Digestive System Lectures

Digestive System Lectures - The Digestive System Lecture 1...

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Unformatted text preview: The Digestive System Lecture 1 Bill Sellers mailto:Bill.Sellers@ed.ac.uk November 30, 1998 Contents 1 Introduction 1 2 Objectives 1 3 General Characteristics 2 4 The Mouth 3 4.1 Teeth . . . . . . . . . . . . . . . 4 4.2 Tongue . . . . . . . . . . . . . . 4 4.3 Swallowing . . . . . . . . . . . . 5 4.4 Salivary Glands . . . . . . . . . . 5 5 Oesophagus 5 6 Stomach 6 7 The Small Intestine 8 7.1 Duodenum . . . . . . . . . . . . . 8 7.2 Jejunum and Ileum . . . . . . . . 8 8 Pancreas 9 9 Liver 10 10 Gall Bladder 10 11 Large Intestine 11 11.1 Caecum . . . . . . . . . . . . . . 11 11.2 Colon . . . . . . . . . . . . . . . 11 11.3 Rectum . . . . . . . . . . . . . . 12 12 Anus 12 13 Portal Circulation 12 1 Introduction The purpose of these lectures is to describe the structures involved in digestion and to relate these structures to their functions. The information I will provide will follow very closely what is given in Hole and Koos, chapter 12, but because my re- search interest is in the interaction of form and function over the last 100 million years or so, I will also try to provide an evolutionary context for some of these observations. 2 Objectives The objectives of these three lectures are as follows (taken straight from the textbook): 1. Name and describe the location of the organs of the digestive system and their major parts. 2. Describe the structure and general function of each digestive organ and the liver. 3. Describe the structure of the wall of the ali- mentary canal. 4. Explain how the contents of the alimentary canal are mixed and moved. 5. Describe the mechanism of swallowing. 1 6. Explain how the products of digestion are ab- sorbed. 3 General Characteristics The major components of the digestive system that we will cover can be seen in figure 1. As you can see, the digestive system in humans is basi- cally a long tube and associated glandular struc- tures. Food is ingested cranially and processed in- crementally as it passes caudally. This processing is both mechanical and chemical, leading to the ab- sorption of some of the chemical components of the food items whilst other, indigestible compo- nents are passed straight through. You will proba- bly already be familiar with the basic structure and the location of the major components, but we will cover each organ in detail. The muscular tube through which the food passes is called the alimentary canal . The exact histological appearance of this tube varies down the length of the tube, but it basically consists of four concentric layers (see figure 2). The inner- most layer is called the mucosa . This itself con- sists of three thin layers: an epithelium lining the inner surface, some underlying connective tissue ( lamina propria ), and a small amount of smooth muscle, confusingly named the muscularis mu- cosae . The next layer is the submucosa . This is loose connective tissue containing blood and lymph vessels and nerves. The next layer is a thicker muscular layer called the muscularis...
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Digestive System Lectures - The Digestive System Lecture 1...

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