Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu To View the presentation as a slideshow with effects select “View”

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” To advance through the presentation, click the right-arrow key or the space bar. From the resources slide, click on any resource to see a presentation for that resource. From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. You may exit the slide show at any time by pressing the Esc key. How to Use This Presentation

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Digestive and Excretory Systems Chapter 39 Table of Contents Section 1 Your Body’s Need for Food Section 2 Digestion Section 3 Excretion

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Your Body’s Need for Food Objectives Identify five nutrients found in food. Relate the role of carbohydrates, proteins, lipids, vitamins, minerals, and water in maintaining a healthy body. Describe each part of the USDA food guide pyramid. Name one health disorder associated with high levels of saturated fats in the diet. Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Food A nutrient is a substance required by the body for energy, growth, repair, and maintenance. Nutrients in food and beverages include carbohydrates, lipids, proteins, vitamins, and minerals. The process of breaking down food into molecules the body can use is called digestion. The energy available in food is measured by using a unit called a calorie. A calorie is the amount of heat required to raise the temperature of 1 g of water 1°C (1.8°F) Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Building Materials Each nutrient plays a different role in maintaining a healthy body. Carbohydrates, proteins, and lipids are involved in providing both energy and building materials to the cells. Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Building Materials, continued Carbohydrates Carbohydrates that exist as single sugar molecules are called monosaccharides or simple carbohydrates. Carbohydrates made of two or many sugar molecules linked together by chemical bonds are called complex carbohydrates. Complex carbohydrates must be broken down into simple sugars before cells can use their energy. Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Building Materials, continued Proteins Amino acids from proteins are used by the body for making additional proteins. Extra amino acids in the diet are used for energy or converted to fat. The body needs 20 different amino acids to function. Ten amino acids (called essential amino acids) must be obtained directly from food. Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Building Materials, continued Lipids The body uses lipids to make steroid hormones and cell membranes and to store energy. Fats are lipids that store energy in plants and animals. Fats are also stored around organs and act as padding and insulation. Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Building Materials, continued Balancing Nutrients and Energy If excess calories are eaten, they will be stored as either glycogen or body fat. Obesity is described as being more than 20 per cent heavier than your ideal body weight. Obesity increases an individual’s risk of diabetes, heart disease, and many other disorders. Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vitamins, Minerals, and Water Vitamins are organic substances that occur in foods in small amounts. They are necessary in trace amounts for the normal metabolic functioning of the body. Minerals are naturally occurring inorganic substances that re used to make certain body structures and substances. They are also needed for normal nerve and muscle function. Two-thirds of the body’s weight is water. Section 1 Your Body’s Need for Food Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Digestion Objectives Relate the four major functions of the digestive system to the processing of food. Summarize the path of food through the digestive system and the major digestive processes that occur in the mouth, stomach, small intestine, and large intestine. Describe how nutrients are absorbed from the digestive system into the bloodstream or lymphatic system. Identify the role of the pancreas and liver in digestion. Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Breaking Down Food The process of breaking down food into molecules the body can use is called digestion. The digestive system takes in food, breaks it down into molecules small enough for the body to absorb, and gets rid of undigested molecules and waste. Food travels more than 8 m (26 ft) through the human digestive tract. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Breaking Down Food, continued Starting Digestion In the mouth, saliva moistens and lubricates the food as it is chewed. Saliva contains amylases, enzymes that begin the breakdown of carbohydrates such as starch into monosaccharides. After chewing, food enters the esophagus. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Breaking Down Food, continued The Esophagus The esophagus is a long tube that connects the mouth to the stomach. Waves of smooth muscle contractions move the food toward the stomach. No digestion occurs in the esophagus. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Breaking Down Food, continued The Stomach The stomach mechanically breaks down food and chemically unravels and breaks down proteins. The cells that line the inside of the stomach release gastric juice. Gastric juice is a combination of hydrochloric acid and pepsin. Pepsin is a digestive enzyme produced by the stomach. Pepsin breaks down proteins. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Small Intestine Food passes from the stomach into the small intestine. The small intestine functions mainly in the digestion and absorption of nutrients. Pancreatic enzymes called lipases are released into the first part of the small intestine, where they digest fats. The lining of the small intestine is covered with fingerlike projections called villi, which increase the surface area available for absorption of nutrients. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Large Intestine Wastes move into the large intestine, or colon. No digestion takes place in the colon. Mineral ions and water are absorbed through the walls of the large intestine. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Large Intestine, continued The Liver’s Role in Digestion The liver secretes bile, which aids the breakdown of fats. Bile also promotes the absorption of fatty acids and the fat-soluble vitamins A, D, E, and K. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Large Intestine, continued The Liver’s Role in Metabolism Digested food molecules in the bloodstream are transported to the liver. The liver stabilizes blood sugar by converting extra sugar to glycogen for storage. Section 2 Digestion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Excretion Objectives Identify major wastes produced by humans and the organ or tissue where they are eliminated from the body. Relate the role of nephrons to the filtering of blood in the kidneys. Summarize how nephrons form urine. Describe the path of urine through the human urinary system. Predict how kidney damage might affect homeostasis and threaten life. Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Water and Metabolic Wastes Excretion is the process that rids the body of toxic chemicals, excess water, salts, and carbon dioxide while maintaining osmotic and pH balance. The lungs, the kidneys, and the skin all function as excretory organs. In the liver, ammonia is converted to a less toxic nitrogen waste called urea, which is transported to the kidneys, then removed from the blood. Section 3 Excretion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Kidneys The kidneys are a pair of bean-shaped, reddish brown organs located in the lower back. The kidneys regulate the amount of water and salts contained in blood plasma. They play a vital role in maintaining homeostasis. Section 3 Excretion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Kidneys, continued Blood Filters Each kidney is composed of blood-filtering units called nephrons. The kidneys filter out toxins, urea, water, and mineral salts from the blood. The body reabsorbs useful molecules and water. Urine is formed from the remaining water, urea, and salts. Ureters are tubes that carry the urine from the kidney to the urinary bladder. Section 3 Excretion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Kidneys, continued Elimination of Urine The ureters direct the urine into the urinary bladder, a hollow, muscular sac that stores urine. Urine leaves the bladder and exits the body through a tube called the urethra. The elimination of urine from the body through the urethra is called urination. Section 3 Excretion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Kidneys, continued Damage to the Kidneys Diseases affecting the kidneys may be life- threatening. If both kidneys fail, treatment options include kidney dialysis or a kidney transplant from a healthy donor. Kidney dialysis, also called hemodialysis, is a procedure for filtering the blood by using a dialysis machine. Section 3 Excretion Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice Use the food label below and your knowledge of science to answer questions 1–3. Standardized Test Prep Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 1.What is the main function of dietary fiber? A.to provide energy B.to provide materials for making enzymes C.to help food pass through the digestive tract D.to maintain osmotic balance Standardized Test Prep Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 2.Approximately what percentage of the calories in this food come from fats? F.1 percent G.5 percent H.10 percent J.14 percent Standardized Test Prep Chapter 39

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Choice, continued 3.A food is considered to be a good source of a vitamin or mineral if it provides at least 10 percent of that vitamin or mineral. Based on that criterion, the food is a good source of A.vitamin A, vitamin C, calcium, and iron. B.vitamin A, vitamin C, riboflavin, and niacin. C.iron, thiamin, riboflavin, and niacin. D.calcium, iron, thiamin, and riboflavin. Standardized Test Prep Chapter 39

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