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Chapter 38

Chapter 38. Digestive and Excretory System. 38-1 Food and Nutrition. Calorie —The energy stored in food is measured in Calories (with a capital C!). 1 Calorie = 1000 calories. Nutrients the body needs are: Carbohydrates, fats, proteins, vitamins, and minerals

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Chapter 38

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  1. Chapter 38 Digestive and Excretory System

  2. 38-1 Food and Nutrition • Calorie—The energy stored in food is measured in Calories (with a capital C!). 1 Calorie = 1000 calories. • Nutrients the body needs are: • Carbohydrates, fats, proteins, vitamins, and minerals • The most important nutrient the body needs is water.

  3. 38-2 Process of Digestion • Mouth—Converts food to a clump called a bolus. • Chewing—Begins mechanical digestion. • Amylase—Found in saliva, begins chemical digestion. • Teeth—Responsible for the majority of mechanical digestion. • Salivary glands—Secrete Amylase. • Pharynx • Back of “throat”. • Esophagus—Transports bolus to stomach. • Peristalsis—Muscle contractions that squeeze the bolus down into the stomach. • Stomach—Continues mechanical and chemical digestion. • Contains mucus, hydrochloric acid, and the enzyme pepsin. • Pepsin—Breaks down proteins into small fragments. • Chyme—Mixture produced by the combination of all the stomach’s fluids and food as it churns and mixes its contents.

  4. Small Intestine – Site of most chemical digestion and absorption. • Duodenum—The first of three parts of the small intestine. • Receives chyme from the stomach and digestive fluids from the ACCESSORY STRUCTURES OF DIGESTION. • Villi—Fingerlike projections that increase absorption in the small intestine. • Accessory Structures of Digestion • Pancreas—Produces: • Hormones—regulate blood sugar. • Enzymes—Break down macromolecules. • Sodium Bicarbonate—Neutralizes stomach acid. • Liver • Produces bile—dissolves fat. • Large Intestine – removes excess water from leftover food. • Transports excess waste material to the rectum. • Rectum—Site of waste elimination.

  5. 38-3 Excretory System • Normal metabolic wastes include excess salts, carbon dioxide, and urea • Organs of excretion • Skin – rid body of salts, and some urea • Lungs – rid body of carbon dioxide • Liver – converts amino acids into nitrogen wastes, which it then converts to urea • Kidneys – remove waste products from blood, maintain pH, regulate water content, and blood volume

  6. In the Kidneys • Nephrons – Functional units of the kidney.Each nephron has its own blood supply! • Filtration—Removal of wastes from the blood. • Takes place in glomerulus—small network of blood vessels located in the upper end of each nephron. • Bowman’s Capsule—Encases the blood vessels of the glomerulusand absorbs waste from the blood, called Filtrate. • Filtrate—Composed of water, urea, glucose, salts, amino acids, and vitamins. • Reabsorption—Process of the filtrate making its way back into the blood. • Water, amino acids, fats, and glucose are reabsorbed back into the bloodstream. The remaining waste is called urine. • Kidneys (nephrons) Ureter  Urinary bladder  Urethra Excreted

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