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

Site of physical and chemical digestion

Salivary amylase breaks down starch and glycogen

Mouth pharynx esophagus stomach

Peristalsis 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 12-24 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

Carbon dioxide

Urea

Excess salts

The Excretory SystemThe 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 CO2

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%