This section is from the book "The Human Body: An Elementary Text-Book Of Anatomy, Physiology, And Hygiene", by H. Newell Martin. Also available from Amazon: The Human Body.
We may now return to our immediate subject, the alimentary canal. This is not a simple tube, but presents several dilatations on its course; nor is it a comparatively straight tube, as dia-grammatically represented in Fig. 1, but, being much longer than the regions of the body which it traverses, much of it is packed away by being coiled up in the abdominal cavity.
The mouth-opening leads into a chamber containing the teeth and tongue, and named the mouth-chamber or buccal cavity. This primary dilatation is separated by a constriction (the isthmus of the fauces) at the back of the mouth, from another, the pharynx or throat chamber, which narrows again at the top of the neck into the gullet or aesophagus, which runs as a comparatively narrow tube through the thorax, and then, passing through the diaphragm, dilates in the upper part of the abdominal cavity to form the stomach (see Fig. 1). Beyond the stomach the channel again narrows to form a long and greatly coiled tube, the small intestine, which terminates by opening into the large intestine, which, though shorter is wider, and ends by opening on the exterior.
A compound? How does it happen that the secretion is sometimes poured out at a distance from the main mass of the gland?
Describe a fully developed gland. How is it that glands make such different secretions? On what does the nature of the secretion of a gland depend?
How does the alimentary canal differ from a simple uniform tube? Why is a great part of it coiled?
Into what does the opening between the lips lead?