Respiratory System – Key Vocabulary

A comprehensive set of vocabulary flashcards covering anatomy, physiology, gas laws, mechanics, transport, regulation, and common diseases of the respiratory system.

Respiratory system

Body system whose major function is to supply the body with O₂ and dispose of CO₂; also involved in smell and speech.

Pulmonary ventilation

Breathing; movement of air into (inspiration) and out of (expiration) the lungs.

External respiration

Gas exchange between the lungs and the blood; O₂ diffuses into blood, CO₂ diffuses into alveoli.

Transport of respiratory gases

Delivery of O₂ from lungs to tissues and CO₂ from tissues to lungs via blood and cardiovascular system.

Internal respiration

Gas exchange between systemic blood and tissue cells; O₂ moves into tissues, CO₂ moves into blood.

Nose

Only externally visible respiratory organ; warms, moistens, filters air, resonates speech, houses olfactory receptors.

Paranasal sinuses

Air-filled cavities in frontal, sphenoid, ethmoid, and maxillary bones that lighten skull and help warm and moisten air.

Pharynx

Throat; connects nasal cavity and mouth to larynx and esophagus; divided into nasopharynx, oropharynx, and laryngopharynx.

Larynx

Voice box; provides open airway, routes air and food, houses vocal folds for voice production.

Trachea

Windpipe; flexible tube with C-shaped cartilage rings that conduct air from larynx to main bronchi.

Bronchi

Air passages branching from trachea; include main, lobar, and segmental branches.

Bronchioles

Airways <1 mm in diameter; lack cartilage, have smooth muscle that regulates airflow resistance.

Alveoli

Microscopic air sacs; primary sites of gas exchange; clustered in alveolar sacs.

Respiratory zone

Microscopic structures—respiratory bronchioles, alveolar ducts, and alveoli—where gas exchange occurs.

Conducting zone

All respiratory passageways from nose to terminal bronchioles that cleanse, warm, and humidify incoming air.

Type I alveolar cell

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

Type II alveolar cell

Cuboidal cell that secretes surfactant and antimicrobial proteins.

Surfactant

Detergent-like secretion that reduces alveolar surface tension, preventing collapse.

Respiratory membrane

0.5 µm barrier composed of alveolar epithelium, fused basement membranes, and capillary endothelium where diffusion occurs.

Pleurae

Serous membranes of the lungs; parietal pleura lines thoracic wall, visceral pleura covers lung surface.

Parietal pleura

Outer pleural layer lining thoracic cavity, diaphragm, and mediastinum.

Visceral pleura

Inner pleural layer covering lungs and dipping into fissures.

Intrapulmonary pressure (Ppul)

Pressure within alveoli; equalizes with atmospheric pressure between breaths.

Intrapleural pressure (Pip)

Pressure in pleural cavity; about 4 mm Hg less than Ppul, forming partial vacuum.

Transpulmonary pressure

Difference between Ppul and Pip; keeps lungs from collapsing.

Boyle’s Law

At constant temperature, pressure of a gas varies inversely with its volume (P × V = constant).

Tidal volume (TV)

Amount of air inhaled or exhaled with each quiet breath (~500 mL).

Inspiratory reserve volume (IRV)

Air that can be forcibly inhaled after a normal inspiration (≈2100–3200 mL).

Expiratory reserve volume (ERV)

Air that can be forcibly exhaled after a normal expiration (≈1000–1200 mL).

Residual volume (RV)

Air remaining in lungs after maximal expiration (~1200 mL); prevents collapse.

Vital capacity (VC)

Total exchangeable air; VC = TV + IRV + ERV.

Total lung capacity (TLC)

Sum of all lung volumes; TLC = VC + RV (~6000 mL in males).

Dead space

Volume of inspired air that does not participate in gas exchange; anatomical plus any alveolar dead space.

Spirometry

Clinical test measuring lung volumes and capacities to assess pulmonary function.

Dalton’s Law

Total pressure of a gas mixture equals the sum of the partial pressures of each component gas.

Henry’s Law

Amount of gas dissolved in a liquid is proportional to its partial pressure and solubility.

Oxyhemoglobin (HbO₂)

Hemoglobin bound to oxygen; fully saturated when four O₂ molecules are attached.

Bohr effect

Decrease in hemoglobin’s O₂ affinity caused by increased CO₂, H⁺, or temperature, enhancing O₂ unloading.

Haldane effect

Lower O₂ saturation increases hemoglobin’s ability to carry CO₂ and H⁺, facilitating CO₂ transport.

Carbaminohemoglobin

Compound formed when CO₂ binds to globin’s amino acids in hemoglobin.

Bicarbonate ion (HCO₃⁻)

Major form (≈70%) in which CO₂ is transported in blood plasma.

Chloride shift

Exchange of Cl⁻ for HCO₃⁻ across RBC membrane during CO₂ transport.

Hypercapnia

Elevated arterial PCO₂; strongest stimulus for increased ventilation.

Hypoxia

Inadequate O₂ delivery to tissues; causes include anemia, ischemia, or CO poisoning.

Hyperventilation

Ventilation exceeding metabolic needs, leading to low CO₂ (hypocapnia) and alkalosis.

Hyperpnea

Increased ventilation in response to metabolic demands, as during exercise; blood gases remain stable.

Ventilation–perfusion coupling

Automatic matching of alveolar airflow with pulmonary capillary blood flow via local controls.

Bronchopulmonary segment

Pyramid-shaped lung portion served by its own artery, vein, and segmental bronchus; surgically resectable.

Ventral respiratory group (VRG)

Medullary neural network generating basic breathing rhythm and integrating input.

Central chemoreceptor

Brain-stem receptor monitoring H⁺ derived from CO₂ in cerebrospinal fluid to regulate ventilation.

Peripheral chemoreceptor

Receptor in carotid and aortic bodies sensitive to arterial O₂, CO₂, and pH.

Inflation (Hering–Breuer) reflex

Protective reflex that inhibits inspiration when lungs are overstretched.

Compliance (lung)

Measure of lung distensibility; change in lung volume per change in transpulmonary pressure.

Airway resistance

Friction in air passages; greatest in medium bronchi, negligible in terminal bronchioles.

Surface tension (alveolar)

Attractive force of liquid film in alveoli; reduced by surfactant to ease expansion.

Infant respiratory distress syndrome (IRDS)

Premature newborn condition caused by insufficient surfactant leading to alveolar collapse.

Valsalva maneuver

Forced expiration against a closed glottis, increasing intra-abdominal pressure for defecation or lifting.

Carina

Keel-shaped cartilage at tracheal bifurcation; contact triggers violent cough reflex.

Epiglottis

Elastic cartilage flap that closes laryngeal inlet during swallowing, guarding the airways.

Glottis

Opening between vocal folds through which air passes in the larynx.

Diaphragm

Primary inspiratory muscle; contraction increases thoracic height to draw air in.

External intercostal muscles

Inspiratory muscles that elevate ribs and sternum, expanding thorax laterally and anteriorly.

COPD (Chronic Obstructive Pulmonary Disease)

Irreversible airflow obstruction, usually from emphysema or chronic bronchitis; linked to smoking.

Emphysema

COPD subtype with permanent enlargement of alveoli, loss of elasticity, and air trapping.

Chronic bronchitis

COPD subtype with chronic mucus hypersecretion and inflamed, fibrosed lower airways.

Asthma

Reversible obstructive disease with airway inflammation, bronchospasm, and episodic wheezing.

Tuberculosis (TB)

Mycobacterium tuberculosis infection forming lung tubercles; reactivates when immunity wanes.

Lung cancer

Leading cancer killer; strongly associated with smoking; includes adenocarcinoma, squamous cell carcinoma, and small-cell carcinoma.

Sleep apnea

Sleep disorder with temporary breathing cessation; may be obstructive (airway collapse) or central (reduces respiratory drive).