Fundamentals of Anatomy and Physiology

Nutrition and the Digestive System 377

Oral cavity Salivary glands

Pharynx

Esophagus

Liver^
Stomach^
Gallbladder

Pancreas

Large

intestine

Small intestine^
Appendix

Rectum^
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Figure 16- 1 The gastrointestinal tract, or alimentary canal, and its accessory organs.

tremendously increase the digestive and absorptive

area of the small intestine.^

2. The tunica submucosa consists of loose connective
   tissue that binds the tunica mucosa to the next layer,
   the tunica muscularis.^


3. The tunica muscularis of the mouth, pharynx, and
   the first part of the esophagus consists of skeletal
   muscle that allows the voluntary act of swallowing.
   The rest of the tract consists of smooth muscle: an
   inner circular layer and an outer longitudinal layer of
   fibers. Involuntary contractions of these smooth
   muscle fibers break down food physically, mix it
   with the digestive secretions that break down food
   chemically, and propel the food through the ca-nal.
   The tunica muscularis also contains the major nerve
   supply to the alimentary canal, the plexus of
   Auerbach.
   4.^ The tunica serosa^ is the outermost layer. It consists^
   of serous membrane made up of connective and ep-
   ithelial tissue. It is also known as the visceral perito-
   neum (VISS-er-al pair-ih-TOH-nee-um). This layer
   covers organs and has large folds that weave in and
   between the organs, thus binding the organs to each
   other and to the walls of the cavity. This layer also
   contains blood vessels, lymph vessels, and nerves^
   that supply the organs. One extension of the visceral
   peritoneum forms the mesentery (MEZ-in-tehr-ee).

The Mouth or Oral Cavity

The mouth or oral cavity can also be called the buccal

(BUCK-ull) cavity. Its sides are formed by the cheeks. The

roof consists of the hard and soft palates, and its floor is

formed by the tongue. The lips are fleshy folds that