. The animans and man; an elementary textbook of zoology and human physiology. understanding thisstructure in the human body. It is a continuous tube fromthe mouth to the anus. Part of the tube is twisted anddoubled back upon itself, as shown in the figure. Itsentire length, were it stretched out, is about thirty diameter varies at different points, being widest at thestomach. There are outgrowths at different points calledglands that furnish the digestive juices for dissolving andpreparing the food. These glands pour their secretionsinto the various parts of the alimentary canal wher
. The animans and man; an elementary textbook of zoology and human physiology. understanding thisstructure in the human body. It is a continuous tube fromthe mouth to the anus. Part of the tube is twisted anddoubled back upon itself, as shown in the figure. Itsentire length, were it stretched out, is about thirty diameter varies at different points, being widest at thestomach. There are outgrowths at different points calledglands that furnish the digestive juices for dissolving andpreparing the food. These glands pour their secretionsinto the various parts of the alimentary canal where theybecome thoroughly mixed with the food. The alimentary canal is lined with a soft mucous membranelike that within the mouth. Its secreting cells furnishmucous for keeping the inner surface moist. The mouth or buccal cavity.—If we close the lips andfeel around with the tongue we find the mouth bounded on 3°3 3°4 THE ANIMALS AND MAN the front and sides by the lips, the teeth, the gums and tongue (fig. 157) lies on the floor of the mouth. The Salivary Gland. Lerge. tntezfme. Vermiform Appendix -• FIG. 156. Diagram of the alimentary canal. (Modified from Landois.) hard palate and soft palate form the roof of the mouth. Thependant hanging from the soft palate is the uvula. Duringdeglutition or swallowing the uvula closes the inner passage DIGESTION AND ABSORPTION 305 into the nasal cavity which lies above the palate (see fig. 157).The teeth and tongue act mechanically upon the food, masticating it or breaking it up. The teeth are important structures since they initiate the work of digestion. Those that grow in during the first two yearsof life are called milkteeth. They have small-er roots than the per-manent teeth and ap-pear while the jaws aresmall. As the jawsenlarge (during the sixthand seventh years) thesecond set or perma-nent teeth grow in andone by one replace themilk teeth. The perma-nent teeth need muchcare and attention asthey must last
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Keywords: ., bookcentury1900, bookd, booksubjectphysiology, booksubjectzoology
