Breathing and Gas Exchange Lecture (02–25.06.2025)

Vocabulary flashcards summarizing key terms and definitions related to respiration, lungs, gas transport, regulation, and disorders from the lecture notes.

Respiration (biochemical)

The oxidation of organic food in the presence of O₂ to release ATP and CO₂.

Amphibolic process

A metabolic pathway that is both catabolic and anabolic, such as respiration.

ATP

The energy currency produced during cellular respiration.

CO₂ and body pH

An increase in CO₂ lowers blood pH, affecting cellular function.

Diffusion

Passive movement of gases from high to low partial pressure across respiratory surfaces.

Poriferan respiration

Gas exchange by simple diffusion across the body surface in sponges.

Tracheal system

Air-filled tubes for gas exchange in insects and some arthropods.

Book lungs

Stacked, leaf-like respiratory organs in spiders and scorpions.

Book gills

Respiratory organs in horseshoe crabs (Limulus) used in water.

Cutaneous respiration

Gas exchange through moist skin, seen in earthworms and adult amphibians.

Pulmonary respiration

Gas exchange via lungs, typical of reptiles, birds, and mammals.

Upper respiratory part

Nostrils to larynx; conducts, filters, humidifies, and warms air.

Lower respiratory part

Trachea to alveoli; includes conducting and respiratory portions.

Conducting zone

Airways where no gaseous exchange occurs; ends at terminal bronchioles.

Respiratory zone

Portion of lungs where diffusion occurs (respiratory bronchioles to alveoli).

Larynx

Voice box composed of nine cartilages; involved in sound production.

Epiglottis

Leaf-shaped cartilage that prevents food from entering the trachea.

Thyroid cartilage

Largest laryngeal cartilage; forms the Adam’s apple.

Cricoid cartilage

Ring-shaped cartilage below the thyroid cartilage in the larynx.

Trachea

Windpipe with C-shaped hyaline cartilage rings preventing collapse.

Bronchi

Primary branches of trachea that enter the lungs at the 5th thoracic vertebra.

Pleura

Double membrane surrounding lungs; visceral (inner) and parietal (outer).

Pleural fluid

Lubricant between pleural layers that reduces friction during breathing.

Right lung lobes

Three lobes: superior, middle, and inferior, separated by horizontal and oblique fissures.

Left lung lobes

Two lobes: superior and inferior; contains the cardiac notch.

Lecithin (surfactant)

Phospholipid from Type II cells that lowers surface tension in alveoli.

Type I pneumocyte

Simple squamous alveolar cell specialized for gas diffusion.

Type II pneumocyte

Alveolar cell that secretes pulmonary surfactant.

Dust cell

Alveolar macrophage that engulfs debris and microbes.

Negative-pressure lungs

Lungs where inspiration occurs by creating pressure below atmospheric levels.

Diaphragm

Primary muscle of quiet inspiration; contracts to enlarge thoracic cavity.

External intercostals

Muscles that lift ribs outward during inspiration.

Internal intercostals

Muscles that aid forced expiration by pulling ribs inward.

Tidal Volume (TV)

Air inhaled or exhaled in a normal breath (~500 mL).

Inspiratory Reserve Volume (IRV)

Extra air that can be inhaled after a normal inspiration (≈2.5–3 L).

Expiratory Reserve Volume (ERV)

Extra air that can be exhaled after a normal expiration (≈1–1.1 L).

Residual Volume (RV)

Air remaining in lungs after maximum exhalation (~1.1–1.2 L).

Vital Capacity (VC)

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

Total Lung Capacity (TLC)

Total volume in lungs after maximal inspiration (VC + RV).

Functional Residual Capacity (FRC)

Air left in lungs after normal expiration (ERV + RV).

Alveolar Ventilation Rate (AVR)

Volume of air participating in gas exchange per minute (≈350 mL × breaths/min).

Dead-space volume

Air that fills conducting zone (~150 mL) and does not participate in exchange.

Partial pressure (P)

Pressure exerted by an individual gas in a mixture; drives diffusion.

Bohr effect

Rise in CO₂ or H⁺ shifts O₂-Hb curve right, promoting O₂ release at tissues.

Oxyhaemoglobin

Unstable complex of O₂ bound to haemoglobin (HbO₂).

O₂-Hb dissociation curve

Sigmoid graph showing Hb saturation at different PO₂ values.

Carbaminohaemoglobin

Complex of CO₂ bound to haemoglobin (~20–25 % of transported CO₂).

Bicarbonate transport

Major form (≈70 %) of CO₂ carried as HCO₃⁻ in plasma.

Carbonic anhydrase (CA)

Enzyme in RBCs catalyzing CO₂ + H₂O ⇌ H₂CO₃.

Chloride shift (Hamburger phenomenon)

Exchange of Cl⁻ and HCO₃⁻ between plasma and RBCs to maintain charge balance.

Haldane effect

Oxygenation of blood facilitates release of CO₂ from Hb at alveoli.

Medullary rhythm centre

Neuronal group in medulla that initiates inspiration and expiration rhythm.

Pneumotaxic centre

Centre in pons sending inhibitory signals to limit inspiration depth.

Chemoreceptors

Sensors in medulla, aortic and carotid bodies that detect pCO₂ and pH.

Asthma

Allergic inflammation of bronchi/bronchioles causing wheezing and dyspnoea.

Emphysema

Chronic lung disorder with destruction of alveolar walls, reducing surface area; linked to smoking.

Pneumoconiosis

Occupational lung disease from inhaling dust (e.g., silicosis, asbestosis).