Exchanging Oxygen and Carbon Dioxide - Lung and Airway Disorders - MSD Manual Consumer Version
Low surface tension between lung capillaries and alveoli is necessary for normal surfactant was found to have the following relationship with area of an alveoli [ 6]: . Wide variation exists among replacement lung surfactants on the market. Study Alveolar Capillary Membrane Surface Area flashcards from Hannah Taylor's Explain alveolar surface tension change and its relationship to lung volume. The two main bronchi may be thought of as the first branches of what is often called of the gases takes place across the alveolar capillary membrane (Fig 3).
The rate at which oxygen is used by the body is one measure of the rate of energy expended by the body. Breathing in and out is accomplished by respiratory muscles. The exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them.
As shown below, inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli.
Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: Ventilation is the process by which air moves in and out of the lungs.
Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, between the gas in the alveoli and the blood in the capillaries in the lungs. Coordinated, active movements of the thorax and the diaphragm, result in inspiration and expiration.
Gaseous Exchange at the Lungs Oxygen diffuses along a partial pressure gradient from the alveolar air spaces in to the pulmonary capillaries through the lining of the alveoli simple squamous epitheliumthe thin interstitium and the endothelium of the pulmonary capillaries, which is collectively known as the blood-gas barrier. Carbon-dioxide diffuses in the opposite direction through the blood-gas barrier in to the alveoli. Transport of Oxygen and Carbon-dioxide in Blood Oxygen which enters the blood stream by simple diffusion through the alveolar respiratory membrane is transported mainly bound to haemoglobin.
A small percentage of oxygen is transported dissolved in the plasma. Carbon-dioxide is transported mainly in the dissolved form in plasma and the formed bicarbonate ions are transported within the cytoplasm of the red blood cells. Diffusion of Gases in between the Cells and the Capillaries Oxygen is released from the haemoglobin to which it is bound and diffuses along a concentration gradient towards the cells in the peripheral tissues.
Carbon dioxide produced as a by-product of cellular respiration diffuses in the opposite direction and is dissolved in the plasma of the blood and the cytosol of the red blood cells. Cellular Respiration The organic substances undergo oxidation by losing electrons during the passage of tricarbolic acid cycle and the electrone transport chain.
In the process oxygen acts as an electrone and hydrogen acceptor and is converted to water. During the process, carbon dioxide is produced as a by-product. Upper respiratory tract nose, pharynx and larynx Lower respiratory tract trachea and the divisions of the airways 1. The Upper Respiratory Tract The upper respiratory tract is formed by the nose, pharynx and the larynx.
Alveoli & Capillaries - The Respiratory System
The upper respiratory tract is responsible for the conduction of air, which is in the external environment, to the lower respiratory tract. Combinations of surface tension and compressibility that lie above this curve will not be able to maintain a stable volume. Lung surfactant must change the surface tension appropriately with changes in air pressure to maintain a consistent radius, preventing a collapse of the alveoli during the respiration cycle.
This figure demonstrates alveoli function with and without proper lung surfactant. In addition to preventing alveoli collapse, reductions in the surface tension reduce the amount of energy necessary to inflate the lungs, making breathing easier . Lung surfactant deficiencies are associated with a range of lung problems including oxygen starvation, lung collapse and pulmonary edema .
Patients with acute respiratory distress syndrome ARDS often have lung surfactant that lacks the full range of surface tension modulation upon compression . Although this disease is caused by improperly functioning lung surfactant, patients respond poorly to replacement lung surfactant RLS therapies that are successful in premature babies born without lung surfactant . Doctors believe that ARDS in adults may result from surfactant inactivation caused by plasma and inflammatory leaking into alveoli .
Such processes dramatically alter the surfactants' response to changes in pressure and reduce lung function. Some research on synthetic lung surfactants also focuses on understanding surfactant inactivation.
Alveolar Capillary Membrane Surface Area Flashcards Preview
Treatments that specifically target reducing surfactant inactivation would be more effective in adults than replacement lung surfactant therapies that were developed to provide premature babies with lung surfactant.
The rest are unsaturated phosphoatidylcholines, saturated and unsaturated phophatidynlglycerols, other anionic lipids and cholesterol . Replacement lung surfactants often lack water soluble SP-A and SP-D proteins because they do not affect surface activity and are thought to be involved in immune system .
Doctors believe that a person's immune system might react to the presence of proteins involved in the immune response of other animals. Although it is not believed to be part of the surface layer, SP-A may also play a role in surfactant transportation and adsorption .
In this role, it could regulate the surface layer's composition. Synthetic lung surfactants Replacement lung surfactant RLS therapies are often refined from either bovine or porcine lungs due to limited human lung surfactant supplies. Since most RLS are generated from biological sources, virus transmission from animals to humans is a risk, and manufacturing costs are high. Ongoing research focuses on developing cheaper, safer synthetic lung surfactants and adding synthetic additives to biological based lung surfactants.
Proteins are often removed from animal derived lung surfactants during processing for use in humans for safety concerns. Often this affects a surfactant's properties, and ongoing research also examines how additives may improve an RLS's effectiveness. Properties of a functioning lung surfactant Any replacement lung surfactant must have three main properties to ensure proper lung function.
It must have a low surface tension on compression to prevent alveoli from collapsing. At the same time, RLS must remain viscous to avoid leaking out of alveoli after exhalation. During inhalation, lung surfactant must quickly adsorb to and re-spread along the interface .
Native lung surfactant beautifully balances these key features. Measuring properties of thin layers Traditionally the phase behavior of a lung surfactant's thin monolayer was studied using a Langmuir trough method.
More recently, experiments have measured expansion and contraction of captive bubbles to probe the same behavior. Typically this device consists of a teflon trough partially filled with water with a movable barrier at one end. A thin film is generated by dissolving a known amount of apmhiphillic molecules into a spreading solvent. This mixture is dropped into the trough, and the solvent is permitted to evaporate, leaving a thin film of amphiphillic molecules behind.
The figure below shows an example of a Langmuir trough.