CHAPTER 38 DIGESTIVE & EXCRETORY SYSTEM

Chapter 38.1Food & NutritionHW: 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 SYSTEMHW: 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 SYSTEMHW: 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