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– ## Chapter_015.rtf

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**## Chapter_015.rtf**

15-4

Audio Chapter Summaries

Copyright © 2025 by Elsevier Inc. All rights reserved, including those for text and data mining, AI training, and similar technologies.

Copyright © 2025 by Elsevier Inc. All rights reserved, including those for text and data mining, AI training, and similar technologies.

**Patton: Structure & Function of the Body, 17th Edition**

**Chapter 15: Respiratory System**

****Audio Chapter Summaries****

****Welcome to the audio review of Chapter 15: Respiratory System.****

**First, we’ll review the organization of the respiratory system.**

**A 3-dimensional visual of the respiratory system would be similar to an inverted tree if it were hollow; branches would be the bronchi, and leaves of the tree would be comparable to alveoli, with the microscopic sacs enclosed by networks of capillaries.**

**The passive transport process of diffusion is responsible for the exchange of gases that occurs during respiration.**

**The respiratory tract is divided into upper and lower portions.**

**The upper respiratory tract includes the nose, pharynx, and larynx.**

**The lower respiratory tract contains the trachea, bronchial tree, alveoli, and lungs.**

**The respiratory mucosa is a specialized membrane that lines the air distribution tubes in the respiratory tree. Three types of epithelium are present in the respiratory mucosa:**

**Ciliated pseudostratified epithelium lines most of the tract and produces mucus.**

**Stratified squamous epithelium lines the nostrils, vocal folds, and pharynx; it serves a protective function.**

**Simple squamous epithelium lines the alveoli and facilitates gas exchange.**

**The respiratory mucosa serves several functions:**

**More than 125 mL of mucus is produced each day. It forms a “mucous blanket” over much of the respiratory mucosa.**

**Mucus serves as an air purification mechanism by trapping inspired irritants such as dust and pollen.**

**The respiratory mucosa also supports what could be called the ciliary escalator; cilia on mucosal cells beat in only one direction, moving mucus upward to the pharynx for removal.**

**Now we’ll review some specifics about the upper respiratory tract.**

**A nasal septum separates the interior of the nose into two cavities, called nares or nostrils.**

**Frontal, maxillary, sphenoidal, and ethmoidal sinuses of the skull drain into the nose.**

**Three shelflike structures in the nasal cavity called conchae or turbinates warms and moistens inhaled air. The nose also houses the sense organs of smell.**

**The pharynx or throat is about 12.5 cm (or 5 inches) long. It is divided into the nasopharynx, oropharynx, and the laryngopharynx.**

**The two nasal cavities, mouth, esophagus, larynx, and auditory tubes all have openings into the pharynx.**

**Pharyngeal tonsils and the openings of auditory tubes open into the nasopharynx. The tonsils are found in the oropharynx.**

**The pharynx functions as a passageway for food and liquids, as well as a passageway for air.**

**Nine pieces of cartilage form the framework of the last structure of the upper respiratory tract, the larynx.**

**The thyroid cartilage (also called the Adam’s apple) is the largest.**

**Note that the epiglottis partially covers the opening into the larynx.**

**Vocal cords stretch across the interior of the larynx.**

**Thus, one of the larynx’s functions is voice production. The other is air distribution; like the pharynx, it serves as a passageway for air to move to and from the lungs.**

**Next is a review of information about the lower respiratory tract.**

**The trachea is a tube about 11 cm (or 4.5 in) long and 2.5 cm (or 1 in) in diameter.**

**It extends from the larynx into the thoracic cavity.**

**C-shaped rings of cartilage hold the trachea open, but allow for swallowing.**

**The trachea functions as a passageway for air to move to and from the lungs.**

**Blockage of the trachea occludes the airway and, if complete, causes death in minutes.**

**In fact, tracheal obstruction causes more than 74000 deaths annually in the United States.**

**The bronchial tree is the next structure in the lower respiratory tract.**

**The trachea branches into right and left bronchi.**

**Each bronchus branches into smaller and smaller tubes, eventually leading to bronchioles.**

**Bronchioles end in clusters of microscopic alveolar sacs, the walls of which are made up of alveoli.**

**The function of the bronchial tree is air distribution; it serves as a passageway for air to move to and from alveoli.**

**The function of alveoli is the exchange of gases between air and blood.**

**The respiratory membrane is the thin wall that separates pulmonary blood from alveolar air, allowing diffusion of gases.**

****Surfactant is a substance released into alveoli to reduce surface tension and thus prevent collapse of the alveoli.****

**The lungs are large enough to fill the chest cavity, except for the middle space (the mediastinum) occupied by the heart, large blood vessels, thymus, and esophagus.**

**The apex of the lung is the narrow upper part, situated under the collarbone.**

**The base is the broad lower part of each lung; it rests on the diaphragm.**

**The pleura is the moist, smooth, slippery membrane that lines the chest cavity (the parietal pleura) and covers the outer surface of the lungs (the visceral pleura); The pleura reduces friction between the lungs and chest wall during breathing.**

**The function of lungs is respiration.**

**Next, we’ll review respiration and pulmonary ventilation.**

**Respiration involves several processes and mechanisms.**

**External respiration is pulmonary ventilation (or breathing) and pulmonary gas exchange.**

**These gases are transported by the blood and serve a function in the regulation of set point levels of blood gases.**

**Internal respiration is the gas exchange between the blood and systemic tissues. The term cellular respiration refers to the use of oxygen by cells in the process of metabolism.**

**To understand pulmonary ventilation, first you need to know the basic principles of the mechanics of breathing.**

**Pulmonary ventilation includes two phases called**
**_inspiration_ (movement of air into lungs) and**
**_expiration_ (movement of air out of lungs).**

**Changes in the size and shape of the thorax cause changes in air pressure within that cavity and in the lungs.**

**Pressure differences (or gradients) cause air to move into and out of the lungs.**

**Inspiration is the active process whereby air moves into the lungs.**

**Inspiratory muscles include the diaphragm and external intercostals.**

**The diaphragm flattens when stimulated by the phrenic nerve during inspiration, which increases the top-to-bottom length of the thorax.**

**The external intercostal muscles contract and elevate the ribs, which increases the size of the thorax from the front to the back and from side to side.**

**Increase in the size of the chest cavity reduces pressure within it; air then enters the lungs by moving down its pressure gradient.**

**Quiet expiration is ordinarily a passive process.**

**During expiration, the thorax returns to its resting size and shape.**

**Elastic recoil of lung tissues aids in expiration.**

**Expiratory muscles used in forceful expiration are the internal intercostals and abdominal muscles.**

**Contraction of the internal intercostals depresses the rib cage and decreases the size of the thorax from the front to back.**

**Contraction of abdominal muscles elevates the diaphragm, thus decreasing the size of the thoracic cavity from the top to bottom.**

**Reduction in the size of the thoracic cavity increases its pressure and air leaves the lungs.**

**Pulmonary volumes are volumes of air exchanged in breathing; they can be measured with a spirometer.**

**Tidal volume is the amount normally breathed in or out with each breath.**

**Vital capacity is the greatest amount of air that one can breathe out in one expiration.**

**Expiratory reserve volume is the amount of air that can be forcibly exhaled after expiring the tidal volume.**

**Inspiratory reserve volume is the amount of air that can be forcibly inhaled after a normal inspiration.**

**Residual volume is the air that remains in the lungs after the most forceful expiration.**

**Regulation of respiration permits the body to adjust to varying demands for oxygen supply and carbon dioxide removal by maintaining set point concentrations of blood gases.**

**Several mechanisms control respiration: the brainstem, cerebral cortex, and respiratory reflexes.**

**The most important central regulatory centers in both the medulla and pons in the brainstem are called**
**_respiratory control centers._**

**_Under resting conditions, the medullary rhythmicity area produces a normal rate and depth of respirations. A normal rate is considered to be 12 to 18 breaths/min._**
**_As conditions in the body vary, centers in the pons called the pontine respiratory group, can alter the activity of the medullary rhythmicity area, thus adjusting breathing rhythm._**

**_Brainstem centers are influenced by information from other parts of the brain and from sensory receptors located in other body regions._**

**_Control of respiratory activity by the cerebral cortex is voluntary but limited._**

**_Respiratory reflexes include chemoreflexes and pulmonary stretch reflexes._**

**_In chemoreflexes, chemoreceptors respond to changes in carbon dioxide, oxygen, and blood acid levels; these receptors are located in carotid and aortic bodies._**

**_Pulmonary stretch reflexes respond to the stretch receptors in lungs, thus protecting respiratory organs from overinflation._**

**_Be sure you understand the following terms for breathing patterns:_**

**_Eupnea is normal breathing._**

**_Hyperventilation means rapid and deep respirations._**

**_Hypoventilation indicates slow and shallow respirations._**

**_Dyspnea is labored or difficult respirations._**

**_Apnea is stopped respiration, absence of breathing._**

**_Respiratory arrest is the failure to resume breathing after a period of apnea._**

**_Cheyne-Stokes respiration are cycles of alternating apnea and hyperventilation associated with critical conditions._**

**_Gas exchange and transport is the final section to review in Chapter 15._**

**_Pulmonary gas exchange is the exchange of gases in the lungs. The following steps take place in pulmonary gas exchange._**

**_Carbaminohemoglobin breaks down into carbon dioxide and hemoglobin._**

**_Carbon dioxide moves out of lung capillary blood into alveolar air and out of the body into expired air._**

**_Oxygen moves from alveoli into the lung capillaries._**

**_Hemoglobin combines with oxygen, producing oxyhemoglobin._**

**_Systemic gas exchange is the exchange of gases in tissues. The following steps take place in systemic gas exchange._**

**_Oxyhemoglobin breaks down into oxygen and hemoglobin._**

**_Oxygen moves out of tissue capillary blood into tissue cells._**

**_Carbon dioxide moves from tissue cells into tissue capillary blood._**

**_Hemoglobin combines with carbon dioxide, forming carbaminohemoglobin._**

**_Blood transportation of gases includes transport of oxygen and carbon dioxide._**

**_Only small amounts of oxygen gas can be dissolved in blood. Most oxygen combines with hemoglobin to form oxyhemoglobin to be carried in the blood._**

**_Dissolved carbon dioxide is about 10% of the total carbon dioxide transported in the blood._**

**_Carbaminohemoglobin is about 20%._**

**_About 70% of the total carbon dioxide transported in the blood is carried in the form of bicarbonate ions._**

**_This concludes the audio review of chapter 15._**

**20260321_000027.jpg**

This file is too large to display. [View in new window](https://www.sweetstudy.com/files/20260321-000027-jpg)

**20260321_000027.jpg**

This file is too large to display. [View in new window](https://www.sweetstudy.com/files/20260321-000027-jpg)

**## Chapter_015.rtf**

15-4

Audio Chapter Summaries

Copyright © 2025 by Elsevier Inc. All rights reserved, including those for text and data mining, AI training, and similar technologies.

Copyright © 2025 by Elsevier Inc. All rights reserved, including those for text and data mining, AI training, and similar technologies.

**Patton: Structure & Function of the Body, 17th Edition**

**Chapter 15: Respiratory System**

****Audio Chapter Summaries****

****Welcome to the audio review of Chapter 15: Respiratory System.****

**First, we’ll review the organization of the respiratory system.**

**A 3-dimensional visual of the respiratory system would be similar to an inverted tree if it were hollow; branches would be the bronchi, and leaves of the tree would be comparable to alveoli, with the microscopic sacs enclosed by networks of capillaries.**

**The passive transport process of diffusion is responsible for the exchange of gases that occurs during respiration.**

**The respiratory tract is divided into upper and lower portions.**

**The upper respiratory tract includes the nose, pharynx, and larynx.**

**The lower respiratory tract contains the trachea, bronchial tree, alveoli, and lungs.**

**The respiratory mucosa is a specialized membrane that lines the air distribution tubes in the respiratory tree. Three types of epithelium are present in the respiratory mucosa:**

**Ciliated pseudostratified epithelium lines most of the tract and produces mucus.**

**Stratified squamous epithelium lines the nostrils, vocal folds, and pharynx; it serves a protective function.**

**Simple squamous epithelium lines the alveoli and facilitates gas exchange.**

**The respiratory mucosa serves several functions:**

**More than 125 mL of mucus is produced each day. It forms a “mucous blanket” over much of the respiratory mucosa.**

**Mucus serves as an air purification mechanism by trapping inspired irritants such as dust and pollen.**

**The respiratory mucosa also supports what could be called the ciliary escalator; cilia on mucosal cells beat in only one direction, moving mucus upward to the pharynx for removal.**

**Now we’ll review some specifics about the upper respiratory tract.**

**A nasal septum separates the interior of the nose into two cavities, called nares or nostrils.**

**Frontal, maxillary, sphenoidal, and ethmoidal sinuses of the skull drain into the nose.**

**Three shelflike structures in the nasal cavity called conchae or turbinates warms and moistens inhaled air. The nose also houses the sense organs of smell.**

**The pharynx or throat is about 12.5 cm (or 5 inches) long. It is divided into the nasopharynx, oropharynx, and the laryngopharynx.**

**The two nasal cavities, mouth, esophagus, larynx, and auditory tubes all have openings into the pharynx.**

**Pharyngeal tonsils and the openings of auditory tubes open into the nasopharynx. The tonsils are found in the oropharynx.**

**The pharynx functions as a passageway for food and liquids, as well as a passageway for air.**

**Nine pieces of cartilage form the framework of the last structure of the upper respiratory tract, the larynx.**

**The thyroid cartilage (also called the Adam’s apple) is the largest.**

**Note that the epiglottis partially covers the opening into the larynx.**

**Vocal cords stretch across the interior of the larynx.**

**Thus, one of the larynx’s functions is voice production. The other is air distribution; like the pharynx, it serves as a passageway for air to move to and from the lungs.**

**Next is a review of information about the lower respiratory tract.**

**The trachea is a tube about 11 cm (or 4.5 in) long and 2.5 cm (or 1 in) in diameter.**

**It extends from the larynx into the thoracic cavity.**

**C-shaped rings of cartilage hold the trachea open, but allow for swallowing.**

**The trachea functions as a passageway for air to move to and from the lungs.**

**Blockage of the trachea occludes the airway and, if complete, causes death in minutes.**

**In fact, tracheal obstruction causes more than 74000 deaths annually in the United States.**

**The bronchial tree is the next structure in the lower respiratory tract.**

**The trachea branches into right and left bronchi.**

**Each bronchus branches into smaller and smaller tubes, eventually leading to bronchioles.**

**Bronchioles end in clusters of microscopic alveolar sacs, the walls of which are made up of alveoli.**

**The function of the bronchial tree is air distribution; it serves as a passageway for air to move to and from alveoli.**

**The function of alveoli is the exchange of gases between air and blood.**

**The respiratory membrane is the thin wall that separates pulmonary blood from alveolar air, allowing diffusion of gases.**

****Surfactant is a substance released into alveoli to reduce surface tension and thus prevent collapse of the alveoli.****

**The lungs are large enough to fill the chest cavity, except for the middle space (the mediastinum) occupied by the heart, large blood vessels, thymus, and esophagus.**

**The apex of the lung is the narrow upper part, situated under the collarbone.**

**The base is the broad lower part of each lung; it rests on the diaphragm.**

**The pleura is the moist, smooth, slippery membrane that lines the chest cavity (the parietal pleura) and covers the outer surface of the lungs (the visceral pleura); The pleura reduces friction between the lungs and chest wall during breathing.**

**The function of lungs is respiration.**

**Next, we’ll review respiration and pulmonary ventilation.**

**Respiration involves several processes and mechanisms.**

**External respiration is pulmonary ventilation (or breathing) and pulmonary gas exchange.**

**These gases are transported by the blood and serve a function in the regulation of set point levels of blood gases.**

**Internal respiration is the gas exchange between the blood and systemic tissues. The term cellular respiration refers to the use of oxygen by cells in the process of metabolism.**

**To understand pulmonary ventilation, first you need to know the basic principles of the mechanics of breathing.**

**Pulmonary ventilation includes two phases called**
**_inspiration_ (movement of air into lungs) and**
**_expiration_ (movement of air out of lungs).**

**Changes in the size and shape of the thorax cause changes in air pressure within that cavity and in the lungs.**

**Pressure differences (or gradients) cause air to move into and out of the lungs.**

**Inspiration is the active process whereby air moves into the lungs.**

**Inspiratory muscles include the diaphragm and external intercostals.**

**The diaphragm flattens when stimulated by the phrenic nerve during inspiration, which increases the top-to-bottom length of the thorax.**

**The external intercostal muscles contract and elevate the ribs, which increases the size of the thorax from the front to the back and from side to side.**

**Increase in the size of the chest cavity reduces pressure within it; air then enters the lungs by moving down its pressure gradient.**

**Quiet expiration is ordinarily a passive process.**

**During expiration, the thorax returns to its resting size and shape.**

**Elastic recoil of lung tissues aids in expiration.**

**Expiratory muscles used in forceful expiration are the internal intercostals and abdominal muscles.**

**Contraction of the internal intercostals depresses the rib cage and decreases the size of the thorax from the front to back.**

**Contraction of abdominal muscles elevates the diaphragm, thus decreasing the size of the thoracic cavity from the top to bottom.**

**Reduction in the size of the thoracic cavity increases its pressure and air leaves the lungs.**

**Pulmonary volumes are volumes of air exchanged in breathing; they can be measured with a spirometer.**

**Tidal volume is the amount normally breathed in or out with each breath.**

**Vital capacity is the greatest amount of air that one can breathe out in one expiration.**

**Expiratory reserve volume is the amount of air that can be forcibly exhaled after expiring the tidal volume.**

**Inspiratory reserve volume is the amount of air that can be forcibly inhaled after a normal inspiration.**

**Residual volume is the air that remains in the lungs after the most forceful expiration.**

**Regulation of respiration permits the body to adjust to varying demands for oxygen supply and carbon dioxide removal by maintaining set point concentrations of blood gases.**

**Several mechanisms control respiration: the brainstem, cerebral cortex, and respiratory reflexes.**

**The most important central regulatory centers in both the medulla and pons in the brainstem are called**
**_respiratory control centers._**

**_Under resting conditions, the medullary rhythmicity area produces a normal rate and depth of respirations. A normal rate is considered to be 12 to 18 breaths/min._**
**_As conditions in the body vary, centers in the pons called the pontine respiratory group, can alter the activity of the medullary rhythmicity area, thus adjusting breathing rhythm._**

**_Brainstem centers are influenced by information from other parts of the brain and from sensory receptors located in other body regions._**

**_Control of respiratory activity by the cerebral cortex is voluntary but limited._**

**_Respiratory reflexes include chemoreflexes and pulmonary stretch reflexes._**

**_In chemoreflexes, chemoreceptors respond to changes in carbon dioxide, oxygen, and blood acid levels; these receptors are located in carotid and aortic bodies._**

**_Pulmonary stretch reflexes respond to the stretch receptors in lungs, thus protecting respiratory organs from overinflation._**

**_Be sure you understand the following terms for breathing patterns:_**

**_Eupnea is normal breathing._**

**_Hyperventilation means rapid and deep respirations._**

**_Hypoventilation indicates slow and shallow respirations._**

**_Dyspnea is labored or difficult respirations._**

**_Apnea is stopped respiration, absence of breathing._**

**_Respiratory arrest is the failure to resume breathing after a period of apnea._**

**_Cheyne-Stokes respiration are cycles of alternating apnea and hyperventilation associated with critical conditions._**

**_Gas exchange and transport is the final section to review in Chapter 15._**

**_Pulmonary gas exchange is the exchange of gases in the lungs. The following steps take place in pulmonary gas exchange._**

**_Carbaminohemoglobin breaks down into carbon dioxide and hemoglobin._**

**_Carbon dioxide moves out of lung capillary blood into alveolar air and out of the body into expired air._**

**_Oxygen moves from alveoli into the lung capillaries._**

**_Hemoglobin combines with oxygen, producing oxyhemoglobin._**

**_Systemic gas exchange is the exchange of gases in tissues. The following steps take place in systemic gas exchange._**

**_Oxyhemoglobin breaks down into oxygen and hemoglobin._**

**_Oxygen moves out of tissue capillary blood into tissue cells._**

**_Carbon dioxide moves from tissue cells into tissue capillary blood._**

**_Hemoglobin combines with carbon dioxide, forming carbaminohemoglobin._**

**_Blood transportation of gases includes transport of oxygen and carbon dioxide._**

**_Only small amounts of oxygen gas can be dissolved in blood. Most oxygen combines with hemoglobin to form oxyhemoglobin to be carried in the blood._**

**_Dissolved carbon dioxide is about 10% of the total carbon dioxide transported in the blood._**

**_Carbaminohemoglobin is about 20%._**

**_About 70% of the total carbon dioxide transported in the blood is carried in the form of bicarbonate ions._**

**_This concludes the audio review of chapter 15._**

**20260321_000027.jpg**

This file is too large to display. [View in new window](https://www.sweetstudy.com/files/20260321-000027-jpg)

**## Chapter_015.rtf**

15-4

Audio Chapter Summaries

Copyright © 2025 by Elsevier Inc. All rights reserved, including those for text and data mining, AI training, and similar technologies.

Copyright © 2025 by Elsevier Inc. All rights reserved, including those for text and data mining, AI training, and similar technologies.

**Patton: Structure & Function of the Body, 17th Edition**

**Chapter 15: Respiratory System**

****Audio Chapter Summaries****

****Welcome to the audio review of Chapter 15: Respiratory System.****

**First, we’ll review the organization of the respiratory system.**

**A 3-dimensional visual of the respiratory system would be similar to an inverted tree if it were hollow; branches would be the bronchi, and leaves of the tree would be comparable to alveoli, with the microscopic sacs enclosed by networks of capillaries.**

**The passive transport process of diffusion is responsible for the exchange of gases that occurs during respiration.**

**The respiratory tract is divided into upper and lower portions.**

**The upper respiratory tract includes the nose, pharynx, and larynx.**

**The lower respiratory tract contains the trachea, bronchial tree, alveoli, and lungs.**

**The respiratory mucosa is a specialized membrane that lines the air distribution tubes in the respiratory tree. Three types of epithelium are present in the respiratory mucosa:**

**Ciliated pseudostratified epithelium lines most of the tract and produces mucus.**

**Stratified squamous epithelium lines the nostrils, vocal folds, and pharynx; it serves a protective function.**

**Simple squamous epithelium lines the alveoli and facilitates gas exchange.**

**The respiratory mucosa serves several functions:**

**More than 125 mL of mucus is produced each day. It forms a “mucous blanket” over much of the respiratory mucosa.**

**Mucus serves as an air purification mechanism by trapping inspired irritants such as dust and pollen.**

**The respiratory mucosa also supports what could be called the ciliary escalator; cilia on mucosal cells beat in only one direction, moving mucus upward to the pharynx for removal.**

**Now we’ll review some specifics about the upper respiratory tract.**

**A nasal septum separates the interior of the nose into two cavities, called nares or nostrils.**

**Frontal, maxillary, sphenoidal, and ethmoidal sinuses of the skull drain into the nose.**

**Three shelflike structures in the nasal cavity called conchae or turbinates warms and moistens inhaled air. The nose also houses the sense organs of smell.**

**The pharynx or throat is about 12.5 cm (or 5 inches) long. It is divided into the nasopharynx, oropharynx, and the laryngopharynx.**

**The two nasal cavities, mouth, esophagus, larynx, and auditory tubes all have openings into the pharynx.**

**Pharyngeal tonsils and the openings of auditory tubes open into the nasopharynx. The tonsils are found in the oropharynx.**

**The pharynx functions as a passageway for food and liquids, as well as a passageway for air.**

**Nine pieces of cartilage form the framework of the last structure of the upper respiratory tract, the larynx.**

**The thyroid cartilage (also called the Adam’s apple) is the largest.**

**Note that the epiglottis partially covers the opening into the larynx.**

**Vocal cords stretch across the interior of the larynx.**

**Thus, one of the larynx’s functions is voice production. The other is air distribution; like the pharynx, it serves as a passageway for air to move to and from the lungs.**

**Next is a review of information about the lower respiratory tract.**

**The trachea is a tube about 11 cm (or 4.5 in) long and 2.5 cm (or 1 in) in diameter.**

**It extends from the larynx into the thoracic cavity.**

**C-shaped rings of cartilage hold the trachea open, but allow for swallowing.**

**The trachea functions as a passageway for air to move to and from the lungs.**

**Blockage of the trachea occludes the airway and, if complete, causes death in minutes.**

**In fact, tracheal obstruction causes more than 74000 deaths annually in the United States.**

**The bronchial tree is the next structure in the lower respiratory tract.**

**The trachea branches into right and left bronchi.**

**Each bronchus branches into smaller and smaller tubes, eventually leading to bronchioles.**

**Bronchioles end in clusters of microscopic alveolar sacs, the walls of which are made up of alveoli.**

**The function of the bronchial tree is air distribution; it serves as a passageway for air to move to and from alveoli.**

**The function of alveoli is the exchange of gases between air and blood.**

**The respiratory membrane is the thin wall that separates pulmonary blood from alveolar air, allowing diffusion of gases.**

****Surfactant is a substance released into alveoli to reduce surface tension and thus prevent collapse of the alveoli.****

**The lungs are large enough to fill the chest cavity, except for the middle space (the mediastinum) occupied by the heart, large blood vessels, thymus, and esophagus.**

**The apex of the lung is the narrow upper part, situated under the collarbone.**

**The base is the broad lower part of each lung; it rests on the diaphragm.**

**The pleura is the moist, smooth, slippery membrane that lines the chest cavity (the parietal pleura) and covers the outer surface of the lungs (the visceral pleura); The pleura reduces friction between the lungs and chest wall during breathing.**

**The function of lungs is respiration.**

**Next, we’ll review respiration and pulmonary ventilation.**

**Respiration involves several processes and mechanisms.**

**External respiration is pulmonary ventilation (or breathing) and pulmonary gas exchange.**

**These gases are transported by the blood and serve a function in the regulation of set point levels of blood gases.**

**Internal respiration is the gas exchange between the blood and systemic tissues. The term cellular respiration refers to the use of oxygen by cells in the process of metabolism.**

**To understand pulmonary ventilation, first you need to know the basic principles of the mechanics of breathing.**

**Pulmonary ventilation includes two phases called**
**_inspiration_ (movement of air into lungs) and**
**_expiration_ (movement of air out of lungs).**

**Changes in the size and shape of the thorax cause changes in air pressure within that cavity and in the lungs.**

**Pressure differences (or gradients) cause air to move into and out of the lungs.**

**Inspiration is the active process whereby air moves into the lungs.**

**Inspiratory muscles include the diaphragm and external intercostals.**

**The diaphragm flattens when stimulated by the phrenic nerve during inspiration, which increases the top-to-bottom length of the thorax.**

**The external intercostal muscles contract and elevate the ribs, which increases the size of the thorax from the front to the back and from side to side.**

**Increase in the size of the chest cavity reduces pressure within it; air then enters the lungs by moving down its pressure gradient.**

**Quiet expiration is ordinarily a passive process.**

**During expiration, the thorax returns to its resting size and shape.**

**Elastic recoil of lung tissues aids in expiration.**

**Expiratory muscles used in forceful expiration are the internal intercostals and abdominal muscles.**

**Contraction of the internal intercostals depresses the rib cage and decreases the size of the thorax from the front to back.**

**Contraction of abdominal muscles elevates the diaphragm, thus decreasing the size of the thoracic cavity from the top to bottom.**

**Reduction in the size of the thoracic cavity increases its pressure and air leaves the lungs.**

**Pulmonary volumes are volumes of air exchanged in breathing; they can be measured with a spirometer.**

**Tidal volume is the amount normally breathed in or out with each breath.**

**Vital capacity is the greatest amount of air that one can breathe out in one expiration.**

**Expiratory reserve volume is the amount of air that can be forcibly exhaled after expiring the tidal volume.**

**Inspiratory reserve volume is the amount of air that can be forcibly inhaled after a normal inspiration.**

**Residual volume is the air that remains in the lungs after the most forceful expiration.**

**Regulation of respiration permits the body to adjust to varying demands for oxygen supply and carbon dioxide removal by maintaining set point concentrations of blood gases.**

**Several mechanisms control respiration: the brainstem, cerebral cortex, and respiratory reflexes.**

**The most important central regulatory centers in both the medulla and pons in the brainstem are called**
**_respiratory control centers._**

**_Under resting conditions, the medullary rhythmicity area produces a normal rate and depth of respirations. A normal rate is considered to be 12 to 18 breaths/min._**
**_As conditions in the body vary, centers in the pons called the pontine respiratory group, can alter the activity of the medullary rhythmicity area, thus adjusting breathing rhythm._**

**_Brainstem centers are influenced by information from other parts of the brain and from sensory receptors located in other body regions._**

**_Control of respiratory activity by the cerebral cortex is voluntary but limited._**

**_Respiratory reflexes include chemoreflexes and pulmonary stretch reflexes._**

**_In chemoreflexes, chemoreceptors respond to changes in carbon dioxide, oxygen, and blood acid levels; these receptors are located in carotid and aortic bodies._**

**_Pulmonary stretch reflexes respond to the stretch receptors in lungs, thus protecting respiratory organs from overinflation._**

**_Be sure you understand the following terms for breathing patterns:_**

**_Eupnea is normal breathing._**

**_Hyperventilation means rapid and deep respirations._**

**_Hypoventilation indicates slow and shallow respirations._**

**_Dyspnea is labored or difficult respirations._**

**_Apnea is stopped respiration, absence of breathing._**

**_Respiratory arrest is the failure to resume breathing after a period of apnea._**

**_Cheyne-Stokes respiration are cycles of alternating apnea and hyperventilation associated with critical conditions._**

**_Gas exchange and transport is the final section to review in Chapter 15._**

**_Pulmonary gas exchange is the exchange of gases in the lungs. The following steps take place in pulmonary gas exchange._**

**_Carbaminohemoglobin breaks down into carbon dioxide and hemoglobin._**

**_Carbon dioxide moves out of lung capillary blood into alveolar air and out of the body into expired air._**

**_Oxygen moves from alveoli into the lung capillaries._**

**_Hemoglobin combines with oxygen, producing oxyhemoglobin._**

**_Systemic gas exchange is the exchange of gases in tissues. The following steps take place in systemic gas exchange._**

**_Oxyhemoglobin breaks down into oxygen and hemoglobin._**

**_Oxygen moves out of tissue capillary blood into tissue cells._**

**_Carbon dioxide moves from tissue cells into tissue capillary blood._**

**_Hemoglobin combines with carbon dioxide, forming carbaminohemoglobin._**

**_Blood transportation of gases includes transport of oxygen and carbon dioxide._**

**_Only small amounts of oxygen gas can be dissolved in blood. Most oxygen combines with hemoglobin to form oxyhemoglobin to be carried in the blood._**

**_Dissolved carbon dioxide is about 10% of the total carbon dioxide transported in the blood._**

**_Carbaminohemoglobin is about 20%._**

**_About 70% of the total carbon dioxide transported in the blood is carried in the form of bicarbonate ions._**

**_This concludes the audio review of chapter 15._**

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