PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 22 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Digestive System PART 1

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Overview of the Digestive System  Organs are divided into two groups  Alimentary canal  Mouth, pharynx, and esophagus  Stomach, small intestine, and large intestine  Accessory digestive organs  Teeth and tongue  Gallbladder, salivary glands, liver, and pancreas

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.1 The Alimentary Canal and Accessory Digestive Organs

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes  Ingestion – occurs in the mouth  Propulsion – movement of food  Peristalsis – major means of propulsion  Mechanical digestion – prepares food for chemical digestion  Chewing, churning of food in stomach, segmentation  Segmentation is rhythmic local constrictions of intestine

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes  Chemical digestion – complex molecules broken down to chemical components  Mouth  Stomach  Small intestine  Absorption – transport of digested nutrients  Defecation – elimination of indigestible substances as feces

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Processes Figure 22.2

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Peristalsis  Major means of propulsion  Adjacent segments of the alimentary canal relax and contract Figure 22.3a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Segmentation  Rhythmic local contractions of the intestine  Mixes food with digestive juices Figure 22.3b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nine Regions of Anterior Abdominal Surface Figure 22.4a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nine Regions of Anterior Abdominal Surface  How regions relate to abdominal viscera Figure 22.4b Spleen Pancreas deep to stomach R. Colic or hepatic flexure L colic (splenic)flexure

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Abdominal Quadrants  A simpler scheme defining four quadrants Figure 22.4c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Wall  The muscularis externa – external to the submucosa  Two layers  Circular muscularis – inner layer  Longitudinal muscularis – outer layer  The serosa – the outermost layer  Is the visceral peritoneum

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Histology of the Alimentary Canal Figure 22.5

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle  Primarily found in walls of viscera  Fibers elongated  Have one centrally-located nucleus  Grouped into sheets  Longitudinal layer – parallel to long axis of organ  Circular layer – deeper layer, fibers run around circumference of organ

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Figure 22.6a, b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Smooth Muscle Contraction  Myofilaments operate by interaction with cytoskeleton  Dense bodies – correspond to Z- discs of skeletal muscle Figure 22.7a–c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle  Innervated by ANS  Few fibers per sheet innervated  Sheet of smooth muscle contracts as a unit

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation of Smooth Muscle Figure 22.8

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Plexuses  Myenteric nerve plexus  Lies between circular and longitudinal muscularis  Controls peristalsis and segmentation  Submucosal nerve plexus  Lies in submucosa  Signals glands to secrete  Innervation  Sympathetic and parasympathetic motor fibers  Visceral sensory fibers

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Peritoneal Cavity and Peritoneum  Peritoneum – a serous membrane  Visceral peritoneum – surrounds digestive organs  Parietal peritoneum – lines the body wall  Peritoneal cavity – a slit-like potential space

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Peritoneal Cavity and Peritoneum  Mesentery – a double layer of peritoneum  Holds organs in place  Sites of fat storage  Provides a route for circulatory vessels and nerves Figure 22.9a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 22.9b The Peritoneal Cavity and Peritoneum  Retroperitoneal organs  Behind the peritoneum  Peritoneal organs  Digestive organs that keep their mesentery

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Superficial view of abdominal organs Figure 22.10a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Lesser omentum attaches to lesser curvature of stomach Figure 22.10b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Greater omentum – a “fatty apron” of peritoneum-attaches to the greater curvature and the porta hepatis of the liver  Greater omentum and transverse colon reflected Figure 22.10c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings  The lesser omentum extends between the A)greater curvature of the stomach and the posterior abdominal wall.  B)sigmoid colon and the posterior pelvic wall.  C)transverse colon and the posterior abdominal wall.  D)lesser curvature of the stomach and the porta hepatis of the liver.

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Mesenteries  Sagittal section through the abdominopelvic cavity  Mesenteries attach to posterior abdominal wall Figure 22.10d

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Summary of Intraperitoneal and Secondarily Retroperitoneal Organs Table 22.1