, following an infection of the joint or simply as a result of aging and the deterioration of articular cartilage. Furthermore, there
170-726: A trait still present in Holostei ( bowfins and gars ). In some fish like the arapaima , the swim bladder has been modified for breathing air again, and in other lineages it have been completely lost. The teleosts have urinary and reproductive tracts that are fully separated, while the Chondrostei have common urogenital ducts, and partially connected ducts are found in Cladistia and Holostei. Ray-finned fishes have many different types of scales ; but all teleosts have leptoid scales . The outer part of these scales fan out with bony ridges, while
204-411: A vital role in the human body, contributing to movement, stability, and overall function. They are essential for mobility and flexibility, connecting bones and facilitating a wide range of motions, from simple bending and stretching to complex actions like running and jumping. Beyond enabling movement, joints provide structural support and stability to the skeleton, helping to maintain posture, balance, and
238-587: Is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of skin supported by radially extended thin bony spines called lepidotrichia , as opposed to the bulkier, fleshy lobed fins of the sister class Sarcopterygii (lobe-finned fish). Resembling folding fans , the actinopterygian fins can easily change shape and wetted area , providing superior thrust-to-weight ratios per movement compared to sarcopterygian and chondrichthyian fins. The fin rays attach directly to
272-444: Is a great way to exercise the joints with minimal damage. A joint disorder is termed arthropathy , and when involving inflammation of one or more joints the disorder is called arthritis . Most joint disorders involve arthritis, but joint damage by external physical trauma is typically not termed arthritis. Arthropathies are called polyarticular (multiarticular) when involving many joints and monoarticular when involving only
306-505: Is a less common form of gout that is caused by the formation of rhomboidal-shaped crystals of calcium pyrophosphate . This form of gout is known as pseudogout . Temporomandibular joint syndrome (TMJ) involves the jaw joints and can cause facial pain, clicking sounds in the jaw, or limitation of jaw movement, to name a few symptoms. It is caused by psychological tension and misalignment of the jaw ( malocclusion ), and may be affecting as many as 75 million Americans. The English word joint
340-484: Is according to the number and shapes of the articular surfaces: flat, concave and convex surfaces. Types of articular surfaces include trochlear surfaces. Joints can also be classified based on their anatomy or on their biomechanical properties. According to the anatomic classification, joints are subdivided into simple and compound , depending on the number of bones involved, and into complex and combination joints: The joints may be classified anatomically into
374-747: Is artificial and some of the species do not actually belong in it. The black ghost knifefish ( Apteronotus albifrons ) and brown ghost knifefish ( Apteronotus leptorhynchus ) are readily available as aquarium fish. Others are known to appear in the trade but are quite rare. FishBase lists 89 species in 16 genera, However, after a number of recent taxonomic advances, Eschmeyer's Catalog of Fishes recognizes 94 species in 16 genera. Ray-finned fish Actinopterygii ( / ˌ æ k t ɪ n ɒ p t ə ˈ r ɪ dʒ i aɪ / ; from actino- 'having rays' and Ancient Greek πτέρυξ (ptérux) 'wing, fins'), members of which are known as ray-finned fish or actinopterygians ,
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#1732855354364408-486: Is determined by how the bones connect to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications. Structural classification names and divides joints according to the type of binding tissue that connects the bones to each other. There are four structural classifications of joints: Joints can also be classified functionally according to
442-540: Is divided into the infraclasses Holostei and Teleostei . During the Mesozoic ( Triassic , Jurassic , Cretaceous ) and Cenozoic the teleosts in particular diversified widely. As a result, 96% of living fish species are teleosts (40% of all fish species belong to the teleost subgroup Acanthomorpha ), while all other groups of actinopterygians represent depauperate lineages. The classification of ray-finned fishes can be summarized as follows: The cladogram below shows
476-436: Is emerging evidence that abnormal anatomy may contribute to early development of osteoarthritis. Other forms of arthritis are rheumatoid arthritis and psoriatic arthritis , which are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. Additionally, there
510-432: Is relatively rare and is found in about 6% of living teleost species; male care is far more common than female care. Male territoriality "preadapts" a species for evolving male parental care. There are a few examples of fish that self-fertilise. The mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to
544-500: The Cyprinidae (in goldfish and common carp as recently as 14 million years ago). Ray-finned fish vary in size and shape, in their feeding specializations, and in the number and arrangement of their ray-fins. In nearly all ray-finned fish, the sexes are separate, and in most species the females spawn eggs that are fertilized externally, typically with the male inseminating the eggs after they are laid. Development then proceeds with
578-587: The deep sea to subterranean waters to the highest mountain streams . Extant species can range in size from Paedocypris , at 8 mm (0.3 in); to the massive ocean sunfish , at 2,300 kg (5,070 lb); and to the giant oarfish , at 11 m (36 ft). The largest ever known ray-finned fish, the extinct Leedsichthys from the Jurassic , has been estimated to have grown to 16.5 m (54 ft). Ray-finned fishes occur in many variant forms. The main features of typical ray-finned fish are shown in
612-481: The oviparous teleosts, most (79%) do not provide parental care. Viviparity , ovoviviparity , or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction (21%) of the 422 teleost families; no care is likely the ancestral condition. The oldest case of viviparity in ray-finned fish is found in Middle Triassic species of † Saurichthys . Viviparity
646-651: The sister lineage of all other actinopterygians, the Acipenseriformes (sturgeons and paddlefishes) are the sister lineage of Neopterygii, and Holostei (bowfin and gars) are the sister lineage of teleosts. The Elopomorpha ( eels and tarpons ) appear to be the most basal teleosts. The earliest known fossil actinopterygian is Andreolepis hedei , dating back 420 million years ( Late Silurian ), remains of which have been found in Russia , Sweden , and Estonia . Crown group actinopterygians most likely originated near
680-932: The Devonian-Carboniferous boundary. The earliest fossil relatives of modern teleosts are from the Triassic period ( Prohalecites , Pholidophorus ), although it is suspected that teleosts originated already during the Paleozoic Era . The listing below is a summary of all extinct (indicated by a dagger , †) and living groups of Actinopterygii with their respective taxonomic rank . The taxonomy follows Phylogenetic Classification of Bony Fishes with notes when this differs from Nelson, ITIS and FishBase and extinct groups from Van der Laan 2016 and Xu 2021. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Articulation (anatomy) Joints play
714-498: The ability to bear weight during daily activities. The clinical significance of joints is highlighted by common disorders that affect their health and function. Osteoarthritis , a degenerative joint disease, involves the breakdown of cartilage, leading to pain, stiffness, and reduced mobility. Rheumatoid arthritis , an autoimmune disorder, causes chronic inflammation in the joints, often resulting in swelling, pain, and potential deformity. Another prevalent condition, gout , arises from
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#1732855354364748-556: The accumulation of uric acid crystals in the joints, triggering severe pain and inflammation. Joints also hold diagnostic importance, as their condition can indicate underlying health issues. Symptoms such as joint pain and swelling may signal inflammatory diseases, infections, or metabolic disorders. Effective treatment and management of joint-related conditions often require a multifaceted approach, including physical therapy, medications, lifestyle changes, and, in severe cases, surgical interventions. Preventive care, such as regular exercise,
782-402: The adjacent diagram. The swim bladder is a more derived structure and used for buoyancy . Except from the bichirs , which just like the lungs of lobe-finned fish have retained the ancestral condition of ventral budding from the foregut , the swim bladder in ray-finned fishes derives from a dorsal bud above the foregut. In early forms the swim bladder could still be used for breathing,
816-463: The bichirs and holosteans (bowfin and gars) in having gone through a whole-genome duplication ( paleopolyploidy ). The WGD is estimated to have happened about 320 million years ago in the teleosts, which on average has retained about 17% of the gene duplicates, and around 180 (124–225) million years ago in the chondrosteans. It has since happened again in some teleost lineages, like Salmonidae (80–100 million years ago) and several times independently within
850-706: The different actinopterygian clades (in millions of years , mya) are from Near et al., 2012. Jaw-less fishes ( hagfish , lampreys ) [REDACTED] Cartilaginous fishes ( sharks , rays , ratfish ) [REDACTED] Coelacanths [REDACTED] Lungfish [REDACTED] Amphibians [REDACTED] Mammals [REDACTED] Sauropsids ( reptiles , birds ) [REDACTED] Polypteriformes ( bichirs , reedfishes ) [REDACTED] Acipenseriformes ( sturgeons , paddlefishes ) [REDACTED] Teleostei [REDACTED] Amiiformes ( bowfins ) [REDACTED] Lepisosteiformes ( gars ) [REDACTED] The polypterids (bichirs and reedfish) are
884-432: The fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below 19 °C (66 °F) and can fertilise eggs that are then spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred. Actinopterygii is divided into the subclasses Cladistia , Chondrostei and Neopterygii . The Neopterygii , in turn,
918-408: The following groups: Unmyelinated nerve fibers are abundant in joint capsules and ligaments, as well as in the outer part of intra-articular menisci. These nerve fibers are responsible for pain perception when a joint is strained. Damaging the cartilage of joints ( articular cartilage ) or the bones and muscles that stabilize the joints can lead to joint dislocations and osteoarthritis. Swimming
952-458: The genus Sternarchella are very unusual, preying on the tails of other electric fishes. Other species, such as Sternarchorhynchus and Sternarchorhamphus , have tubular snouts and forage on the beds of aquatic insect larvae and other small animals which burrow into the river bottom. At least one species ( Sternarchogiton nattereri ) eats freshwater sponges which grow on submerged trees, stumps, and other woody debris. The genus Apteronotus
986-438: The inner part is crossed with fibrous connective tissue. Leptoid scales are thinner and more transparent than other types of scales, and lack the hardened enamel - or dentine -like layers found in the scales of many other fish. Unlike ganoid scales , which are found in non-teleost actinopterygians, new scales are added in concentric layers as the fish grows. Teleosts and chondrosteans (sturgeons and paddlefish) also differ from
1020-616: The largest. It has been claimed that Apteronotus magdalenensis is up to 130 cm (4.3 ft), but this is not supported by recent studies, which indicate that it does not surpass about 50 cm (1.6 ft). These nocturnal fish have small eyes. Also, sexual dimorphism exists in some genera in snout shape and jaws. Apteronotids use a high frequency tone-type (also called wave-type) electric organ discharge (EOD) to communicate. Many Apteronotids are aggressive predators of small aquatic insect larvae and fishes, though there are also piscivorous and planktivorous species. Species of
1054-461: The main clades of living actinopterygians and their evolutionary relationships to other extant groups of fishes and the four-limbed vertebrates ( tetrapods ). The latter include mostly terrestrial species but also groups that became secondarily aquatic (e.g. whales and dolphins ). Tetrapods evolved from a group of bony fish during the Devonian period . Approximate divergence dates for
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1088-494: The proximal or basal skeletal elements, the radials, which represent the articulation between these fins and the internal skeleton (e.g., pelvic and pectoral girdles). The vast majority of actinopterygians are teleosts . By species count, they dominate the subphylum Vertebrata , and constitute nearly 99% of the over 30,000 extant species of fish . They are the most abundant nektonic aquatic animals and are ubiquitous throughout freshwater and marine environments from
1122-516: The type and degree of movement they allow: Joint movements are described with reference to the basic anatomical planes . Joints can also be classified, according to the number of axes of movement they allow, into nonaxial (gliding, as between the proximal ends of the ulna and radius), monoaxial (uniaxial), biaxial and multiaxial . Another classification is according to the degrees of freedom allowed, and distinguished between joints with one, two or three degrees of freedom. A further classification
1156-436: The unrelated Notopteridae , which are also commonly called knifefishes. They are distinguished from other gymnotiform fishes by the presence of a caudal fin (all other families lack a caudal fin) as well as a fleshy dorsal organ represented by a longitudinal strip along the dorsal midline. They vary greatly in size, ranging from about 15 cm (6 in) in total length in the smallest species to 60 cm (2 ft) in
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