Digestive System
Function
• Ingestion• Digestion• Absorption• Elimination
Types of Digestion
• Physical digestion: – Mechanically breaking down the food
• Chemical digestion:– Chemically breaking down the food with the
help of chemicals (Enzymes)
Principle Structures
• Mouth (Ingestion/Digestion)– Physical : teeth, water, mucus– Chemical: saliva – salivary amylase - starch– Bolus– Epiglottis– Esophagus– Peristalsis– Esophageal sphincter
• Stomach (Digestion/Absorption)– Physical: Churning –– Chemical: Gastric Juice
(gastrin)• Water• Mucus (protection)• HCl – parietal cells (pH 1-3)• Pepsinogen –chief cells →(HCl) Pepsin – Proteins
– Pyloric Sphincter
• Small Intestine (Digestion/Absorption)– Duodenum, Jejunum, Ileum– absorption of nutrients into
blood stream– villi/microvilli → capillaries (proteins/sugars) and lacteals (lipids) → liver via diffusion,
– Chemical (mostly duodenum)• pH 8 – bicarbonate ion –
pancreas (secretin)• Accessory organs
– Pancreas (enzymes -proteins, CHO’s, lipids)
– Liver (bile salts –emulsifies lipids; conversion into glucose/glycogen; deamination)
– Gallbladder (stores/releases bile -cholecystokinin )
• Large Intestine (Absorption/Elimination)– Concentrates/stores/
eliminates waste– Colon- absorbs water,
salts; produce Vit B-12 and K
– Rectum/Anal canal –stores feces
– Elimination via 2 sets of sphincters (peristalsis)
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