The Digestive System

The digestive system in animals has evolved in an effort to provide the means to access nutrients from the surrounding environment. This includes devices to capture or collect nutrients/particles/matter/prey from the outside world, the tools to mechanically and chemically digest these nutrients into smaller particles/molecules. These nutrients can now be absorbed so they ultimately can be distributed to the numerous cells that make up the organism. There is often a mechanism to eliminate any matter that is not digestable.

1. What is the overall physiological problem that is resolved by the digestive system in animals?
2. Outline the fundamental process of the digestive system.
3. Nutrients and energy move through different levels in the ecosystem via producers and consumers. Define producers and consumers as well as their roles in ecosystems.
4. Distinguish between autotrophs and heterotrophs.
5. Distinguish between herbivores, omnivores and carnivores.
6. Briefly outline the evolution of the digestive tract in animals by using several examples from class.
7. Animals can be categorized by the method used to capture food. Describe four major methods. Give examples of animals in each category.
8. Outline the anatomy of the digestive tract as exemplified by the human species.
9. Do the same for the digestive process in a human.
10. Many animals initiate the digestive process with a mechanical breakdown. This can occur in the mouth region or further down in the digestive tract depending on the animal. Briefly explain the process and its purpose.
11. Mammals have a variety of teeth to accommodate the task of mechanical breakdown. Briefly describe the variety of teeth and their function in mammals.
12. Do all vertebrates use their teeth to accomplish mechanical breakdown of their food items? Use reptiles as an examples to illustrate differences between them and the mammals.
13. What is the function of the tongue in the digestive system?
14. How is chemical breakdown different from mechanical breakdown?
15. Explain the process of peristalsis.
16. Describe the structure of the human stomach.
17. Why are there muscular sphincters present between the stomach and the esophagus (cardiac sphincter) and between the stomach and the duodenum (pyloric sphincter)? What is their purpose?
18. What is the function of the stomach?
19. Describe the chemical environment of the stomach. Are any enzymes released from this organ to participate in chemical digestion?
20. What is chyme?
21. How do the stomachs of a ruminant differ from the human system?
22. How do ruminants accomplish the difficult process of digesting cellulose? Is the process evolutionarily and ecologically important?
23. The size and length of the small intestine varies greatly between different mammals. Briefly explain this observation.
24. What is the function of the small intestine?
25. What is the function of bile? Where is bile produced? Where is it stored?
26. What is the role of the pancreas in the digestive process?
27. The small intestine is a highly vascularized organ. Explain.
28. The small intestine has a very high surface area relative to its size. Explain how this is accomplished from an anatomical perspective.
29. How do the three major macromolecules differ from each other in terms of their breakdown and absorption (carbohydrates, proteins and lipids)?
30. What is the role of the appendix? The cecum?
31. Does the cecum vary in function between different animals? Explain.
32. What is the function of the large intestine?
33. What is the purpose of elimination? How is elimination controlled?
34. Summarize: What is the overall physiological problem that is resolved by the digestive system in animals?
35. Summarize: Briefly describe the digestive process by focusing on the following steps - a. ingestion, b. digestion, c. absorption and d. elimination.

• A great overview of the digestive process
• Fly through the human digestive system : - )
• The film "Super Size Me" is an interesting documentary providing a perspective on nutrition and the influence of the fast food industry in our nation. Highly recommended.
  

• The Anatomy and Physiology of the Digestive System
• Animation showing the digestive process in a human [with a timeline]
• Digestive Physiology of Herbivores
• Biology Book - Digestive System
• Anatomy of the Human Digestive Tract - Quiz [just for fun]

Omnivores
Herbivores
Carnivores
Suspension Feeders
Substrate Feeders
Fluid Feeders
Bulk Feeders

Overview
1. Ingestion
2. Digestion
 Mechanical
 Chemical
3. Absorption
4. Elimination

Compartments
Lower animals
Mouth
Gastrovascular cavity
Alimentary canal
 Pharynx
 Esophagus
 Crop
 Gizzard (stomach)
 Anus
Comparing animals

The "Journey"
The Human System
Oral Cavity

 Teeth (mechanical)
 Saliva (chemical)
  amylase
 Tongue (mechanical/ sensory)
Bolus
Swallowing
Esophagus
Peristalsis as a phenomenon
Role of the cardiac sphincter

Stomach
 Structure (muscular/ surface A)
Gastric glands (HCl [pH 2], mucus)
Pepsinogen (digest proteins)
Acidic chyme
Ulcers (link to Helicobacter pylori)
Pyloric sphincter

The Small Intestine
Duodenum - Link to
 Gall bladder (bile)
  Emulsifies fats (no enzymatic action)
 Pancreas (alkaline; enzymes)
Mucus; Enzymes
Structure
 Folds; villi; microvilli
 Enormous surface area
Villi and circulation
Absorption of nutrients and water
    Carbohydrates
    Proteins
    Lipids
    Routes of transport
 

The Large Intestine
Cecum (role in herbivores)
Compare herbivores and carnivores
Ruminant animals (e.g. cows)
Appendix
Absorption of water
Feces
Role of bacteria in the colon
Rectum
Role of infections (diarrhea)
Defecation

Nutrition
Food pyramid
Macro- and microminerals
Organic compunds (building blocks from macromolecules)
Essential amino acids
Essential fatty acids
Protein deficiency
Energy
    calories as a measurement of intake
Daily intake levels
Vitamins
    fat soluble (A,D, E, K)
    water soluble (B, C)
 
 

Page created by: Peter Svensson Updated: November 9,  2009