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Questions and Answers
What is primarily responsible for directly stimulating the respiratory center?
Which cranial nerves innervate the diaphragm?
Where is the respiratory center located within the brain?
What type of nerve control allows both involuntary and voluntary functions of respiratory muscles?
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Which chemical has the smallest effect on ventilation?
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What is the primary function of the respiratory zone?
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What structure is considered part of the upper airways?
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Which of the following describes the function of goblet cells?
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What is the significance of the mucociliary escalator?
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What happens to ciliary movement during smoking?
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How many capillaries are typically associated with each alveolus?
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What is the role of smooth muscle in the respiratory system?
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What is affected by cystic fibrosis in the respiratory system?
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What is the main method by which oxygen is transported in the blood?
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Which factor does NOT affect the diffusion of gases through the respiratory membrane?
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How is carbon dioxide primarily transported in the blood?
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What effect does hypoxia have compared to hypercapnia?
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In pulmonary circulation, which statement is true regarding pulmonary arteries?
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What is the primary role of the pulmonary lymphatic system?
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What is the Bohr effect primarily associated with?
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Which statement accurately describes the distribution of pulmonary air?
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What effect does increased sympathetic activity have on the bronchi?
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Which local factors can affect bronchial contraction?
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What measurement does the spirometry assess?
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In a healthy individual, what is the typical FEV1/FVC percentage?
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What technique uses inert gas to measure lung volumes like RV and TLC?
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What is the primary determinant of the work of breathing?
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Which pulmonary capacity measures the sum of vital capacity and residual volume?
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What is the primary purpose of measuring FEF50 in a flow-volume loop?
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What is the role of pulmonary surfactant in the alveoli?
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Which muscle primarily facilitates inspiration?
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During expiration, what is the state of intrapleural pressure?
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What determines lung compliance?
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Which disorder is categorized as restrictive pulmonary disease?
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What occurs to the alveoli when there is a lack of pulmonary surfactant?
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In a series configuration of airways, how is total resistance calculated?
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What happens to airway resistance during expiration compared to inspiration?
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What is the typical number of alveoli in a single lung?
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What primarily contributes to the negative pleural pressure during inspiration?
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Study Notes
Respiratory System Structures
- The respiratory system is divided into the upper and lower airways.
- The upper airways include the nasal and oral cavity, pharynx, and larynx.
- The lower airways include the trachea, bronchi, bronchioles, and alveoli.
- The conducting zone consists of the upper and lower airways and is responsible for conducting air to the respiratory zone for gas exchange.
- The respiratory zone includes the respiratory bronchioles, alveolar ducts, and alveolar sacs.
Mucociliary Escalator
- The mucociliary escalator is a protective mechanism that removes foreign particles from the airways.
- Goblet cells secrete mucus, which traps foreign particles.
- Ciliated epithelial cells move the mucus up the airways, where it is swallowed.
- Bronchitis is caused by a thick mucus secretion in the airways.
- Cystic fibrosis is characterized by a decreased fluidic secretion.
Alveoli
- Alveoli are the small air sacs where gas exchange occurs.
- The alveolar-capillary unit is composed of the alveoli and capillary networks.
- Each alveolus has approximately 1000 capillaries.
- The average lung contains 300–500 million alveoli, resulting in a respiratory area of approximately 75m2.
- The alveolar membrane is very thin, only 0.2um.
- Alveolar pores allow for gas exchange between adjacent alveoli.
Gas Exchange
- Gas exchange occurs across the alveolar-capillary membrane via diffusion.
- The barrier to gas exchange includes the alveolar fluid lining, alveolar epithelial cells, interstitial space, capillary endothelial cells, and blood plasma.
Respiratory Mechanics
- Inspiration is an active process that requires the contraction of inspiratory muscles, primarily the diaphragm.
- Inspiration overcomes elastic recoil and surface tension, and results in negative pleural pressure.
- Weakness of inspiratory muscles can lead to respiratory difficulties.
- Expiration is a passive process that relies on elastic recoil and surface tension.
- Maximal expiratory pressure can be used to overcome airway resistance during forced expiration.
Lung Volume Change
- Lung volume changes during inhalation and exhalation.
- Alveolar pressure decreases during inspiration and increases during expiration.
- Pleural pressure becomes more negative during inspiration and less negative during expiration.
- Air flow is greatest during the middle of inspiration and expiration.
Surface Tension and Compliance
- Surface tension in the alveoli creates pressure that makes inspiration more difficult.
- Pulmonary surfactant, produced by type 2 alveolar cells, reduces surface tension by 4 cm H2O, improving lung compliance and stability.
- Surfactant deficiency, as seen in infant respiratory distress syndrome, can lead to alveolar collapse.
Lung Diseases
- Obstructive pulmonary diseases, such as asthma, chronic bronchitis, and emphysema, are characterized by increased airway resistance.
- Restrictive pulmonary diseases, such as fibrosis, are characterized by decreased lung compliance.
Airway Resistance
- Airways in series have greater resistance than airways in parallel.
- Expiration often has greater resistance than inspiration.
- Bronchial diameters are regulated by the autonomic nervous system.
- Sympathetic activation causes bronchodilation.
- Parasympathetic activation causes bronchoconstriction.
- Local factors like pollen, smoke, and dust can also stimulate bronchoconstriction.
Pulmonary Function Tests
- Pulmonary function tests evaluate lung function and identify respiratory diseases.
- Spirometry measures lung volumes and airflow.
- Tidal volume is the amount of air inhaled or exhaled during normal breathing.
- Inspiratory reserve volume is the maximum amount of air that can be inhaled after a normal inspiration.
- Expiratory reserve volume is the maximum amount of air that can be exhaled after a normal expiration.
- Residual volume is the amount of air remaining in the lungs after a maximal expiration.
- Vital capacity is the maximum amount of air that can be exhaled after a maximal inspiration.
- Inspiratory capacity is the maximum amount of air that can be inhaled after a normal expiration.
- Functional residual capacity is the amount of air remaining in the lungs after a normal expiration.
- Total lung capacity is the maximum amount of air that the lungs can contain.
Gas Exchange in the Alveoli
- Gas exchange occurs in the alveoli.
- Ventilation is the movement of air into and out of the lungs.
- Inspiratory gas is warmed and humidified during inhalation.
- Gas movement occurs due to differences in partial pressure.
- Gravity influences the distribution of pulmonary air.
- Diffusion is the movement of gases across the alveolar-capillary membrane according to partial pressure gradients.
- Factors affecting diffusion include surface area, distance, gas solubility, and partial pressure differences.
- Arterial blood gas analysis assesses respiratory and acid-base status.
Pulmonary Circulation
- Pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs.
- Pulmonary blood flow is characterized by low pressure and resistance.
- Pulmonary hypertension is abnormally high pressure in the pulmonary arteries.
- The lymphatic system plays a role in fluid drainage and immune defense in the lungs.
- Gravity influences blood flow in the pulmonary circulation.
- Pulmonary edema is an accumulation of fluid in the lungs.
Ventilation/Perfusion Ratio
- The ventilation/perfusion (VQ) ratio represents the balance between air flow and blood flow in the lungs.
- A well-matched VQ ratio allows for efficient gas exchange.
- Mismatched VQ ratios occur when ventilation and perfusion are not balanced, leading to hypoxemia or hypercapnia.
Transport of Gases in the Blood
- Oxygen is transported in the blood in two forms: dissolved in plasma (1.5%) and bound to hemoglobin (98.5%).
- Hemoglobin is a protein in red blood cells that binds oxygen.
- Factors affecting oxygen transport include anemia, hemoglobinopathies, and carbon monoxide intoxication.
- Cyanosis is a bluish discoloration of the skin and mucous membranes due to low oxygen levels in the blood.
Oxyhemoglobin Dissociation Curve
- The oxyhemoglobin dissociation curve illustrates the relationship between oxygen partial pressure and hemoglobin saturation.
- The Bohr effect describes the shift of the curve to the right, indicating a decreased affinity of hemoglobin for oxygen in the presence of increased carbon dioxide, hydrogen ions, or temperature.
Transport of Carbon Dioxide
- Carbon dioxide is transported in the blood in three forms: dissolved in plasma, bound to blood proteins as carbamino compounds, and as bicarbonate.
- CO2 is highly soluble in lipids and diffuses easily across cell membranes.
- Hypoxia (low oxygen levels) is more common than hypercapnia (high carbon dioxide levels) because CO2 is transported more readily than oxygen.
Regulation of Respiration
- Breathing is an automatic process regulated by the respiratory center in the medulla oblongata and pons.
- The respiratory center is responsible for generating the basic rhythm of breathing.
- The diaphragm is innervated by the phrenic nerve, allowing for both voluntary and involuntary control of breathing.
- Chemoreceptors monitor the levels of CO2, H+, and O2 in the blood and cerebrospinal fluid.
- CO2 is the most potent stimulus for ventilation, directly stimulating the respiratory center.
- H+ also stimulates the respiratory center directly.
- O2 levels are monitored by peripheral chemoreceptors in the carotid and aortic bodies.
Autonomic Nervous System
- Controls involuntary functions.
- Divided into sympathetic and parasympathetic divisions.
- Sympathetic nervous system ("fight or flight"): prepares body for stressful situations; increases heart rate and breathing, dilates pupils, and inhibits digestion.
- Parasympathetic nervous system ("rest and digest"): conserves energy and promotes digestion; slows heart rate, constricts pupils, and stimulates digestion.
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Description
Explore the essential structures of the respiratory system, including upper and lower airways. This quiz covers the mucociliary escalator's protective role and the function of alveoli in gas exchange. Test your knowledge on the key concepts of respiratory anatomy and physiology.