10.2 The Human Digestive System - Weebly
Transcript of 10.2 The Human Digestive System - Weebly
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10.2 The Human Digestive System
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digestive tract and accessory organs transform food into
energy
> 6m long, 2.5 cm wide
1.5m long, 5 cm wide
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The Mouth Salivary glands secrete saliva
Parotid gland parotid duct
Submandibular gland submandibular duct
Sublingual glands many smaller ducts
Chemical digestion
Amylase: Starch simple sugars
Mechanical digestion
Teeth
Tongue: food soft bolus
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The Esophagus
Epiglottis prevents bolus from entering the lungs
Esophagus transport bolus through peristalsis (wave-like
muscular contractions)
Mucus keeps passage moist
Video: peristalsis
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The Stomach
Esophagus esophageal / cardiac sphincter stomach
Food triggers secretion of gastric juice (salts, enzymes, HCl,
water, mucus)
Mucus – protects stomach from acid
Pepsin – enzyme to digest protein
HCl – activates pepsinogen pepsin
Mechanical digestion:
3 layers of muscle fibres
Bolus chime (a thick liquid)
pyloric sphincter small intestine
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The Small Intestine
3 parts: duodenum, jejunum, ileum
To absorb nutrients:
Many villi and microvilli
Long length
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The Small Intestine
Duodenum
digestion and absorption
Pancreas: pancreatic enzymes for all macromolecules
Gall bladder: fat fat droplets
Jejunum
more folds,
continues breakdown and absorption of proteins and
carbohydrates
Ileum
fewer villi
continues absorption
push unabsorbed particles through
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The Accessory Organs
Pancreas:
Secretes 1L of fluid into duodenum daily
Carbohydrases, proteases, lipases: chemical digestion
Bicarbonate: raise the pH to help enzymes
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The Accessory Organs
Liver:
Secretes bile (bile pigments & salts)
Fat fat droplets
Bile is stored in gall bladder and released into duodenum
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Chemical Digestion
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Enzyme Action
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Enzyme Action
Enzyme functions affected by
Temperature
pH
Different enzymes have
different optimal range
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Nutrient Absorption - Monosaccharides
Absorbed and carried by blood to liver
Liver converts monosaccharides to glucose
Blood carried glucose to all cells (source of energy)
Liver: excess glucose glycogen
Glycogen stored in liver and muscles
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Nutrient Absorption – Amino acids
Absorbed and carried by blood to liver
Liver converts amino acids to:
Sugars
energy-releasing chemicals
New proteins
waste
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Nutrient Absorption – Glycerol + fatty
acids
Absorbed by cells in small intestine
Reassembled to form triglycerides
Coated with proteins bloodstream
broken down by lipase
absorbed by cells for energy
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The Large Intestine
Shorter, wider
Aka colon
Re-absorb water
Anaerobic bacteria break down food and produce vitamins
Muscle contraction push undigested materials to rectum
feces
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Digestion Timeline
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Homework
P.419 #1-11, 13-15