digestion

• Food is any material that contains nutrients.
• A nutrient is a substance that an organism needs to remain alive. Examples include carbohydrates, proteins, or fat.
• We need to eat food to obtain the chemical energy and carbon-containing building blocks from carbohydrates, proteins, and fat.
• The four steps of obtaining nutrients include ingestion, digestion, absorption, and elimination.
• Ingestion is the process of bringing food into the digestive tract
• Digestion is the process of breaking down food.
• Absorption is the uptake of specific ions and molecules across the epithelium that lines the digestive tract.
• Elimination is the release of wastes from the digestive tract.
• The four food getting strategies in animals include:

  • suspension feeders
  • deposit feeders
  • fluid feeders
  • mass feeders
• Suspension feeders filter small organisms or bits of organic debris from water via cilia, mucus-lined "nets", or other structures.
• Deposit feeders swallow sediments and other types of deposited material rich in organic matter.
• Fluid feeders, suck or lap up blood, nectar, or other fluids.
• Mass feeders seize and manipulate chunks of food.
• Structures correlate with functions.
• The mouth is used to mechanically and chemically digest food, where salivary amylase digests carbohydrates and lingual lipase digests fatty acids.
• The esophagus is used to transport food from the mouth to the stomach.
• The stomach is the site of mechanical and chemical processing, where pepsin digests proteins.
• The small intestine is the site of chemical processing and absorption. In it, nucleases break down nucleic acids, pancreatic amylase breaks down carbohydrates, pancreatic lipase breaks down lipids, and trypsin, chymotrpsin, and carboxypeptidase breaks down proteins.
• The pancreas produces carboxypeptidase, chymotrypsin, nucleases, pancreatic amylase, pancreatic lipase, and trypsin.
• Pepsin is produced in the stomach
• The salivary glands synthesize lingual lipase and salivary amylase.
• The large intestine is used to absorb water and form feces; it also contains symbiotic bacteria.
• The appendix contains immune tissue and harbours symbiotic bacteria.
• The anus is used to eliminate feces.
• The salivary glands secrete enzymes that digest carbohydrates, supply lubricating mucus.
• The liver secretes molecules that help in fat digestion.
• The gallbladder stores secretions from the liver and empties them into small intestine.
• The pancreas secretes enzymes and other materials into the small intestine.
• The mouth is used for mechanical and chemical digestion.
• Food is digested mechanically by the teeth to increase surface area.
• The salivary glands secrete saliva, which contains water and mucus to lubricate the food, and salivary amylase and lingual lipase
• Salivary amylase digests starch to release maltose
• lingual lipase digests fats to release fatty acids.
• Purpose of Digestive Systems = to obtain nutrients from food

  
• Nutrients: substances that organisms need to survive. nutrients can provide energy and building blocks for maintenance, growth, and reproduction.
• Food


  Any material that contains nutrients. But these nutrients are usually not ready for absorption and use by animals, yet
• As animals, we must digest food and absorb the nutrients, to get energy and building blocks (e.g. essential amino acids, vitamins)
• Animals are well adapted for eating particular foods (e.g. jaws and teeth)
• Animals are well adapted for eating particular foods (e.g. digestive systems)
• Overview: What overall trends do you notice?

  • Alimentary canal (i.e. gut) is one long tube, and food moves through in one direction only!
  • Many glands secrete into specific regions, to help digest different components of food
  • Nutrients (and water) absorbed in small (and large) intestine, after earlier digestion
  • Each part of the digestive system holds the food for a different amount of time, and at a different pH