The air sacs which make up most of the lungs of mammals are known as what?
"continue directly through to become mesobronchi. Ten different air sacs attach to the lungs to form areas for respiration. The most posterior air sacs (abdominal and post-thoracic) differ in that the right abdominal air sac is relatively small, lying to the right of the mesentery, and dorsally to the liver. While the left abdominal air sac is large and lies to the left of the mesentery. The connection from the main mesobronchi to the more anterior air sacs including the interclavicular, lateral clavicular, and pre-thoracic sacs known as the ventrobronchi region. While the caudal end of the mesobronchus branches into"
"Lung The lungs are the primary organs of the respiratory system in humans and many other animals including a few fish and some snails. In mammals and most other vertebrates, 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 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 different muscles to support and"
"the airways. Birds have lungs but no diaphragm. They rely mostly on air sacs for ventilation. These air sacs do not play a direct role in gas exchange, but help to move air unidirectionally across the gas exchange surfaces in the lungs. During inhalation, fresh air is taken from the trachea down into the posterior air sacs and into the parabronchi which lead from the posterior air sacs into the lung. The air that enters the lungs joins the air which is already in the lungs, and is drawn forward across the gas exchanger into anterior air sacs. During exhalation,"
"animals that are active but too large to get rid of all the excess heat through their skins. The palaeontologist Peter Ward has argued that the evolution of the air sac system, which first appears in the very earliest dinosaurs, may have been in response to the very low (11%) atmospheric oxygen of the Carnian and Norian ages of the Triassic Period. Birds have spurs called ""uncinate processes"" on the rear edges of their ribs, and these give the chest muscles more leverage when pumping the chest to improve oxygen supply. The size of the uncinate processes is related to"
"ventilation comes from a reconstruction of the air exchange volume (the volume of air exchanged with each breath) of ""Plateosaurus"", which when expressed as a ratio of air volume per body weight at 29 ml/kg is similar to values of geese and other birds, and much higher than typical mammalian values. So far no evidence of air sacs has been found in ornithischian dinosaurs. But this does not imply that ornithischians could not have had metabolic rates comparable to those of mammals, since mammals also do not have air sacs. Three explanations have been suggested for the development of air"
"air sacs may interconnect or be fused with the anterior thoracic sacs. During inhalation, environmental air initially enters the bird through the nostrils from where it is heated, humidified, and filtered in the nasal passages and upper parts of the trachea. From there, the air enters the lower trachea and continues to just beyond the syrinx, at which point the trachea branches into two primary bronchi, going to the two lungs. The primary bronchi enter the lungs to become the intrapulmonary bronchi, which give off a set of parallel branches called ventrobronchi and, a little further on, an equivalent set"
"thoraco-abdominal cavities, thus rhythmically changing the volumes of all their air sacs in unison (illustration on the right). The active phase of respiration in birds is exhalation, requiring contraction of their muscles of respiration. Relaxation of these muscles causes inhalation. Three distinct sets of organs perform respiration — the anterior air sacs (interclavicular, cervicals, and anterior thoracics), the lungs, and the posterior air sacs (posterior thoracics and abdominals). Typically there are nine air sacs within the system; however, that number can range between seven and twelve, depending on the species of bird. Passerines possess seven air sacs, as the clavicular"
"of air sacs connected to the lungs. The use of air sacs forms the basis for the three main avian respiratory characteristics: Inhalation begins at the mouth and the nostrils located at the front of the beak. The air then flows through the anatomical dead space of a highly vascular trachea (c. ) and expansive bronchial system, where it is further conducted to the posterior air sacs. Air flow through the parabronchi of the paleopulmo is in the same direction to the dorsobronchi during inspiration and expiration. Inspired air moves into the respiratory system as a result of the expansion"
"sacs has been found in ornithischian dinosaurs. But this does not imply that ornithischians could not have had metabolic rates comparable to those of mammals, since mammals also do not have air sacs. Three explanations have been suggested for the development of air sacs in dinosaurs: Calculations of the volumes of various parts of the sauropod ""Apatosaurus""’ respiratory system support the evidence of bird-like air sacs in sauropods: On this basis, ""Apatosaurus"" could not have had a reptilian respiratory system, as its tidal volume would have been less than its dead-space volume, so that stale air was not expelled but"
"several dorsobronchi. Together, the ventrobronchi and dorsobronchi are connected by intra-pulmonary airways, the parabronchi, which form an arcade structure within the lung called the paleopulmo. It is the only structure found in primitive birds such as ratites. The largest air sacs found within the respiratory system are those of the post-thoracic region, while the others decrease in size respectively, the interclavicular (unpaired), abdominal, pre-thoracic, and lateral clavicular sacs. The adult common ostrich lung lacks connective tissue known as interparabronchial septa, which render strength to the non-compliant avian lung in other bird species. Due to this the lack of connective tissue"
"Another test is that of the lung's diffusing capacity – this is a measure of the transfer of gas from air to the blood in the lung capillaries. The lungs of birds are relatively small, but are connected to 8 or 9 air sacs that extend through much of the body, and are in turn connected to air spaces within the bones. On inhalation, air travels through the trachea of a bird into the air sacs. Air then travels continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, to the air sacs"
"air sacs found so far. Early sauropodomorphs, including the group traditionally called ""prosauropods"", may also have had air sacs. Although possible pneumatic indentations have been found in ""Plateosaurus"" and ""Thecodontosaurus"", the indentations are very small. One study in 2007 concluded that prosauropods likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods). The study concluded that it was impossible to determine whether prosauropods had a bird-like flow-through lung, but that the air sacs were almost certainly present. A further indication for the presence of air sacs and their use in lung"
"Book lung A book lung is a type of respiration organ used for atmospheric gas exchange that is found in many arachnids, such as scorpions and spiders. Each of these organs is found inside an open ventral abdominal, air-filled cavity (atrium) and connects with the surroundings through a small opening for the purpose of respiration. Book lungs are not related to the lungs of modern land-dwelling vertebrates. Their name describes their structure. Stacks of alternating air pockets and tissue filled with hemolymph (the arthropod equivalent of blood) give them an appearance similar to a ""folded"" book.(Their number varies from just"
"action of other respiratory muscles. Consequently, air is sucked into or expelled out of the lungs, always moving down its pressure gradient. This type of lung is known as a bellows lung due to its resemblance to blacksmith [[bellows]]. The mammalian [[heart]] has four chambers, two upper [[atrium (heart)|atria]], the receiving chambers, and two lower [[ventricle (heart)|ventricles]], the discharging chambers. The heart has four valves, which separate its chambers and ensures blood flows in the correct direction through the heart (preventing backflow). After [[gas exchange]] in the pulmonary capillaries (blood vessels in the lungs), oxygen-rich blood returns to the left"
"gas exchange, despite being thin-walled, as they are poorly vascularised. The air sacs expand and contract due to changes in the volume in the thorax and abdomen. This volume change is caused by the movement of the sternum and ribs and this movement is often synchronised with movement of the flight muscles. Parabronchi in which the air flow is unidirectional are called ""paleopulmonic parabronchi"" and are found in all birds. Some birds, however, have, in addition, a lung structure where the air flow in the parabronchi is bidirectional. These are termed ""neopulmonic parabronchi"". The lungs of most reptiles have a"
"lungs in mammals occurs via the respiratory centers in the medulla oblongata and the pons of the brainstem. These areas form a series of neural pathways which receive information about the partial pressures of oxygen and carbon dioxide in the arterial blood. This information determines the average rate of ventilation of the alveoli of the lungs, to keep these pressures constant. The respiratory center does so via motor nerves which activate the diaphragm and other muscles of respiration. The breathing rate increases when the partial pressure of carbon dioxide in the blood increases. This is detected by central blood gas"
"sacs may have been capable of sustaining higher activity levels than mammals of similar size and build can sustain. In addition to providing a very efficient supply of oxygen, the rapid airflow would have been an effective cooling mechanism, which is essential for animals that are active but too large to get rid of all the excess heat through their skins. The palaeontologist Peter Ward has argued that the evolution of the air sac system, which first appears in the very earliest dinosaurs, may have been in response to the very low (11%) atmospheric oxygen of the Carnian and Norian"
"Diaphragmatic breathing Diaphragmatic breathing, or deep breathing, is breathing that is done by contracting the diaphragm, a muscle located horizontally between the thoracic cavity and abdominal cavity. Air enters the lungs and the chest rises and the belly expands during this type of breathing. Diaphragmatic breathing is also known scientifically as ""eupnea"", which is a natural and relaxed form of breathing in all mammals. Eupnea occurs in mammals whenever they are in a state of relaxation, i.e. when there is no clear and present danger in their environment. According to the National Center for Complementary and Integrative Health, ""12.7 percent"
"is called the 'spout' and varies across species in shape, angle and height. Species can be identified at a distance using this characteristic. The structure of the respiratory and circulatory systems is of particular importance for the life of marine mammals. The oxygen balance is effective. Each breath can replace up to 90% of the total lung volume. For land mammals, in comparison, this value is usually about 15%. During inhalation, about twice as much oxygen is absorbed by the lung tissue as in a land mammal. As with all mammals, the oxygen is stored in the blood and the"
"epipubic bone, the exception being modern placentals. [[File:Lung expansion simulation with Raccoon.gif|thumb|left|Raccoon lungs being inflated manually.]] The majority of mammals have seven [[cervical vertebrae]] (bones in the neck), including [[bat]]s, [[giraffe]]s, whales and [[human]]s. The exceptions are the [[manatee]] and the [[two-toed sloth]], which have just six, and the [[three-toed sloth]] which has nine cervical vertebrae. All mammalian brains possess a [[neocortex]], a brain region unique to mammals. Placental mammals have a [[corpus callosum]], unlike monotremes and marsupials. The [[lung]]s of mammals are spongy and honeycombed. Breathing is mainly achieved with the [[diaphragm (anatomy)|diaphragm]], which divides the thorax from the"
"lung; and the lower back and sacral (hip) vertebrae, by the abdominal air sac. These organs constitute a complex and very efficient method of respiration. ""Prosauropods"" are the only major group of saurischians without an extensive system of pneumatic foramina. Although possible pneumatic indentations have been found in ""Plateosaurus"" and ""Thecodontosaurus"", the indentations were very small. One study in 2007 concluded that basal sauropodomorphs like ""Massospondylus"" likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods). The study concluded that it was impossible to determine whether basal sauropodomorphs had a bird-like"
"the posterior air sacs and lungs. In comparison to the mammalian respiratory tract, the dead space volume in a bird is, on average, 4.5 times greater than it is in mammals of the same size. Birds with long necks will inevitably have long tracheae, and must therefore take deeper breaths than mammals do to make allowances for their greater dead space volumes. In some birds (e.g. the whooper swan, ""Cygnus cygnus"", the white spoonbill, ""Platalea leucorodia"", the whooping crane, ""Grus americana"", and the helmeted curassow, ""Pauxi pauxi"") the trachea, which some cranes can be 1.5 m long, is coiled back"
"or one like birds', with multiple air sacs and a flow-through lung. Furthermore, an avian system would only need a lung volume of about 600 liters while a mammalian one would have required about 2,950 liters, which would exceed the estimated 1,700 liters of space available in a 30-ton ""Apatosaurus""′ chest. Dinosaur respiratory systems with bird-like air sacs may have been capable of sustaining higher activity levels than mammals of similar size and build can sustain. In addition to providing a very efficient supply of oxygen, the rapid airflow would have been an effective cooling mechanism, which is essential for"
"Allantois The allantois (plural ""allantoides"" or ""allantoises"") is a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste. The allantois, along with the amnion and chorion (other extraembryonic membranes), identify humans and other mammals as well as reptiles, dinosaurs, and birds as amniotes. Of the vertebrates, only the anamniotes (fish and amphibians) lack this structure. This sac-like structure, whose name is the New Latin equivalent of ""sausage"" (in reference to its shape when first formed) is"
"is at almost body temperature by the time it reaches the larynx. Part of this moisture and heat is recaptured as the exhaled air moves out over the partially dried-out, cooled mucus in the nasal passages, during breathing out. The sticky mucus also traps much of the particulate matter that is breathed in, preventing it from reaching the lungs. The anatomy of a typical mammalian respiratory system, below the structures normally listed among the ""upper airways"" (the nasal cavities, the pharynx, and larynx), is often described as a respiratory tree or tracheobronchial tree (figure on the left). Larger airways give"
"Two bony projections—the upper and lower mandibles—covered with a thin keratinized layer of epidermis known as the rhamphotheca. In most species, two holes known as nares lead to the respiratory system. Due to the high metabolic rate required for flight, birds have a high oxygen demand. Their highly effective respiratory system helps them meet that demand. Although birds have lungs, theirs are fairly rigid structures that do not expand and contract as they do in mammals, reptiles and many amphibians. Instead, the structures that act as the bellows that ventilate the lungs are the air sacs, which are distributed throughout"
"sacs can be clearly seen. They extend quite far caudally into the abdomen. Thoracic diaphragm The thoracic diaphragm, or simply the diaphragm (), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity and performs an important function in respiration: as the diaphragm contracts, the volume of the thoracic cavity increases and air is drawn into the lungs. The term ""diaphragm"" in anatomy can refer to other flat structures such as the urogenital diaphragm"
"single bronchus running down the centre, from which numerous branches reach out to individual pockets throughout the lungs. These pockets are similar to alveoli in mammals, but much larger and fewer in number. These give the lung a sponge-like texture. In tuataras, snakes, and some lizards, the lungs are simpler in structure, similar to that of typical amphibians. Snakes and limbless lizards typically possess only the right lung as a major respiratory organ; the left lung is greatly reduced, or even absent. Amphisbaenians, however, have the opposite arrangement, with a major left lung, and a reduced or absent right lung."
"underwater for long periods of time while breathing through its trunk which emerges as a snorkel. In the elephant the lungs are attached to the diaphragm and breathing relies mainly on the diaphragm rather than the expansion of the ribcage. The respiratory system of birds differs significantly from that found in mammals. Firstly, they have rigid lungs which do not expand and contract during the breathing cycle. Instead an extensive system of air sacs (Fig. 15) distributed throughout their bodies act as the bellows drawing environmental air into the sacs, and expelling the spent air after it has passed through"
"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 main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human 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, which shares space in the chest with the heart. The lungs together weigh approximately , and the right is heavier. The"
"lungs are part of 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. The conducting zone ends at the terminal bronchioles. These divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the microscopic alveoli, where gas exchange takes place. Together, the lungs contain approximately of airways and 300 to 500 million alveoli. Each lung is enclosed within a pleural sac which allows the inner and outer walls to slide over each other whilst breathing"
"Cloaca In animal anatomy, a cloaca (plural cloacae or ) is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals, opening at the vent. All amphibians, birds, reptiles, and a few mammals (monotremes, tenrecs, golden moles, and marsupial moles) have this orifice, from which they excrete both urine and feces; this is in contrast to most placental mammals, which have two or three separate orifices for evacuation. Excretory openings with analogous purpose in some invertebrates are also sometimes referred to as cloacae. Mating by cloaca is known"
"the final partial pressure of oxygen of the mixed pulmonary venous blood is higher than that of the exhaled air, but is nevertheless less than half that of the inhaled air, thus achieving roughly the same systemic arterial blood partial pressure of oxygen as mammals do with their bellows-type lungs. The trachea is an area of dead space: the oxygen-poor air it contains at the end of exhalation is the first air to re-enter the posterior air sacs and lungs. In comparison to the mammalian respiratory tract, the dead space volume in a bird is, on average, 4.5 times greater"