11: Respiratory Systems
- Page ID
- 100155
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 11.1: Respiratory System Introduction
- The respiratory system moves air in and out of the lungs, allowing oxygen to enter the bloodstream and carbon dioxide to be removed through gas exchange in the alveoli. Working closely with the circulatory system, it ensures that cells receive the oxygen needed for cellular respiration while helping maintain stable blood pH. By adjusting breathing rate, the body regulates carbon dioxide levels to prevent acidosis or alkalosis and preserve homeostasis.
- 11.2: Anatomical Regions of the Respiratory Tract
- The respiratory tract is divided into upper and lower regions that guide, filter, warm, and ultimately exchange the air we breathe. Air travels from the nose and pharynx through the larynx, trachea, bronchi, and bronchioles until it reaches the alveoli, where gas exchange occurs. The lungs, housed within the thoracic cavity and supported by the pleural membranes, expand and recoil smoothly to make efficient breathing possible.
- 11.3: Functional Anatomy of the Respiratory Tract
- Functionally, the respiratory system consists of a conducting zone that moves and conditions air, and a respiratory zone where gas exchange occurs in the alveoli. The respiratory epithelium filters debris, while the thin respiratory membrane allows rapid diffusion of oxygen and carbon dioxide. Type I alveolar cells form the exchange surface, type II cells produce surfactant, and alveolar macrophages protect the lungs from pathogens.
- 11.4: A Closer Look at the Air We Breathe
- Inhaled air contains about 21% oxygen and very little carbon dioxide, while exhaled air has less oxygen, much more carbon dioxide, and is saturated with water vapor, reflecting gas exchange in the alveoli. Measuring these changes with tools such as capnography, CO₂ detectors, oxygen analyzers, and indirect calorimetry helps clinicians assess ventilation and metabolic activity. Air quality also matters, as pollutants can irritate airways and reduce efficient oxygen exchange, especially in sensiti
- 11.5: Overview of Respiratory Physiology
- Respiratory physiology explains how the body moves air, exchanges gases, transports oxygen and carbon dioxide in the blood, and delivers oxygen to tissues while removing metabolic waste. These four coordinated processes — pulmonary ventilation, external respiration, gas transport, and internal respiration — work together to support cellular respiration and maintain acid–base balance.
- 11.6: Mechanics of Breathing — Pulmonary Ventilation
- Pulmonary ventilation relies on pressure differences created by changes in thoracic volume: when the diaphragm and external intercostals contract, thoracic volume increases, intrapulmonary pressure falls, and air flows in; when they relax, elastic recoil pushes air out. Quiet expiration is mostly passive, while forced breathing recruits additional muscles to increase airflow. The pleural membranes, pleural fluid, and negative intrapleural pressure keep the lungs adhered to the chest wall.
- 11.7: Pulmoany Function Tests — Spirometry
- Pulmonary function tests measure how well the lungs move air and exchange gases, giving clinicians important information about respiratory health. Spirometry, one of the most common tests, records how much air a person can inhale and exhale and how quickly it can be expelled. These measurements help distinguish between obstructive disorders, where airflow is limited, and restrictive disorders, where lung expansion is reduced.
- 11.8: Normal and Altered Breathing Patterns
- Normal breathing matches ventilation to the body’s metabolic needs, maintaining stable oxygen, carbon dioxide, and blood pH levels. Altered patterns, such as rapid shallow breathing during anxiety, can disrupt this balance by lowering carbon dioxide too quickly, leading to symptoms like lightheadedness and tingling despite normal oxygen levels. Restoring a slower, controlled breathing pattern helps reestablish proper gas balance and relieve symptoms.
- 11.9: External Respiration
- External respiration is the exchange of oxygen and carbon dioxide between the alveoli and pulmonary capillaries, driven by partial pressure gradients. Oxygen diffuses into the blood and carbon dioxide diffuses out across the extremely thin respiratory membrane, whose large surface area and minimal thickness make diffusion efficient. Effective gas exchange also depends on proper ventilation–perfusion matching to ensure airflow and blood flow remain balanced in the lungs.
- 11.10: Transport of Gases
- Oxygen is transported primarily bound to hemoglobin in red blood cells, where each hemoglobin molecule can carry up to four oxygen molecules and adjust its affinity based on tissue needs, temperature, and pH. Carbon dioxide returns to the lungs dissolved in plasma, bound to hemoglobin, or mostly converted to bicarbonate through reversible chemical reactions in red blood cells.
- 11.11: Internal Respiration
- Internal respiration is the exchange of gases between systemic capillaries and body tissues, where oxygen diffuses from the blood into cells and carbon dioxide diffuses from cells into the blood. Hemoglobin releases more oxygen in active tissues with low PO₂, higher CO₂, increased temperature, and lower pH, ensuring delivery matches metabolic demand.
- 11.12: When Smoke Meets Biology — The Cost to Your Cells and Tissues
- Smoking reduces oxygen delivery because carbon monoxide binds hemoglobin more strongly than oxygen, limiting how much oxygen reaches tissues. At the same time, nicotine increases heart rate, blood pressure, and vessel constriction, placing extra strain on the cardiovascular system. Over time, chronic airway and vascular damage lead to impaired lung function and increased risk of heart and vascular disease.
- 11.13: Heimlich Maneuver — A Quick Introduction to Choking Rescue
- Choking is a life-threatening emergency caused by partial or complete airway obstruction, most commonly in the right primary bronchus in adults. A complete blockage prevents airflow and gas exchange, leading to rapid hypoxia, unconsciousness, and possible death within minutes. Immediate intervention — such as abdominal thrusts for adults, chest thrusts for pregnant individuals, or back slaps and chest thrusts for infants — is critical to restore airflow and save a life.
- 11.14: Cystic Fibrosis
- Cystic fibrosis is an autosomal recessive disorder caused by mutations in the CFTR gene, leading to defective chloride transport and thick, dehydrated mucus in the airways. This sticky mucus impairs mucociliary clearance, promotes chronic infections, and progressively damages lung tissue. Treatment focuses on airway clearance, infection control, CFTR-modulating medications, and in advanced cases, lung transplantation.