Key terms
58 terms- External respiration§47.1
- Ventilation — moving air or water past the respiratory membrane
- Internal respiration§47.1
- Transport of O₂ and CO₂ in blood between respiratory organs and tissues
- Fick's Law of Diffusion§47.1
- R = D·A·Δp/d — rate rises with area and pressure difference, falls with distance
- Diffusion constant (D)§47.1
- Accounts for molecule size, membrane permeability, and temperature
- Gills§47.2
- Tissue extensions projecting into water to increase exchange surface area
- External gills§47.2
- Gills not enclosed by body structures; easily damaged, must be waved constantly
- Branchial chamber§47.2
- Protected chamber that pumps water past stationary gills
- Mantle cavity§47.2
- Mollusk chamber housing gills; water in via inhalant siphon, out via exhalant siphon
- Operculum§47.2
- Gill cover of bony fishes; acts as part of the pumping system
- Ram ventilation§47.2
- Swimming with the mouth ajar to force water over the gills (tuna, remora)
- Gill arch / filament / lamella§47.2
- Three levels of gill structure; lamellae are the actual exchange plates
- Countercurrent flow§47.2
- Blood flowing opposite to water, keeping a positive O₂ gradient the entire length
- Concurrent flow§47.2
- Blood and water in the same direction; both equalize near 50% and diffusion stops
- Neuroepithelial cells§47.2
- Oxygen-sensing chemoreceptors in fish gills
- Cutaneous respiration§47.2
- Gas exchange across moist, highly vascularized skin
- Tracheae / tracheoles§47.2
- Branched cuticle-lined air tubes of arthropods, delivering air straight to cells
- Spiracles§47.2
- Valved exoskeletal openings admitting air to the tracheal system
- Partial pressure§47.3
- The share of total gas pressure contributed by one gas
- Positive pressure breathing§47.3
- Pushing air into the lungs, as amphibians do with the mouth floor
- Negative pressure breathing§47.3
- Expanding the chest so atmospheric pressure pushes air in
- Glottis§47.3
- Opening between the vocal cords into the trachea
- Trachea§47.3
- Windpipe held open by C-shaped cartilage rings
- Bronchi / bronchioles§47.3
- Branching airways delivering air from trachea to alveoli
- Alveoli§47.3
- Grapelike sacs, one cell thick, where all gas exchange occurs; ~300 million per lung
- Parabronchi§47.3
- One-way air vessels of the bird lung where exchange occurs
- Anterior / posterior air sacs§47.3
- Bird structures producing unidirectional flow across two breathing cycles
- Crosscurrent flow§47.3
- Blood at 90° to airflow in the avian lung
- Visceral pleural membrane§47.4
- Thin membrane covering the outside of each lung
- Parietal pleural membrane§47.4
- Membrane lining the inner thoracic wall
- Pleural cavity§47.4
- Fluid-filled space coupling lung to chest wall
- Diaphragm§47.4
- Striated sheet between thorax and abdomen; flattens to inhale
- External intercostal muscles§47.4
- Muscles between ribs that raise the rib cage during inhalation
- Tidal volume§47.4
- Air moved per resting breath, about 500 mL
- Anatomical dead space§47.4
- The ~150 mL in conducting airways where no gas exchange happens
- Inspiratory reserve volume§47.4
- Air that can be inhaled beyond a normal breath
- Expiratory reserve volume§47.4
- Air that can be forced out beyond a normal breath
- Vital capacity§47.4
- Tidal + IRV + ERV; ~4.6 L young men, ~3.1 L young women
- Residual volume§47.4
- Air that can never be exhaled; prevents lung collapse
- Hypoventilation§47.4
- Breathing too little, so blood P_CO₂ rises
- Hyperventilation§47.4
- Breathing beyond metabolic need, so blood P_CO₂ falls
- Respiratory control center§47.4
- Neurons of the medulla oblongata and pons that initiate each breath
- Aortic and carotid bodies§47.4
- Peripheral chemoreceptors sensing falling blood pH
- Central chemoreceptors§47.4
- Brain receptors sensing cerebrospinal fluid pH
- Mountain sickness§47.4
- Headache, nausea, weakness and impaired thinking from low P_O₂ at altitude
- COPD§47.4
- Chronic obstructive pulmonary disease — asthma, chronic bronchitis, emphysema
- Emphysema§47.4
- Alveolar walls break down; fewer, larger alveoli and stiff, fibrotic lungs
- Hemoglobin§47.5
- Four chains (2α, 2β), each with an iron-containing heme; carries up to 4 O₂
- Oxyhemoglobin§47.5
- Hemoglobin loaded with oxygen; bright red
- Deoxyhemoglobin§47.5
- Hemoglobin after unloading oxygen; darker red
- Hemocyanin§47.5
- Copper-based oxygen carrier of mollusks and arthropods, free in the fluid
- Hemerythrin§47.5
- Iron-based oxygen carrier found mainly in several worm phyla
- Myoglobin§47.5
- Single-chain muscle oxygen store with higher affinity than hemoglobin
- Oxyhemoglobin dissociation curve§47.5
- Plot of saturation against P_O₂; shows how much O₂ is unloaded
- Bohr effect§47.5
- Low pH lowers hemoglobin O₂ affinity, shifting the curve right
- Carbonic anhydrase§47.5
- Red blood cell enzyme catalyzing CO₂ + H₂O → H₂CO₃
- Carbaminohemoglobin§47.5
- CO₂ bound to hemoglobin protein (not the iron), so it does not compete with O₂
- Chloride shift§47.5
- One Cl⁻ enters the red blood cell for each HCO₃⁻ that leaves
- Carbon monoxide§47.5
- Binds hemoglobin far more tightly than O₂; poisoning gives bright red skin