Chp 28 Digestion Flashcards
Digestion
Break down of large food molecules into smaller, soluble ones
Mechanical digestion
Physical breakdown of food into smaller pieces
Chemical digestion
Breakdown of food into smaller molecules by enzymes, stomach acid or bile
Steps of human digestion
Ingestion
Digestion
Absorption
Egestion
Mouth : Physical
Reduce food into smaller pieces increasing surface area for enzymes to work on
Food is turned into bolus
Teeth formula
2I 1C 2PM 3M
Incisor
Cutting + bitting
Canine
Gripping + tearing
Premolar + molars
Grinding + Crushing
Mouth : Chemical
Salivary amylase
Consists of water, salt, mucin, amylase and lysozyme
Oesophagus
Pushes food down into stomach
Peristalsis
Rhythmic contraction and relaxation of muscles
Stomach
Entrance : Cardiac sphincter muscle
Exit : Pyloric sphincter muscle
Muscular
Expandable
J-Shaped bag
Gastric gland
Produces gastric hormones which causes production of gastric juice
HCl in stomach
Converts pepsinogen into pepsin
Kills microorganism
Loosen fibrous food
Deactivates salivary amylase
Pepsinogen
Activated becomes pepsin
Breaks down protein into peptides
Mucus
Thick alkaline substance that protects the stomach from acid and enzymes
Small intestine
absorption of nutrients through diffusion
covered in villus
Deamination
Amino acids not used broken down in liver forming urea
Lacteal
Absorbs fatty acid and glycerol into cells of villus lining
Adaptation of villi
Large number
Large number of microvillus
Walls only one cell thick
Rich in blood supply
Adaptation for small intestine
Very long
Numerous villi and microvilli
Thin walls
Lymph supply to carry fat away
Duodenum
Secretes intestinal juice, bile and pancreatic juice
Pancreatic juice
Produce in pancreas, enters duodenum via pancreatic duct
Contains water, sodium bicarbonate and enzymes
Sodium bicarbonate neutralises acid chyme
Bile
Produced in liver, stored in gall bladder, enters duodenum via bile duct
Consists of water, bile salt, bile pigments, cholesterol and phospholipids
Bile salt emulsifies fat
Excretes pigments biliverdin and bilirubin
Excretes excess cholesterol
Intestinal juice
Produced in duodenum
Maltase, sucrase, peptidase
Pancreas
Makes enzymes
Starch -> amylase -> maltose
Lipids -> lipase ->Fatty acid + glycerol
Protein -> protease -> peptides
Ileum
Absorption of digested food into circulatory system
Blood capillaries->hepatic portal vein -> Liver
Large intestine
Water reabsorption and elimination of faeces
Caecum
Ends in appendix (Both useless)
Colon
Reabsorbs water + mineral salts
Prevents dehydration
Rectum
Store semi-solid waste
Anus
Waste passes out of body as faeces
Liver
Storage of fat soluable vitamins, glycogen and minerals
Detoxification of poisonous substance
Produce heat
Formation of cholesterol
Hepatic artery
Brings oxygenated blood to liver
Hepatic vein
Carries deoxygenated blood + other nutrients from liver
Fibres in diet
Stimulates peristalsis - absorbs water providing bulk for intestine to push
Prevents constipation - keeps faeces soft
Prevents over-eating
Balanced diet
Contain all essential nutrients in correct amount