Digestive system (Carnivore and herbivores)

• Important molecules consumed by animals

  • Carbohydrates: provide a source for immediate energy
  • Lipids (fats): energy storage in animals
  • Proteins: structural component of cells, receptors, and enzymes
  • Vitamins: small amounts used to create enzymes
  • Minerals: small amounts used in structural components
• Phase 1: ingestion


  1. Mechanical: teeth & tongue tear and chew food to reduce size of food into mush (bolus)

  2. Chemical: enzymes in saliva (amylase) breaks down complex carbohydrates, saliva acts as a lubricant
• Phase 2: digestion - Oesophagus


  1. Tube that connects the mouth to the stomach

  2. Uses a series of tonic muscles that contract in a wave-like motion called peristalsis

  3. Peristalsis pushes the food in one direction, down

  4. Amylase continues to break down carbohydrates
• Phase 2: digestion - Stomach

  1. Mechanical: stomach churns bolus into a frothy, pulpy chyme

  2. Chemical: Hydrochloric acid (HCL) maintains stomachs pH around 1-3 (denatures amylase), stomach releases pepsin (enzyme) to break down protein into amino acids
• Phase 3: Absorption - Small intestine (1)


  Duodenum: most enzymatic digestion occurs, neutralisation of stomach acid, releases pancreatic juices (protein, carbs, fat), releases liver bile (fats)
• Phase 3: Absorption - Small intestine (2)


  Jejunum: Middle and largest section of the S.I, where the nutrients (carbohydrates, amino acids, lipids) are absorbed into blood stream, walls are lined with protrusions call villi (the structures the nutrients absorb into), each villi has microvilli to further increase SA:V
• Phase 3: Absorption - Small intestine (3)


  Ileum: connects the small intestine to the large, absorbs remaining nutrients as well as bile to be recycled to the liver
• Phase 3: Absorption - Large intestine


  Water and mineral absorption, condenses waste into solid mass called faeces
• Phase 4: Elimination - rectum and anus


  Faeces is collected and stored in the rectum, once rectum stretches to a certain point (full), positive feedback loop triggers the defecation process
• Accessory digestive organ - Liver


  • Produces bile, bile salts help to reduce large fat droplets into smaller fat droplets, bile is stored in the gall bladder
• Accessory digestive organ - Pancreas

  • Releases pancreatic juices which have the following enzymes: Lipase (fats), protease (protein), amylases (carbohydrates)
  • Helps neutralise the stomach acid with bicarbonate soda solutions
  • Produces hormones for glucose regulation - insulin (sugar intake into cells. Too high), glucagon (sugar stores release. Too low)
• Sphincters


  One-way doors, muscles that open and close (contract) to keep things flowing in the same direction
• Types of teeth


  • Incisors: long flat teeth at the front of the mouth used for cutting
  • Canines: sharp pointy teeth often in the corners of the mouth used for piercing meat
  • Molars: large flat or spiky teeth at the back of the mouth for grinding
  • Premolars: smaller versions of molars that sit in front of molars
• Carnivore vs herbivore


  Carnivores have a short and simple digestive system, only have one large stomach, shorter intestinal length, sharper teeth

  Herbivores have a longer, more complex digestive system, can use either a foregut or hindgut and a caecum for fermentation, long intestinal tract, wide flat teeth
• Hindgut fermenters


  • Horse, rabbits, koalas
  • Have a simple stomach
  • Relatively long intestine (compared to carnivores, short to foregut)
  • Large caecum (after small intestine)
  • Complex colon
  • Glucose produced enters colon for absorption
  • Bacteria ferments glucose via its own cellular respiration
• Foregut fermenters


  • Sheep, deer, cows
  • Fermentation occurs before the stomach
  • Smaller caecum
  • Foregut fermenting animals with rumen are called ruminates (cows and sheep)
  • Complex oesophagus and stomach
• What are the functions of the mouth?

  The mouth chews food to make smaller pieces and contains amylase that starts to break down carbohydrates
• What is the function of the stomach?

  Churn food to break it down into smaller pieces, and release pepsin/protease to break down proteins
• What is the function of the small intestine?

  The small intestine is responsible for absorption of nutrients from food. Does this via releasing liver bile and pancreatic juices and by villi/microvilli
• What is the function of the large intestine?

  Absorb remaining water and salts, while condensing wastes into faeces
• What is the function of the liver?

  Produces bile which is stored in the gallbladder
• What is the function of the pancreas?

  Produce enzyme rich juices and to neutralise stomach acid via sodium carbonate
• Where are Pepsin, Amylase and Lipase found?

  Stomach, Mouth, Small intestine/Pancreas
• What are the enzymes called the break down protein, carbs and fats?

  Protease/pepsin, amylase, lipase
• What is the purpose of mechanical digestion

  To increase SA:V so enzymes are more efficient
• How are nutrients absorbed within the small intestine? How is it made more efficient?

  Passive diffusion and Villi/Microvilli increase SA:V to increase efficiency