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5.3 Digestive System
1. Overview of the Digestive System
Complex network of organs and glands.
Breaks down food into smaller molecules for absorption and utilization.
Consists of the gastrointestinal (GI) tract and accessory organs.
2. Organs of the GI Tract
Mouth:
Mechanical (chewing) and chemical (saliva) digestion begins.
Pharynx:
Passageway for food and air.
Esophagus:
Transports food to stomach via peristalsis.
Stomach:
Storage, mixing, protein digestion begins (chyme formation).
Small Intestine:
Primary site for chemical digestion and nutrient absorption (duodenum, jejunum, ileum).
Large Intestine:
Absorbs water/electrolytes, forms feces.
Rectum:
Stores feces.
Anus:
Expels feces.
2.2 Accessory Digestive Glands
Salivary Glands:
Produce saliva (moistens food, initiates carb digestion).
Liver:
Produces bile (emulsifies fats).
Gallbladder:
Stores and concentrates bile.
Pancreas:
Produces pancreatic juice (digestive enzymes for carbs, fats, proteins) and bicarbonate.
3. Enzymes and Their Functions
Carbohydrate-Digesting:
Salivary Amylase, Pancreatic Amylase, Disaccharidases.
Protein-Digesting:
Pepsin, Trypsin, Chymotrypsin, Peptidases.
Fat-Digesting:
Lingual Lipase, Gastric Lipase, Pancreatic Lipase.
4. Processes of Digestion, Absorption, and Assimilation
4.1 Digestion:
Breaking down food.
Mechanical:
Physical breakdown (chewing, churning).
Chemical:
Enzymatic breakdown (complex to simple molecules).
4.2 Absorption:
Digested nutrients pass into bloodstream/lymphatic system (mainly small intestine).
4.3 Assimilation:
Absorbed nutrients transported to cells and utilized for energy, growth, repair, storage.
5. Peristalsis
Meaning:
Involuntary, wave-like muscular contractions in GI tract walls.
Role:
Propulsion:
Moves food along the digestive tract.
Mixing:
Churns food with digestive juices.
Efficiency:
Ensures optimal digestion and absorption.