Chapter 20 – The Respiratory System: Vocabulary Review

A set of key vocabulary flashcards covering anatomy, physiology, and gas-exchange concepts from the Chapter 28 respiratory-system lecture.

Respiration (Ventilation)

The macro-level process of moving air into and out of the lungs to exchange O₂ for CO₂.

Cellular Respiration

Metabolic reactions inside cells that use O₂ to produce ATP and generate CO₂ as a waste product.

Pharynx

Muscular funnel at the back of the throat that directs air toward the larynx and food toward the esophagus.

Larynx

Voice box; airway structure housing the vocal cords and guarding the entrance to the trachea.

Epiglottis

Leaf-shaped flap of cartilage that folds over the glottis to keep food and drink out of the airway.

Glottis

Opening between the vocal cords through which air passes.

Vocal Cords

Paired folds of tissue in the larynx that vibrate to produce sound.

Trachea

Windpipe; air tube supported by 16–20 C-shaped cartilage rings conveying air to the bronchi.

Trachealis Muscle

Smooth muscle on the posterior aspect of each tracheal ring that can constrict to increase airflow speed.

Bronchial Tree

Branching system of air tubes—including main, lobar, and segmental bronchi—that distributes air within the lungs.

Main (Primary) Bronchus

First branch of the trachea entering each lung (right and left).

Lobar (Secondary) Bronchus

Bronchus that supplies an entire lung lobe (three on the right, two on the left).

Segmental (Tertiary) Bronchus

Smaller bronchus that ventilates a bronchopulmonary segment within a lobe.

Lobe of the Lung

Anatomical subsection of a lung; right lung has three, left lung has two.

Diaphragm

Dome-shaped skeletal muscle separating thoracic and abdominal cavities; its contraction drives inspiration.

Apex of Lung

Narrow superior tip of a lung that extends above the clavicle.

Base of Lung

Broad inferior portion of a lung resting on the diaphragm.

Alveolus (plural: Alveoli)

Microscopic air sac where O₂ and CO₂ are exchanged between air and blood.

Squamous (Type I) Alveolar Cell

Thin epithelial cell forming most of the alveolar wall for gas diffusion.

Great (Type II) Alveolar Cell

Cuboidal cell that secretes pulmonary surfactant and repairs alveolar epithelium.

Surfactant

Mixture of lipoproteins that reduces surface tension inside alveoli, preventing collapse during exhalation.

Alveolar Macrophage

Mobile immune cell within alveoli that phagocytizes dust, debris, and pathogens.

Respiratory Membrane

Thin barrier (alveolar epithelium + shared basement membrane + capillary endothelium) across which gases diffuse.

Atmospheric Pressure

Pressure exerted by the air at sea level—defined as 1 atm or 760 mm Hg.

Intrapulmonary Pressure

Air pressure within the alveoli; equals atmospheric pressure at rest.

Boyle’s Law

Physical law stating that pressure of a gas varies inversely with its volume (P₁V₁ = P₂V₂).

Dalton’s Law

Total atmospheric pressure equals the sum of the partial pressures of each gas present.

Partial Pressure Gradient

Difference in partial pressure of a gas between two regions that drives diffusion.

Inspiration

Process of drawing air into the lungs by increasing thoracic volume and lowering intrapulmonary pressure.

Expiration

Process of expelling air from the lungs as thoracic volume decreases and intrapulmonary pressure rises.

Bronchodilation

Widening of bronchioles due to smooth-muscle relaxation, reducing airflow resistance.

Bronchoconstriction

Narrowing of bronchioles due to smooth-muscle contraction, increasing airflow resistance (e.g., in asthma).

Surface Tension (Alveolar)

Attractive force of the water film lining alveoli; counteracted by surfactant to keep sacs open.

Central Chemoreceptor

Brainstem receptor detecting pH changes in cerebrospinal fluid to adjust breathing rate.

Peripheral Chemoreceptor

Receptor in carotid and aortic bodies sensing blood O₂, CO₂, and pH to influence ventilation.

Stretch Receptor

Pulmonary receptor that signals lung inflation to modulate breathing depth.

Irritant Receptor

Airway receptor that triggers protective reflexes (e.g., coughing) when stimulated by dust or smoke.

Ventilation–Perfusion Coupling

Matching of airflow (ventilation) to blood flow (perfusion) in the lungs for optimal gas exchange.

Hemoglobin

Iron-containing protein in red blood cells that binds and transports O₂ (and some CO₂).

Oxyhemoglobin Dissociation Curve

Graph showing the percentage saturation of hemoglobin with O₂ at varying partial pressures.

Carbon Dioxide Loading

Movement of CO₂ from tissues into blood for transport to the lungs.

Bicarbonate Ion (HCO₃⁻)

Form in which most CO₂ is carried in blood after combining with water; part of the carbonic acid–bicarbonate buffer.

Acidosis

Condition in which blood pH falls below 7.35, often corrected by increased ventilation.

Hyperventilation

Ventilation that exceeds metabolic needs, lowering CO₂ levels and potentially raising blood pH.