digestive system

• What is chemical digestion?

  the enzymic breakdown of macromolecules into smaller units
• mechanical digestion


  the physical breakdown of food into smaller pieces so it can be chemically digested
• Absorption


  The process of taking nutrients from the digestive system into the blood so they can be used in the body.
• Ingestion


  the process of taking food, drink, or another substance into the body by swallowing or absorbing it.
• Egestion


  the act or process of discharging undigested or waste material from a cell or organism
• Mouth (chemical)


  salivary amylase is produced in the salivary gland which assists in the breakdown of starch in the mouth. Final product is a bolus
• Mouth (mechanical)


  Mastication (chewing) by teeth breaks down food into smaller pieces to increase

  A) teeth can indicate different diet

  
• Oesophagus


  • Muscular tube that connects the oral cavity to the stomach
  • peristalsis carries the bolus
• Peristalsis


  fluids and food are propelled in 1 direction via rhythmic contraction of the smooth muscle found in the walls of the digestive tract

  
• Stomach

  • muscular and elastic organ
  • holds up to 1.5-4L
  • final product is called a chyme
  • the pyloric sphincter controls the amount of chyme that enters duodenum
• Stomach (chemical)


  -main target of chemical digestion in stomach are proteins.

  -when food enters stomach it releases:

  .mucus

  .water

  .HCl

  .gastric protease (trypsin, pepsin)
• Stomach (mechanical)


  -The stomach's smooth muscle undergoes strong contractions to churn the food.

  -Secretes HCl which denatures the proteins (unfold the proteins)
• Small intestine (duodenum)


  -pancreatic juice (amylase, trypsin, lipase and bicarbonate) and bile is secreted into the duodenum.

  • villi and microvilli off epithelial layer increases SA:V
• Trypsin


  enzyme that breaks down proteins (polypeptides)
• Amylase


  breaks down starch
• Protease


  an enzymes that break down protein (e.g. trypsin is a protease)
• liver

  accessory organ

  makes bile
• Gall bladder


  -accessory organ

  -bile from the liver is stored here
• pancreas


  -accessory organ

  -secretes enzymes to assists with the BD of the chyme
• Bile


  -secreted into duodenum

  -emulsify lipids of fat

  -Note: it is not an enzyme
• Lipid

  -fatty compounds

  -lipase (enzyme) to break down lipid

  -bile emulsify lipid/fats to increase SA:V for absorption

  
• Small intestine (chemical)

  -Intestinal protease breaks down polypeptides into amino acids

  -Intestinal amylase breaks down disaccharides into monosaccharides
• SMall intestine (chemical)

  Maltose(2 chemicaly bonded) ->(maltase BD)->glucose + glucose

  Lactose (2) ->(lactase BD) -> glucose +glucose

  Sucrose (2) -> (sucrase BD) -> glucose +fructose

  (-BD refers to the enzyme that breaks the disaccharides into monosaccharides)
• by the time the food has reached the ileum the food has been broken down into its monomer component:

  -glucose, fructose

  -amino acids

  -fatty acids

  -glycerol
• Glucose and amino acids are absorbed int the capillaries of the villi
• Fatty acids and glycerol are absorbed into lacteal and enter the lymphatic system.

  
• Large Intestine (chemical - cecum)


  -cecum stores bacteria that break down cellulose called cellulase

  -herbivores have larger cecum
• Large intestine


  -main function of the LI is absorption and egestion

  -peristalsis pushes the waste material into the rectum

  -defecation eliminates the faeces

  -houses commensal bacteria that help breakdown polysaccharides