Human Digestion

• Egestion


  removal of undigested waste
• Ingestion


  Intake of food
• Digestion

  Break down of food
• Absorbtion


  The process by which nutrient molecules pass through the wall of the digestive system into the blood
• Assimilation


  Process in which organisms absorb and use nutrients
• How is the small intestine adapted for absorption?


  1. Wall of the small intestine is covered in villi and each villus is covered in microvilli. These increase the surface area for absorption.

  2. The wall of the small intestine is thin which shortens the distance that the digested food products have to diffuse across

  3. Each villus has a rich blood supply which maintains a steep concentration gradient for diffusion to occur rapidly
• Mouth


  Where the food is ingested and chewed by teeth (mechanical digestion). It is also mixed with Saliva, containing amylase.
• Salivary glands


  Produces saliva, containing the enzyme amylase.
• Oesophagus


  Carries food to stomach, lubricated with mucus (in saliva)
• Stomach


  Churns and mixes with Hydrochloric acid, which kills bacteria. Proteases released to breakdown proteins.
• Liver


  Produces bile and stores glucose as glycogen.
• Gall Blader


  Stores and releases bile into small intestine
• Pancreas


  Releases proteases, lipases, and amylase enzymes into the small intestine.
• large intestine (colon)


  Where water is absorbed into the bloodstream.
• Anus


  Waste is egested
• Small Intestine


  Main point of chemical digestion and where nutrients is absorbed into the bloodstream.
• rectum


  Undigested material becomes feces
• Amylase

  Substrate - starch

  Optimum pH - 7

  Products - Maltose

  Found in - Mouth, Small intestine

  Produced in - Salivary glands, Pancreas, Small Intestine
• Maltase


  Substrate - maltose

  Optimum pH - 8-10

  Products - glucose

  Found in - small intestine

  Produced in - Pancreas, Small Intestine
• Protease e.g. pepsin


  Substrate - proteins/polypeptides

  Optimum pH - 2-3

  Products - small peptide chains

  Found in - stomach

  Produced in - stomach lining
• Protease e.g. Trypsin


  Substrate - small peptide chains

  Optimum pH - 8-10

  Products - Amino acids

  Found in - Small intestine

  Produced in - Pancreas, Small Intestine
• Lipase


  Substrate - Lipids

  Optimum pH - 8-10

  Products - Fatty acids and Glycerol

  Found in - small intestine

  Produced in - Pancreas, Small Intestine
• The Mouth, oesophagus, stomach, and intestines make a tube which passes all the way through your body, this is called the _____________________


  Alementary Canal
• The process of taking food into the mouth is ___________


  Ingestion
• Food is crushed and mixed with saliva to form a ____________


  Bolus
• The food is moved down the oesophagus by a series of muscle contractions called ____________________


  Peristalsis
• The muscles in the wall contract rhythmically, pushing against the indigestible material such as ________________


  Fibre
• The food enters the stomach where it mixes with more enzymes and _______ to form a liquid called _________


  Hydrochloric acid, chyme
• The food then moves into the small intestine where _____ is added to _________ lipids and _________ the pH of the chyme.


  Bile, emulsify, neutralise
• Small soluble molecules are ____________into the bloodstream in the small intestine.


  absorbed
• In the _____________ water is absorbed, and feces is formed.

  Large intestine
• The waste material feces leave the body through the anus in a process called _____________

  Egestion
• Diffusion


  Movement of molecules from an area of higher concentration to an area of lower concentration.
• Role of bile in digestion

  Emulsify lipids and neutralise stomach acids
• Carbohydrates


  - Broken down into glucose to provide energy.
• Protiens


  - help build and maintain body cells and tissues

  - biological catalysts
• Lipids


  - long term energy store

  - fat insulates under skin
• Minerals


  Iron - makes hemoglobin preventing anaemia

  Calcium - Important for bone health, similar to vitamin D
• Water


  Makes up 80% of the cytoplasm

  necessary for all life processes
• Dietary Fibre


  Aids the movement of food through the gut canal