I. Organization of animals as regards feeding.
A. What they eatII. Food processing can be divided into four stages.1. Herbivores - plantsB. How they ingest
2. Carnivores - animals
3. Omnivores - both1. Filter feeders - whales, some crustaceans
2. Suspension feeders - mussels
3. Substrate feeders - worms, caterpillars
4. Fluid feeders - mosquitoes, bugs, ticks
A. Ingestion - taking in the foodIII. No matter what animals we're considering, food processing takes place in compartments.
B. Digestion - food is broken into particles small enough to be absorbed.
C. Absorption - food molecules taken up.
D. Elimination - undigested waste passes out.
A. "Two way" - gastrovascular cavity.IV. Why do we even bother with digestion and absorption? What do we get out of it? We get three things.
B. "One-way" - alimentary canal.
A. Raw materials. Many of the things we eat we break down into smaller parts so that we can build the molecules we need. A good example would be meat. We want the proteins in meat so that we can break them into the amino acids that they're made of. Then our cells can assemble different proteins from those same amino acids.V. Human alimentary canal can be divided into regions with separate functions. Movement through the canal is achieved by smooth muscle contractions. Rhythmic waves of contraction are called peristalsis.
B. Fuel. All that building of molecules requires energy. All the types of work our cells do require energy and we get it from the chemical energy in the food we eat. We absorb digested food molecules and then we carefully break those molecules apart to extract the energy in their chemical bonds. We do that in the mitochondria - but you knew that.
C. Essential nutrients. There are few things that we absolutely need to get from our food. These would be substances that we just couldn't produce on our own. Examples of these are: some amino acids (21.16), vitamins (21.17), and minerals (21.18).
A. Oral cavity - mechanical breakdown of food. Saliva begins the chemical digestion. (Starches)
B. Pharynx - the opening to the lungs and esophagus. The epiglottis prevents us from inhaling our food.
C. Esophagus - conveys food to stomach.
D. Stomach - mucus, acid, and enzymes further digest the food. (Proteins). Food spends about 2 -6 hours here.
E. Small intestine - most of the chemical digestion goes on here. Check out the table in your book on page 438, you should know those enzymes and what they do. Its not too hard, most of the names are self-explanatory. You have about 6 m (19 feet) of small intestine. First 25 cm (called the duodenum) is digestive, the remainder is mostly absorptive.1. The liver makes bile, a compound that enhances the breakdown of fats.F. Colon - about 1.5 m long. Removal of water (it gets returned to the blood stream). Water comes from all those digestive juices. Feces is mostly plant fiber.
2. Pancreas makes enzymes and bicarbonates to neutralize acids.