1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Biology Sylvia S. Mader Michael Windelspecht Chapter 8 Digestive System and Nutrition Lecture Outline Part 1

2 Digestive System and Nutrition

3 Points to ponder What are the digestive system structures and their functions? Where does carbohydrate, protein, and fat digestion and absorption occur? What are proteins, lipids, carbohydrates, minerals and vitamins needed for? What is an essential vs. a nonessential nutrient? What are the 3 accessory organs of digestion? What is obesity and why is it a problem? What is LDL and HDL? What are the components of a healthy diet? Name and explain 4 eating disorders.

4 What are the main steps in the digestive process? ________ – intake of food via the mouth Digestion – mechanically or chemically breaking down foods into their subunits Movement – food must be moved along the GI tract in order to fulfill all functions _________ – movement of nutrients across the GI tract wall to be delivered to cells via the blood _________ – removal of indigestible molecules 8.1 Overview of Digestion

5 What are the 4 major layers that make up the wall of the GI tract? ________ – innermost layer that produces mucus to protect the lining and also produces digestive enzymes __________ – 2 nd layer of loose connective tissue that contains blood vessels, lymphatic vessels, and nerves __________ – 3 rd layer made of 2 layers of smooth muscle that move food along the GI tract ________ – outer lining that is part of the peritoneum 8.1 Overview of Digestion

6 Visualizing the layers of the GI tract Figure 8.2 The layers of the gastrointestinal tract wall. 8.1 Overview of Digestion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lumen central space containing food being digested Mucosa inner mucous membrane layer modified according to the digestive organ Submucosa broad band of loose connective tissue that contains nerves, blood, and lymphatic vessels Muscularis two layers of smooth muscle Serosa thin, outermost tissue that is the visceral peritoneum nerve supply lymph vessel artery vein

7 An overview of the digestive system Figure 8.1 Organs of the GI tract and accessory structures of digestion. 8.1 Overview of Digestion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Liver major metabolic organ ; processes and stores nutrients; produces bile for emulsification of fats Gallbladder stores bile from liver; sends it to the small intestine Pancreas produces pancreatic juice ; contains digestive enzymes, and sends it to the small intestine; produces insulin and secretes it into the blood after eating Digestive tract organs Esophagus passageway where peristalsis pushes food to stomach Stomach secretes acid and digestive enzyme for protein; churns, mixing food with secretions, and sends chyme to small intestine Small intestine mixes chyme with digestive enzymes for final breakdown; absorbs nutrient molecules into body; secretes digestive hormones into blood Large intestine absorbs water and salt to form feces Rectum stores and regulates elimination of feces Mouth teeth chew food; tongue tastes and pushes food for chewing and swallowing Pharynx passageway where food is swallowed Accessory organs Salivary glands secrete saliva which contains digestive enzyme for carbohydrates Anus

8 What is the pathway that food follows? mouth pharynx esophagus stomach small intestine large intestine rectum anus 8.1 Overview of Digestion

9 The mouth 3 pairs of ___________ secrete salivary amylase that begins carbohydrate digestion. Tonsils at the back of the mouth are lymphatic tissues, important in fighting _______. The mouth contains teeth that begin the __________ breakdown of food. The tongue is covered in taste buds and also assists in the mechanical breakdown and movement of food. The tongue forms a ______ (mass of chewed food) and moves it toward the pharynx. 8.2 The Mouth, Pharynx, and Esophagus

10 Anatomy of the mouth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. hard palate soft palate uvula tonsil incisors (2) canine (1) premolars (2) molars (3) Figure 8.3a The functions of the different teeth. 8.2 The Mouth, Pharynx, and Esophagus

11 Teeth There are 32 teeth in adults (20 deciduous teeth in babies). Teeth are used for mechanical breakdown of food. Each tooth is made of a crown and a root. A hard covering of ______ and ______ covers the crown. 8.2 The Mouth, Pharynx, and Esophagus

12 Teeth An inner pulp area has nerves and blood vessels. ____________ (cavities) occurs when bacteria metabolize sugars and produce acids; limiting sugar intake and brushing teeth reduces tooth decay. 8.2 The Mouth, Pharynx, and Esophagus

13 Anatomy of a tooth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. root crown enamel dentin pulp gum jawbone root canal periodontal membrane cementum 8.2 The Mouth, Pharynx, and Esophagus Figure 8.3b A cross section of a tooth showing the crown and root.

14 The pharynx and esophagus The pharynx is a cavity between the mouth and esophagus that serves as a passageway for food (and air). The __________ is a long, muscular tube that carries food to the stomach. 8.2 The Mouth, Pharynx, and Esophagus

15 How do we swallow food? Voluntary phase –In the beginning, when food is being swallowed from the mouth into the pharynx is a voluntary act. 8.2 The Mouth, Pharynx, and Esophagus

16 How do we swallow food? Involuntary phase –Once the food is in the pharynx, swallowing becomes a reflex. –The ___________ covers the voice box to make sure food is routed into the esophagus. –Food moves down the esophagus through ____________ (rhythmic contraction). 8.2 The Mouth, Pharynx, and Esophagus

17 Soft palate closes off nasopharynx. Larynx rises and epiglottis covers glottis. Lower gastroesophageal sphincter relaxes and food enters stomach. hard palatefood bolus nasopharynx soft palate a. Swallowing trachea (airway) open Esophagus is closed. epiglottis esophagus opens b. Peristalsis esophagus peristaltic wave Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. glottis bolus stomach Figure 8.4 The process of swallowing. 8.2 The Mouth, Pharynx, and Esophagus How do we swallow food?