How Nutrients Enter our Body How wastes are Excreted Chapter 32

Evolution of the Digestive System Intracellular - food broken down inside of cell Extracellular food broken down outside of cells in specialized digestive tract

The Digestive System Broken into four categories Ingestion Digestion chemical & mechanical Absorption Excretion

The Mouth SSite of physical and chemical digestion SSalivary amylase breaks down starch and glycogen Mouth pharynx esophagus stomach Peristalsi s begins here

Small Intestine 6 meters long Duodenum- food completely broken down by enzymes into monomers Enzymes secreted by pancreas break down carbohydrates Bile secreted by liver and stored by gallbladder break down fat using lipase Jejunum, Ileum- major site of absorption Villi increase surface area to that of a tennis court

Large Intestine Major function is to absorb water (90% of fluid is reabsorbed) Vitamins and minerals are absorbed here Takes hours for material to move through this organ Escherichia coli live here and feed off the organic material, by product of this metabolism is methane, hydrogen sulfide gas and vitamin K

The Good the Bad  Oxygen  Organic compounds: carbohydrates, lipids, proteins  Vitamins and minerals CC arbon dioxide UU rea EE xcess salts

The Excretory System The skin- The skin- excretes excess water, salts, and a small amount of urea Ammonia is produced when amino acids are used for energy, the liver combines ammonia with carbon dioxide to form Urea The lungs- The lungs- remove CO 2 The kidneys- The kidneys- removes cellular waste from the blood

Kidneys Regulate water content of blood and blood pH All of the blood in the body passes through the kidney’s every 30 minutes 99% of the fluid filtered through the nephron is reabsorbed To ureter

How the nephron works Blood enters through an arteriole and is filtered The filtrate contains water, urea, glucose, salts, amino acids, and some vitamins 99% of the material in the filtrate is returned to the body by reabsorption The 1% that remains is called urine Urine on the average contains 95% water Daily output of water Urine 47% Sweat 31% Air Exhaled 16% Feces 6%