How Nutrients Enter our Body

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How Nutrients Enter our Body

• How wastes are Excreted

Chapter 32
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Evolution of the Digestive System

• Intracellular- food broken down inside of cell

• Extracellular food broken down outside of cells
  in specialized digestive tract

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The Digestive System

• Broken into four categories
• Ingestion
• Digestion chemical mechanical
• Absorption
• Excretion

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The Mouth

• Site of physical and chemical digestion
• Salivary amylase breaks down starch and glycogen

Mouth pharynx esophagus
stomach
Peristalsis begins here
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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

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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

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The Good the Bad

• Oxygen
• Organic compounds carbohydrates, lipids,
  proteins
• Vitamins and minerals

• Carbon dioxide
• Urea
• Excess salts

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The Excretory System

• 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- remove CO2
• The kidneys- removes cellular waste from the blood

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Kidneys
To ureter

• Regulate water content of blood and blood pH
• All of the blood in the body passes through the
  kidneys every 30 minutes
• 99 of the fluid filtered through the nephron is
  reabsorbed

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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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