Respiratory System Quiz

Pulmonary Ventilation

• Pulmonary ventilation is the process of air moving in and out of the lungs.
• The respiratory system includes the trachea, bronchi, bronchioles, and alveoli.
• The lungs facilitate gas exchange, replacing oxygen and removing carbon dioxide. They also regulate acid-base balance.
• Pulmonary ventilation is a mechanical process.
• Diffusion is the random movement of molecules from high to low concentration.

Structure of the Pulmonary System

• The conductive zone transports air to the lungs (nose/mouth to terminal bronchioles).
• The transitional/respiratory zone is where gas exchange occurs (respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli).
• The conducting zones are the anatomical dead space (trachea and terminal bronchioles). Functions include air transport, warming, humidification, particle filtration, vocalization, and immunoglobulin secretion.
• The transitional/respiratory zones perform gas exchange, surfactant production, molecule activation/inactivation, blood clotting regulation, and endocrine function.
• The lungs provide a large surface area (50-100 m²) for gas exchange, and are highly vascularized.
• Alveoli are elastic, thin-walled membranous sacs (600 million) in the lungs, that create a small blood-gas barrier.

Mechanics of Breathing

• Air movement occurs via bulk flow due to pressure differences.
• Inspiration: diaphragm contracts, ribs lift, lung volume expands, intrapulmonary pressure lowers.
• Expiration: diaphragm relaxes, ribs drop, lung volume decreases, intrapulmonary pressure rises.

Airway Resistance

• Air flow depends on the pressure difference across the airway and airway resistance.
• Airway resistance depends on the diameter of the airways.
• Conditions like asthma and COPD affect airway resistance.

Gas Delivery and Circulation

• The lungs have two circulatory systems:
  • Pulmonary circulation supports external respiration.
  • Bronchial circulation provides blood supply to the lungs themselves.

Lung Volumes and Capacities

• Lung volumes are measured with a spirometer.
• Volumes vary based on age, size, and gender.
• Key volumes include Vital Capacity (VC), Residual Volume (RV), Total Lung Capacity (TLC), Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), Forced Vital Capacity (FVC).
• Note: Values are not required for memorization.

Spirometry

• Spirometric tests are used to diagnose lung diseases like COPD.
• Vital capacity (VC) measures the maximal volume of air exhaled after maximal inhalation.
• Forced expiratory volume (FEV1) measures the volume of air exhaled in one second during maximal exhalation.
• FEV1/VC ratio is a normal measure, indicative of airway capacity ≥ 80%.

Measuring Respiration

• Minute ventilation (VE) is the volume of air breathed each minute (VE = VT * f).
• Alveolar ventilation (VA) is the volume of air reaching the respiratory zone (VA = (VT − VD) * f ; VD = total dead space).

Maximum Voluntary Ventilation (MVV)

• MVV assesses ventilatory capacity by measuring the volume of air moved during rapid, deep breathing.
• Values typically exceed exercise ventilation.

Gas Exchange and Transport

• Air contains ~ 21% oxygen, ~0.03% carbon dioxide.
• Dalton's Law: total pressure = sum of individual gas pressures.
• Fick's Law: gas transfer rate is proportional to surface area, and inversely proportional to thickness.
• Henry's Law: gases move from high to low pressure, and solubility affects diffusion rate.
• Alveolar air is altered by CO2 entry.
• Average arterial PO2 ≈ 100 mm Hg.

Gas Transport – Oxygen and Carbon Dioxide

• Oxygen transport: dissolved form (minor) and bound to hemoglobin (major). Hemoglobin (Hb) has four heme groups, each binding one oxygen molecule.
• Carbon dioxide transport: dissolved in blood, combined with hemoglobin, and as bicarbonate ions.

Acid-Base Balance

• Mechanisms regulate H+ concentration in body fluids.
• Hemoglobin and the carbonic acid-bicarbonate buffer system are involved.
• Kidneys also play a role in long-term acid-base balance.

Arteriovenous O2 Difference

• The amount of oxygen released by blood during systemic circulation.
• Indicates oxygen uptake by tissues; higher in exercise.

Oxygen Binding/Dissociation

• Hemoglobin's oxygen binding capacity is dependent on blood PO2, temperature, and pH.
• The oxygen-hemoglobin dissociation curve shows the relationship between blood PO2 and hemoglobin saturation. A right shift indicates reduced oxygen affinity.

Ventilation-Perfusion Ratio (V/Q)

• The ratio of alveolar ventilation to pulmonary blood flow at rest (~0.8).
• Variations occur across different lung sections.

Respiratory Responses to Exercise

• Pulmonary ventilation increases to maintain alveolar ventilation.
• External respiration and internal respiration adjust to meet oxygen demands.
• Exercise increases oxygen extraction from blood.

Effects of Endurance Training

• Endurance training reduces exercise ventilation.

Variations in Breathing Patterns

• Hyperventilation decreases PCO2.
• Dyspnea is inordinate shortness of breath.
• Valsalva maneuver increases intrathoracic pressure during strenuous exertion, affecting venous return and blood pressure.

Respiratory Limitations to Exercise

• Exercise-induced arterial hypoxemia, respiratory muscle fatigue and excessive fluctuations in intrathoracic pressures can limit performance.

Gender and Age Considerations

• Women generally have smaller lung volumes and capacities than men.
• Children and youth are not fully developed, and older adults show reduced lung capacity.

Respiratory Muscle Training

• Techniques like IFRL, VIHT, IPTL can improve respiratory muscle strength.
• Controlled frequency breathing (CFB) has mixed effects.