62-563: See text A planthopper is any insect in the infraorder Fulgoromorpha , in the suborder Auchenorrhyncha , a group exceeding 12,500 described species worldwide. The name comes from their remarkable resemblance to leaves and other plants of their environment and that they often "hop" for quick transportation in a similar way to that of grasshoppers . However, planthoppers generally walk very slowly. Distributed worldwide, all members of this group are plant-feeders, though few are considered pests. Fulgoromorphs are most reliably distinguished from
124-527: A runny nose . Fevers may develop and an affected child may develop difficulty breathing and sepsis . Swelling of the airway can cause narrowing of the airway, causing a hoarse breathing sound called stridor , or even cause complete blockage. Up to 80% of people affected by bacterial tracheitis require the use of mechanical ventilation , and treatment may include endoscopy for the purposes of acquiring microbiological specimens for culture and sensitivity , as well as removal of any dead tissue associated with
186-409: A tracheotomy is often performed to insert a tube for ventilation, usually when needed for particular types of surgery to be carried out so that the airway can be kept open. The provision of the opening via a tracheotomy is called a tracheostomy . Another method procedure can be carried, in an emergency situation, and this is a cricothyrotomy . Tracheal agenesis is a rare birth defect in which
248-552: A hundred species, are marine. Insects such as snow scorpionflies flourish in cold habitats including the Arctic and at high altitude. Insects such as desert locusts , ants, beetles, and termites are adapted to some of the hottest and driest environments on earth, such as the Sonoran Desert . Insects form a clade , a natural group with a common ancestor, among the arthropods . A phylogenetic analysis by Kjer et al. (2016) places
310-445: A length of about 10 to 11 cm (4 to 4 + 1 ⁄ 4 in), wider in males than females. The trachea begins at the lower edge of the cricoid cartilage of the larynx at the level of sixth cervical vertebra (C6) and ends at the carina, the point where the trachea branches into left and right main bronchi., at the level of the fourth thoracic vertebra (T4), although its position may change with breathing . The trachea
372-447: A narrowing of the trachea ( tracheal stenosis ). Obstruction invariably causes a harsh breathing sound known as stridor . A camera inserted via the mouth down into the trachea, called bronchoscopy , may be performed to investigate the cause of an obstruction. Management of obstructions depends on the cause. Obstructions as a result of malignancy may be managed with surgery, chemotherapy or radiotherapy . A stent may be inserted over
434-421: A pair of antennae . Insects are the most diverse group of animals, with more than a million described species ; they represent more than half of all animal species. The insect nervous system consists of a brain and a ventral nerve cord . Most insects reproduce by laying eggs . Insects breathe air through a system of paired openings along their sides, connected to small tubes that take air directly to
496-485: A person who has had their larynx removed. Air travels upwards from the surgical connection to the upper oesophagus and the pharynx, creating vibrations that create sound that can be used for speech. The purpose of the puncture is to restore a person's ability to speak after the vocal cords have been removed. Sometimes as an anatomical variation one or more of the tracheal rings are formed as complete rings, rather than horseshoe shaped rings. These O rings are smaller than
558-416: A resonator to amplify sound. In some birds, the tracheal rings are complete, and may even be ossified . In amphibians , the trachea is normally extremely short, and leads directly into the lungs, without clear primary bronchi. A longer trachea is, however, found in some long-necked salamanders , and in caecilians . While there are irregular cartilagenous nodules on the amphibian trachea, these do not form
620-402: A result of a viral illness affecting other parts of the respiratory tract , such as the larynx and bronchi, called croup , that can result in a cough. Infection with bacteria usually affects the trachea only and can cause narrowing or even obstruction. As a major part of the respiratory tract, when obstructed the trachea prevents air entering the lungs and so a tracheostomy may be required if
682-444: A tendency to get recurrent respiratory tract infections. From 2008, operations have experimentally replaced tracheas, with those grown from stem cells , or with synthetic substitutes, however this is regarded as experimental and there is no standardised method. Difficulties with ensuring adequate blood supply to the replaced trachea is considered a major challenge to any replacement. Additionally, no evidence has been found to support
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#1733085209234744-405: Is a midline structure, it can be displaced normally to the right by the aortic arch. The trachea passes by many structures of the neck and chest ( thorax ) along its course. In front of the upper trachea lies connective tissue and skin. Several other structures pass over or sit on the trachea; the jugular arch , which joins the two anterior jugular veins , sits in front of the upper part of
806-423: Is constrained by the inelastic exoskeleton, so development involves a series of molts . The immature stages often differ from the adults in structure, habit and habitat. Groups that undergo four-stage metamorphosis often have a nearly immobile pupa . Insects that undergo three-stage metamorphosis lack a pupa, developing through a series of increasingly adult-like nymphal stages. The higher level relationship of
868-412: Is lined with a layer of interspersed layers of column-shaped cells with cilia . The epithelium contains goblet cells , which are glandular , column-shaped cells that produce mucins , the main component of mucus . Mucus helps to moisten and protect the airways. Mucus lines the ciliated cells of the trachea to trap inhaled foreign particles that the cilia then waft upward toward the larynx and then
930-468: Is surrounded by 16–20 rings of hyaline cartilage ; these 'rings' are 4 millimetres high in the adult, incomplete and C-shaped. Ligaments connect the rings. The trachealis muscle connects the ends of the incomplete rings and runs along the back wall of the trachea. Also adventitia, which is the outermost layer of connective tissue that surrounds the hyaline cartilage, contributes to the trachea's ability to bend and stretch with movement. Although trachea
992-830: The Latin word insectum from in , "cut up", as insects appear to be cut into three parts. The Latin word was introduced by Pliny the Elder who calqued the Ancient Greek word ἔντομον éntomon "insect" (as in entomology ) from ἔντομος éntomos "cut in pieces"; this was Aristotle 's term for this class of life in his biology , also in reference to their notched bodies. The English word insect first appears in 1601 in Philemon Holland 's translation of Pliny. In common speech, insects and other terrestrial arthropods are often called bugs . Entomologists to some extent reserve
1054-2267: The Paraneoptera , and Kjer et al. 2016 for the Holometabola . The numbers of described extant species (boldface for groups with over 100,000 species) are from Stork 2018. Archaeognatha (hump-backed/jumping bristletails, 513 spp) [REDACTED] Zygentoma (silverfish, firebrats, fishmoths, 560 spp) [REDACTED] Odonata (dragonflies and damselflies, 5,899 spp) [REDACTED] Ephemeroptera (mayflies, 3,240 spp) [REDACTED] Zoraptera (angel insects, 37 spp) [REDACTED] Dermaptera (earwigs, 1,978 spp) [REDACTED] Plecoptera (stoneflies, 3,743 spp) [REDACTED] Orthoptera (grasshoppers, crickets, katydids, 23,855 spp) [REDACTED] Grylloblattodea (ice crawlers, 34 spp) [REDACTED] Mantophasmatodea (gladiators, 15 spp) [REDACTED] Phasmatodea (stick insects, 3,014 spp) [REDACTED] Embioptera (webspinners, 463 spp) [REDACTED] Mantodea (mantises, 2,400 spp) [REDACTED] Blattodea (cockroaches and termites, 7,314 spp) [REDACTED] Psocodea (book lice, barklice and sucking lice, 11,000 spp) [REDACTED] [REDACTED] Hemiptera (true bugs, 103,590 spp) [REDACTED] Thysanoptera (thrips, 5,864 spp) [REDACTED] Hymenoptera (sawflies, wasps, bees, ants, 116,861 spp) [REDACTED] Strepsiptera (twisted-wing flies, 609 spp) [REDACTED] Coleoptera (beetles, 386,500 spp) [REDACTED] Raphidioptera (snakeflies, 254 spp) [REDACTED] Neuroptera (lacewings, 5,868 spp) [REDACTED] Megaloptera (alderflies and dobsonflies, 354 spp) [REDACTED] Lepidoptera (butterflies and moths, 157,338 spp) [REDACTED] Trichoptera (caddisflies, 14,391 spp) [REDACTED] Diptera (true flies, 155,477 spp) [REDACTED] Mecoptera (scorpionflies, 757 spp) [REDACTED] Siphonaptera (fleas, 2,075 spp) [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Trachea#Invertebrates The trachea ( pl. : tracheae or tracheas ), also known as
1116-405: The inferior thyroid arteries and veins; the lower trachea receives blood from bronchial arteries. Arteries that supply the trachea do so via small branches that supply the trachea from the sides. As the branches approach the wall of the trachea, they split into inferior and superior branches, which join with the branches of the arteries above and below; these then split into branches that supply
1178-616: The insects is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonfly-like insects with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have coevolved with flowering plants . Adult insects typically move about by walking and flying; some can swim. Insects are the only invertebrates that can achieve sustained powered flight; insect flight evolved just once. Many insects are at least partly aquatic , and have larvae with gills; in some species,
1240-456: The oesophagus , followed by connective tissue and the vertebral column . To its sides run the carotid arteries and inferior thyroid arteries; and to its sides on its back surface run the recurrent laryngeal nerves in the upper trachea, and the vagus nerves in the lower trachea. The trachealis muscle contracts during coughing , reducing the size of the lumen of the trachea. The upper part of trachea receives and drains blood through
1302-483: The pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate , or rub their wings together, to attract a mate and repel other males. Lampyrid beetles communicate with light. Humans regard many insects as pests , especially those that damage crops, and attempt to control them using insecticides and other techniques. Others are parasitic , and may act as vectors of diseases . Insect pollinators are essential to
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#17330852092341364-470: The trachealis muscle at their ends. The epiglottis closes the opening to the larynx during swallowing. The trachea begins to form in the second month of embryo development, becoming longer and more fixed in its position over time. Its epithelium is lined with column-shaped cells that have hair-like extensions called cilia , with scattered goblet cells that produce protective mucins . The trachea can be affected by inflammation or infection, usually as
1426-460: The windpipe , is a cartilaginous tube that connects the larynx to the bronchi of the lungs , allowing the passage of air , and so is present in almost all animals lungs. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea, the cricoid cartilage attaches it to the larynx. The trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying ligaments , and by
1488-618: The Hemiptera (true bugs), Lepidoptera (butterflies and moths), Diptera (true flies), Hymenoptera (wasps, ants, and bees), and Coleoptera (beetles), each with more than 100,000 described species. Insects are distributed over every continent and almost every terrestrial habitat. There are many more species in the tropics , especially in rainforests , than in temperate zones. The world's regions have received widely differing amounts of attention from entomologists. The British Isles have been thoroughly surveyed, so that Gullan and Cranston 2014 state that
1550-406: The abdominal terga and other parts of the body. These are hydrophobic and help conceal the insects. Adult females of many families also produce wax which may be used to protect eggs. Planthopper nymphs also possess a biological gear mechanism at the base of the hind legs, which keeps the legs in synchrony when the insects jump. The gears, not present in the adults, were known for decades before
1612-404: The adults too are aquatic. Some species, such as water striders , can walk on the surface of water. Insects are mostly solitary, but some, such as bees , ants and termites , are social and live in large, well-organized colonies . Others, such as earwigs , provide maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense
1674-418: The anterior and posterior parts of the trachea. The inferior thyroid arteries arise just below the isthmus of the thyroid, which sits atop the trachea. These arteries join ( anastamoses ) with ascending branches of the bronchial arteries , which are direct branches from the aorta , to supply blood to the trachea. The lymphatic vessels of the trachea drain into the pretracheal nodes that lie in front of
1736-457: The cartilages often unite, partially or completely, and they are sometimes bifurcated at their extremities. The rings are generally highly elastic but they may calcify with age . The trachea's main function is to transport air to and from the lungs. It also helps to warm, humidify, and filter the air before it reaches the lungs. The trachea is made up of rings of cartilage, which help to keep it open and prevent it from collapsing. The inside of
1798-462: The infection. Treatment in such situations usually includes antibiotics . A trachea may be narrowed or compressed , usually a result of enlarged nearby lymph nodes; cancers of the trachea or nearby structures; large thyroid goitres ; or rarely as a result of other processes such as unusually swollen blood vessels . Scarring from tracheobronchial injury or intubation; or inflammation associated with granulomatosis with polyangiitis may also cause
1860-592: The insects among the Hexapoda , six-legged animals with segmented bodies; their closest relatives are the Diplura (bristletails). Collembola (springtails) [REDACTED] Protura (coneheads) [REDACTED] Diplura (two-pronged bristletails) [REDACTED] Insecta (=Ectognatha) [REDACTED] The internal phylogeny is based on the works of Wipfler et al. 2019 for the Polyneoptera , Johnson et al. 2018 for
1922-417: The insertion of a tube down the trachea. This procedure is commonly performed during surgery , in order to ensure a person receives enough oxygen when sedated. The catheter is connected to a machine that monitors the airflow, oxygenation and several other metrics. This is often one of the responsibilities of an anaesthetist during surgery. In an emergency, or when tracheal intubation is deemed impossible,
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1984-524: The laryngotracheal tube. By the start of the fifth week, the left and right main bronchi have begun to form, initially as buds at the terminal end of the trachea. The trachea is no more than 4 mm in diameter during the first year of life, expanding to its adult diameter of approximately 2 cm by late childhood. The trachea is more circular and more vertical in children compared to adults, varies more in size, and also varies more in its position in relation to its surrounding structures. The trachea
2046-419: The lower trachea lies the manubrium of the sternum , the remnants of the thymus in adults. To the front left lie the large blood vessels the aortic arch and its branches the left common carotid artery and the brachiocephalic trunk ; and the left brachiocephalic vein . The deep cardiac plexus and lymph nodes are also positioned in front of the lower trachea. Behind the trachea, along its length, sits
2108-429: The many orders of insects , but in general each segment of the body can have only one pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it. The tracheae are invaginations of the cuticular exoskeleton that branch ( anastomose ) throughout the body with diameters from only a few micrometres up to 0.8 mm. Diffusion of oxygen and carbon dioxide takes place across
2170-565: The most common abnormalities is a separation of the upper and lower ends of the oesophagus, with the upper end finishing in a closed pouch. Other abnormalities may be associated with this, including cardiac abnormalities, or VACTERL syndrome . Such fistulas may be detected before a baby is born because of excess amniotic fluid ; after birth, they are often associated with pneumonitis and pneumonia because of aspiration of food contents. Congenital fistulas are often treated by surgical repair. In adults, fistulas may occur because of erosion into
2232-472: The name Archaeorrhyncha as a replacement for the Fulgoromorpha. Extinct families include: Insect Insects (from Latin insectum ) are hexapod invertebrates of the class Insecta . They are the largest group within the arthropod phylum . Insects have a chitinous exoskeleton , a three-part body ( head , thorax and abdomen ), three pairs of jointed legs , compound eyes , and
2294-402: The name "bugs" for a narrow category of " true bugs ", insects of the order Hemiptera , such as cicadas and shield bugs . Other terrestrial arthropods, such as centipedes , millipedes , woodlice , spiders , mites and scorpions , are sometimes confused with insects, since they have a jointed exoskeleton. Adult insects are the only arthropods that ever have wings, with up to two pairs on
2356-497: The normal C-shaped rings and can cause narrowing ( stenosis ) of the trachea, resulting in breathing difficulties. An operation called a slide tracheoplasty can open up the rings and rejoin them as wider rings, shortening the length of the trachea. Slide tracheoplasty is said to be the best option in treating tracheal stenosis. Mounier-Kuhn syndrome is a rare congenital disorder of an abnormally enlarged trachea, characterised by absent elastic fibres, smooth muscle thinning, and
2418-460: The nymphs produce copious quantities of honeydew , on which sooty mould often grows. One species considered to be a pest is Haplaxius crudus , which is a vector for lethal yellowing , a palm disease that nearly killed off the Jamaican Tall coconut variety. The infraorder contains two superfamilies , Fulgoroidea and Delphacoidea . As mentioned under Auchenorrhyncha , some authors use
2480-658: The obstruction. Benign lesions, such as narrowing resulting from scarring, are likely to be surgically excised. One cause of narrowing is tracheomalacia , which is the tendency for the trachea to collapse when there is increased external pressure, such as when airflow is increased during breathing in or out, due to decreased compliance . It can be due to congenital causes, or due to things that develop after birth, such as compression from nearby masses or swelling, or trauma. Congenital tracheomalacia can occur by itself or in association with other abnormalities such as bronchomalacia or laryngomalacia , and abnormal connections between
2542-410: The organ. Allowing for variations in the length of the neck, the trachea in other mammals is, in general, similar to that in humans. Generally, it is also similar to the reptilian trachea. In birds , the trachea runs from the pharynx to the syrinx , from which the primary bronchi diverge. Swans have an unusually elongated trachea, part of which is coiled beneath the sternum; this may act as
Planthopper - Misplaced Pages Continue
2604-467: The other Auchenorrhyncha by two features; the bifurcate (Y-shaped) anal vein in the forewing, and the thickened, three-segmented antennae , with a generally round or egg-shaped second segment (pedicel) that bears a fine filamentous arista . Planthoppers are laterally flattened and hold their broad wings vertically, in a tent-like fashion, concealing the sides of the body and part of the legs. Nymphs of many planthoppers produce wax from special glands on
2666-464: The pharynx where it can be either swallowed into the stomach or expelled as phlegm . This self-clearing mechanism is termed mucociliary clearance . Directly beneath this mucus layer lies the submucosa layer which is composed primarily of fibrous connective tissue and connects the mucosa to the rings of hyaline cartilage beneath. The trachea is surrounded by 16 to 20 rings of hyaline cartilage; these 'rings' are incomplete and C-shaped. Two or more of
2728-498: The placement of stem cells taken from bone marrow on the trachea as a way of stimulating tissue regeneration, and such a method remains hypothetical. In January 2021, surgeons at Mount Sinai Hospital in New York performed the first complete trachea transplantation. The 18-hour procedure included harvesting a trachea from a donor and implanting it in the patient, connecting numerous veins and arteries to provide sufficient blood flow to
2790-629: The recent description of their function. Planthoppers are often vectors for plant diseases, especially phytoplasmas which live in the phloem of plants and can be transmitted by planthoppers when feeding. A number of extinct planthopper taxa are known from the fossil record, such as the Lutetian -age Emiliana from the Green River Formation ( Eocene ) in Colorado. Both planthopper adults and nymphs feed by sucking sap from plants; in so doing,
2852-535: The reproduction of many flowering plants and so to their ecosystems. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Two species in particular are economically important and were domesticated many centuries ago: silkworms for silk and honey bees for honey . Insects are consumed as food in 80% of the world's nations, by people in roughly 3000 ethnic groups. Human activities are having serious effects on insect biodiversity . The word insect comes from
2914-566: The respiratory tract, such as the larynx and bronchi, known as croup , however bacterial infections may also affect the trachea alone, although they are often associated with a recent viral infection. Viruses that cause croup are generally the parainfluenza viruses 1–3, with influenza viruses A and B also causing croup, but usually causing more serious infections; bacteria may also cause croup and include Staphylococcus aureus , Haemophilus influenzae , Streptococcus pneumoniae and Moraxella catarrhalis . Causes of bacterial infection of
2976-533: The rings found in amniotes . The only vertebrates to have lungs, but no trachea, are the lungfish and the Polypterus , in which the lungs arise directly from the pharynx. The word trachea is used to define a very different organ in invertebrates than in vertebrates. Insects have an open respiratory system made up of spiracles, tracheae, and tracheoles to transport metabolic gases to and from tissues. The distribution of spiracles can vary greatly among
3038-527: The thorax. Whether winged or not, adult insects can be distinguished by their three-part body plan, with head, thorax, and abdomen; they have three pairs of legs on the thorax. Estimates of the total number of insect species vary considerably, suggesting that there are perhaps some 5.5 million insect species in existence, of which about one million have been described and named. These constitute around half of all eukaryote species, including animals , plants , and fungi . The most diverse insect orders are
3100-466: The tissues. The blood therefore does not carry oxygen; it is only partly contained in vessels, and some circulates in an open hemocoel . Insect vision is mainly through their compound eyes , with additional small ocelli . Many insects can hear, using tympanal organs , which may be on the legs or other parts of the body. Their sense of smell is via receptors, usually on the antennae and the mouthparts. Nearly all insects hatch from eggs . Insect growth
3162-518: The total of around 22,500 species is probably within 5% of the actual number there; they comment that Canada's list of 30,000 described species is surely over half of the actual total. They add that the 3000 species of the American Arctic must be broadly accurate. In contrast, a large majority of the insect species of the tropics and the southern hemisphere are probably undescribed. Some 30–40,000 species inhabit freshwater ; very few insects, perhaps
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#17330852092343224-404: The trachea and the oesophagus , amongst others. Congenital tracheomalacia often improves without specific intervention; when required, interventions may include beta agonists and muscarinic agonists , which enhance the tone of the smooth muscle surrounding the trachea; positive pressure ventilation , or surgery, which may include the placement of a stent , or the removal of the affected part of
3286-433: The trachea are most commonly Staphylococcus aureus and Streptococcus pneumoniae . In patients who are in hospital, additional bacteria that may cause tracheitis include Escherichia coli , Klebsiella pneumoniae , and Pseudomonas aeruginosa . A person affected with tracheitis may start with symptoms that suggest an upper respiratory tract infection such as a cough, sore throat , or coryzal symptoms such as
3348-410: The trachea fails to develop. The defect is usually fatal though sometimes surgical intervention has been successful. A tracheoesophageal fistula is a congenital defect in which the trachea and esophagus are abnormally connected (a fistula ). This is because of abnormalities in the separation between the trachea and oesophagus during development. This occurs in approximately 1 in 3,000 births, and
3410-400: The trachea from nearby malignant tumours, which erode into both the trachea and the oesophagus. Initially, these often result in coughing from swallowed contents of the oesophagus that are aspirated through the trachea, often progressing to fatal pneumonia; there is rarely a curative treatment. A tracheo-oesophageal puncture is a surgically created hole between the trachea and the esophagus in
3472-504: The trachea is lined with a mucous membrane, which produces mucus to help trap dirt and dust particles. The cilia, which are tiny hairs that line the mucous membrane, help to move the mucus and trapped particles up and out of the trachea. Inflammation of the trachea is known as tracheitis , usually due to an infection. It is usually caused by viral infections , with bacterial infections occurring almost entirely in children. Most commonly, infections occur with inflammation of other parts of
3534-558: The trachea is obstructed. Additionally, during surgery if mechanical ventilation is required when a person is sedated, a tube is inserted into the trachea, called intubation . The word trachea is used to define a very different organ in invertebrates than in vertebrates . Insects have an open respiratory system made up of spiracles , tracheae, and tracheoles to transport metabolic gases to and from tissues. An adult's trachea has an inner diameter of about 1.5 to 2 centimetres ( 1 ⁄ 2 to 3 ⁄ 4 in) and
3596-406: The trachea, and paratracheal lymph nodes that lie beside it. In the fourth week of development of the human embryo as the respiratory bud grows, the trachea separates from the foregut through the formation of ridges which eventually separate the trachea from the oesophagus, the tracheoesophageal septum . This separates the future trachea from the oesophagus and divides the foregut tube into
3658-407: The trachea. In dogs, particularly miniature dogs and toy dogs , tracheomalacia, as well as bronchomalacia , can lead to tracheal collapse , which often presents with a honking goose-like cough. The trachea may be injured by trauma such as in a vehicle accident, or intentionally by another wilfully inflicting damage for example as practiced in some martial arts . Tracheal intubation refers to
3720-442: The trachea. In the head, thorax, or abdomen , tracheae may also be connected to air sacs. Many insects, such as grasshoppers and bees , which actively pump the air sacs in their abdomen, are able to control the flow of air through their body. In some aquatic insects, the tracheae exchange gas through the body wall directly, in the form of a gill , or function essentially as normal, via a plastron . Note that despite being internal,
3782-448: The trachea. The sternohyoid and sternothyroid muscles stretch along its length. The thyroid gland also stretches across the upper trachea, with the isthmus overlying the second to fourth rings, and the lobes stretching to the level of the fifth or sixth cartilage. The blood vessels of the thyroid rest on the trachea next to the isthmus; superior thyroid arteries join just above it, and the inferior thyroid veins below it. In front of
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#17330852092343844-526: The walls of the smallest tubes, called tracheoles, which penetrate tissues and even indent individual cells. Gas may be conducted through the respiratory system by means of active ventilation or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their hemolymph . This is one of the factors that may limit their size. A tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helices . Taenidia provide strength and flexibility to
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