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What is the primary function of the pulmonary system?
What is the primary function of the pulmonary system?
What is the third step involved in the process of gas exchange in the pulmonary system?
What is the third step involved in the process of gas exchange in the pulmonary system?
What is the function of the nasopharynx and oropharynx in the upper conducting airways?
What is the function of the nasopharynx and oropharynx in the upper conducting airways?
What is the name of the structure that connects the upper and lower airways?
What is the name of the structure that connects the upper and lower airways?
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At what level does the trachea divide into the two main airways?
At what level does the trachea divide into the two main airways?
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What is the name of the smallest of the conducting airways?
What is the name of the smallest of the conducting airways?
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What is the term used to describe the continued branching of the conducting airways?
What is the term used to describe the continued branching of the conducting airways?
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Where does gas exchange occur in the pulmonary system?
Where does gas exchange occur in the pulmonary system?
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What is the primary function of Type II epithelial cells in the alveoli?
What is the primary function of Type II epithelial cells in the alveoli?
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What is the main function of the pulmonary circulation?
What is the main function of the pulmonary circulation?
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What is the approximate number of alveoli in the lungs at birth?
What is the approximate number of alveoli in the lungs at birth?
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What is the main function of alveolar macrophages?
What is the main function of alveolar macrophages?
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What is the mean pulmonary artery pressure?
What is the mean pulmonary artery pressure?
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What is the respiratory membrane composed of?
What is the respiratory membrane composed of?
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What is the function of the bronchial circulation?
What is the function of the bronchial circulation?
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What is the approximate number of alveoli in the lungs in adulthood?
What is the approximate number of alveoli in the lungs in adulthood?
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Which of the following conditions would increase the thickness of the respiratory membrane, thereby impeding gas exchange?
Which of the following conditions would increase the thickness of the respiratory membrane, thereby impeding gas exchange?
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What is the primary factor that determines the rate of gas diffusion across the respiratory membrane?
What is the primary factor that determines the rate of gas diffusion across the respiratory membrane?
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Which of the following gases diffuses most rapidly through the respiratory membrane?
Which of the following gases diffuses most rapidly through the respiratory membrane?
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What is the result of a decrease in surface area of the alveolar and capillary membranes?
What is the result of a decrease in surface area of the alveolar and capillary membranes?
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Which of the following conditions would lead to a decrease in surface area of the respiratory membrane?
Which of the following conditions would lead to a decrease in surface area of the respiratory membrane?
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What is the primary direction of gas movement across the respiratory membrane?
What is the primary direction of gas movement across the respiratory membrane?
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What is the primary component of the respiratory system that deals with ventilation?
What is the primary component of the respiratory system that deals with ventilation?
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Which of the following gases has a lower diffusion coefficient in the respiratory membrane?
Which of the following gases has a lower diffusion coefficient in the respiratory membrane?
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What is the main difference between ventilation and respiration?
What is the main difference between ventilation and respiration?
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What is required to measure PaCO2?
What is required to measure PaCO2?
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What type of receptors are sensitive to noxious stimuli like pollens, smoke, and perfume?
What type of receptors are sensitive to noxious stimuli like pollens, smoke, and perfume?
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What is the location of the neurons that receive impulses from the lung receptors?
What is the location of the neurons that receive impulses from the lung receptors?
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What is the term used to describe the control of respiration?
What is the term used to describe the control of respiration?
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What is the location of the respiratory center that controls respiration?
What is the location of the respiratory center that controls respiration?
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What type of information does the respiratory center use to control respiration?
What type of information does the respiratory center use to control respiration?
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What is the term used to describe the mechanical movement of gas into and out of the lung?
What is the term used to describe the mechanical movement of gas into and out of the lung?
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What is the main function of surfactant in the alveoli?
What is the main function of surfactant in the alveoli?
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What does increased compliance of the lungs indicate?
What does increased compliance of the lungs indicate?
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What is the term used to describe reduced oxygenation of arterial blood?
What is the term used to describe reduced oxygenation of arterial blood?
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What is the most common cause of hypoxemia?
What is the most common cause of hypoxemia?
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What is the term used to describe the ratio of airflow into the lungs divided by pulmonary blood flow?
What is the term used to describe the ratio of airflow into the lungs divided by pulmonary blood flow?
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What is the term used to describe the passage of blood through the pulmonary circulation to be oxygenated?
What is the term used to describe the passage of blood through the pulmonary circulation to be oxygenated?
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What is the role of surfactant in host defense?
What is the role of surfactant in host defense?
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What is the term used to describe the ease of stretching of the lungs and chest wall?
What is the term used to describe the ease of stretching of the lungs and chest wall?
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Study Notes
Pulmonary System Function
- The primary function of the pulmonary system is the exchange of gases between the environmental air and the blood.
- Three steps are involved in this process: ventilation, diffusion, and perfusion.
Structure of the Pulmonary System
- The pulmonary system is made up of conducting airways (upper and lower) that deliver air to each section of the lung.
- Upper conducting airways consist of the nasopharynx and oropharynx, which filter and moisturize the air that is inhaled.
- The larynx connects the upper and lower airways and has supporting cartilage that prevents collapse during inspiration, expiration, and swallowing.
- The lower conducting airways begin at the level of the trachea and branch into two main airways (or bronchi).
- There is continued branching of the conducting airways, known as generations, with the smallest being the terminal bronchioles.
Gas Exchange
- Gas exchange occurs in the alveoli, which are the primary gas-exchange units of the lung.
- There are two major types of epithelial cells in the alveoli: Type I, which provide structure (elastin), and Type II, which secrete surfactant.
- Alveolar macrophages ingest foreign material that reaches the alveolus and prepare it for removal through the lymphatics.
Pulmonary Circulation
- Pulmonary circulation facilitates gas exchange, delivers nutrients to the lungs, acts as a reservoir for the left ventricle, and serves as a filtering system that removes clots, air, and debris from the circulation.
Alveolo-Capillary Membrane
- The alveolo-capillary membrane is composed of the shared alveolar and capillary walls.
- Gas exchange occurs over this membrane, and any disorder that thickens the membrane impairs gas exchange.
Factors Affecting Gas Exchange
- Four major factors determine how rapidly a gas (O2 or CO2) will pass through the membrane:
- Thickness of the membrane
- Surface area of the membrane
- Diffusion coefficient of the gas
- Pressure difference between the two sides of the membrane
Ventilation
- Ventilation is the mechanical movement of gas (air) into and out of the lung.
- Alveolar ventilation cannot be determined by observation of vent rate, pattern, or effort; it requires an arterial blood gas analysis to measure PaCO2.
- Ventilation is controlled by the respiratory center in the lower brain stem, which transmits impulses to the respiratory muscles based on information from peripheral chemoreceptors and lung receptors.
Lung Receptors
- Three types of lung receptors send impulses from the lungs to the dorsal respiratory group (neurons located in the brain stem):
- Irritant receptors, found on the epithelium of the conducting airways, sensitive to noxious stimuli
- Stretch receptors, found in the lungs and airways, sensitive to changes in lung volume
- J-receptors, found in the alveolar walls, sensitive to increases in interstitial fluid
Properties of Lung and Chest Wall
- Compliance is a measure of lung and chest wall distensibility, determined by alveolar surface tension and elastic recoil of the lung and chest wall.
- Increased compliance is seen in emphysema, resulting in chronic overinflation of the lungs.
- Decreased compliance is seen in pneumonia, edema, fibrosis, or adult respiratory distress syndrome (ARDS).
Hypoxia and Hypoxemia
- Hypoxia is reduced oxygenation of cells in tissues.
- Hypoxemia is reduced oxygenation of arterial blood.
- Causes of hypoxemia include:
- Inadequate oxygenation of lungs due to extrinsic reasons (high altitudes, hypoventilation)
- Pulmonary disease (hypoventilation, abnormal V/Q)
- Shunting of blood
- Inadequate oxygen transport by blood to tissues (anemias, abnormal hemoglobin, tissue edema)
- Inadequate tissue capability of using oxygen (poisoning, vitamin deficiencies)
Ventilation-Perfusion Ratio (V/Q)
- The ventilation-perfusion ratio, V/Q, is the ratio of airflow into the lungs divided by the pulmonary blood flow.
- An abnormal V/Q ratio is the most common cause of hypoxemia.
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Description
Understand the three steps involved in the exchange of gases between the environment and the blood through the pulmonary system.
