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Questions and Answers
What is the approximate volume of air that reaches the respiratory zone and contributes to gas exchange?
What type of sounds are produced by air rushing through the large respiratory passageways?
What is the normal respiratory rate referred to as?
Which of the following is a chemical factor that influences respiratory rate and depth?
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What is the term for inadequate oxygen delivery to body tissues?
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What is the nerve that regulates the activity of the diaphragm?
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Which of the following is NOT a physical factor that influences respiratory rate and depth?
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What is the location of the neural centers that control respiratory rhythm and depth?
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What is a unique type of hypoxia?
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What type of breathing sounds occur as air fills the alveoli?
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Study Notes
Respiratory Physiology
- The total gas exchange surface provided by the alveolar walls of a healthy man is approximately 50 to 70 square meters, which is 40 times greater than the surface area of his skin.
Pulmonary Ventilation
- Pulmonary ventilation is the process of moving air into and out of the lungs to continuously change and refresh the gases in the air sacs (alveoli) of the lungs.
- This process is commonly called breathing.
External Respiration
- Gas exchange (oxygen loading and carbon dioxide unloading) occurs between the pulmonary blood and alveoli (exterior).
- In external respiration, gas exchanges are made between the blood and the body exterior.
Respiratory Gas Transport
- Oxygen and carbon dioxide must be transported to and from the lungs and tissue cells of the body via the bloodstream.
- Internal respiration involves gas exchanges between the blood and tissue cells.
Mechanics of Breathing
- Breathing, or pulmonary ventilation, is a completely mechanical process that depends on volume changes occurring in the thoracic cavity.
- Volume changes lead to pressure changes, which lead to the flow of gases to equalize the pressure.
Inspiration
- The size of the thoracic cavity increases due to the contraction of the inspiratory muscles (diaphragm and external intercostals).
Expiration
- Exhalation in healthy people is largely a passive process that depends on the natural elasticity of the lungs rather than on muscle contraction.
- As the inspiratory muscles relax and resume their initial resting length, the ribcage descends and the lungs recoil, decreasing the thoracic and intrapulmonary volumes.
- As the intrapulmonary volume decreases, the gases inside the lungs are forced more closely together, and the intrapulmonary pressure rises to a point higher than atmospheric pressure.
- This causes the gases to flow out to equalize the pressure inside and outside the lungs.
Active Expiration (Forced Expiration)
- The internal intercostal muscles are activated to help depress the rib cage.
- The abdominal muscles contract to squeeze the abdominal organs upward against the diaphragm.
Pleural Pressure
- The normal pressure within the pleural space is always negative.
- This negative pressure prevents the collapse of the lungs.
- If the intrapleural pressure becomes equal to the atmospheric pressure, the lungs immediately recoil and collapse.
Non-respiratory Air Movements
- Coughs and sneezes clear the air passages of debris or collected mucus.
- Laughing and crying reflect our emotions.
- The functional volume of air that actually reaches the respiratory zone and contributes to gas exchange is about 350 ml.
Respiratory Sounds
- Bronchial sounds are produced by air rushing through the large respiratory passageways (trachea and bronchi).
- Vesicular breathing sounds occur as air fills the alveoli, resembling a soft, muffled breeze.
Control of Respiration
- Neural regulation sets the basic rhythm and regulates the activity of the respiratory muscles.
- The neural centers that control respiratory rhythm and depth are located in the medulla and pons.
- Impulses going back and forth between the pons and medulla centers maintain a rate of 12–15 respirations/minute, referred to as eupnea.
Factors Influencing Respiratory Rate and Depth
- Physical factors: talking, coughing, exercising
- Emotional factors
- Chemical factors: levels of carbon dioxide and oxygen in the blood
Hypoxia
- Inadequate oxygen delivery to body tissues.
- Skin and mucosae take on a bluish cast (become cyanotic).
- Carbon monoxide (CO) poisoning represents a unique type of hypoxia.
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Description
This quiz covers the structure and function of alveoli, gas exchange, and pulmonary ventilation in respiratory physiology.
