Transcript Chapter 38 - Midway ISD

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
• The most important nutrient the body needs is water.
38-2 Process of Digestion
• Mouth—Converts food to a clump called a bolus.
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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.
• 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.
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
• 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 glomerulus and
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