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%
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