human nutrition

• ingestion

  when food is taken into the digestive system
• digestion(mechanical)

  physical digestion is the mechanical breakdown of food and occurs when one chews or churns food
• digestion(chemical)

  chemical digestion is the breakdown of food using enzymes
• absorption

  digested food passes from the digestive system into the bloodstream
• egestion

  removal of unabsorbed waste from the body
• the mouth

  incisors-cut and slice. canines-grip and tear. premolars-crush and grind. molars- same as premolars
• dental formula

  2(I 2/2 C 1/1 P 2/2 M 3/3) 32 all together
• digestion m= chewing and grinding of teeth. c= action of the enzyme amylase found in saliva
• saliva

  made by water, mucus, lysozomes and amylase
• amylase

  breaks down starch to maltose. active in the mouth. made in the salivary gland. has a ph of 7-9
• food in digestion

  pushed towards the pharynx, connects the mouth to the oesophagus
• epiglottis

  closes over the trachea, ensures food passes down the oesophagus
• oesophagus

  carries food to the stomach by an involuntary wave of muscular contraction. (peristalsis)
• peristalsis

  helps break down food mechanically.

  forces food into the large/small intestine and rectum.

  fibre stimulates peristalsis and absorbs/stores water
• pancreas(gland)


  leaf shaped.

  secretes both enzymes and hormones(insulin).

  produces pancreatic juices(alkaline) acts to neutralise chyme from the stomach.

  produces enzymes amylase and lipase . enters the duodenum through the pancreatic duct
• stomach

  muscular bag that holds and digests food.

  digestion m=churning physically breaks up food particles.

  c= using gastric juices containing mucus, HCI and pepsinogen
• functions of gastric juices

  mucus= coats the stomach and prevents self-digestion. pepsinogen= inactive enzyme converted to pepsin.

  digests protein to peptides.

  hydrochloric acid= kills bacteria, activates pepsinogen, denatures amylase cellular food
• liver

  breaks down RBCs.

  produces bile.

  stores vit d. breaks

  down amino acids to form urea.

  role= bile (yellow and green lipuid)

  bile is stored in the gall bladder.

  enters the duodenum through the bile duct.

  bile is made up of water , bile salts and bile pigments.
• small intestine 


  duodenum= site of digestion.

  produces digestive enzymes and products of the liver and pancreas enters the duodenum. (cells lining).

  The final stages of digestion take place in the duodenum.

  tube that connects the stomach to the ileum
• ileum


  absorb nutrients ( by diffusion).

  food entering the ileum has completed digestion.

  carbs=monosaccharides.

  protein=amino acids.

  lipids=fatty acids and glycerol
• adaptations of the villi for absorption

  • lined with villi and microvilli
  • rich blood supply (capillaries)
  • walls are one cell thick
  • conatin a lacteal
• villi(villus)


  food is pushed through the intestines by the process of peristalsis.

  The lining of the small intestine contains many infoldings (villi).

  each villus has many microvilli.

  numerous infoldings increase the surface area both for digestion or absorption.
• large intestine

  caecum, appendix, rectum, colon
• caecum and appendix

  no known functions in humans

  now vestigial organs( lost their former use)
• colon

  reabsorbs water

  produces vit B and K (symbiotic bacteria and prevents the growth of pathogenic bacteria and fungi)

  egestion