Digestive system

• The components of the digestive system include: oesophagus, stomach, mouth, pancreas, liver, duodenum, ileum, glands
• The function of the digestive system if to facilliate the break down of large insoluable molecules into smaller soluble molecules, so they can be asorbed and assimilated
• Assimilated means when the cells use it up
• Carbohydrates are broken into the monomers: polysaccharides. disaccharides, monosaccharides
• Proteins are broken down into the monomers : dipeptides and amino acids
• Lipids are not polymers, but are broken down into fatty acids and glycerol
• Oesophagus carries food from mouth into the stomach. It is adapted to transport rather than absorb. It has a thick muscle wall
• Stomach secretes HCL (hydrochloric acid) which kills bacteria and activates pepsinogen to form pepsin. Pepsin breaks proteins down into peptones. The stomach also produces mucous to protect itself against its own enzyme
• Small intestine absorbs nutrients through villi and microvilli. It contains bile salts that emulsify lipids and alkaline juices that neutralise gastric juice. It also contains pancreatic juice containing trypsin, chymotrypsin, carboxypeptidase, lipases and amylase. These all break down their respective macromolecules.
• Large Intestine reabsorbs water and electrolytes back into bloodstream. It also stores faeces until defaecation occurs. It contains symbiotic gut flora that ferment undigested carbohydrate residues producing short chain fatty acids. This provides energy for colonocytes and helps maintain normal pH
• The stomach stores and digests food. It has an inner layer of glandular tissue, it also produces proteases and mucus
• The small intestine produces enzymes to digest food, and is where absorption takes place. It has a long muscular tube and its inner walls are folded in VILLI. Epithelial cells of villi have microvilli
• LARGEINTESTINE has A muscular tube

  Water is reabsorbed here to produce faeces
• RECTUM -Final section of intestines

  Faeces are stored here prior to egestion through the anus
• SALIVARY GLANDS -Situated near mouth

  Secretions contain amylase which breaks starch into maltose
• PANCREAS -A large gland  below the stomach

  Produces proteases, lipases and carbohydrase's
• MUCUS -Produced by glandular tissue

  Prevents stomach wall been digested by its own enzymes
• The oesophagus carries food from the mouth to the stomach. It is made up of a thick muscular wall, which helps to push the food along by peristalsis
• MECHANICAL DIGESTION IS

  •Large pieces of food are broken into smaller pieces

  •This is done by the teeth and the stomach muscles which churn the food up

  •Provides a large surface area for chemical digestion
• Chemical digestion is

  •Large insoluble molecules broken down into smaller ones

  •Brought about by enzymes, HCL and Bile

  •All digestive enzymes function by hydrolysis

  •This is the splitting of molecules by adding water

  •Enzymes are specific, with the specific teritary structure
• •Bile is an alkaline substance that emulsifies fatsenzymes to work more efficiently on them to break the large molecules down to small ones

  •Bile is made by the liver and stored in the gall bladder.

  •It helps in the digestion of fats by neutralising acid from the stomach and emulsifying fats.

  •This increases their surface area and allows
• The 4 parts of the gastrointestinal tract are:

  1. Oesophagus
  2. Stomach
  3. Small intestine
  4. Large intestine
• The 4 layers of the walls and guts are:

  1. Mucosa
  2. Submucosa
  3. Muscularis Externia
  4. Serosa
• Where is the exact location of the absorbtion of the products of digestion?

  Ileum
• The enzyme, salivary amylase, is located in saliva and digests starch(polysaccharides) into maltose(dissachardies)
• The enzyme pancreatic amylase, is located in the pancreatic fluid, and completes the the digestion of starch into maltose
• Disaccharides which are located in the duodenum, are: maltase, sucrase, lactase.
• Disaccharides convert back into their original monosaccharides,

  Maltose is converted into 2 glucose molecules

  Sucrase is converted into glucose and fructose

  Lactase is converted into glucose and galactose
• Proteases, trypisin, chymotrypipsin, carboxypeptide, is located in the pancreatic fluid and converts proteins into smalller fragments, peptides and amino acids
• lipases are located in thr pancreatic fluid, and break down lipids into fatty acids and glyercol
• stomach muscles contract to churn / mix the food (1), breaking the food into smaller molecules so it can be utilised by the body