Respiration & Gas Exchange (Vocabulary)

Vocabulary flashcards covering key terms from the respiration and gas exchange notes.

Respiration

The process of exchanging O2 and CO2 between the external environment and body tissues, including ventilation, diffusion, transport, and cellular respiration.

Diffusion

Movement of molecules from higher to lower concentration or partial pressure across a membrane, enabling gas exchange.

Partial pressure

The pressure contributed by a single gas within a mixture; determines the direction of diffusion.

Alveolus

An air sac in the lung where gas exchange with surrounding capillaries occurs.

Alveolar-capillary membrane

The thin barrier formed by alveolar epithelium and capillary endothelium through which gases diffuse.

Haemoglobin

Iron-containing protein in red blood cells that binds and transports O2 and CO2; consists of four subunits.

Oxyhaemoglobin (HbO2)

Haemoglobin bound to oxygen.

Carbaminohaemoglobin (HbCO2)

Haemoglobin bound to carbon dioxide.

Oxygen dissociation curve

Sigmoid relation between PO2 and haemoglobin saturation; shifts with pH, CO2, and temperature.

Bohr effect

Increased CO2 and H+ reduce Hb's affinity for O2, aiding O2 release in tissues.

Chloride shift (Hamburger shift)

Exchange of Cl- into red blood cells for bicarbonate moving out, balancing charge during CO2 transport.

Carbonic anhydrase

Enzyme that converts CO2 and water to carbonic acid, then bicarbonate in red blood cells.

Diffusion distance / diffusion membrane thickness

Thinner membranes allow faster gas diffusion.

Pulmonary ventilation

Movement of air into and out of the lungs (inspiration and expiration).

Tidal volume (TV)

Volume of air moved per breath (~500 mL) during normal breathing.

Inspiratory Reserve Volume (IRV)

Extra air that can be inhaled after a normal inspiration (≈2500–3000 mL).

Expiratory Reserve Volume (ERV)

Extra air that can be exhaled after a normal expiration (≈1000–1100 mL).

Residual Volume (RV)

Air remaining in the lungs after maximal expiration (≈1100–1200 mL).

Vital capacity (VC)

Maximum air expelled after a maximum inhalation (IRV + TV + ERV).

Functional Residual Capacity (FRC)

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

Total Lung Capacity (TLC)

Total volume of air in the lungs after a maximum inspiration (RV + ERV + TV + IRV).

Diaphragm

Primary muscle of respiration; its contraction increases thoracic volume during inspiration.

External intercostal muscles

Muscles between ribs that assist inspiration by elevating the rib cage.

Internal intercostal muscles

Muscles mainly involved in forced expiration by depressing the rib cage.

Nasal turbinates

Bony projections in the nasal cavity that filter, warm, and humidify air.

Epiglottis

Flap that prevents food from entering the trachea during swallowing.

Trachea

Windpipe; reinforced with C-shaped cartilage rings; conducts air to the bronchi.

Primary bronchi

Two main airways branching from the trachea; right bronchus is wider and more vertical.

Alveolar ducts

Passages leading to alveoli where gas exchange occurs.

Alveoli

Tiny air sacs where gas exchange between air and blood occurs.

Pleura

Membranes surrounding the lungs (visceral and parietal) with pleural fluid in between.

Double circulation

Circulation involving the pulmonary (to lungs) and systemic (to body) circuits.

Pulmonary vein

Vein carrying oxygenated blood from the lungs to the left atrium.

Pulmonary artery

Artery carrying deoxygenated blood from the heart to the lungs.

Oxygen saturation

Percentage of haemoglobin binding sites occupied by O2.

Oxygen carrying capacity

Maximum amount of O2 blood can carry, determined by Hb concentration and affinity.

Carbon dioxide transport

CO2 is carried in blood as bicarbonate, bound to haemoglobin, or dissolved in plasma.

Central chemoreceptors

Chemoreceptors in the brainstem (medulla/pons) that respond to pH changes due to CO2.

Peripheral chemoreceptors

Chemoreceptors in carotid and aortic bodies responding to O2, CO2, and pH.

Asthma

Allergic respiratory disorder with inflammation, bronchoconstriction, and wheeze.

Emphysema

Lung disease with destruction of alveolar walls, reducing surface area for diffusion.

Silicosis

Pneumoconiosis caused by inhalation of silica dust.

Asbestosis

Pneumoconiosis caused by asbestos exposure, causing fibrosis.

Pneumoconiosis

Lung disease caused by inhalation of inorganic dust (e.g., silica, asbestos).