Fish have sacs {air bladder}| that hold air for buoyancy.
Animals with tracheal respiratory systems have exoskeleton breathing pores {spiracle}|.
Air enters nose openings {external nares} {nostril}|.
After nostrils, air goes to open regions {nasal chamber} for smell and then goes to pharynx.
Above larynx, oral tract and nasal tract {vocal tract, throat}| produce speech.
Over larynx is a tissue flap {epiglottis}|.
Epiglottis has two epithelium folds {vocal cord}|, controlled by muscles that can vibrate air from 60 Hz to 350 Hz.
Birds can have thin muscles {syrinx}| that form vocal organ where trachea become bronchi.
Vocal cords are in upper middle larynx {glottis}|.
Air goes to throat {larynx}|. Larynx is behind adam's apple. In infants and vertebrates, flat tongue and high larynx allow simultaneous drinking and breathing, but adult humans have low larynx and downward curving tongue to make a sound chamber and allow non-nasal sounds. Early Homo sapiens [-400000] had tongue and larynx like modern people. Homo erectus had arching in larynx [-2000000], but Australopithecus had no arching and so only nasal sounds.
Larynx is behind cartilage {adam's apple}| at neck front.
Lung cavity {lung}| is closed chamber, at same pressure as air pressure.
Air goes to a tube {trachea, lung} {windpipe}| to lungs.
Windpipe branches into two tubes {bronchus}| {bronchi}, at first-rib level. Bronchi have smooth muscle and cilia, which send foreign particles back toward larynx. In response to irritation or stress, asthma can cause smooth muscle to contract uncontrollably.
Bronchi branch many times and end in open regions {air sac, lung}.
Air sacs have cavities {alveoli}| {alveolus} that have moist mucus walls surrounded by capillaries, which allow gas diffusion into and out of blood. They have air that is higher in carbon dioxide, lower in oxygen, warmer, and more humid, than outside air. Elastic connective tissue surrounds alveoli to aid contraction.
lung cavity and lung lining {pleura, lung}|.
When lung muscles {diaphragm, lung}| contract and rib muscles relax, air cavity expands, pressure lowers, and lungs draw in air for inhalation.
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Date Modified: 2022.0225