The thorax ( pl. : thoraces or thoraxes ) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen .
59-452: Ichthyostraca is a class of parasitic crustaceans . It is composed of two subclasses; Pentastomida and Branchiura . They mainly parasitize various vertebrates and feed on their blood or mucus. Crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are a part of the subphylum Crustacea ( / k r ə ˈ s t eɪ ʃ ə / ),
118-403: A large, diverse group of mainly aquatic arthropods including decapods ( shrimps , prawns , crabs , lobsters and crayfish ), seed shrimp , branchiopods , fish lice , krill , remipedes , isopods , barnacles , copepods , opossum shrimps , amphipods and mantis shrimp . The crustacean group can be treated as a subphylum under the clade Mandibulata . It is now well accepted that
177-468: A larger Pancrustacea clade . The traditional classification of Crustacea based on morphology recognised four to six classes. Bowman and Abele (1982) recognised 652 extant families and 38 orders, organised into six classes: Branchiopoda , Remipedia , Cephalocarida , Maxillopoda, Ostracoda , and Malacostraca . Martin and Davis (2001) updated this classification, retaining the six classes but including 849 extant families in 42 orders. Despite outlining
236-468: A limbless abdomen, except from a telson and caudal rami which is present in many groups. The abdomen in malacostracans bears pleopods , and ends in a telson, which bears the anus , and is often flanked by uropods to form a tail fan . The number and variety of appendages in different crustaceans may be partly responsible for the group's success. Crustacean appendages are typically biramous , meaning they are divided into two parts; this includes
295-495: A spiral format. Structures that function as kidneys are located near the antennae. A brain exists in the form of ganglia close to the antennae, and a collection of major ganglia is found below the gut. In many decapods , the first (and sometimes the second) pair of pleopods are specialised in the male for sperm transfer. Many terrestrial crustaceans (such as the Christmas Island red crab ) mate seasonally and return to
354-431: A symptom of myocardial infarctions ('heart attack'). If this condition is present in the body, discomfort will be felt in the chest that is similar to a heavy weight placed on the body. Sweating, shortness of breath, lightheadedness , and irregular heartbeat may also be experienced. If a heart attack occurs, the bulk of the damage is caused during the first six hours, so getting the proper treatment as quickly as possible
413-438: Is an open circulatory system , where blood is pumped into the haemocoel by a heart located near the dorsum. Malacostraca have haemocyanin as the oxygen-carrying pigment, while copepods, ostracods, barnacles and branchiopods have haemoglobins . The alimentary canal consists of a straight tube that often has a gizzard-like "gastric mill" for grinding food and a pair of digestive glands that absorb food; this structure goes in
472-401: Is blocked and traps air. The blockage may be caused by something inside the bronchus , such as a plug of mucus, a tumour , or an inhaled foreign object such as a coin, piece of food, or a toy. It is possible for something outside of the bronchus to cause the blockage. Pneumothorax is the condition where air or gas can build up in the pleural space. It can occur without a known cause or as
531-404: Is generally felt when deep breaths are taken or during a cough. Another non-cardiac cause of chest pain is atelectasis . It is a condition that occurs when a portion of the lung collapses from being airless. When bronchial tubes are blocked, this condition develops and causes patients to feel shortness of breath. The most common cause of atelectasis is when a bronchi that extends from the windpipe
590-526: Is important. Some people, especially those who are elderly or have diabetes, may not have typical chest pain but may have many of the other symptoms of a heart attack. It is important that these patients and their caregivers have a good understanding of heart attack symptoms. Just like with a heart attack, not all chest pain is caused by conditions involving the heart . Chest wall pain can be experienced after an increase in activity. Persons who add exercise to their daily routine generally feel this type of pain at
649-530: Is produced in Asia, with China alone producing nearly half the world's total. Non-decapod crustaceans are not widely consumed, with only 118,000 tons of krill being caught, despite krill having one of the greatest biomasses on the planet. Thorax#In arthropods In insects , crustaceans , and the extinct trilobites , the thorax is one of the three main divisions of the body, each in turn composed of multiple segments. The human thorax includes
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#1732790842633708-694: Is some debate as to whether or not Cambrian animals assigned to Ostracoda are truly ostracods , which would otherwise start in the Ordovician . The only classes to appear later are the Cephalocarida , which have no fossil record, and the Remipedia , which were first described from the fossil Tesnusocaris goldichi , but do not appear until the Carboniferous . Most of the early crustaceans are rare, but fossil crustaceans become abundant from
767-526: Is thought to be just 1 ⁄ 10 to 1 ⁄ 100 of the total number as most species remain as yet undiscovered . Although most crustaceans are small, their morphology varies greatly and includes both the largest arthropod in the world – the Japanese spider crab with a leg span of 3.7 metres (12 ft) – and the smallest, the 100- micrometre -long (0.004 in) Stygotantulus stocki . Despite their diversity of form, crustaceans are united by
826-617: The Marmorkrebs crayfish. In many crustaceans, the fertilised eggs are released into the water column , while others have developed a number of mechanisms for holding on to the eggs until they are ready to hatch. Most decapods carry the eggs attached to the pleopods , while peracarids , notostracans , anostracans , and many isopods form a brood pouch from the carapace and thoracic limbs. Female Branchiura do not carry eggs in external ovisacs but attach them in rows to rocks and other objects. Most leptostracans and krill carry
885-713: The Carboniferous , as are the first true mantis shrimp. In the Decapoda , prawns and polychelids appear in the Triassic, and shrimp and crabs appear in the Jurassic . The fossil burrow Ophiomorpha is attributed to ghost shrimps, whereas the fossil burrow Camborygma is attributed to crayfishes. The Permian–Triassic deposits of Nurra preserve the oldest (Permian: Roadian) fluvial burrows ascribed to ghost shrimps (Decapoda: Axiidea, Gebiidea) and crayfishes (Decapoda: Astacidea, Parastacidea), respectively. However,
944-471: The Carboniferous period onwards. Within the Malacostraca, no fossils are known for krill , while both Hoplocarida and Phyllopoda contain important groups that are now extinct as well as extant members (Hoplocarida: mantis shrimp are extant, while Aeschronectida are extinct; Phyllopoda: Canadaspidida are extinct, while Leptostraca are extant ). Cumacea and Isopoda are both known from
1003-401: The Japanese spider crab with a leg span of up to 3.8 m (12.5 ft) and a mass of 20 kg (44 lb). Like other arthropods , crustaceans have an exoskeleton , which they moult to grow. They are distinguished from other groups of arthropods, such as insects , myriapods and chelicerates , by the possession of biramous (two-parted) limbs, and by their larval forms , such as
1062-414: The axillae and the heads of the humeri . In the middle line the suprasternal notch is seen above, while about three fingers' breadth below it a transverse ridge can be felt, which is known as the sternal angle and this marks the junction between the manubrium and body of the sternum . Level with this line the second ribs join the sternum, and when these are found the lower ribs can often be counted. At
1121-441: The diaphragm , the esophagus , the trachea , and a part of the sternum known as the xiphoid process . Arteries and veins are also contained – ( aorta , superior vena cava , inferior vena cava and the pulmonary artery ); bones (the shoulder socket containing the upper part of the humerus , the scapula , sternum , thoracic portion of the spine , collarbone , and the rib cage and floating ribs ). External structures are
1180-509: The hexapods ( insects and entognathans ) emerged deep in the Crustacean group, with the completed pan-group referred to as Pancrustacea . The three classes Cephalocarida , Branchiopoda and Remipedia are more closely related to the hexapods than they are to any of the other crustaceans ( oligostracans and multicrustaceans ). The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to
1239-634: The nauplius stage of branchiopods and copepods . Most crustaceans are free-living aquatic animals , but some are terrestrial (e.g. woodlice , sandhoppers ), some are parasitic (e.g. Rhizocephala , fish lice , tongue worms ) and some are sessile (e.g. barnacles ). The group has an extensive fossil record , reaching back to the Cambrian . More than 7.9 million tons of crustaceans per year are harvested by fishery or farming for human consumption, consisting mostly of shrimp and prawns . Krill and copepods are not as widely fished, but may be
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#17327908426331298-413: The pereon or thorax , and the pleon or abdomen . The head and thorax may be fused together to form a cephalothorax , which may be covered by a single large carapace . The crustacean body is protected by the hard exoskeleton , which must be moulted for the animal to grow. The shell around each somite can be divided into a dorsal tergum , ventral sternum and a lateral pleuron. Various parts of
1357-429: The skin and nipples . In the human body , the region of the thorax between the neck and diaphragm in the front of the body is called the chest. The corresponding area in an animal can also be referred to as the chest. The shape of the chest does not correspond to that part of the thoracic skeleton that encloses the heart and lungs . All the breadth of the shoulders is due to the shoulder girdle, and contains
1416-470: The thoracic cavity and the thoracic wall . It contains organs including the heart , lungs , and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain . The word thorax comes from the Greek θώραξ thṓrax " breastplate , cuirass , corslet " via Latin : thorax . In humans and other hominids ,
1475-515: The zoea (pl. zoeæ or zoeas ). This name was given to it when naturalists believed it to be a separate species. It follows the nauplius stage and precedes the post-larva . Zoea larvae swim with their thoracic appendages , as opposed to nauplii, which use cephalic appendages, and megalopa, which use abdominal appendages for swimming. It often has spikes on its carapace , which may assist these small organisms in maintaining directional swimming. In many decapods , due to their accelerated development,
1534-723: The Asian shore crab, Hemigrapsus sanguineus . Since the opening of the Suez Canal , close to 100 species of crustaceans from the Red Sea and the Indo-Pacific realm have established themselves in the eastern Mediterranean sub-basin, with often significant impact on local ecosystems. Most crustaceans have separate sexes , and reproduce sexually . In fact, a recent study explains how the male T. californicus decide which females to mate with by dietary differences, preferring when
1593-706: The Hexapoda is distinctly closer to e.g. a Multicrustacean than an Oligostracan is. Crustaceans have a rich and extensive fossil record , which begins with animals such as Canadaspis and Perspicaris from the Middle Cambrian age Burgess Shale . Most of the major groups of crustaceans appear in the fossil record before the end of the Cambrian, namely the Branchiopoda , Maxillopoda (including barnacles and tongue worms ) and Malacostraca ; there
1652-567: The United States. The major pathophysiologies encountered in blunt chest trauma involve derangements in the flow of air, blood, or both in combination. Sepsis due to leakage of alimentary tract contents, as in esophageal perforations, also must be considered. Blunt trauma commonly results in chest wall injuries (e.g., rib fractures). The pain associated with these injuries can make breathing difficult, and this may compromise ventilation. Direct lung injuries, such as pulmonary contusions (see
1711-406: The animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology (alternatively, malacostracology , crustaceology or crustalogy ), and a scientist who works in carcinology is a carcinologist . The body of a crustacean is composed of segments, which are grouped into three regions: the cephalon or head ,
1770-429: The beginning. It is important to monitor the pain to ensure that it is not a sign of something more serious. Pain can also be experienced in persons who have an upper respiratory infection . This virus is also accompanied by a fever and cough. Shingles is another viral infection that can give symptoms of chest or rib pain before a rash develops. Injuries to the rib cage or sternum is also a common cause of chest pain. It
1829-425: The cartilage attached to the sternum, as 1 through 7 are, and therefore are termed "floating". Whereas ribs 8 through 10 are termed false ribs as their costal cartilage articulates with the costal cartilage of the rib above. The thorax bones also have the main function of protecting the heart, lungs, and major blood vessels in the thorax area, such as the aorta . The anatomy of the chest can also be described through
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1888-421: The cause of the pain. While cardiac issues cause feelings of sudden pressure in the chest or a crushing pain in the back, neck, and arms, pain that is felt due to noncardiac issues gives a burning feeling along the digestive tract or pain when deep breaths are attempted. Different people feel pains differently for the same condition. Only a patient truly knows if the symptoms are mild or serious. Chest pain may be
1947-448: The eggs between their thoracic limbs; some copepods carry their eggs in special thin-walled sacs, while others have them attached together in long, tangled strings. Crustaceans exhibit a number of larval forms, of which the earliest and most characteristic is the nauplius . This has three pairs of appendages , all emerging from the young animal's head, and a single naupliar eye. In most groups, there are further larval stages, including
2006-684: The evidence that Maxillopoda was non-monophyletic, they retained it as one of the six classes, although did suggest that Maxillipoda could be replaced by elevating its subclasses to classes. Since then phylogenetic studies have confirmed the polyphyly of Maxillipoda and the paraphyletic nature of Crustacea with respect to Hexapoda. Recent classifications recognise ten to twelve classes in Crustacea or Pancrustacea, with several former maxillopod subclasses now recognised as classes (e.g. Thecostraca , Tantulocarida , Mystacocarida , Copepoda , Branchiura and Pentastomida ). The following cladogram shows
2065-444: The exoskeleton may be fused together. Each somite , or body segment can bear a pair of appendages : on the segments of the head, these include two pairs of antennae , the mandibles and maxillae ; the thoracic segments bear legs , which may be specialised as pereiopods (walking legs) and maxillipeds (feeding legs). Malacostraca and Remipedia (and the hexapods) have abdominal appendages. All other classes of crustaceans have
2124-414: The extinct trilobites , the thorax is one of the three main divisions of the creature's body, each of which is in turn composed of multiple segments. It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites. In most insects, the thorax itself is composed of three segments; the prothorax , the mesothorax , and the metathorax . In extant insects,
2183-456: The females are algae-fed instead of yeast-fed. A small number are hermaphrodites , including barnacles , remipedes , and Cephalocarida . Some may even change sex during the course of their life. Parthenogenesis is also widespread among crustaceans, where viable eggs are produced by a female without needing fertilisation by a male. This occurs in many branchiopods , some ostracods , some isopods , and certain "higher" crustaceans, such as
2242-434: The functional thorax is composed of four segments, and is therefore typically called the mesosoma to distinguish it from the "thorax" of other insects. Each thoracic segment in an insect is further subdivided into various parts, the most significant of which are the dorsal portion (the notum ), the lateral portion (the pleuron ; one on each side), and the ventral portion (the sternum ). In some insects, each of these parts
2301-674: The great radiation of crustaceans occurred in the Cretaceous , particularly in crabs, and may have been driven by the adaptive radiation of their main predators, bony fish . The first true lobsters also appear in the Cretaceous. Many crustaceans are consumed by humans, and nearly 10,700,000 tons were harvested in 2007; the vast majority of this output is of decapod crustaceans : crabs , lobsters , shrimp , crawfish , and prawns . Over 60% by weight of all crustaceans caught for consumption are shrimp and prawns, and nearly 80%
2360-445: The image below), are frequently associated with major chest trauma and may impair ventilation by a similar mechanism. Chest pain can be the result of multiple issues, including respiratory problems, digestive issues, and musculoskeletal complications. The pain can trigger cardiac issues as well. Not all pain that is felt is associated with the heart, but it should not be taken lightly either. Symptoms can be different depending on
2419-422: The layer allow light to reach the retina. As the larvae mature into adults, the layer migrates to a new position behind the retina where it works as a backscattering mirror that increases the intensity of light passing through the eyes, as seen in many nocturnal animals. In an effort to understand whether DNA repair processes can protect crustaceans against DNA damage , basic research was conducted to elucidate
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2478-491: The lower part of the sternum, where the seventh or last true ribs join it, the ensiform cartilage begins, and above this there is often a depression known as the pit of the stomach . The bones of the thorax, called the "thoracic skeleton" is a component of the axial skeleton . It consists of the ribs and sternum . The ribs of the thorax are numbered in ascending order from 1–12. 11 and 12 are known as floating ribs because they have no anterior attachment point in particular
2537-514: The lung or as a shortness of breath. In mammals , the thorax is the region of the body formed by the sternum , the thoracic vertebrae , and the ribs . It extends from the neck to the diaphragm , and does not include the upper limbs . The heart and the lungs reside in the thoracic cavity , as well as many blood vessels . The inner organs are protected by the rib cage and the sternum. Thoracic vertebrae are also distinguished in birds , but not in reptiles . In insects , crustaceans , and
2596-408: The most common condition, chest pain. These conditions can be hereditary or caused by birth defects or trauma . Any condition that lowers the ability to either breathe deeply or to cough is considered a chest disease or condition. Injury to the chest (also referred to as chest trauma, thoracic injury, or thoracic trauma) results in up to 1 / 4 of all deaths due to trauma in
2655-401: The oceans as insects are on land. Most crustaceans are also motile , moving about independently, although a few taxonomic units are parasitic and live attached to their hosts (including sea lice , fish lice , whale lice , tongue worms , and Cymothoa exigua , all of which may be referred to as "crustacean lice"), and adult barnacles live a sessile life – they are attached headfirst to
2714-417: The prothorax never has wings, though legs are always present in adults; wings (when present) are restricted to at least the mesothorax, and typically also the metathorax, though the wings may be reduced or modified on either or both segments. In the apocritan Hymenoptera , the first abdominal segment is fused to the metathorax, where it forms a structure known as the propodeum . Accordingly, in these insects,
2773-429: The repair mechanisms used by Penaeus monodon (black tiger shrimp). Repair of DNA double-strand breaks was found to be predominantly carried out by accurate homologous recombinational repair. Another, less accurate process, microhomology-mediated end joining , is also used to repair such breaks. The expression pattern of DNA repair related and DNA damage response genes in the intertidal copepod Tigriopus japonicus
2832-413: The result of a lung disease or acute lung injury. The size of the pneumothorax changes as air or gas builds up, so a medical procedure can release the pressure with a needle. If it is untreated, blood flow can be interrupted and cause a drop in blood pressure known as tension pneumothorax. It is possible for smaller cases to clear up on their own. Symptoms of this condition are often felt only on one side of
2891-446: The sea to release the eggs. Others, such as woodlice , lay their eggs on land, albeit in damp conditions. In most decapods, the females retain the eggs until they hatch into free-swimming larvae. Most crustaceans are aquatic, living in either marine or freshwater environments, but a few groups have adapted to life on land, such as terrestrial crabs , terrestrial hermit crabs , and woodlice . Marine crustaceans are as ubiquitous in
2950-518: The second pair of antennae, but not the first, which is usually uniramous , the exception being in the Class Malacostraca where the antennules may be generally biramous or even triramous. It is unclear whether the biramous condition is a derived state which evolved in crustaceans, or whether the second branch of the limb has been lost in all other groups. Trilobites , for instance, also possessed biramous appendages. The main body cavity
3009-436: The second to the sixth rib vertically and from the edge of the sternum to the mid-axillary line laterally. The female nipple is surrounded for half an inch by a more or less pigmented disc, the areola . The apex of a normal heart is in the fifth left intercostal space, three and a half inches from the mid-line. Different types of diseases or conditions that affect the chest include pleurisy , flail chest , atelectasis , and
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#17327908426333068-479: The special larval form known as the nauplius . The exact relationships of the Crustacea to other taxa are not completely settled as of April 2012 . Studies based on morphology led to the Pancrustacea hypothesis, in which Crustacea and Hexapoda ( insects and allies) are sister groups . More recent studies using DNA sequences suggest that Crustacea is paraphyletic , with the hexapods nested within
3127-510: The substrate and cannot move independently. Some branchiurans are able to withstand rapid changes of salinity and will also switch hosts from marine to non-marine species. Krill are the bottom layer and most important part of the food chain in Antarctic animal communities. Some crustaceans are significant invasive species , such as the Chinese mitten crab, Eriocheir sinensis , and
3186-422: The thorax is the chest region of the body between the neck and the abdomen , along with its internal organs and other contents. It is mostly protected and supported by the rib cage , spine , and shoulder girdle . The contents of the thorax include the heart and lungs (and the thymus gland); the major and minor pectoral muscles, trapezius muscles , and neck muscle; and internal structures such as
3245-412: The updated relationships between the different extant groups of the paraphyletic Crustacea in relation to the class Hexapoda . Ostracoda Mystacocarida Branchiura Pentastomida Malacostraca Copepoda Tantulocarida Thecostraca Cephalocarida Branchiopoda Remipedia Hexapoda According to this diagram, the Hexapoda are deep in the Crustacea tree, and any of
3304-427: The use of anatomical landmarks . The nipple in the male is situated in front of the fourth rib or a little below; vertically it lies a little external to a line drawn down from the middle of the clavicle ; in the female it is not so constant. A little below it the lower limit of the great pectoral muscle is seen running upward and outward to the axilla; in the female this is obscured by the breast , which extends from
3363-426: The zoea is the first larval stage. In some cases, the zoea stage is followed by the mysis stage, and in others, by the megalopa stage, depending on the crustacean group involved. Providing camouflage against predators, the otherwise black eyes in several forms of swimming larvae are covered by a thin layer of crystalline isoxanthopterin that gives their eyes the same color as the surrounding water, while tiny holes in
3422-450: Was analyzed after ultraviolet irradiation. This study revealed increased expression of proteins associated with the DNA repair processes of non-homologous end joining , homologous recombination , base excision repair and DNA mismatch repair . The name "crustacean" dates from the earliest works to describe the animals, including those of Pierre Belon and Guillaume Rondelet , but the name
3481-412: Was not used by some later authors, including Carl Linnaeus , who included crustaceans among the " Aptera " in his Systema Naturae . The earliest nomenclatural valid work to use the name "Crustacea" was Morten Thrane Brünnich 's Zoologiæ Fundamenta in 1772, although he also included chelicerates in the group. The subphylum Crustacea comprises almost 67,000 described species , which
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