A waste product of aerobic respiration is carbon dioxide. Carbon dioxide must be removed from the body or it makes the blood dangerously acidic. Oxygen and carbon dioxide enter and leave the blood by diffusion through the lining of the lungs. Air gets from the mouth and nose to the lungs through the windpipe trachea. The trachea branches into two tubes called bronchi one to each lung. The bronchi split into smaller and smaller tubes called bronchioles, which then end in microscopic alveoli air sacs.
The binding of oxygen to hemoglobin can be plotted as a function of the partial pressure of oxygen in the blood x-axis versus the relative Hb-oxygen saturation y-axis. The resulting graph—an oxygen dissociation curve —is sigmoidal, or S-shaped Figure As the partial pressure of oxygen increases, the hemoglobin becomes increasingly saturated with oxygen.
If the kidneys fail, what would happen to blood pH and to hemoglobin affinity for oxygen? The oxygen-carrying capacity of hemoglobin determines how much oxygen is carried in the blood.
In addition to P O2 , other environmental factors and diseases can affect oxygen carrying capacity and delivery. Carbon dioxide levels, blood pH, and body temperature affect oxygen-carrying capacity Figure This increase in carbon dioxide and subsequent decrease in pH reduce the affinity of hemoglobin for oxygen. The oxygen dissociates from the Hb molecule, shifting the oxygen dissociation curve to the right. Therefore, more oxygen is needed to reach the same hemoglobin saturation level as when the pH was higher.
A similar shift in the curve also results from an increase in body temperature. Increased temperature, such as from increased activity of skeletal muscle, causes the affinity of hemoglobin for oxygen to be reduced.
In sickle cell anemia , the shape of the red blood cell is crescent-shaped, elongated, and stiffened, reducing its ability to deliver oxygen Figure In this form, red blood cells cannot pass through the capillaries. This is painful when it occurs. Thalassemia is a rare genetic disease caused by a defect in either the alpha or the beta subunit of Hb.
Patients with thalassemia produce a high number of red blood cells, but these cells have lower-than-normal levels of hemoglobin. Therefore, the oxygen-carrying capacity is diminished.
Carbon dioxide molecules are transported in the blood from body tissues to the lungs by one of three methods: dissolution directly into the blood, binding to hemoglobin, or carried as a bicarbonate ion. Several properties of carbon dioxide in the blood affect its transport. First, carbon dioxide is more soluble in blood than oxygen. About 5 to 7 percent of all carbon dioxide is dissolved in the plasma.
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Sign in via Shibboleth. AccessBiomedical Science. AccessEmergency Medicine. Case Files Collection. Clinical Sports Medicine Collection. Davis AT Collection. Davis PT Collection. Murtagh Collection. About Search. Enable Autosuggest. You have successfully created a MyAccess Profile for alertsuccessName. Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure.
In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream.
At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair.
Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium.
Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli.
The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar. Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries.
Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli.
If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation.
External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences. Answer the question s below to see how well you understand the topics covered in the previous section.
Skip to main content. Module 6: The Respiratory System. Search for:. Gas Exchange Learning Objectives By the end of this section, you will be able to: Compare the composition of atmospheric air and alveolar air Describe the mechanisms that drive gas exchange Discuss the importance of sufficient ventilation and perfusion, and how the body adapts when they are insufficient Discuss the process of external respiration Describe the process of internal respiration.
Everyday Connections: Hyperbaric Chamber Treatment A type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment. Figure 4. A smoker develops damage to several alveoli that then can no longer function. How does this affect gas exchange? The damaged alveoli will have insufficient ventilation, causing the partial pressure of oxygen in the alveoli to decrease.
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