Overview of Digestion PDF

Overview of Digestion Learning Outcomes: 1. State the function of each organ of the gastrointestinal tract 2. List the accessory organs and name a function for each Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written con...

Overview of Digestion Learning Outcomes: 1. State the function of each organ of the gastrointestinal tract 2. List the accessory organs and name a function for each Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 1  Overview of Digestion, continued Overview of the digestive system – The organs are located within the gastrointestinal (GI) tract – Function – to break down the macromolecules found in food into subunits (monosaccharides, amino acids, fatty acids, and glycerol) that can cross plasma membranes The nutrients made available are transported by the blood to our cells Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 2 3  Stages of Digestion Stages of digestion – Ingestion – intake of food via the mouth – Digestion – breaking down food into subunits Mechanical digestion – chewing in the mouth and contractions of smooth muscles in the stomach Chemical digestion – digestive enzymes break macromolecules into subunits – Begins in the mouth, continues in the stomach, and is completed in the small intestine Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 4  Stages of Digestion, continued Stages of digestion, cont. – Movement – food is passed from one organ to the next by contractions of smooth muscle called peristalsis – Absorption – movement of nutrients across the GI tract wall into the blood; they are then delivered to cells – Elimination – removal of indigestibles; is called defecation Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 5  Check Your Progress 9.1 1. List the digestive organs and accessory structures of the digestive system 2. Describe the processes that occur during the digestive process Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 6  The Mouth, Pharynx, and Esophagus Learning Outcomes: 1. Identify the structures of the mouth, pharynx, and esophagus and provide a function for each 2. Summarize the diseases and conditions associated with the mouth, pharynx, and esophagus Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 7  The Mouth Mouth (oral cavity) – Receives food; begins mechanical and chemical digestion – The roof of the mouth separates the nasal cavity from the oral cavity Two parts: a bony hard palate and a soft palate – The soft palate is made of muscle; ends in the uvula – Tonsils – in the back of the mouth on either side of the tongue Lymphatic tissue; help protect from disease Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 8 9  The Mouth, continued Mouth (oral cavity), cont. – Three pairs of salivary glands secrete saliva, which contains salivary amylase (begins carbohydrate digestion) – Tongue Covered in taste buds Assists in mechanical breakdown, movement of food Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 10  Teeth Teeth – Mechanically digest food Incisors, canines, premolars and molars – Two main divisions: Crown – the part of the tooth above the gum line Root – the portion below Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 11  Teeth, continued Teeth, cont. – Enamel – extremely hard outer layer – Dentin – under the enamel – Pulp – nerves and blood vessels – Root canal – cavity in root; contains pulp Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 12  Teeth, cont. Teeth, cont. – Dental caries – tooth decay, cavities Occur when bacteria metabolize sugar and produce acids, which erode the teeth Can be painful when it reaches the nerves of the pulp – Gingivitis – inflammation of the gums; can cause loosening of the teeth Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 13  The Pharynx and Esophagus The mouth and nasal passages lead to the pharynx – In turn, the pharynx opens into both the food passage (esophagus) and air passage The esophagus is a muscular tube that leads to the stomach Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 14 15  Peristalsis Peristalsis – contractions that push food through the digestive tract Sphincter – a ring of muscle that acts as a valve – When it contracts, it stops food from moving through; when it relaxes, it allows food through – E.g., the lower esophageal sphincter is between the esophagus and the stomach Heartburn – failure of this sphincter; stomach contents move from the stomach into the esophagus Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 16  Check Your Progress 9.2 1. Describe the relationship of the mouth, pharynx, and esophagus 2. Detail how mechanical digestion and chemical digestion occur in the mouth Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 17  The Stomach and Small Intestine Learning Outcomes: 1. Describe the structure of the stomach and explain its role in digestion 2. Describe the structure of the small intestine and explain its role in digestion 3. Explain how carbohydrates, lipids, and proteins are processed by the small intestine Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 18  The Stomach Stomach – Stores food and starts digestion of proteins – Does not absorb nutrients Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 19 20  The Stomach, continued Stomach, cont. – The inner lining (mucous membrane) has deep folds – Produces: Pepsin – enzyme that digests proteins Hydrochloric acid (HCl) – pH of 2 – Kills bacteria and activates pepsin Mucus Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 21  The Stomach, cont. Stomach, cont. – Chyme – a mixture of food and stomach secretions Pyloric sphincter – allows only a small amount of chyme to enter the small intestine at a time Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 22  Heartburn (GERD) Heartburn – The lining of the esophagus is thinner than the lining of the stomach; if chyme enters the esophagus, it produces a burning sensation – Can be caused by pregnancy and excess fat pushing on the stomach – Gastroesophageal reflux disease (GERD) – chronic heartburn Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 23 24  Digestion Is Completed in the Small Intestine Small intestine – Pancreas – secretes digestive enzymes through a duct into the duodenum, the first portion of the small intestine – Another duct brings bile from the liver and gallbladder into the duodenum – Bile emulsifies fat Mechanical digestion; causes fat droplets to disperse in water to expose more of it to lipase – Produced by the pancreas, it breaks fats down into glycerol and fatty acids Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 25  Digestion Is Completed in the Small Intestine, continued Small intestine, cont. – Pancreatic amylase – produced by the pancreas, secreted into the duodenum Digests carbohydrates – Trypsin – produced by the pancreas, secreted into the duodenum Digests proteins – Pancreatic secretions neutralize acidic chyme (raises its pH) Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 26  Nutrients Are Absorbed in the Small Intestine Small intestine, cont. – The mucosa contains fingerlike projections called villi (sing., villus) – The cells that cover the villi have microvilli These two structures greatly increase the surface area of the small intestine for absorption of nutrients Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 27 28  Nutrients Are Absorbed in the Small Intestine, continued Small intestine, cont. – Nutrients are absorbed into the villi, which contain blood capillaries and a small lymphatic capillary called a lacteal Water-soluble nutrients enter the blood capillaries of a villus Fat-soluble nutrients enter a lacteal – After nutrients are absorbed, they are eventually carried to all the cells of the body by the blood Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 29  Lactose Intolerance Lactose intolerance – Lactose is the primary sugar in milk – Lactase – the enzyme that digests lactose People who are lactose intolerant don’t make enough lactase – Characterized by diarrhea, gas, bloating, and abdominal cramps after ingesting milk and other dairy products Occurs when bacteria break down the lactose Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 30  Check Your Progress 9.3 1. Describe the functions of the stomach and how the wall of the stomach is modified to perform these functions 2. Detail the functions of the small intestine and how the wall of the small intestine is modified to perform these functions 3. Summarize the differences in how carbohydrates, proteins, and fats are digested and absorbed by the small intestine Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 31  The Accessory Organs and Regulation of Secretions Learning Outcomes: 1. Explain the functions of the pancreas, liver, and gallbladder during digestion 2. List the secretions of the pancreas, liver, and gallbladder Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 32  The Accessory Organs Pancreas – Located behind the stomach – Produces pancreatic juice, which enters the duodenum via the pancreatic duct Contains alkaline solution and digestive enzymes – Also an endocrine gland; secretes the hormone insulin when the blood glucose levels rise Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 33 34  The Liver Liver – The hepatic portal vein brings blood to the liver from the GI tract – Stores vitamins – Involved in blood glucose homeostasis Stores glucose as glycogen; when blood glucose is low, it releases glucose by breaking down glycogen – Produces plasma proteins – Produces bile Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 35  The Gallbladder Gallbladder – Just below the liver – Stores bile – Gallstones – made of a stonelike material Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 36  Liver Disorders Liver disorders: hepatitis and cirrhosis – Liver disease can cause bile pigments to leak into the blood, causing jaundice Yellowish tint to the whites of the eyes and the skin – Hepatitis Inflammation of the liver Caused by a virus Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 37  Cirrhosis Cirrhosis – Often seen in alcoholics due to malnutrition and the excessive alcohol (a toxin) the liver is forced to break down – The liver can regenerate and recover if the rate of regeneration exceeds the rate of damage Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 38  Check Your Progress 9.4 1. Name and describe the functions of three main accessory organs that assist with the digestive process 2. Discuss what could occur if each of the accessory organs of digestion did not function properly Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 39  The Large Intestine and Defecation Learning Outcomes: 1. Describe the structure and function of the large intestine 2. List the disorders of the large intestine and provide a cause for each Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 40  The Large Intestine Large intestine – includes the cecum, the colon, the rectum, and the anus – Cecum – the first portion Appendix – projection off of the cecum – Fights infections – Appendicitis – inflamed appendix; can cause peritonitis, a life-threatening infection of the peritoneum (membrane that lines the abdominal cavity) Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 41 42  The Large Intestine, continued Large intestine, cont. – Colon – includes the ascending colon, transverse colon, descending colon, and the sigmoid colon, which enters the rectum The rectum opens at the anus, where defecation, the expulsion of feces, occurs Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 43  Functions of the Large Intestine Functions of the large intestine – Does not produce digestive enzymes – Absorbs water from feces to prevent dehydration – Absorbs vitamins produced by bacteria in the large intestine Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 44  Functions of the Large Intestine, continued Functions of the large intestine, cont. – Forms feces Mostly water, bacteria and dietary fiber (indigestible remains) Bacteria digesting the indigestible materials causes the odor of feces (gas) Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 45  Functions of the Large Intestine, cont. Functions of the large intestine, cont. – Defecation – ridding the body of feces Peristalsis forces feces into the rectum Stretching of the rectal wall initiates nerve impulses to the spinal cord Then rectal muscles contract and the anal sphincters relax, allowing the feces to exit through the anus Can inhibit defecation by contracting the external anal sphincter, which is made of skeletal muscle Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 46  Disorders of the Colon and Rectum Diarrhea – increased peristalsis and failure to absorb water from feces, usually from an infection Constipation – dry, hard feces; may be controlled with water and fiber Hemorrhoids – enlarged, inflamed blood vessels of the anus due to chronic constipation, pregnancy, anal intercourse Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 47  Polyps and Cancer Polyps - small growths in the colon lining – Can be benign or cancerous – If colon cancer is detected while still confined to a polyp, should be a complete cure – Increased dietary fat raises the risk of colon cancer – Dietary fiber prevents colon cancer, and regular elimination reduces the time that the colon wall is exposed to cancer-promoting agents in feces Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 48  Check Your Progress 9.5 1. Describe the parts of the large intestine, and provide the function for each 2. Explain the role of the large intestine in the digestive tract 3. Describe how constipation and diarrhea are related to the large intestine Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 49  Nutrition and Weight Control Learning Outcomes: 1. Calculate a BMI value and interpret its relationship to your overall health 2. Identify the role of each class of nutrient in the human body Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 50  Obesity Obesity – significantly overweight – One of the greatest health problems in the US Almost 36% of adults and 17% of children are obese Causes type 2 diabetes, hypertension, cardiovascular disease, stroke, osteoarthritis, and cancer – Having a body mass index (BMI) of 30 or greater Weight in kilograms (kg) is divided by the height in meters (m) squared Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 51 52  Classes of Nutrients Classes of nutrients – Nutrient – provides energy, promotes growth, and regulates metabolism E.g., carbohydrates, proteins, lipids, minerals, and vitamins Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 53  Carbohydrates Carbohydrates – are either simple or complex – Glucose – simple sugar – Complex carbohydrates are digested to glucose – Should ingest only small amounts of refined grains, such as white bread and cookies During refinement of grains, fiber is removed, along with vitamins and minerals Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 54  Proteins Proteins – made of 20 different amino acids – Complete proteins – contain all amino acids; usually derived from animal sources – Incomplete proteins – plant sources; need to combine them to get all 20 amino acids Must ingest amino acids every day; they are not stored in the body Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 55  Lipids Lipids – include fats, oils, and cholesterol – Saturated fats Usually of animal origin Solid at room temperature (unsaturated fats are usually liquid at room temperature) E.g., butter, meat – Unsaturated fats Don’t promote cardiovascular disease E.g., corn oil Trans fats – cause cardiovascular disease Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 56  Minerals Calcium – Needed for nerve impulse conduction, muscle contraction and blood clotting – Calcium supplements prevent osteoporosis Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 57  Vitamins Vitamins – organic compounds used for metabolism – Are often parts of coenzymes – There are 13 vitamins, two types: fat soluble (A, D, E and K) and water soluble (B and C) Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 58  Eating Disorders Eating disorders have social, cultural, emotional, and biological roots – Anorexia nervosa – a fear of getting fat Usually results in self-induced starvation, high physical activity – Bulimia nervosa – eat large amounts of high-calorie food (binge-eating) followed by purging to avoid weight gain Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 59  Check Your Progress 9.6 1. Briefly describe and give an example of each class of nutrients 2. Discuss why carbohydrates and fats might be the cause of the obesity epidemic today Copyright © 2018 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. 60