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CHAPTER 38 DIGESTIVE & EXCRETORY SYSTEM. Chapter 38.1 Food & Nutrition. HW: P. 977 #1-4. FOOD AND ENERGY. Why do we need to eat? 1 calories = heat needed to raise 1 gram of water by 1ºC Calories in food are actually kilocalories (1000 calories)
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Chapter 38.1Food & Nutrition HW: P. 977 #1-4
FOOD AND ENERGY • Why do we need to eat? • 1 calories = heat needed to raise 1 gram of water by 1ºC • Calories in food are actually kilocalories (1000 calories) • Nutrition: study of food and its effects on the body.
NUTRIENTS • Your body needs: • Water • Important element of many bodily and chemical processes • Need at least 1L of water a day • Water loss in urine, sweat and breathing (homeostasis)
NUTRIENTS • Your body needs: • Carbohydrates • Main source of energy • Simple (mono/disaccharides) • Complex (polysaccharides)
NUTRIENTS • Your body needs: • Fats • Important building block of many cellular organelles • Vitamin absorption • Saturated (single bonds) BAD • Unsaturated (double bonds) GOOD
NUTRIENTS • Your body needs: • Proteins: found in animal products (meats and dairy); need 8 essential amino acids • Vitamins: organic molecules, work with enzymes (ignition, start reactions) • Fat-soluble (A, D, E, K) • Water-soluble (B, C) • Minerals: inorganic molecules, (calcium, sodium, potassium, etc…)
CHAPTER 38.2THE DIGESTIVE SYSTEM HW: P. 984 (1-4)
DIGESTION • Function: breakdown food for absorption • Mechanical: physical breakdown of food • Chemical: chemical breakdown of food • Voluntary and involuntary
THE MOUTH • Mechanical: teeth chew food into smaller pieces • Chemical: saliva contains amylase, enzyme converts carbohydrates to sugar • Tongue pushes food down pharynx
THE ESOPHAGUS • Epiglottis covers trachea; food travels down esophagus • Muscle contractions (peristalsis) push bolus through cardiac sphincter to stomach.
THE STOMACH • Muscles contract and churn (mix) food with gastric juices. • Digested food forms chyme(food and gastic juice) • Pepsin & HCl digest protein • Chyme travels through pyloric sphincter
THE SMALL INTESTINE & ACCESSORY ORGANS • Digestive enzymes from accessory organs complete majority of chemical digestion in duodenum. • Inner layer of villi/microvilli increase surface area and absorption of nutrients • Pancreas: secretes hormones that regulate blood sugar & digestive enzymes • Liver: secretes bile for digestion of fats; stored in gallbladder
THE LARGE INTESTINE • Also called the colon • Remaining chyme: water, cellulose, undigested material • Main function: water absorption • Storage of feces until defacation
DIGESTIVE SYSTEM DISORDERS • Peptic ulcers: holes in stomach due to thin mucus layer, caused by bacteria (H. pylori) • “heartburn”: backflow of acid in esophagus • Diarrhea: excess water in feces • Constipation: lack of water in feces • Colon cancer: development of malignant tumors in colon
CHAPTER 38.3THE EXCRETORY SYSTEM HW: P. 989 (1-4) P. 993 (1-10, 15, 19, 20)
FUNCTIONS OF THE EXCRETORY SYSTEM • Remove waste • Carbon dioxide • Excess water and salts • Urea • Liver: excess amino acids nitrogen compounds urea What happens to all of the urea in the bloodstream?
THE KIDNEYS (FIG. 38.17) • Function: maintain homeostasis • Remove waste • Maintain blood pH • Maintain blood volume • Structure: • Renal Cortex (outer layer) • Renal Medulla (inner layer) • Nephron • Glomerulus in Bowman’s capsule filters blood • Impure blood (renal artery) nephron ( impurities filtered out into collecting duct) purified blood (renal vein) • Waste ureter urinary bladder urethra
