The cradle system consists of the digestive tract—oral cavity, esophagus, stomach, small and big intestines, and also anus—and its connected glands—salivary glands, liver, and also pancreas (Figure 15–1). Additionally called the gastrointestinal (GI) tract or alimentary canal, its function is to achieve from ingested food the molecules necessary for the maintenance, growth, and also energy needs of the body. Throughout digestion proteins, complex carbohydrates, main point acids, and fats are damaged down into their small molecule subunits that space easily absorbed through the little intestine lining. Most water and also electrolytes are absorbed in the large intestine. In addition, the inner great of the whole digestive street forms critical protective obstacle between the content of the tract’s lumen and also the internal milieu the the body connective tissue and vasculature.

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The cradle system is composed of the tract from the mouth (oral cavity) to the anus, as well as the digestive glands emptying into this tract, generally the outstanding glands, liver, and pancreas. These accessory digestive glands are described in chapter 16.


Structures in ~ the cradle tract allow the following:


Ingestion, or arrival of food and liquid into the dental cavity,

Mastication, or chewing, i m sorry divides solid food right into digestible pieces,

Motility, muscular movements of materials through the tract,

Secretion that lubricating and also protective mucus, cradle enzymes, acidic and also alkaline fluids, and bile,

Hormone release because that local regulate of motility and also secretion,

Chemical digestion or enzymatic deterioration of huge macromolecules in food to smaller sized molecules and their subunits,

Absorption the the tiny molecules and also water right into the blood and also lymph,

Elimination of indigestible, unabsorbed contents of food.

All areas of the GI tract have specific structural features in common. The GI street is a hollow tube through a lumen of change diameter and also a wall made increase of four main layers: the mucosa, submucosa, muscularis, and also serosa. Number 15–2 mirrors a basic overview that these four layers; vital features of every layer space summarized here.



Diagram mirroring the structure of the tiny intestine part of the cradle tract, with the 4 main layers and their major components noted on the left. The stomach, little intestine, and huge intestine space suspended by mesenteries that space the website of nerves, blood vessels and also lymphatics indigenous the stomach and intestines.

The mucosa consists of one epithelial lining; an basic lamina propria of loosened connective tissue well-off in blood vessels, lymphatics, lymphocytes, smooth muscle cells, and often containing tiny glands; and also a slim layer that smooth muscle called the muscularis mucosae separating mucosa indigenous submucosa and also ...

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