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The Digestive System

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Comparative Anatomy

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Pre-Quiz Answers
1. Digestion is the process of breaking food down into molecules small enough for the body to absorb.
2. Polysaccharides are broken down into simple sugars.
3. Fats are broken down into glycerol or fatty acids.
4. Proteins are broken down into amino acids.
5. Nucleic acids are broken down into nucleotides.
6. The simplest digestive compartments are food vacuoles which are organelles where a single cell can digest its food without the hydrolytic enzymes mixing with the cell’s cytoplasm.
7. Intercellular digestion is the digestive mechanism where food is digested in food vacuoles (phagocytosis or pinocytosis). Extracellular digestion is the digestive mechanism where hydrolysis occurs with compartments that are outside of the body.
8. Hydrolysis is the splitting of water.
9. Gastrovascular cavities are digestive sacs with single openings that help in both digestion and the distribution of nutrients throughout the body.

10. The organs of the digestive system include: stomach, esophagus, liver, pancreas, gall bladder, small intestine, large intestine, salivary glands.

Post-Quiz Answers
1. The digestive tubes running between the mouth and the anus are alimentary canals. The tubes carry out digestion and absorption of nutrients step by step.
2. Peristalsis is rhythmic waves of contraction by the smooth muscles that help push the food along the tract.
3. The accessory organs are the salivary glands, the pancreas, the liver, and the gall bladder. Accessory glands deliver digestive juices to the canal via ducts.
4. Once the food enters the oral cavity, a nervous reflex is triggered which causes the salivary glands to deliver saliva to the oral cavity.
5. Salivary amylase is a digestive enzyme that hydrolyzes starch and can be found in the saliva.
6. The stomach can hold about 2 liters of food and fluid.
7. Pepsin is an enzyme that hydrolyzes proteins. When pepsin is synthesized and secreted in an inactive form, pepsinogen is formed.
8. Most enzymatic hydrolysis of the macromolecules in food occurs in the small intestine.
9. Bile is produced by the liver and aids in the digestion and absorption of fats.
10. The epiglottis and the vocal cords keep food and fluid from entering the respiratory system.
11. The five steps of digestion: movement, secretion, digestion, absorption, and elimination.

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