DIGESTIVE SYSTEM Copyright 2009 Pearson Education Inc publishing

DIGESTIVE SYSTEM Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Peritoneum: Membrane of the abdominal cavity § Parietal Peritoneum covers the abdominal wall § Visceral Peritoneum covers the inner organs Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Branching from the peritoneum: § Lesser omentum—attaches the liver to the lesser curvature of stomach § Greater omentum: (Apron) Contains fat to insulate, cushion, and protect abdominal organs Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

The Digestive System Functions § Ingestion—taking in food § Digestion—breaking food down both physically and/or chemically § Absorption—movement of nutrients into the bloodstream § Defecation—rids the body of indigestible waste Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Organs of the Digestive System § Two main groups of organs § Alimentary canal (gastrointestinal or GI tract) —continuous coiled hollow tube from mouth to anus § Accessory digestive organs (aid in digestion but food does not pass through) Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Layers of Alimentary Canal Organs § Four layers § Mucosa § Submucosa § Muscularis externa § Serosa Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Layers of Alimentary Canal Organs § Mucosa § Innermost, moist membrane , smooth muscle layer § Submucosa § Just beneath the mucosa, contains blood vessels and nerve endings § Muscularis externa—smooth muscle § Inner circular layer and outer longitudinal layer § Serosa—outer membrane Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Organs of the Alimentary Canal § Mouth § Pharynx § Esophagus § Stomach § Small intestine § Large intestine § Anus Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Mouth (Oral Cavity) Anatomy § Lips (labia)—protect the anterior opening § Cheeks—form the lateral walls § Hard palate—forms the anterior roof § Soft palate—forms the posterior roof § Uvula—fleshy projection of the soft palate Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Mouth Physiology § Ingestion § Mastication (chewing) of food § Mixing masticated food with saliva § Initiation of swallowing by the tongue § Allows for the sense of taste § Enzymes from salivary glands are secreted here § Digestion begins here Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Pharynx Anatomy (REVIEW) § Nasopharynx—not part of the digestive system § Oropharynx—posterior to oral cavity § Laryngopharynx—below the oropharynx and connected to the esophagus Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Pharynx Physiology § Serves as a passageway for air and food § Food is propelled to the esophagus by two muscle layers § Longitudinal inner layer § Circular outer layer § Food movement is by alternating contractions of the muscle layers (peristalsis) http: //www. westga. edu/~lkral/peristalsis/index. html Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Esophagus Anatomy and Physiology § Anatomy § About 10 inches long § Runs from pharynx to stomach through the diaphragm § Physiology § Conducts food by peristalsis (slow rhythmic squeezing) § Passageway for food only (respiratory system branches off after the pharynx) Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Stomach Anatomy § Located on the left side of the abdominal cavity § Food enters at the cardioesophageal sphincter § Contain Rugae—internal folds of the mucosa § Food empties into the small intestine at the pyloric sphincter (valve) Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Stomach Physiology § Temporary storage tank for food § Enzymes released here § Digestion occurs here § Hydrochloric Acid produced here § Delivers chyme (processed food) to the small intestine Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Subdivisions of the Small Intestine § Duodenum § Attached directly to the stomach 6 and 7 m long 19 -25 ft § Jejunum § Attaches anteriorly to the duodenum § Ileum § End portion of the small intestine extends from jejunum to large intestine Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Small Intestine Anatomy § Structural modifications that increase surface area § Microvilli—tiny projections of the plasma membrane (create a brush border appearance) § Villi—fingerlike structures formed by the mucosa § Circular folds (plicae circulares)—deep folds of mucosa and submucosa Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Small Intestine Anatomy Figure 14. 7 b Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine 5 ft long or 1. 5 m § No digestion here § Absorption occurs here § Larger in diameter, but shorter in length, than the small intestine § Frames the internal abdomen Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine Anatomy § Cecum—saclike first part of the large intestine § Appendix § Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) § Hangs from the cecum § Nursery for important digestive bacteria Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine Anatomy § No villi present § Goblet cells produce alkaline mucus which lubricates the passage of feces § Muscularis externa layer is reduced to three bands of muscle called teniae coli § These bands cause the wall to pucker into haustra (pocketlike sacs) § Bacteria produce Vitamins Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine Anatomy § Colon § Ascending—travels up right side of abdomen § Transverse—travels across the abdominal cavity § Descending—travels down the left side § Sigmoid—enters the pelvis § Rectum and anal canal— also in pelvis Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings

Large Intestine Anatomy § Anus—opening of the large intestine § Double sphincter § These sphincters are normally closed except during defecation Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings