Anatomy and Physiology / Unit 9: The Respiratory and Digestive Systems
9.5 Digestive Organs and Their Functions
Notes
The digestive system breaks down food (digestion) and moves nutrients into the blood and lymph (absorption). Processes: ingestion, propulsion (swallowing and peristalsis), mechanical digestion (chewing, churning, segmentation), chemical digestion, absorption and defecation.
- Alimentary canal (GI tract): mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus. Accessory organs: salivary glands, liver, gallbladder, pancreas, teeth, tongue.
- Stomach: churns food with acid (HCl, pH about 2) and the enzyme pepsin to form chyme; mucus protects the lining; ulcers often come from Helicobacter pylori bacteria.
- Liver: makes bile (emulsifies fats), processes nutrients, detoxifies. Gallbladder: stores and concentrates bile. Pancreas: releases digestive enzymes and bicarbonate into the duodenum.
- Small intestine (about 6 m): duodenum, jejunum, ileum; main site of digestion and absorption.
- Large intestine: absorbs water and electrolytes and forms feces; hosts gut bacteria that make some vitamin K.
Practice
Which organ stores bile?
The liver makes bile; the gallbladder stores and concentrates it.
The wave-like contractions that push food along the digestive tract are called:
Peristalsis is rhythmic smooth muscle contraction that propels contents.
Where does most chemical digestion and nutrient absorption occur?
The small intestine has enzymes from the pancreas and a huge absorptive surface.
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