. Principles of modern biology. Biology. 304 - Multicellular Animals, Especially Man WAVE OF CONSTRICTION BOLUS OF FOOD WAVE OF RELAXATION t?S& changes. The emptying of the stomach is relatively rapid (about 10 minutes) in the case of a drink of plain water; but some meals may take 3 to 4 hours in passing through the stomach, depending on the qual- ity and quantity of the food. The Size and Shape of the Stomach. The capacity of the stomach varies according to its contents, and during the ingestion of a meal the muscular wall is capable of expand- ing to a maximum capacity of about 3 quarts
. Principles of modern biology. Biology. 304 - Multicellular Animals, Especially Man WAVE OF CONSTRICTION BOLUS OF FOOD WAVE OF RELAXATION t?S& changes. The emptying of the stomach is relatively rapid (about 10 minutes) in the case of a drink of plain water; but some meals may take 3 to 4 hours in passing through the stomach, depending on the qual- ity and quantity of the food. The Size and Shape of the Stomach. The capacity of the stomach varies according to its contents, and during the ingestion of a meal the muscular wall is capable of expand- ing to a maximum capacity of about 3 quarts, in an average individual. Then during the digestion of the meal, the stomach gradually shrinks, as the semidigested food is passed, little by little, into the small intestine. Fin- ally the gastric cavity is practically obliter- ated, whereupon further peristaltic waves, in which the stomach merely squeezes down upon itself, give rise to "hunger pangs," and it is time to eat again. The anatomy of the stomach is best de- scribed in terms of the half-filled organ such as is outlined in Figure 16-19. Such a stom- ach is distinctly J-shaped, and permits one to identify the three main parts of the stomach. (1) The fundus is a small, bulbous, gas-filled chamber, which occupies the vertical limb of the J, above the opening from the esophagus; (2) the cardiac region consists of the re- mainder of the vertical limb; (3) the pyloric Fig. 16-18. Peristalsis in the esopha- gus. Three stages in the downward movement of a semisolid bolus of food are shown. region extends from the "bend of the )" to the point where the stomach joins the duo- denum, or first part of the small intestine. Guarding the entrance and exit channels of the stomach are ringlike bands of muscle: (1) the cardiac valve, which encircles the esophageal opening and prevents a regurgita- tion of food into the esophagus; and (2) the pyloric valve, which prevents food from pass- ing out of the stomach int
Size: 1592px × 1570px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectbiology
