Human Nutrition Flashcards
Main steps in human nutrition
Ingestion
Digestion
Absorption
Egestion
How come egestion is not equal to excretion
Egestion is the removal of unabsorbed waste
Excretion is the disposal of metabolic waste
Digestion
The physical abd chemical breakdown of food
Dental formula
2(I2/2 C1/1 P2/2 M3/3)
Mechanical digestion
Takes place in the mouth by the chewing and grinding action of teeth on food
Chemical digestion
Occurs in the mouth by the action of the enzyme amylase
Oesophagus
Pushes food to the stomach through a wave of contractions called peristalsis
Peristalsis
A wave of muscular action in the walls of the alimentary canal that moves the contents along
Stomach
Lining of the stomach is heavily folded forming gastric glands
These glands secrete hydrochloric acid and pepsinogen.
Pepsinogen converts into an active enzyme pepsin which breaks down protein, like the muscle in the stomach,
To prevent it from breaking down the stomach lining, the lining is coated in mucus
Hydrochloric acid turns food into chyme
Glands in the digestive system
Salivary glands
Liver
Gall bladder
Pancreas
Pancreas
Produces insulin and pancreatic juice
Pancreatic juice - sodium bicarbonate (neutralised chyme)
- Enzymes e.g lipase and amylase
Enter the duodenum
Liver
Break down red blood cells Make bile Turn excess carbs into fat Turn excess protein into urea Store vitamins
Bile
Emulsifies fat -> increases its surface area
Neutralises chyme from stomach
Excrete pigments biliverdin and bilirubin from rbc
Small intestines
Duodenum-provide enzymes for Digestion Ileum - Adsorption Carbs -> monosaccharides Protein -> amino acids Fat -> fatty acids and glycerol
Small intestines adaptation for absorption
Long
Microvioli and villi increase surface area
Rich blood supply
Thin walls
