digestive system

• We eat food to obtain the energy we need to stay alive and to get the raw materials required for building all of our tissues
• Both you and food contain

  • Matter, made of certain kinds of atoms
  • Energy stored in the bonds between those atoms
• All living things need to take in stuff and energy, and convert it into slightly different stuff and energy
• Human digestion


  1. Ingestion

  2. Propulsion

  3. Mechanical digestion

  4. Chemical digestion

  5. Absorption

  6. Defecation
• Digestive system


  • It is a sort of disassembly line that deconstructs food, both mechanically and chemically, one step at a time
  • It reduces food to the most basic forms that cells can absorb
• Biological molecules (macromolecules)


  The large molecules in food, including lipids, carbohydrates, proteins, and nucleic acids
• Monomers


  The individual components of biological molecules, including fatty acids, sugars, amino acids, and nucleotides
• The simple idea behind the whole digestive system is to break down the polymers of macromolecules in your food, into the smaller monomers that your cells can use to build their own polymers, while also getting the energy they need
• Organs of the digestive system

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
• Mucosal layer


  The innermost epithelial layer of the digestive tract, which contains connective tissue and blood vessels
• Submucosal layer


  The layer of loose areolar connective tissue that provides elasticity to the digestive tract
• Muscularis externa layer


  The layer containing the muscles responsible for moving food through the digestive tract
• Accessory digestive organs


  • Teeth
  • Tongue
  • Gallbladder
  • Salivary glands
  • Liver
  • Pancreas
• Eating, or ingestion, is the process of creating a bulk flow of nutrients from the outside world into your tissues
• Swallowing is a voluntary action, but peristalsis is the involuntary process that propels food through the digestive tract
• Mechanical digestion breaks down food into increasingly tiny pieces to increase surface area, preparing it for chemical digestion
• Chemical digestion occurs when enzymes secreted by the liver, pancreas, and gallbladder break down food into its most basic chemical building blocks
• Absorption is the goal of the entire digestive process, where nutrients pass from the small intestine into the blood
• Defecation is the final step, where indigestible substances are eliminated from the body
• Some digestive processes occur in just one organ, while others require cooperation among multiple organs