lung is the main organ of the respiratory system in humans and many other animals including some fish and some snails. In mammals and most other vertebrates, two lungs are located near the spine on both sides of the heart. Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and release carbon dioxide from the bloodstream into the atmosphere, in the gas exchange process. Respiration is driven by different muscle systems in different species. Mammals, reptiles and birds use their different muscles to support and assist breathing. In early tetrapods, air is pushed into the lungs by the pharyngeal muscles through buccal pumping, a mechanism still seen in amphibians. In humans, the major muscle of respiration that promotes breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech.
Humans have two lungs, right lung and left lung. They are located within the chest cavity. The right lung is bigger than the left, which shares chest space with the heart. The lungs together weigh about 1.3 kilograms (2.9 pounds), and the right is heavier. The lungs are part of the lower respiratory tract that begins in the trachea and branches into the bronchus and bronchioles, and which receives air inhaled through the conduction zone. The conduction zone ends in the terminal bronchioles. It divides into the respiratory bronchioles of the respiratory zone which divides into alveolar channels that give rise to microscopic alveoli, in which gas exchange takes place. Together, the lung contains about 2,400 kilometers (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed in a pleural sac that allows the inner and outer walls to slide over each other while breathing takes place, without much friction. This sac also divides each lung into parts called lobes. The right lung has three lobes and the left has two. The lobes are further divided into bronchopulmonary and lobular segments. The lungs have a unique blood supply, receiving deoxygenated blood from the heart in the pulmonary circulation for the purpose of receiving oxygen and releasing carbon dioxide, and a separate supply of oxygenated blood to the lung tissue, in the bronchial circulation.
The lung tissue can be affected by a number of diseases, including pneumonia and lung cancer. Chronic obstructive pulmonary disease including chronic bronchitis and termed emphysema may be associated with smoking or exposure to harmful substances such as coal dust, asbestos fibers and crystalline silica dust. Diseases such as bronchitis can also affect the respiratory tract. The medical term associated with the lung often begins with pulmonary, from Latin pulmonary (pulmonary) as in pulmonology, or with pneumo - (from the Greek ??????? "lung") as in pneumonia.
In embryonic development, the lungs begin to develop as outpouching of the foregut, a tube that continues to form the top of the digestive system. When the lungs are formed, the fetus is held in an amniotic sac that contains fluid so they do not work to breathe. Blood is also diverted from the lungs through the ductus arteriosus. But at birth, the air begins to pass through the lungs, and the ducts close, so that the lungs can start breathing. The lungs only thrive in early childhood.
Video Lung
Struktur paru-paru manusia
Anatomi
The lungs are located on the chest on either side of the heart in the ribs. They are cone-shaped with narrow rounded tops at the top, and broad, wide concave base on the convex surface of the diaphragm. The peak of the lung extends to the roots of the neck, reaching slightly above the end of the first rib sternal level. The lungs extend closely to the spine in the rib cage to the front of the chest and down from the bottom of the trachea to the diaphragm. The left lung shares the space with the heart, and has a groove on its border called left lung heart notch to accommodate this. The front and outside of the lungs are facing the ribs, which create a curve of light on its surface. The medial surface of the lung is facing the center of the chest, and is located in the heart, the large vessels, and the carina where the trachea is divided into two major bronchi. The heart impression is the indentation that forms on the surface of the lungs where they rest on the heart.
Both lungs have a central recession called hilus at the root of the lungs, where blood vessels and airways enter the lungs. There are also bronchopulmonary lymph nodes in the hilus.
The lungs are surrounded by pulmonary pleura. Pleurae are two serous membranes; the outer parietal pleura of the inner wall of the ribs and visceral pleura in directly lining the surface of the lung. Between the pleurae is a potential space called the pleural cavity containing a thin layer of pleural liquid lubricant. Each lung is divided into lobes by a pleural infusion as a gap. The gap is a pleural double pleat that divides the lungs and helps in their expansion.
The primary or primary bronchus enters the lungs in the hilus and initially branched off to the secondary bronchi is also known as the lobar bronchus that supplies air to every lobe of the lobe. The bronchus lobar branch into tertiary bronchology is also known as the segmental bronchus and air supply to the further division of the lobe known as the bronchopulmonary segment. Each bronchopulmonary segment has its own bronchus and arterial supply (segmental). Segments for left and right lung are shown in the table. Segmental anatomy is useful clinically for the localization of disease in the lungs. Segments are discrete units that can be removed surgically without seriously affecting the surrounding tissue.
Lung right
The right lung has more lobes and segments than the left. It is divided into three lobes, top, middle, and bottom, by two slits, one tilt and one horizontal. The upper fissure, horizontally, separates the upper part of the central lobe. It begins at the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, intersects the anterior border at the level with the sternal end of the fourth costal cartilage; on the surface of the mediastinum can be traced backward to the hilum.
The lower and sloping fissures, separating the lower of the middle and upper lobes, and are closely related to the oblique fissures in the left lung.
The right lung mediastinum surface is indented by a number of nearby structures. The heart sits in an impression called the impression of the heart. Above the hilum of the lung is a curved groove for the azygos vein, and above this is the wide groove for the superior cava vein and the right brachiocephalic vein; behind this, and close to the top of the lung is a groove for brachiocephalic arteries. There is a groove for the esophagus behind the hilum and pulmonary ligaments, and near the bottom of the esophageal groove is a deeper groove for the inferior vena cava before entering the heart.
Lung left
The left lung is divided into two lobes, upper and lower, by oblique fissures, which extend from the rib to the mediastinal surface of the lung above and below the hilum. The left lung, unlike the right, has no central lobe, although it has homologous features, the upper lobe projection is called the "lingula". His name means "little tongue". The left lingula functions as anatomically parallel to the right middle lobe, with both areas tending to the same infection and anatomical complications. There are two segments of bronchopulmonary lingula: superior and inferior.
The left lung mediastinum surface has a large cardiac impression in which the heart is located. It's deeper and bigger than the right lung, where the heart rate is projecting to the left.
On the same surface, just above the hilum, is a well-marked curve for the aortic arch, and the groove underneath for descending aorta. The left subclavian artery, the branch of the aortic arch, sits in the curve of the arch to the top of the lung. A shallow groove in front of the artery and near the edge of the lung, causing the left brachiocephalic vein. The esophagus may sit in a broader shallow impression at the base of the lung.
Microanatomy
The lungs are part of the lower respiratory tract, and accommodate the bronchial airways when they branch out of the trachea. The lungs include the bronchial airways that end in the alveoli, the lung tissue in between, and the veins, arteries, nerves and lymphatic vessels. Trachea and bronchus have a lymphatic capillary plexus in the mucosa and submucosa. The smaller bronchi have one layer and they are not in the alveoli.
All lower respiratory tracts include the trachea, bronchi, and bronchioles coated with respiratory epithelium. It is a ciliated epithelium interspersed with goblet cells that produce mucus, and club cells with actions similar to macrophages. Incomplete cartilage rings in the smaller trachea and cartilage plates in the bronchus, keeping the airways open. Bronchioles are too narrow to support cartilage and their walls are smooth muscle, and these are mostly absent in narrow breathing bronchioles that are primarily just of epithelial. The respiratory tract ends in the lobules. Each lobule consists of a respiratory bronchiole, which branches into the alveolar duct and alveolar sac, which then divides the alveoli.
Epithelial cells throughout the respiratory tract secrete epithelial epithelial fluid (ELF), a tightly regulated composition and determine how well mucociliary cleansing works.
Alveoli consists of two types of alveolar cells and alveolar macrophages. These two types of cells are known as type I and type II alveolar cells (also known as pneumocytes). Types I and II form the walls and alveolar septa. Type I cells give 95% of the surface area of ​​each alveoli and are flat ("squamous"), and Type II cells are generally clustered at the corners of the alveoli and have a cube-shaped shape. However, cells occur in ratios of approximately equal to 1: 1 or 6: 4.
Type I is a squamous epithelial cell that forms an alveolar wall structure. They have very thin walls that allow easy gas exchange. These type I cells also form an alveolar septa that separates each alveolus. Septa consists of layers of epithelium and associated basement membranes. Type I cells can not divide, and consequently depend on the differentiation of Type II cells.
Type II is larger and they coat the alveoli and produce and secrete epithelial layer fluids, and lung surfactants. Type II cells are able to divide and differentiate into Type 1 cells.
Alveolar macrophages have an important immunological role. They remove substances stored in the alveoli including loose red blood cells that have been forced out of the blood vessels.
The lungs are surrounded by a visceral pleural pleural membrane, which has a loose connective tissue layer attached to the lung substance.
Respiratory
The lower respiratory tract is part of the respiratory system, and consists of the following trachea and structures including the lungs. The trachea receives air from the pharynx and runs to the place where it divides (carina) into the right and left bronchi. It supplies air to the right and left lungs, dividing progressively into the secondary and tertiary bronchi for the lung lobe, and becomes smaller and smaller bronchioles until they become bronchioles of breathing. This in turn supplies air through the alveolar canal to the alveoli, where gas exchange takes place. The oxygen is inhaled in, diffuses through the alveoli wall to the capillary wrap and into the circulation, and carbon dioxide diffuses from the blood to the lungs to be inhaled out.
Estimated total lung surface area varies from 50 to 75 square meters (540 to 810 sq.s., Ft); roughly the same area with one side of the tennis court.
The bronchi in the conduction zone is reinforced with hyaline cartilage to withstand the opening of the airways. Bronchioles have no cartilage and are surrounded by smooth muscle. The air is heated to 37 ° C (99 ° F), moisturized and cleaned by conduction zone; the particles from the air are removed by the cilia on the respiratory epithelium lining the streets.
Pulmonary stretch receptors in the smooth muscle of the airways begin a reflex known as the Breering-Breuer reflex that prevents the lungs from over-inflation, during powerful inspiration.
Blood supply
The lungs have a double blood supply provided by bronchial and pulmonary circulation. The circulation of the bronchus supplies oxygenated blood to the airways of the lungs, through the bronchial artery that leaves the aorta. Usually there are three arteries, two to the left lung and one to the right, and they branch off beside the bronchi and bronchioles. Pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns oxygenated blood to the heart to supply the rest of the body.
The blood volume of the lungs, about 450 milliliters on average, is about 9 percent of the total blood volume of the entire circulatory system. This amount can easily fluctuate from between one and a half and twice the normal volume.
Supply of nerves
The lungs are supplied by the nerves of the autonomic nervous system. Input from the parasympathetic nervous system occurs through the vagus nerve. When stimulated by acetylcholine, this causes a smooth muscle constriction that lines the bronchi and bronchioles, and increases the secretion of the gland. The lungs also have sympathetic tones of norepinephrine that acts on beta 2 receptors in the respiratory tract, which causes bronchodilation.
Respiratory action occurs because of the nerve signals sent by the respiratory center in the brain stem, along the phrenic nerve to the diaphragm.
Maps Lung
Development
The development of the human lung arises from the laryngotracheal groove and develops to maturity for several weeks in the fetus and for several years after birth.
The larynx, the trachea, the bronchi and the lungs that form the respiratory tract, begin to form during the fourth week of embryogenesis of the lung shoot that appears ventralally to the caustic part of the foregut.
The respiratory tract has a branched structure like a tree. In embryos, these structures are developed in a branched morphogenesis process, and are produced by repeated cleavage of the tip of the branch. In the development of the lungs (as in some other organs), the epithelium forms a branching tube. The lungs have left-right symmetry and every shoot known as the bronchus sprout grows out as the tubular epithelium becomes bronchial. Each branch of the bronchus becomes bronchioles. Branching is the result of the end of each bifurcation tube. The branching process forms the bronchi, bronchioles, and ultimately the alveoli. The four genes most associated with branched morphogenesis in the lungs are intercellular signaling proteins - sonic hedgehog (SHH), fibroblast growth factor FGF10 and FGFR2b, and BMP4 bone morphogenetic protein. FGF10 looks to have the most prominent role. FGF10 is the parallel signaling molecule necessary for epithelial branching, and SHH inhibits FGF10. The development of the alveoli is influenced by different mechanisms in which the continued bifurcation is stopped and the distal end becomes dilated to form the alveoli.
At the end of the fourth week the lung bud is divided into two, the main right and left bronchial buds on each side of the trachea. During the fifth week the right bud splits into three secondary bronchial buds and the left branch becomes two secondary bronchial buds. This gives rise to the lung lobes, three on the right and two on the left. Over the next week, the branch of the secondary shoot becomes tertiary buds, about ten on each side. From the sixth week until the sixteenth week, the main elements of the lung appear except the alveoli. From week 16 to week 26, the bronchial is enlarged and the lung tissue becomes highly vascularized. Bronchioles and alveolar canals also develop. By the 26th week the terminal bronchioles have formed branches into two bronchioles of breathing. During the period covering the 26th week until birth, an important blood-air barrier has been established. A special type I alveolar cell in which gas exchange takes place, together with a type II alveolar cell secreting a pulmonary surfactant, appears. The surfactant reduces the surface tension on the alveolar air surface allowing the expansion of the alveolar sac. The alveolar sac contains a primitive alveoli formed at the end of the alveolar duct, and their appearance around the seventh month marks the point at which a limited respiration is possible, and the premature infant may survive.
After birth
At birth, the baby's lungs are filled with fluid secreted by the lungs and are not elevated. After birth, the baby's central nervous system reacts to sudden changes in temperature and environment. It triggers the first breath, within about 10 seconds after delivery. Before birth, the lungs are filled with fluid from the lungs of the fetus. After the first breath, the fluid is quickly absorbed into the body or exhaled. Resistance in the pulmonary blood vessels decreases thereby increasing the surface area for gas exchange, and the lungs begin to breathe spontaneously. This accompanies another change that results in an increase in the amount of blood entering the lung tissue.
At birth the lungs develop greatly with only about one-sixth of the alveoli of the adult lungs present. Alveolus continues to form into early adulthood, and their ability to shape when necessary is seen in lung regeneration. Alveolar septa has a double capillary network instead of a single lung tissue developed. Only after capillary tissue maturation can the lungs enter a normal growth phase. After the initial growth in the amount of alveoli there is another stage of the enlarged alveoli.
Function
Gas exchange
The main function of the lungs is the exchange of gas between the lungs and blood. Alveolar and pulmonary capillary gas balances across the thin blood barrier. This thin membrane (about 0.5 -2Ã, m thick) folded into about 300 million alveoli, giving a very large surface area (estimates varying between 70 and 145 m 2 ) for gas exchange to occur.
The lungs can not develop to breathe on their own, and will only do so when there is an increase in the volume of the thoracic cavity. This is achieved by the muscles of respiration, through the contraction of the diaphragm, and the intercostal muscles that pull the ribs upward as shown in the diagram. During breathing the relaxed muscles, returning the lungs to their resting position. At this point the lungs contain the functional residual capacity (FRC) of the air, which, in adult humans, has a volume of about 2.5-3.0 liters.
During heavy breathing when in exertion, a large number of accessory muscles in the neck and abdomen are recruited, which during breathing pulls the ribs down, reducing the volume of the thoracic cavity. FRC is now declining, but since the lungs can not be fully emptied there is still about one liter of remaining air remaining. Pulmonary function testing is performed to evaluate lung volume and capacity.
Protection
The lungs have several characteristics that protect against infection. The respiratory tract is coated by epithelium with a projection like a hair called cilia that beats rhythmically and carries the mucus. This mucociliary permit is an important defense system against airborne infections. The dust and bacteria particles in the inhaled air are captured on the mucosal surface of the airways, and move upwards into the pharynx by the rhythmic upswing action of the cilia. The lung layer also secretes immunoglobulin A which protects against respiratory infections; Goblet cells secrete mucus which also contains some antimicrobial compounds such as defensin, antiprotease, and antioxidants. In addition, the lung layer also contains macrophages, immune cells that swallow and destroy debris and microbes that enter the lungs in a process known as phagocytosis; and dendritic cells that present antigens to activate components of the adaptive immune system such as T-cells and B-cells.
The size of the respiratory tract and air flow also protects the lungs from larger particles. Smaller particles accumulate in the mouth and behind the mouth in the oropharynx, and larger particles trapped in the nose hair after inhalation.
More
In addition to its function in respiration, the lungs have a number of other functions. They are involved in maintaining homeostasis, assisting in regulating blood pressure as part of the renin-angiotensin system. The inner layer of blood vessels secretes an angiotensin-converting enzyme (ACE) an enzyme that catalyzes the conversion of angiotensin I to angiotensin II. The lungs are involved in blood-acid-base homeostasis by removing carbon dioxide when breathing.
The lungs also serve as a protector. Some blood-containing substances, such as some types of prostaglandins, leukotrienes, serotonin and bradykinin, are excreted through the lungs. Drugs and other substances can be absorbed, modified or excreted in the lungs. The lungs filter small blood clots from the veins and prevent them from entering the arteries and causing strokes.
The lungs also play an important role in speaking by providing air and airflow for the creation of vowel sounds, and other paralanguage communications such as sighing and panting.
New research shows the role of the lungs in the production of blood platelets.
Gene and protein expression
About 20,000 protein-encoding genes are expressed in human cells and nearly 75% of these genes are expressed in normal lungs. A little less than 200 of these genes are more specifically expressed in the lung with less than 20 genes that are very specific to the lungs. Suitable specific proteins are expressed in different cellular compartments such as pneumocytes in the alveoli, and ciliated goblet cells and mucus secreting in the respiratory mucosa. The highest expression of lung specific protein is the different surfactant proteins, such as SFTPA1, SFTPB and SFTPC, and napsin, expressed in type II pneumocytes. Other proteins with high expression in the lungs are DNAH5 dynein protein in ciliated cells, and SCGB1A1 protein secreted in mucus that secretes goblet cells from the airway mucosa.
Clinical interests
The lungs can be affected by various diseases. Pulmonology is a medical specialty associated with diseases involving the respiratory tract, and cardiothoracic surgery is a surgical field associated with pulmonary surgery.
Inflammatory conditions of the lung tissue are pneumonia, from the respiratory tract are bronchitis and bronchiolitis, and from the pleura surrounding the pleurisy lung. Inflammation is usually caused by bacterial or viral infections. When the lung tissue is inflamed due to other causes it is called pneumonitis. One of the main causes of bacterial pneumonia is tuberculosis. Chronic infection often occurs in those with immunodeficiency and may include fungal infections by Aspergillus fumigatus which can lead to the formation of aspergilloma in the lungs.
Pulmonary embolus is a blood clot that is involved in the pulmonary artery. The majority of emboli occur from deep vein thrombosis in the legs. Pulmonary embolism can be investigated using ventilation/perfusion scans, CT scans of pulmonary arteries, or blood tests such as D-dimers. Pulmonary hypertension represents an increase in pressure at the beginning of the pulmonary artery that has many different causes. Other rare conditions can also affect the blood supply of the lungs, such as granulomatosis with polyangiitis, which causes inflammation of small blood vessels in the lungs and kidneys.
Bruise of the lungs is a bruise caused by chest trauma. This results in alveolar bleeding that causes a buildup of fluid that can interfere with breathing, and this can be mild or severe. Lung function may also be affected by the compression of the fluid in the pleural cavity of the pleural effusion, or other substances such as air (pneumothorax), blood (hemothorax), or less common causes. These can be investigated using chest x-ray or CT scan, and may require insertion of the surgical drain until the underlying cause is identified and treated.
Asthma, chronic bronchitis, bronchiectasis and chronic obstructive pulmonary disease (COPD) are all obstructive pulmonary diseases characterized by airway obstruction. This limits the amount of air that can enter the alveoli due to constriction of the bronchial tree, due to inflammation. Obstructive pulmonary disease is often identified due to symptoms and is diagnosed with lung function tests such as spirometry. Many obstructive pulmonary diseases are managed by avoiding triggers (such as dust mites or smoking), with symptom controls such as bronchodilators, and with inflammatory suppression (such as via corticosteroids) in severe cases. One common cause of COPD and emphysema is smoking, and common causes of bronchiectasis include severe infections and cystic fibrosis. The exact cause of asthma is unknown.
Some types of chronic lung disease are classified as restrictive lung disease, due to the limitation of the amount of lung tissue involved in respiration. These include pulmonary fibrosis that can occur when the lung is inflamed for a long period of time. Fibrosis in the lungs replaces lung tissue with fibrous connective tissue. This can be caused by various occupational diseases such as pneumoconiosis from Coalworker, autoimmune disease, or less frequent reactions to drugs.
Lung cancer can arise directly from the lung tissue or as a result of metastasis from other parts of the body. There are two main types of primary tumors that are described as small or non-small cell lung carcinomas. The main risk factor for cancer is smoking. Once the cancer is identified it is staged using a scan such as a CT scan and a tissue sample (biopsy) is taken. Cancer can be treated by surgically removing the tumor, radiotherapy, chemotherapy or its combination, or with the purpose of symptom control. Lung cancer screening is being recommended in the United States for high-risk populations.
Congenital disorders include cystic fibrosis, pulmonary hypoplasia (incomplete lung development) congenital diaphragm hernia, and infant respiratory distress syndrome caused by pulmonary surfactant deficiency. The azygos lobe is a variation of an innate anatomy which, although usually without effect, can cause problems in a thoracoscopic procedure.
Pneumothorax (lung collapse) is a collection of abnormal air in the pleural space that causes the lung to escape from the chest wall. The lungs can not expand against the air pressure inside the pleural space. An easy to understand example is traumatic pneumothorax, in which air enters the external pleural space, as is the case with a puncture to the chest wall. Similarly, scuba diver rises while holding the breath with their fully charged lungs can cause the air sacs (alveoli) to burst and release high-pressure air into the pleural cavity.
Pulmonary function testing
Lung function testing is done by evaluating one's capacity to inhale and exhale in different situations. The volume of air inhaled and exhaled by a person at rest is a tidal volume (usually 500-750mL); volume of inspiration reserves and expiratory reserve volume is the additional amount that can be forcibly breathed in and exhaled respectively. The total number of forced and expired inspirations is one's vital capacity. Not all air is removed from the lungs even after being forced out; the rest of the air is called the residual volume. Together these terms are referred to as lung volumes.
Pulmonary plethysmographs are used to measure functional residual capacity. Functional residual capacity can not be measured by tests that rely on breathing, because one can only breathe up to 80% of its total functional capacity. The total lung capacity depends on the age, height, weight, and gender of a person, and usually ranges between 4 and 6 liters. Women tend to have a capacity of 20-25% lower than men. High people tend to have greater total lung capacity than shorter people. Smokers have a lower capacity than nonsmokers. Lean people tend to have greater capacity. Lung capacity can be increased by 40% physical exercise but the effect can be modified by exposure to air pollution.
Other lung function tests include spirometry, measuring the amount (volume) and airflow that can be inhaled and exhaled. The maximum volume of breath that can be breathed is called vital capacity. In particular, how many people are capable of exhaling in one second (called forced expiratory volume (FEV1)) as a proportion of how much they can exhale totally (FEV). This ratio, the ratio FEV1/FEV, it is important to distinguish whether the lung disease is restrictive or obstructive. Another test is the capacity of the lungs to spread - this is the size of the transfer of gas from air to blood in the lung capillaries.
Other animals
Bird
The bird's lungs are relatively small, but are connected to 8 or 9 air sacs that extend through most of the body, and in turn connect to the air space inside the bone. When inhaled, the air travels through the bird trachea into the air sac. The air then runs continuously from the air sacs at the back, through the lungs, which are relatively fixed in size, into the air sacs at the front. From here, the air is exhaled. This fixed size of the lungs is called "lung circulatory", different from the "lung bellows" found in most other animals.
The bird's lungs contain millions of tiny parallel parasites called parabronchi. A small pouch called atria radiates from a small alley wall; This, like the alveoli in other lungs, is a gas exchange place with simple diffusion. The flow of blood around the parabronchi and their atria forms the current gas exchange process (see diagram on the right).
The air sacs, which hold the air, do not contribute much to gas exchange, although thin-walled, because they lack vascularization. The air bag inflates and contracts due to volume changes in the thorax and abdomen. This volume change is caused by movement of the sternum and ribs and this movement is often synchronized with the movement of the flight muscles.
Parabronchi where air flow is not unidirectional is called paleopulmonic parabronchi and is found in all birds. Some birds, however, have, in addition, lung structures in which airflow in parabronchi is bidirectional. This is called parabronchi neopulmonik .
Reptile
The lungs of most reptiles have a single bronchus that flows in its center, from which many branches reach individual pockets throughout the lungs. These pouches are similar to alveoli in mammals, but the numbers are much larger and fewer. It gives a spongy-like texture to the lungs. In tuatara, snakes, and some lizards, the lungs are simpler in structure, similar to typical amphibians.
Snakes and limbs without legs usually have only the right lung as the primary respiratory organ; the left lung is greatly reduced, or even absent. Amphisbaenians, however, have the opposite arrangement, with the left main lung, and the right lung being reduced or absent.
Both crocodiles and monitor lizards have developed lungs that are similar to birds, providing direct air flow and even have airbags. The now extinct pterosaurs seem to further refine this type of lung, expand airsacs into the wing membrane and, in the case of lonchodectids, tupuxuara, and azhdarchoids, hindlimbs.
Reptilian lungs usually receive air through the expansion and contraction of ribs that are moved by axial muscles and buccal pumping. Crocodilians also rely on the method of liver pistons, where the liver is recalled by the muscles anchored to the pubic bone (part of the pelvis) called the diaphragmatic, which in turn creates negative pressure in the crocodile thoracic cavity, allowing air to move into the lungs by Boyle's law. Turtles, which can not move their ribs, instead use the forelimbs and chest corsets to force air in and out of the lungs.
Amphibians
The lungs of most frogs and other amphibians are simple and resemble balloons, with limited gas exchange on the outer surface of the lungs. These are not very efficient, but amphibians have low metabolic requirements and can also quickly dispose of carbon dioxide through diffusion in their skin in water, and supplement their oxygen supply by the same method. Amphibians use positive pressure systems to drain air into their lungs, forcing air into the lungs by pumping buccal. This differs from the highest vertebrates, which use the respiratory system driven by negative pressure in which the lungs increase by enlarging the ribs. In buccal pumping, the floor of the mouth is lowered, filling the oral cavity with air. The throat muscles then press down the throat to the underside of the skull, forcing air into the lungs.
Because of the possibility of skin respiration combined with small sizes, all non-pulmonary tetrapods are known as amphibians. The majority of species of salamanders are salamanders without lungs, which fester through the skin and tissue of those lining their mouths. This certainly limits their size: they are small and somewhat like yarn, maximizing the surface of the skin relative to body volume. Other known non-pulmonary tetrapods are neutral-headed frog and Atretochoana eiselti, a caecilian.
Amphibian lungs usually have some narrow internal walls (septa) of soft tissue around the outer wall, increasing the surface area of ​​the breathing and giving the appearance of a honey comb on the lungs. In some salamanders even this is lacking, and the lungs have smooth walls. In caecilians, as in snakes, only the right lung reaches any size or development.
Lungfish
Lungfish lung is similar to amphibians, with some, if any, internal septa. In Australian lungfish, there is only one lung, although it is divided into two lobes. The other lungs and Polypterus , however, have two lungs, which are located at the top of the body, with connecting channels curved around and above the esophagus. The blood supply also revolves around the esophagus, indicating that the lungs initially evolved in the abdomen of the body, as in other vertebrates.
Invertebrates
Some invertebrates have lunglike structures that serve the same purpose of breathing as, but are not evolutionarily related to, the lungs of vertebrates. Some arachnids, such as spiders and scorpions, have structures called lung books that are used for atmospheric gas exchange. Some species of spiders have four pairs of book lungs but most have two pairs. Scorpions have spiracles in their bodies for air entry into the book's lungs.
Coconut crabs are terrestrial and use a structure called branchiostegal lung to breathe air. They can not swim and will drown in water, but they have an imperfect set of gills. They can breathe on land and hold their breath under water. The branchiostegal lungs are seen as a stage of developmental adaptation of aquatic life to allow life on land, or from fish to amphibians.
Pulmonatus is a land snail and snail that has developed a simple lung from the mantle cavity. An external opening called a pneumostome allows air to be carried into the mantle cavity of the mantle.
The origins of evolution
The lungs of today's terrestrial vertebrates and contemporary fish gas pockets are believed to have evolved from a simple sac, as an esophageal imaging, allowing early fish to swallow air under conditions of poor oxygen. These outpocketings first appeared on bony fish. In most finned fishes, the sac evolved into a closed gas bag, while a number of goldfish, trout, herring, catfish, and eels maintained the physical condition with open sacks to the esophagus. In more basal bony fish, such as gar, bichir, bowfin and lobe-finned fish, the bladder has evolved to function primarily as the lungs. The lobe-finned fish gives rise to ground tetrapods. Thus, the lungs of the vertebrate are homologous to the fish gas sacs (but not the gills).
See also
- Atelectasis
- Bronchiectasis
- Sink
- Interstitial lung disease
- Liquid breath
- Lung abscess
- Lung microbiome
- Mechanical Ventilation
- Kohn Pores
References
Further reading
External links
- Lung in Human Protein Atlas
Source of the article : Wikipedia
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