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Ch 44 Respiration
Overview of Animal Respiratory Organs, one thing
common to all respiratory organs is that their surfaces moist be wet. Skin or body walls (see fig. 44.1) are
adequate respiratory surfaces from many small animals that live in moist
or aquatic environments. Examples
include many invertebrates (earthworms, flatworms, hydra) and even a few
vertebrates (lungless salamanders). Tracheal System of Insects (see fig. 44.3) –
a system of branching windpipes (tracheae) delivers air directly to the
body tissues. These windpipes
open external to the body at special structures called spiracles. Gills – respiratory tissues extended from
the body, that is they are projections from the body, exposed to some
degree. Bony fish protect
their gills with covers (lids) called opercula (operculum, sing.). Lungs – contain internal air chambers called alveoli (one is an alveolus, each of your lungs has thousands). The air chambers must be ventilated to remove stale air. Ventilation in mammals occurs by expansion and contraction of the thoracic cavity. When our rib cage is lifted up and our diaphragm contracts downward the thoracic cavity is enlarged. Air rushes into the lungs causing them to swell with air thus filling the expanding volume of the thoracic cavity. Stated differently, the diaphragm and rib cage create a sucking action that draws air into the chest. Thus, we use a negative pressure to move air into our lungs. When the rib cage and diaphragm relax they push air out of the lungs. Even when we breathe deeply we leave some stale air behind in the lungs. Birds have evolved a mechanism of ventilation that removes all stale air when they breathe. Fig. 44.5 shows the one-way flow of air through the lungs of a bird. Air sacs and lungs with multiple airways allow air fresh air to enter the lungs at the same time stale air is ventilated. Human Lung Disorders (fig. 44.10) Tuberculosis – tubercles form trapping the
tubercle bacillus. Pneumonia – caused by bacteria or viruses;
alveoli fill with thick fluid Emphysema – caused by long term exposure to
irritants; alveoli burst, create less surface area for gas exchange. Asthma – a type of allergy where airways are
constricted, hard to breath. Bronchitis – airways inflamed due to infection or irritant.
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