1 The Digestive System Digestive System • Digestion Mechanical & chemical breakdown of food into a form that can be used by cells Mechanical – breaks large pieces into smaller pieces Chemical – breaks food into simpler chemicals. Ex. Carbohydrates broken into glucose, proteins into amino acids Digestive Processes • Ingestion – taking in food • Digestion – mechanical & chemical breakdown • Deglutition – swallowing • Propulsion – movement of food thru system • Absorption – nutrients & water move into surrounding cells • Defecation – removal of ingestible waste
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1
The Digestive System
Digestive System
• Digestion
�Mechanical & chemical breakdown of food into a form that can be used by cells
�Mechanical – breaks large pieces into smaller pieces
�Chemical – breaks food into simpler chemicals. Ex. Carbohydrates broken into glucose, proteins into amino acids
Digestive Processes
• Ingestion – taking in food
• Digestion – mechanical & chemical
breakdown
• Deglutition – swallowing
• Propulsion – movement of food thru system
• Absorption – nutrients & water move into
surrounding cells
• Defecation – removal of ingestible waste
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Digestive System• 2 main divisions
� Alimentary canal(GI tract) – continuous coiled hollow tube from mouth to anus
� Accessory digestive organs – release secretions into GI tract
Organs of the Alimentary Canal
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Anal canal
• Salivary glands
• Liver
• Gallbladder
• Pancreas
Accessory Organs
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Anus
ACCESSORY ORGANS
Salivary glandsSecrete saliva, which containsenzymes that initiate breakdownof carbohydrates
LiverProduces bile, whichemulsifies fat
GallbladderStores bile and introduces it into small intestine
PancreasProduces and secretes pancreatic juice, containing digestive enzymes and bicarbonate ions, into small intestine
ALIMENTARY CANAL
MouthMechanical breakdown of food; begins chemical digestion of carbohydrates
PharynxConnects mouth with esophagus
EsophagusPeristalsis pushes food to stomach
StomachSecretes acid and enzymes; mixes foodwith secretions to begin enzymaticdigestion of proteins
Small intestineMixes food with bile and pancreatic juice; final enzymatic breakdown of food molecules; main site of nutrient absorption
Large intestineAbsorbs water and electrolytes to form feces
RectumRegulates elimination of feces
• Muscular tube ~ 8 meters long (~26 ft)
• Peristalsis – wavelike motion of muscular contractions that propel food forward
• 4 layers
� Mucosa membrane
� Inner epithelial layer surrounding lumen
� Villi present – tiny folds or projections that absorb nutrients