What the tradition says. Yoga and Ayurveda describe prana, the life-breath, moving in five ways, the pancha vayu: prana draws in at the chest and head; apana moves down and out from the pelvis (elimination, menstruation, birth); samana gathers at the navel and digests; udana rises at the throat (speech and effort, and in the tradition it carries awareness up at death); vyana pervades the whole body, moving outward. Tamil Siddha counts ten vayus, these five and five minor ones. The winds travel in nadis, 72,000 of them in the Hatha Yoga Pradipika. Three matter most: ida (left, cooling, lunar), pingala (right, heating, solar) and sushumna, the central channel along the spine, which the tradition says flows when the two sides are even. This is the tradition's model, drawn as the tradition draws it; vyana has no single seat and is placed mid-column only for the drawing. The wind colours are this figure's choice, since the tradition gives no single scheme; the nadi colours follow its moon (ida, silver-blue) and sun (pingala, red-gold) association, with sushumna gold.

What anatomy shows. Breathing is driven by the diaphragm, a dome that flattens downward as it contracts, and by the intercostal muscles between the ribs. At rest an adult breathes about 12–20 times a minute and moves about 500 mL each breath (the tidal volume); the figure runs at 12. The nasal cycle is real: in most people congestion shifts slowly between the left and right nostril over a few hours, a physical echo of ida and pingala taking turns (the figure compresses hours into seconds). Breathing out slowly raises vagal (parasympathetic) tone, and the heart slows a little on each exhale (respiratory sinus arrhythmia), a real basis for breath practice calming the body. Reading ida as parasympathetic and pingala as sympathetic is a modern reading, not an equivalence. No channels called nadis or vayus have been found in the body; nadi is a model of practice, which is why the chambers and side tubes go dim and their colours drain to grey.