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Encyclopedia > Gas exchange

Gas exchange or respiration takes place at a respiratory surface—a boundary between the external environment and the interior of the body. For unicellular organisms the respiratory surface is simply the cell membrane, but for large organisms it usually is carried out in respiratory systems. Image File history File links Question_book-3. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... Look up cell membrane in Wiktionary, the free dictionary. ... Among quadrupeds, the respiratory system generally includes tubes, such as the bronchi, used to carry air to the lungs, where gas exchange takes place. ...


In biology, the word "respiration" can also refer to cellular respiration or metabolism (ATP generation inside cells). Cellular respiration was discovered by mad scientist Mr. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ...

Contents

Process

Gasses cross the respiratory surface by diffusion, so from Fick's law we can predict that respiratory surfaces must have: diffusion (disambiguation). ... Ficks laws of diffusion describe diffusion. ...

  • a large surface area
  • a thin permeable surface
  • a moist exchange surface

Many also have a mechanism to maximise the diffusion gradient by replenishing the source and/or sink.


Control of respiration is due to rhythmical breathing generated by the phrenic nerve to stimulate contraction and relaxation of the diaphragm during inspiration and expiration. Ventilation is controlled by partial pressures of oxygen and carbon dioxide and the concentration of hydrogen ions. The control of respiration can vary in certain circumstances such as during exercise. The bodys involuntary control of respiration is mediated by the brains respiratory center located in the brainstem, particularly in the medulla oblongata and pons. ... The phrenic nerve arises from the third, fourth, and fifth cervical spinal nerves (C3-C5) in humans. ... In the anatomy of mammals, the diaphragm is a shelf of muscle extending across the bottom of the ribcage. ... Ä· Look up inspiration in Wiktionary, the free dictionary. ... For expiration as part of respiration, see Exhalation. ...


Gas exchange in humans and mammals

Gaseous exchange in the lung.

In humans and mammals, respiratory gas exchange or ventilation is carried out by mechanisms of the heart and lungs. The actual exchange of gases occurs in the alveoli, but the blood is subjected to a transient electric field (QRS waves of the EKG) in the heart which dissociates molecules of different charge. The blood, being a polar fluid, aligns dipoles with the electric field, is released, and then oscillates in a damped driven oscillation to form J or Osborn Waves, T, U, and V waves. The electric field exposure and subsequent damped driven oscillation dissociate gas from hemoglobin, primarily CO2, but more importantly BPG, which has a higher affinity for hemoglobin than does oxygen, due in part to its opposite charge. Completely dissociated hemoglobin (which will even effervesce if the electric field is too strong—the reason defibrillation joules are limited, to avoid bubble emboli that may clog vessels in the lung) enters the lung in RBC's ready to be oxygenated. The alveoli (singular:alveolus), tiny hollow sacs which are continuous with the airways, are the sites of gas exchange with the blood. ... The joule (IPA: or ) (symbol: J) is the SI unit of energy. ...


Convection occurs over the majority of the transport pathway. Diffusion occurs only over very short distances. The primary force applied in the respiratory tract is supplied by atmospheric pressure. Total atmospheric pressure at sea level is 760 mmHg (101 kPa), with oxygen (O2) providing a partial pressure (pO2) of 160 mmHg, 21% by volume, at the entrance of the nares, a partial pressure of 150 mmHg in the trachea due to the effect of partial pressure of water vapor, and an estimated pO2 of 100 mmHg in the alveoli sac, pressure drop due to conduction loss as oxygen travels along the transport passageway. Atmospheric pressure decreases as altitude increases making effective breathing more difficult at higher altitudes. Higher BPG levels in the blood are also seen at higher elevations, as well. Convection in the most general terms refers to the movement of currents within fluids (i. ... diffusion (disambiguation). ... Atmospheric pressure is the pressure at any given point in the Earths atmosphere. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... One way of defining pressure is in terms of the height of a column of fluid that may be supported by that pressure; or the height of a column of fluid that exerts that pressure at its base. ... The pascal (symbol Pa) is the SI unit of pressure. ... This article is about nares, the scientific term for a birds or a frogs([[for Mr. ... This article is about the chemical element and its most stable form, or dioxygen. ...


Similarly CO2 which is a result of tissue cellular respiration also exchange. The pCO2 changes from 45 mmHg to 40 mmHg in the alveoli. The concentration of this gas in the breath can be measured using a capnograph. As a secondary measurement, respiration rate can be derived from a CO2 breath waveform. A capnograph is an instrument used to measure the carbon dioxide (CO2) concentration in an air sample. ...


Gas exchange occurs only at pulmonary and systemic capillary beds, but anyone can perform simple experiments with electrodes in blood on the bench-top to observe electric field stimulated effervescence. The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... Systemic Relating to, or affecting a particular body system; especially the nervous system. ...


Trace gases present in breath at levels lower than a part per million are ammonia, acetone, isoprene. These can be measured using selected ion flow tube mass spectrometry. Selected ion flow tube mass spectrometry is a sensitive and quantitative mass spectrometry technique for trace gas analyses using chemical ionisation of sample trace gases by selected positive ions during a well-defined time period along a flow tube. ...


Diffusion

Blood carries oxygen, carbon dioxide and hydrogen ions between tissues and the lungs. This article is about the chemistry of hydrogen. ... This article is about the electrically charged particle. ...


The majority (70%) of CO2 transported in the blood is dissolved in plasma (primarily as dissolved bicarbonate; 60%). A smaller fraction (30%) is transported in red blood cells combined with the globin portion of hemoglobin as carbaminohaemoglobin. For baking soda, see Sodium bicarbonate In inorganic chemistry, a bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. ... Structure of hemoglobin. ...


As CO2 diffuses into the blood stream 93% goes into RBCs and 7% is dissolved in plasma. 70% is converted into H2CO3 by carbonic anhydrase. The H2CO3 dissociates into H+ and HCO−3. The HCO−3 moves out of the RBC in exchange for CL (chloride shift). The hydrogen is removed by buffers in the blood (Hb).


External links

Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Among quadrupeds, the respiratory system generally includes tubes, such as the bronchi, used to carry air to the lungs, where gas exchange takes place. ... Human Physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. ... It has been suggested that Gas exchange be merged into this article or section. ... Lung Volumes Lung volumeizing refer to physical differences in lung volume, while lung capacities represent different combinations of lung volumes, usually in relation to inhalation and exhalation. ... Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation. ... Functional Residual Capacity (FRC) is a medical term referring to the amount of air present in the lungs at the end of passive expiration. ... Respiratory minute volume (or minute ventilation, or flow of gas) is the volume of air which can be inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a persons lungs in one minute. ... The closing capacity (CC) is the volume in the lungs at which its smallest airways, the alveoli collapse. ... In physiology, dead space is air that is inhaled by the body in breathing, but does not partake in gas exchange. ... Flow-Volume loop showing successful FVC maneuver. ... Body Plethysmographs-To do a body plethysomograph, the person is enclosed in an airtight chamber often referred to as a body box. ... A peak flow meter is a small, hand-held device used to manage asthma by monitoring airflow through the bronchi and thus the degree of restriction in the airways. ... A term coined by Dr. Gerald Gause of the University of Florida College of Pharmacy, Thoracic Independent Volume is the volume of the thoracic cavity without the lungs. ... There are some respiratory diseases such as exercise-induced asthma that are not apparent unless the patient is exposed to some sort of trigger, such as a chemical irritant, an allergen, cold or dry air, or rigorous exercise. ... In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. ... Positive Pressure ventilators help patients with respiratory problems to breathe easier. ... Breathing transports oxygen into the body and carbon dioxide out of the body. ... Exhalation (or expiration) is the movement of air out of the bronchial tubes, through the airways, to the external environment during breathing. ... It has been suggested that this article or section be merged with Minute volume. ... ... Diagram of the alveoli with both cross-section and external view Pulmonary surfactant is a surface-active lipoprotein complex formed by type II alveolar cells. ... Compliance is the ability of the lungs to stretch in a change in volume relative to an applied change in pressure. ... “Hysteresivity” derives from “hysteresis”, meaning “lag”. It is the tendency to react slowly to an outside force, or to not return completely to its original state. ... Airway resistance is a concept used in respiratory physiology to describe mechanical factors which limit the access of inspired air to the pulmonary alveoli, and thus determine airflow. ... Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. ... In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. ... Hypoxic Pulmonary Vasoconstriction is the phenomenon when pulmonary arterioles vasoconstrict in the presence of hypoxia (low oxygen levels) without hypercapnia (high carbon dioxide levels). ... Pulmonary shunts exist when there is normal perfusion to an alveolus, but ventilation fails to supply the perfused region. ... In respiratory physiology, the ventilation/perfusion ratio (or V/Q ratio) is a measurement used to the efficiency and adequacy of the matching of two variables:[1] V - ventilation - the air which reaches the lungs Q - perfusion - the blood which reaches the lungs A normal value is approximately 0. ... A ventilation/perfusion scan, also called a V/Q scan, is a medical test to measure the circulation of air and blood within a patients lungs. ... The zones of the lung proposed by West in 1964,[1] divide the lung into three vertical regions, based upon the relationship between the pressure in the alveoli (PA), in the arteries (Pa), and the veins (Pv): #1: alveolar > arterial > venous #2: arterial > alveolar > venous #3: arterial > venous > alveolar The... Following is a list of average partial pressures (in torr) for a human at rest: // The alveolar oxygen pressure is lower than the atmospheric O2 partial pressure for two reasons. ... The alveolar pO2 is not routinely measured but is calculated from blood gas measurements by the Alveolar gas equation: where: R is the Respiratory quotient (normally about 0. ... Structure of hemoglobin. ... The oxygen-haemoglobin dissociation curve plots the proportion of haemoglobin in its saturated form on the vertical axis against the prevailing oxygen tension on the horizontal axis. ... 2,3-Bisphosphoglycerate (2,3-BPG, also known as 2,3-diphosphoglycerate or 2,3-DPG) is a three carbon isomer of the glycolytic intermediate 1,3-bisphosphoglycerate. ... Oxyhaemoglobin Dissociation Curve. ... The Haldane effect is a property of hemoglobin first described by the British physician John Scott Haldane. ... Carbonic anhydrase (carbonate dehydratase) is a family of metalloenzymes (enzymes that contain one or more metal atoms as a functional component of the enzyme) that catalyze the rapid interconversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. ... In red blood cells, synthesis of carbonic acid by carbonic anhydrase produces bicarbonate and a free proton. ... The Respiratory Quotient is used in BMR calculations (basal metabolic rate) and is a form of indirect calorimetry. ... Arterial blood gas measurement is a blood test that is performed to determine the concentration of oxygen, carbon dioxide and bicarbonate, as well as the pH, in the blood. ... In biology, diffusion capacity is a measurement of the lungs ability to transfer gases. ... There are very few or no other articles that link to this one. ... Control of ventilation (control of respiration) refers to the physiological mechanisms involved in the control of physiologic ventilation. ... For other uses, see Pons (disambiguation). ... The pneumotaxic center of the upper pons antagonises the apneustic centre. ... The apneustic center of the lower pons appears to promote inspiration by stimulation of the I neurons in the medulla oblongata providing a constant stimulus. ... The medulla oblongata is the lower portion of the brainstem. ... The dorsal repiratory group is found in many types of fish and marine mammals. ... The ventral respiratory group is a group of neurons in the medulla which initiates inhalation. ... A Chemosensor, also known as chemoreceptor, is a cell or group of cells that transduce a chemical signal into an action potential. ... Central chemoreceptors of the central nervous system, located on the ventrolateral medullary surface, are sensitive to the pH of their environment. ... Peripheral chemoreceptors act most importantly to detect variation of the oxygen in the arterial blood, in addition to detecting arterial carbon dioxide and pH. These nodes, called the aortic body and carotid body, are located on the arch of the aorta and on the common carotid artery, respectively. ... Pulmonary stretch receptors are mechanoreceptors found in the lungs. ... The Hering-Breuer reflex is a reflex triggered to prevent overinflation of the lungs. ... There are several effects of high altitude on humans: The percentage saturation of hemoglobin with oxygen determines the content of oxygen in our blood. ... Oxygen toxicity or oxygen toxicity syndrome is severe hyperoxia caused by breathing oxygen at elevated partial pressures. ... Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. ...

  Results from FactBites:
 
Method for effecting a gas exchange in a multiplate insulating glass unit - Patent 5454893 (1963 words)
In a method according to the invention for using the device for effecting a gas exchange according to the invention at least one device is inserted through the sealant spacer at at least one location through the sealant spacer into the space between the glass plates.
After that, the gas exchange is effected, the device extracted after the gas exchange and the space between the glass plates is subsequently closed by insertion of the drill core into the drilled passage.
While the invention has been illustrated and described as embodied in a device for effecting a gas exchange in a multiplate insulating glass unit, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing from the spirit of the present invention.
Reference.com/Encyclopedia/Gas exchange (520 words)
Gas exchange or respiration takes place at a respiratory surface - a boundary between the external environment and the interior of the body.
In humans and other mammals, respiratory gas exchange or ventilation is carried out by mechanisms of the lungs.
The actual exchange of gases occurs in the alveoli.
  More results at FactBites »

 
 

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