2. alveolus Cupped, thin-walled outpouching of respiratory bronchiole where lungs and blood exchange O2 and CO2.
3. bronchiole Finely branched airway; part of the bronchial tree inside the lung.
4. bronchus Tubular airway; branches from trachea and leads into lungs.
5. carbamino hemoglobin HbCO2, the form in which 30% of the CO2 in blood is transported.
6. carbonic anhydrase Red blood cell enzyme that converts CO2 to bicarbonate, the form in which 60% of the CO2 in blood is transported.
7. countercurrent flow Movement of two fluids in opposing directions, as in a fish gill.
8. diaphragm Muscular partition between thoracic and abdominal cavities with role in breathing. Also a contraceptive device inserted into the vagina to prevent sperm from entering uterus.
9. epiglottis Flap like structure between pharynx and larynx; its controlled positional changes direct air into trachea or food into esophagus.
10. erythropoietin Hormone secreted by kidney cells; induces stem cells in bone marrow to divide and give rise to red blood cells.
11. Fick's law The larger the surface area and the greater the partial pressure gradient, the faster gases will diffuse across a respiratory surface.
12. gill Respiratory organ. Most gills have a thin, moist, vascularized layer for gas exchange.
13. glottis Opening between two vocal cords.
14. heme group Iron-containing functional group that reversibly binds oxygen; one associated with each of the four chains in hemoglobin.
15. hemoglobin An iron-containing respiratory protein of red blood cells.
16. integumentary exchange Respiration across a thin, moist, and often vascularized surface layer of animal body.
17. larynx Tubular airway leading to lungs. Contains vocal cords in some animals.
18. lung Internal, sac-shaped respiratory surface that originally evolved in oxygen-poor aquatic habitats. A few fishes and amphibians, birds, reptiles, and mammals have paired lungs.
19. myoglobin A pigment with a higher oxygen binding capacity than hemoglobin; abundant in cardiac and skeletal muscle cells that can contract slowly and resist fatiguing.
20. oxyhemoglobin Oxygen bound to hemoglobin (HbO2) inside red blood cells.
21. partial pressure Characteristic of a gas; its contribution to total atmospheric pressure.
22. pharynx A dual entrance to the esophagus and trachea.
23. pressure gradient A difference in pressure between two adjoining regions.
24. respiration For all animals, exchange of environmental oxygen with CO2 from cells
25. respiratory cycle One inhalation, exhalation.
26. respiratory surface Thin, moist epithelium that functions in gas exchange.
27. respiratory system Type of organ system that exchanges gases between the body and the environment and contributes to homeostasis.
28. tidal volume The volume of air flowing into or out of the lungs during the respiratory cycle.
29. trachea An air-conducting tube of respiratory systems. Of land vertebrates, the windpipe through which air passes between the larynx and bronchi.
30. tracheal respiration Of certain invertebrates (e.g., insects), respiration by way of finely branching tubes that start at openings in the integument and dead-end in body tissues.
31. vital capacity Air volume expressed from the lungs in one breath after maximal inhalation.
32. vocal cord Of humans and certain animals, one of the thickened, muscular folds of the larynx that help produce sound waves for vocalization.