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88-580: Its length is 67 km (15 in Slovakia, 52 in Hungary). Its watershed area is 13,579 km of which 972 km is in Hungary. The river is rich in fish . 48°07′N 21°25′E  /  48.117°N 21.417°E  / 48.117; 21.417 This article related to a river in Slovakia is a stub . You can help Misplaced Pages by expanding it . This Borsod-Abaúj-Zemplén location article

176-1054: A dagger (†); groups of uncertain placement are labelled with a question mark (?) and dashed lines (- - - - -). Jawless fishes (118 species: hagfish , lampreys ) [REDACTED] † Thelodonti , † Conodonta , † Anaspida [REDACTED] [REDACTED] [REDACTED] † Galeaspida [REDACTED] † Osteostraci [REDACTED] † Placodermi [REDACTED] † Acanthodii [REDACTED]  (>1,100 species: sharks , rays , chimaeras ) [REDACTED]  (2 species: coelacanths ) [REDACTED] Dipnoi (6 species: lungfish ) [REDACTED] Tetrapoda (>38,000 species, not considered fish: amphibians, reptiles, birds, mammals) [REDACTED]  (14 species: bichirs , reedfish ) [REDACTED]  (27 species: sturgeons , paddlefish ) [REDACTED] Ginglymodi (7 species: gars , alligator gars ) [REDACTED] Halecomorphi (2 species: bowfin , eyetail bowfin ) [REDACTED]  (>32,000 species) [REDACTED] Fishes (without tetrapods) are

264-579: A paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal classifications. Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes. Fish account for more than half of vertebrate species. As of 2016, there are over 32,000 described species of bony fish, over 1,100 species of cartilaginous fish, and over 100 hagfish and lampreys. A third of these fall within

352-443: A pleural sac of two pleurae which allows the inner and outer walls to slide over each other whilst breathing takes place, without much friction. The inner visceral pleura divides each lung as fissures into sections called lobes. The right lung has three lobes and the left has two. The lobes are further divided into bronchopulmonary segments and lobules. The lungs have a unique blood supply, receiving deoxygenated blood sent from

440-417: A lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum . The left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula . Its name means "little tongue". The lingula on the left lung serves as an anatomic parallel to the middle lobe on

528-436: A more spherical lens . Their retinas generally have both rods and cones (for scotopic and photopic vision ); many species have colour vision , often with three types of cone. Teleosts can see polarized light ; some such as cyprinids have a fourth type of cone that detects ultraviolet . Amongst jawless fish , the lamprey has well-developed eyes, while the hagfish has only primitive eyespots. Hearing too

616-768: A mostly terrestrial clade of vertebrates that have dominated the top trophic levels in both aquatic and terrestrial ecosystems since the Late Paleozoic , evolved from lobe-finned fish during the Carboniferous , developing air-breathing lungs homologous to swim bladders. Despite the cladistic lineage, tetrapods are usually not considered to be fish, making "fish" a paraphyletic group. Fish have been an important natural resource for humans since prehistoric times, especially as food . Commercial and subsistence fishers harvest fish in wild fisheries or farm them in ponds or in breeding cages in

704-419: A protective bony cover or operculum . They are able to oxygenate their gills using muscles in the head. Some 400 species of fish in 50 families can breathe air, enabling them to live in oxygen-poor water or to emerge on to land. The ability of fish to do this is potentially limited by their single-loop circulation, as oxygenated blood from their air-breathing organ will mix with deoxygenated blood returning to

792-424: A quantum radical pair mechanism . Lung The lungs are the primary organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods , two lungs are located near the backbone on either side of the heart . Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from

880-485: A right lung with only two lobes, or a left lung with three lobes. A variation in the airway branching structure has been found specifically in the central airway branching. This variation is associated with the development of COPD in adulthood. The development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth. The larynx , trachea , bronchi and lungs that make up

968-441: A sense of touch and of hearing . Blind cave fish navigate almost entirely through the sensations from their lateral line system. Some fish, such as catfish and sharks, have the ampullae of Lorenzini , electroreceptors that detect weak electric currents on the order of millivolt. Vision is an important sensory system in fish. Fish eyes are similar to those of terrestrial vertebrates like birds and mammals, but have

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1056-485: A tail fin, jaws, skin covered with scales , and lays eggs. Each criterion has exceptions, creating a wide diversity in body shape and way of life. For example, some fast-swimming fish are warm-blooded, while some slow-swimming fish have abandoned streamlining in favour of other body shapes. Fish species are roughly divided equally between freshwater and marine (oceanic) ecosystems; there are some 15,200 freshwater species and around 14,800 marine species. Coral reefs in

1144-589: A true "land fish" as this worm-like catfish strictly lives among waterlogged leaf litter . Cavefish of multiple families live in underground lakes , underground rivers or aquifers . Like other animals, fish suffer from parasitism . Some species use cleaner fish to remove external parasites. The best known of these are the bluestreak cleaner wrasses of coral reefs in the Indian and Pacific oceans. These small fish maintain cleaning stations where other fish congregate and perform specific movements to attract

1232-422: A typical fish is adapted for efficient swimming by alternately contracting paired sets of muscles on either side of the backbone. These contractions form S-shaped curves that move down the body. As each curve reaches the tail fin, force is applied to the water, moving the fish forward. The other fins act as control surfaces like an aircraft's flaps, enabling the fish to steer in any direction. Since body tissue

1320-422: Is a stub . You can help Misplaced Pages by expanding it . This article related to a river in Hungary is a stub . You can help Misplaced Pages by expanding it . Fish A fish ( pl. : fish or fishes ) is an aquatic , anamniotic , gill -bearing vertebrate animal with swimming fins and a hard skull , but lacking limbs with digits . Fish can be grouped into the more basal jawless fish and

1408-414: Is also responsible for the elastic recoil needed. Elastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions. The connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance. The alveoli have interconnecting air passages in their walls known as the pores of Kohn . All of the lower respiratory tract including

1496-465: Is an important sensory system in fish. Fish sense sound using their lateral lines and otoliths in their ears, inside their heads. Some can detect sound through the swim bladder. Some fish, including salmon, are capable of magnetoreception ; when the axis of a magnetic field is changed around a circular tank of young fish, they reorient themselves in line with the field. The mechanism of fish magnetoreception remains unknown; experiments in birds imply

1584-431: Is denser than water, fish must compensate for the difference or they will sink. Many bony fish have an internal organ called a swim bladder that allows them to adjust their buoyancy by increasing or decreasing the amount of gas it contains. The scales of fish provide protection from predators at the cost of adding stiffness and weight. Fish scales are often highly reflective; this silvering provides camouflage in

1672-422: Is divided into three lobes by a horizontal fissure , and an oblique fissure . The left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung. In the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe. The lower, oblique fissure separates the lower lobe from the middle and upper lobes. Variations in

1760-401: Is held in the fluid-filled amniotic sac and so they do not function to breathe. Blood is also diverted from the lungs through the ductus arteriosus . At birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire. The lungs only fully develop in early childhood. In humans the lungs are located in the chest on either side of

1848-427: Is likely to be made up of between 30 and 50 primary lobules. The lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles. The respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch. Each lobule is enclosed by an interlobular septum. Each acinus is incompletely separated by an intralobular septum. The respiratory bronchiole gives rise to

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1936-428: Is the diaphragm . The lungs also provide airflow that makes vocalisation including speech possible. Humans have two lungs, a right lung and a left lung. They are situated within the thoracic cavity of the chest . The right lung is bigger than the left, the left lung shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of

2024-465: Is the biggest part of the brain; it is small in hagfish and lampreys , but very large in mormyrids , processing their electrical sense . The brain stem or myelencephalon controls some muscles and body organs, and governs respiration and osmoregulation . The lateral line system is a network of sensors in the skin which detects gentle currents and vibrations, and senses the motion of nearby fish, whether predators or prey. This can be considered both

2112-435: Is the part of the lung distal to the respiratory bronchiole. Thus, it includes the alveolar ducts, sacs, and alveoli but not the respiratory bronchioles. The unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule . This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid. The secondary pulmonary lobule

2200-582: The Cambrian as small filter feeders ; they continued to evolve through the Paleozoic , diversifying into many forms. The earliest fish with dedicated respiratory gills and paired fins , the ostracoderms , had heavy bony plates that served as protective exoskeletons against invertebrate predators . The first fish with jaws , the placoderms, appeared in the Silurian and greatly diversified during

2288-519: The Devonian , the "Age of Fishes". Bony fish, distinguished by the presence of swim bladders and later ossified endoskeletons , emerged as the dominant group of fish after the end-Devonian extinction wiped out the apex placoderms. Bony fish are further divided into the lobe-finned and ray-finned fish . About 96% of all living fish species today are teleosts , a crown group of ray-finned fish that can protrude their jaws . The tetrapods ,

2376-617: The Gnathostomata or (for bony fish) Osteichthyes , also contains the clade of tetrapods (four-limbed vertebrates, mostly terrestrial), which are usually not considered fish. Some tetrapods, such as cetaceans and ichthyosaurs , have secondarily acquired a fish-like body shape through convergent evolution . Fishes of the World comments that "it is increasingly widely accepted that tetrapods, including ourselves, are simply modified bony fishes, and so we are comfortable with using

2464-723: The Indo-Pacific constitute the center of diversity for marine fishes, whereas continental freshwater fishes are most diverse in large river basins of tropical rainforests , especially the Amazon , Congo , and Mekong basins. More than 5,600 fish species inhabit Neotropical freshwaters alone, such that Neotropical fishes represent about 10% of all vertebrate species on the Earth. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon ) to

2552-571: The Silurian , with giant armoured placoderms such as Dunkleosteus . Jawed fish, too, appeared during the Silurian: the cartilaginous Chondrichthyes and the bony Osteichthyes . During the Devonian , fish diversity greatly increased, including among the placoderms, lobe-finned fishes, and early sharks, earning the Devonian the epithet "the age of fishes". Fishes are a paraphyletic group, since any clade containing all fish, such as

2640-477: The abyssal and even hadal depths of the deepest oceans (e.g., cusk-eels and snailfish ), although none have been found in the deepest 25% of the ocean. The deepest living fish in the ocean so far found is a cusk-eel, Abyssobrotula galatheae , recorded at the bottom of the Puerto Rico Trench at 8,370 m (27,460 ft). In terms of temperature, Jonah's icefish live in cold waters of

2728-425: The carina where the trachea divides into the two main bronchi. The cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart. Both lungs have a central recession called the hilum , where the blood vessels and airways pass into the lungs making up the root of the lung . There are also bronchopulmonary lymph nodes on the hilum. The lungs are surrounded by

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2816-470: The circulation , and carbon dioxide diffuses from the blood into the lungs to be breathed out . Estimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being "the size of a tennis court", it is actually less than half the size of a singles court . The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open

2904-438: The esophagus behind the hilum and the pulmonary ligament , and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart. The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb). The left lung is divided into two lobes, an upper and

2992-418: The heart in the rib cage . They are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm . The apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib . The lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from

3080-676: The immune system . They remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels. There is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis. The microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD . For example significant changes can take place in COPD following infection with rhinovirus . Fungal genera that are commonly found as mycobiota in

3168-400: The intertidal zone , are facultative air breathers, able to breathe air when out of water, as may occur daily at low tide , and to use their gills when in water. Some coastal fish like rockskippers and mudskippers choose to leave the water to feed in habitats temporarily exposed to the air. Some catfish absorb air through their digestive tracts. The digestive system consists of a tube,

3256-400: The lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles , and which receive air breathed in via the conducting zone . These divide until air reaches microscopic alveoli , where gas exchange takes place. Together, the lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed within

3344-427: The pulmonary pleurae . The pleurae are two serous membranes ; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs. Between the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid . Middle Lower Lingula Lower Each lung is divided into sections called lobes by

3432-425: The stout infantfish . Swimming performance varies from fish such as tuna, salmon , and jacks that can cover 10–20 body-lengths per second to species such as eels and rays that swim no more than 0.5 body-lengths per second. A typical fish is cold-blooded , has a streamlined body for rapid swimming, extracts oxygen from water using gills, has two sets of paired fins, one or two dorsal fins, an anal fin and

3520-601: The Southern Ocean, including under the Filchner–Ronne Ice Shelf at a latitude of 79°S, while desert pupfish live in desert springs, streams, and marshes, sometimes highly saline, with water temperatures as high as 36 C. A few fish live mostly on land or lay their eggs on land near water. Mudskippers feed and interact with one another on mudflats and go underwater to hide in their burrows. A single undescribed species of Phreatobius has been called

3608-473: The airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration. The lungs have a dual blood supply provided by a bronchial and a pulmonary circulation . The bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta . There are usually three arteries, two to

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3696-399: The airways. The bronchioles have no cartilage and are surrounded instead by smooth muscle . Air is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone. Particles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance . Pulmonary stretch receptors in the smooth muscle of

3784-464: The alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli. The walls of the alveoli are extremely thin allowing a fast rate of diffusion . The alveoli have interconnecting small air passages in their walls known as the pores of Kohn . Alveoli consist of two types of alveolar cell and an alveolar macrophage . The two types of cell are known as type I and type II cells (also known as pneumocytes). Types I and II make up

3872-474: The alveolar septa which separate each alveolus. The septa consist of an epithelial lining and associated basement membranes . Type I cells are not able to divide, and consequently rely on differentiation from Type II cells. Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant . Type II cells are able to divide and differentiate to Type I cells. The alveolar macrophages have an important role in

3960-462: The alveoli. The four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4 . FGF10 is seen to have the most prominent role. FGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10. The development of

4048-556: The attention of the cleaners. Cleaning behaviors have been observed in a number of fish groups, including an interesting case between two cichlids of the same genus, Etroplus maculatus , the cleaner, and the much larger E. suratensis . Fish occupy many trophic levels in freshwater and marine food webs . Fish at the higher levels are predatory , and a substantial part of their prey consists of other fish. In addition, mammals such as dolphins and seals feed on fish, alongside birds such as gannets and cormorants . The body of

4136-410: The base of the lung. By standard reference range , the weight of the left lung is 110–675 g (0.243–1.488 lb) in men and 105–515 g (0.231–1.135 lb) in women. The lungs are part of the lower respiratory tract , and accommodate the bronchial airways when they branch from the trachea. The bronchial airways terminate in alveoli which make up the functional tissue ( parenchyma ) of

4224-425: The bloodstream into the atmosphere, in a process of gas exchange . Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their musculoskeletal systems to support and foster breathing. In early tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping , a mechanism still seen in amphibians. In humans, the primary muscle that drives breathing

4312-550: The body, and produce a concentrated urine. The reverse happens in freshwater fish : they tend to gain water osmotically, and produce a dilute urine. Some fish have kidneys able to operate in both freshwater and saltwater. Fish have small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal. However, some fish have relatively large brains, notably mormyrids and sharks , which have brains about as large for their body weight as birds and marsupials . At

4400-416: The branch. In the development of the lungs (as in some other organs) the epithelium forms branching tubes. The lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus. Each bronchus branches into bronchioles. The branching is a result of the tip of each tube bifurcating. The branching process forms the bronchi, bronchioles, and ultimately

4488-402: The bronchus and bronchioles, and increases the secretions from glands. The lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation . The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem , along the phrenic nerve from the cervical plexus to

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4576-533: The composition of which is tightly regulated and determines how well mucociliary clearance works. Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 percent of the total epithelial population. PNECs are innervated airway epithelial cells that are particularly focused at airway junction points. These cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products. Cytoplasmic processes from

4664-423: The diaphragm. The lobes of the lung are subject to anatomical variations . A horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases. An accessory fissure was also found in 14% and 22% of left and right lungs, respectively. An oblique fissure was found to be incomplete in 21% to 47% of left lungs. In some cases a fissure is absent, or extra, resulting in

4752-515: The exact root is unknown; some authorities reconstruct a Proto-Indo-European root * peysk- , attested only in Italic , Celtic , and Germanic . About 530 million years ago during the Cambrian explosion , fishlike animals with a notochord and eyes at the front of the body, such as Haikouichthys , appear in the fossil record . During the late Cambrian , other jawless forms such as conodonts appear. Jawed vertebrates appear in

4840-460: The fissures are fairly common being either incompletely formed or present as an extra fissure as in the azygos fissure , or absent. Incomplete fissures are responsible for interlobar collateral ventilation , airflow between lobes which is unwanted in some lung volume reduction procedures. The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of

4928-405: The front of the brain are the olfactory lobes , a pair of structures that receive and process signals from the nostrils via the two olfactory nerves . Fish that hunt primarily by smell, such as hagfish and sharks, have very large olfactory lobes. Behind these is the telencephalon , which in fish deals mostly with olfaction. Together these structures form the forebrain. Connecting the forebrain to

5016-412: The gills flows in the opposite direction to the water, resulting in efficient countercurrent exchange . The gills push the oxygen-poor water out through openings in the sides of the pharynx. Cartilaginous fish have multiple gill openings: sharks usually have five, sometimes six or seven pairs; they often have to swim to oxygenate their gills. Bony fish have a single gill opening on each side, hidden beneath

5104-532: The gills. Oxygen-rich blood then flows without further pumping, unlike in mammals, to the body tissues. Finally, oxygen-depleted blood returns to the heart. Fish exchange gases using gills on either side of the pharynx . Gills consist of comblike structures called filaments. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide . Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. Capillary blood in

5192-447: The gut, leading from the mouth to the anus. The mouth of most fishes contains teeth to grip prey, bite off or scrape plant material, or crush the food. An esophagus carries food to the stomach where it may be stored and partially digested. A sphincter, the pylorus, releases food to the intestine at intervals. Many fish have finger-shaped pouches, pyloric caeca , around the pylorus, of doubtful function. The pancreas secretes enzymes into

5280-457: The heart for the purposes of receiving oxygen (the pulmonary circulation ) and a separate supply of oxygenated blood (the bronchial circulation ). The tissue of the lungs can be affected by a number of respiratory diseases , including pneumonia and lung cancer . Chronic diseases such as chronic obstructive pulmonary disease and emphysema can be related to smoking or exposure to harmful substances. Diseases such as bronchitis can also affect

5368-457: The heart from the rest of the body. Lungfish, bichirs, ropefish, bowfins, snakefish, and the African knifefish have evolved to reduce such mixing, and to reduce oxygen loss from the gills to oxygen-poor water. Bichirs and lungfish have tetrapod-like paired lungs, requiring them to surface to gulp air, and making them obligate air breathers. Many other fish, including inhabitants of rock pools and

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5456-406: The hilum, is a well-marked curved groove for the aortic arch , and a groove below it for the descending aorta . The left subclavian artery , a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung. A shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein . The esophagus may sit in a wider shallow impression at

5544-413: The infoldings of the visceral pleura as fissures. Lobes are divided into segments, and segments have further divisions as lobules. There are three lobes in the right lung and two lobes in the left lung. The fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion. The right lung

5632-455: The intestine to digest the food; other enzymes are secreted directly by the intestine itself. The liver produces bile which helps to break up fat into an emulsion which can be absorbed in the intestine. Most fish release their nitrogenous wastes as ammonia . This may be excreted through the gills or filtered by the kidneys . Salt is excreted by the rectal gland. Saltwater fish tend to lose water by osmosis ; their kidneys return water to

5720-458: The left lung and one to the right, and they branch alongside the bronchi and bronchioles. The pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body. The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system. This quantity can easily fluctuate from between one-half and twice

5808-420: The lower part of the trachea to the diaphragm. The left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this. The front and outer sides of the lungs face the ribs, which make light indentations on their surfaces. The medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels , and

5896-495: The lung, and veins, arteries, nerves, and lymphatic vessels . The trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa. The smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli. The lungs are supplied with the largest lymphatic drainage system of any other organ in the body. Each lung is surrounded by a serous membrane of visceral pleura , which has an underlying layer of loose connective tissue attached to

5984-415: The lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments . Each bronchopulmonary segment has its own (segmental) bronchus and arterial supply . Segments for the left and right lung are shown in the table. The segmental anatomy is useful clinically for localising disease processes in

6072-419: The lungs. A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue. The right lung has both more lobes and segments than the left. It is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal. The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near

6160-409: The microbiota include Candida , Malassezia , Saccharomyces , and Aspergillus . The lower respiratory tract is part of the respiratory system , and consists of the trachea and the structures below this including the lungs. The trachea receives air from the pharynx and travels down to a place where it splits (the carina ) into a right and left primary bronchus . These supply air to

6248-419: The midbrain is the diencephalon ; it works with hormones and homeostasis . The pineal body is just above the diencephalon; it detects light, maintains circadian rhythms, and controls color changes. The midbrain contains the two optic lobes . These are very large in species that hunt by sight, such as rainbow trout and cichlids . The hindbrain controls swimming and balance.The single-lobed cerebellum

6336-476: The more common jawed fish , the latter including all living cartilaginous and bony fish , as well as the extinct placoderms and acanthodians . Most fish are cold-blooded , their body temperature varying with the surrounding water, though some large active swimmers like white shark and tuna can hold a higher core temperature . Many fish can communicate acoustically with each other, such as during courtship displays . The earliest fish appeared during

6424-443: The nine largest families; from largest to smallest, these are Cyprinidae , Gobiidae , Cichlidae , Characidae , Loricariidae , Balitoridae , Serranidae , Labridae , and Scorpaenidae . About 64 families are monotypic , containing only one species. Fish range in size from the huge 16-metre (52 ft) whale shark to some tiny teleosts only 8-millimetre (0.3 in) long, such as the cyprinid Paedocypris progenetica and

6512-416: The normal volume. Also, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation. The lungs are supplied by nerves of the autonomic nervous system . Input from the parasympathetic nervous system occurs via the vagus nerve . When stimulated by acetylcholine , this causes constriction of the smooth muscle lining

6600-500: The ocean. Fish are caught for recreation , or raised by fishkeepers as ornaments for private and public exhibition in aquaria and garden ponds . Fish have had a role in human culture through the ages, serving as deities , religious symbols, and as the subjects of art, books and movies. The word fish is inherited from Proto-Germanic , and is related to German Fisch , the Latin piscis and Old Irish īasc , though

6688-402: The open ocean. Because the water all around is the same colour, reflecting an image of the water offers near-invisibility. Fish have a closed-loop circulatory system . The heart pumps the blood in a single loop throughout the body; for comparison, the mammal heart has two loops, one for the lungs to pick up oxygen, one for the body to deliver the oxygen. In fish, the heart pumps blood through

6776-406: The posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage ; on the mediastinal surface it may be traced back to the hilum . The lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung. The mediastinal surface of

6864-467: The pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas. In the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open. Bronchioles are too narrow to support cartilage and their walls are of smooth muscle , and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium. The absence of cartilage in

6952-404: The respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut . The respiratory tract has a branching structure, and is also known as the respiratory tree. In the embryo this structure is developed in the process of branching morphogenesis , and is generated by the repeated splitting of the tip of

7040-456: The respiratory tract. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων "lung") as in pneumonia. In embryonic development , the lungs begin to develop as an outpouching of the foregut , a tube which goes on to form the upper part of the digestive system . When the lungs are formed the fetus

7128-429: The right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles . These in turn supply air through alveolar ducts into the alveoli , where the exchange of gases take place. Oxygen breathed in , diffuses through the walls of the alveoli into the enveloping capillaries and into

7216-403: The right lung is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the lung is an arched groove for the azygos vein , and above this is a wide groove for the superior vena cava and right brachiocephalic vein ; behind this, and close to the top of the lung is a groove for the brachiocephalic artery . There is a groove for

7304-425: The right lung, with both areas being predisposed to similar infections and anatomic complications. There are two bronchopulmonary segments of the lingula: superior and inferior. The mediastinal surface of the left lung has a large cardiac impression where the heart sits. This is deeper and larger than that on the right lung, at which level the heart projects to the left. On the same surface, immediately above

7392-441: The substance of the lung. The connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls. Elastin is the key protein of the extracellular matrix and is the main component of the elastic fibres . Elastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance . It

7480-415: The taxon Osteichthyes as a clade, which now includes all tetrapods". The biodiversity of extant fish is unevenly distributed among the various groups; teleosts , bony fishes able to protrude their jaws , make up 96% of fish species. The cladogram shows the evolutionary relationships of all groups of living fishes (with their respective diversity ) and the tetrapods. Extinct groups are marked with

7568-467: The terminal bronchioles gives them an alternative name of membranous bronchioles . The conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles. This marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs , and alveoli. An acinus measures up to 10 mm in diameter. A primary pulmonary lobule

7656-451: The trachea, bronchi, and bronchioles is lined with respiratory epithelium . This is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus , ciliated cells, basal cells , and in the terminal bronchioles – club cells with actions similar to basal cells, and macrophages . The epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL),

7744-464: The walls and alveolar septa . Type I cells provide 95% of the surface area of each alveoli and are flat (" squamous "), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape. Despite this, cells occur in a roughly equal ratio of 1:1 or 6:4. Type I are squamous epithelial cells that make up the alveolar wall structure. They have extremely thin walls that enable an easy gas exchange. These type I cells also make up

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