Questions and Answers
How is CO2 primarily transported in plasma?
What is the equation for the formation of bicarbonate (HCO3-) in the presence of carbonic anhydrase?
CO2 + H2O = H2CO3 = H+ + HCO3-
HCO3- moves out of red blood cells due to its concentration gradient.
True
What mechanism maintains cellular electroneutrality during the HCO3- shift?
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Where are peripheral chemoreceptors located?
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What response occurs when peripheral chemoreceptors are activated?
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Central chemoreceptors primarily respond to oxygen levels.
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What displacement in the CO2 dissociation curve is known as the Haldane Shift?
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What are the three kinds of respiration?
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In human lungs, the diffusion distance between air and blood is about ______ micrometres.
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What is the primary function of the nasal cavity?
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The conducting airways consist of the respiratory bronchioles and alveoli.
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What structure supports the trachea?
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What are the main muscles responsible for quiet breathing?
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How many lobes does the right lung have?
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The diaphragm is innervated by the ______ nerve.
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What is the process of pulmonary ventilation?
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What is the diffusion barrier in the lungs?
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What enables the pleurae to slide past each other?
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What is the function of respiration?
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Which muscles are primarily involved in inspiration? (Select all that apply)
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Expiration is a passive process at rest.
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The volume of air moving into the lungs at rest is called the ______.
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What is the tidal volume (VT) for an average adult human?
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How is lung compliance calculated?
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What is the impact of surface tension within the lungs?
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The pulmonary circulation is a high pressure system.
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What does the VA/Q ratio ideally equal?
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What role do beta2-adrenoceptors play in the bronchioles?
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The pressure gradient in the pleural space is ______.
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Study Notes
Introduction to the Respiratory System
- Lungs facilitate gas exchange between atmospheric air and pulmonary capillaries.
- Efficient gas exchange requires minimal diffusion distance (~0.5 micrometers) and large surface area (~100 m², about half the size of a tennis court).
Types of Respiration
- External Respiration: Gas exchange in lungs, absorbing oxygen and excreting carbon dioxide.
- Internal Respiration: Exchange of gases between blood in systemic capillaries and surrounding tissues (not covered in lectures).
- Cellular Respiration: Energy production in cells by breaking down glucose, occurs in mitochondria.
Structure of the Respiratory System
- The conducting zone includes the nasal cavities, pharynx, larynx, trachea, bronchi, and bronchioles, which conduct and condition air.
- The respiratory zone consists of respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli, where gas exchange occurs.
Components of the Nasal Cavity
- Lined with mucous membrane that humidifies and warms air.
- Features conchae that increase surface area for better air conditioning.
- Olfactory epithelium located at the roof for smell detection.
Anatomy of the Pharynx
- Divided into three parts: nasopharynx, oropharynx, and laryngopharynx, serving as both an airway and digestive passage.
- Structural features prevent food from entering the airway during swallowing.
Airway Branching Pattern
- Trachea leads to main stem bronchi, followed by lobar and segmental bronchi.
- Conducting airways progressively branch, with terminal bronchioles leading to respiratory bronchioles for gas exchange.
Trachea Characteristics
- Approximately 12 cm long with "C-shaped" cartilage rings for structural support.
- Lined with ciliated pseudostratified columnar epithelium aiding in mucociliary clearance.
Bronchial and Alveolar Structure
- Bronchi and bronchioles possess varying epithelial types and smooth muscle content.
- Alveoli are surrounded by capillaries, allowing for efficient gas exchange through thin walls.
Lung Subdivisions and Pleurae
- Right and left lungs divided into lobes and segments for localized surgical intervention.
- Pleura envelops each lung and lines the thoracic cavity, with a fluid layer facilitating movement during breathing.
Ventilation Mechanics
- Quiet Breathing: Rib cage movements account for 25% of air movement; diaphragm contraction is responsible for 75% of air flow.
- Diaphragm: Flat muscle, innervated by the phrenic nerve, primarily facilitates inspiration by increasing thoracic volume.
Summary of Respiratory Function
- Respiration serves to extract oxygen for metabolism while removing carbon dioxide from tissues.
- Involves rhythmic contractions of respiratory muscles for both inspiration (active) and expiration (passive at rest).
Respiratory Muscles and Innervation
- Main muscles: diaphragm and external intercostals (inspiration), internal intercostals and abdominal muscles (active expiration).
- Inspiratory muscles are primarily innervated by cervical segments (C3-C5 for diaphragm) and thoracic segments (T1-L1 for intercostals).
Pressure Dynamics in the Thoracic Cavity
- Intrapleural pressure is typically negative, which assists lung expansion.
- The pressure gradient facilitates the movement of air during the breathing cycle.### Mechanics of Ventilation
- Negative pleural pressure (Ppl) keeps lungs from collapsing, adhering them to the chest wall.
- Inspiration involves diaphragm contraction and rib movement ("bucket handle" effect), increasing chest volume and decreasing pulmonary pressure (Ppul) below atmospheric pressure, facilitating inhalation.
Lung Volumes
- Tidal volume (VT) at rest for an average adult is approximately 0.5 L.
- Vital capacity = volume of air from maximal expiration to maximal inspiration; residual volume assesses lung capacity via helium dilution.
- Lung capacities sum multiple volumes; residual volume = total lung capacity (TLC) - vital capacity.
Respiratory Volumes
- Measured volumes include tidal breath (VT), inspiratory reserve volume, and expiratory reserve volume.
- Minute ventilation (VE) calculated as VE = VT x respiratory frequency (f); average at rest is 6 L/min.
Alveolar Ventilation
- Dead space (VD) is ~2.2 ml/kg (about 150 ml); account for anatomical dead space in alveolar ventilation (VA).
- Alveolar ventilation calculated as VA = (VT - VD) x f; typically 4.2 L/min.
Lung Compliance and Surface Tension
- Compliance = change in lung volume/change in pressure; high compliance indicates easier lung expansion, important for gas exchange.
- Surfactant reduces surface tension in alveoli, crucial for lung inflation and deflation.
- La Place’s law relates alveolar pressure (PA) to surface tension and radius, indicating smaller radii create greater pressures.
Airway Anatomy and Ventilation
- The upper airway comprises cartilaginous structures (trachea, bronchi), forming the conducting zone with anatomical dead space.
- The respiratory zone includes bronchioles and alveolar sacs, relying on the lung parenchyma for patency.
- The funnel effect increases cross-sectional area from trachea to alveoli, altering airflow dynamics.
Airway Resistance and Control
- Airway resistance highest in upper airway, lowest in bronchioles; lung inflation reduces airway resistance via radial traction.
- Bronchoconstriction occurs through parasympathetic innervation, while sympathetic innervation leads to bronchodilation.
- Reflexes triggered by stretch receptors during lung inflation promote bronchodilation, enhancing airflow.
Pulmonary Circulation and Perfusion
- Pulmonary circulation operates at low pressure; typical pulmonary artery pressure is 28/10 mmHg.
- Physiological shunts exist due to mixed venous blood; ventilation-perfusion ratio (V:Q) ideally equals 1, but averages around 0.8 in practice.
Regional Blood Flow in the Lung
- Blood flow varies regionally due to gravity; best perfusion at the lung base.
- Three pulmonary zones (Zone 1: low perfusion, Zone 2: moderate, Zone 3: highest) reflect pressures (hydrostatic, arterial, and alveolar).
Gas Exchange and Transport
- Oxygen is transported mainly by binding to hemoglobin (Hb) and dissolved in plasma.
- Oxygen dissociation curve illustrates the cooperative binding of O2 to Hb; Bohr effect describes shifts in the curve due to pH, CO2 levels, temperature, and DPG.
Carbon Dioxide Transport
- CO2 transported as dissolved gas, as carbamino compounds, and as bicarbonate (HCO3-) in red blood cells.
- Chloride shift maintains ionic balance in red blood cells during gas transport reactions.
Respiratory Control Mechanisms
- Ventilation controlled by chemoreceptors, sensitive to changes in blood gases.
- Peripheral chemoreceptors located at the carotid bodies and aortic arch respond to hypoxia and CO2, increasing ventilation rates.
- Central chemoreceptors primarily evaluate CO2 levels, regulating breathing depth and rate.
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Description
Test your knowledge of the illustrations and concepts from Fig. 23.08 of Tortora & Grabowski's 'Principles of Anatomy and Physiology' 10th edition. This quiz will help reinforce your understanding of key anatomical structures and physiological processes covered in this important text.
