Video 3 - Respiration & Pulmonary Physiology – Core Vocabulary

These flashcards review fundamental vocabulary for respiratory mechanics, gas exchange, and pulmonary volumes as discussed in the lecture.

Boyle's Law

Physical law stating that at constant temperature, the pressure of a gas varies inversely with its volume—used to explain how changes in chest volume drive breathing.

Diaphragm

Primary muscle of inspiration; contracts and moves downward to enlarge thoracic cavity and lower intrapulmonary pressure.

External Intercostals

Muscles between ribs that lift the rib cage up and out during quiet inspiration, increasing thoracic volume.

Internal Intercostals

Rib muscles recruited during forced expiration to pull the ribs down and in, decreasing thoracic volume.

Abdominal Muscles (Rectus Abdominis, etc.)

Muscular group that contracts during active/forced exhalation to push the diaphragm upward and expel air quickly.

Pleura

Double-layered serous membrane (parietal and visceral) surrounding lungs; lubricated gap allows lungs to move without direct attachment.

Alveoli

Microscopic air sacs ("raspberries") that provide large surface area and minimal diffusion distance for gas exchange.

Respiratory Membrane

Two-cell-layer barrier (alveolar epithelium + capillary endothelium) across which O₂ and CO₂ diffuse.

Partial Pressure (PO₂ / PCO₂)

Pressure exerted by an individual gas in a mixture; used as a measure of gas concentration in physiology.

Gas Solubility

Ability of a gas to dissolve in a liquid; CO₂ is highly soluble in plasma, facilitating diffusion despite small pressure gradients.

Hemoglobin (Hb)

Tetrameric protein in red blood cells that reversibly binds and transports oxygen and some carbon dioxide.

Globin Chains

Four protein subunits (2 α, 2 β) that make up hemoglobin and each contain a heme group.

Heme

Iron-containing porphyrin ring within each globin that binds one O₂ molecule.

Oxyhemoglobin (HbO₂)

Hemoglobin saturated with oxygen after loading in the lungs.

Deoxyhemoglobin (HHb)

Hemoglobin that has released its oxygen to tissues.

Loading Reaction

Process in pulmonary capillaries where hemoglobin binds oxygen due to high alveolar PO₂.

Unloading Reaction

Release of oxygen from hemoglobin in systemic tissues where PO₂ is lower.

Oxygen–Hemoglobin Dissociation Curve

Sigmoidal graph showing percentage saturation of hemoglobin at varying PO₂ levels; illustrates cooperative binding and reserve capacity.

Carbon Monoxide (CO)

Colorless, odorless gas that binds hemoglobin with higher affinity than O₂, preventing oxygen transport.

Carboxyhemoglobin (HbCO)

Complex formed when hemoglobin irreversibly binds carbon monoxide, leading to hypoxia.

Carbonic Acid (H₂CO₃)

Weak acid formed when CO₂ reacts with water in blood; quickly dissociates into bicarbonate and H⁺.

Bicarbonate (HCO₃⁻)

Major blood buffer produced from carbonic acid that transports CO₂ and helps regulate pH.

Chloride Shift

Exchange of Cl⁻ for HCO₃⁻ across red blood cell membrane that maintains electrical neutrality during CO₂ transport.

Eupnea

Normal, quiet breathing at rest.

Hyperpnea

Forced or deep breathing, often during exercise, involving active exhalation muscles.

Apnea

Temporary cessation of breathing, triggered by pain, cold, or sleep disorders.

Tidal Volume (TV)

Amount of air inhaled or exhaled during a normal breath (~500 mL).

Inspiratory Reserve Volume (IRV)

Additional volume that can be inhaled after a normal inspiration.

Expiratory Reserve Volume (ERV)

Extra volume that can be exhaled after a normal expiration.

Residual Volume (RV)

Air remaining in respiratory passages and lungs after maximal exhalation (≈1000 mL females; 1200 mL males).

Dead Space

Volume of conducting airways where no gas exchange occurs; approximated by residual volume in calculations.

Vital Capacity (VC)

Maximum amount of air exhaled after a maximal inspiration (TV + IRV + ERV).

Total Lung Capacity (TLC)

Total volume of lungs at maximal inflation (VC + RV).

Alveolar Ventilation Rate (AVR)

Volume of air reaching alveoli per minute: (TV – dead space) × respiratory rate (~4 L/min at rest).

Compliance

Ease with which lungs and thoracic wall expand; normally high due to elasticity and surfactant.

Surfactant

Phospholipid-protein mixture secreted by type II alveolar cells that reduces surface tension and prevents alveolar collapse.

Thoracic Volume

Space within the chest cavity whose changes drive pressure gradients for ventilation.

Interpulmonary Pressure

Pressure inside lung alveoli that rises and falls with breathing, guiding air movement.

Interpleural Pressure

Slightly negative pressure between pleural layers that keeps lungs inflated.