Powerpint digestive system
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Transcript of Powerpint digestive system
THE ALIMENTARY CANAL• INGESTION: taking substances (e.g. food, drink) into the body
through the mouth.
• DIGESTION: the break-down of large, insoluble foodmolecules into small, water-soluble molecules usingmechanical and chemical processes.
• ABSORPTION: the movement of digestive foodmoleculesthrough the wall of the intestine into the blood orlymph.
• ASSIMILATION: the movement of digestive food moleculesinto the cells of the body where they are used, becoming partof the cells.
• EGESTION: the ´passing out of food that has not been digeste, as faeces, through the anus.
PERISTALSISA contraction in one region of the alimentary canal is followed by another contractionjust below it so that a wave of contraction passes along the canal pushing food in front
of it.
Chemical digestion
FOOD ENZYMES PRODUCTS
Starch amylase glucose
Proteins protease Amino acids
Fats lipase Fatty acids + glycerol
How to reduce the risk of toothdecay
-Eating food with a low sugar content.
- Regular and effective brushing of teeth at least twice a day to prevent the build up of
plaque.
- Use a fluoride toothpaste regularly. Itmakes your teeth more resistant to decay
SWALLOWING
• Ensures that food does not enter the windpipe(trachea) and cause choking.
• Beginning: voluntary
• Then: involuntary
STOMACH
• Functions:
- stores food from a meal.
- turns food into a liquid (peristalticmovements)
- releases food in small quantities at a time tothe rest of the alimentary canal (pyloricsphincter)
Chemical digestion:
• Production of gastric juice (glands in thelining)
- Enzyme: pepsin (protease)
Proteins → peptides
- Hydrochloric acid: provides the best degree of
acidity for pepsin to work in and kills many bacteria
of food.
THE SMALL INTESTINE
Duodenum Ileum
• Chemical digestion
Enzymes from:
1. Pancreatic juices
2. Bile
3. Intestinal juices
PANCREAS• Secretion of pancreatic juice:delivered to the
duodenum by the pancreatic duct.
i) Enzymes:-Proteases:
Proteins → peptides → aa- Pancreatic amylase:
Starch → maltose- Lipase:
Fats → fatty acids + glycerol
ii) Sodium hydrogencarbonate: neutralizes the acid liquid from
the stomach so that pancreatic enzymes work correctly. (alkaline conditions)
BILE
• Produced by the liver.
• Stored in the gall bladder.
• Delivered to the duodenum by the bile duct.
• No enzymes
• Bile pigment:from the break down of haemoglobin in the
liver.
• Bile salts: Emulsify the fats: they break them up into
small drops which are more easily digested by lipase.
INTESTINAL JUICES
• The epithelial cells of the villi produce enzymes which complete the breakdown of:
- Maltose
- Peptides
before they are absorbed.
Maltose → glucose
Peptides → aa
FINAL PRODUCTS OF DIGESTION
FOOD FINAL PRODUCTS
Starch Glucose
Proteins Amino acids
Fats Fatty acids + glycerol
Molecules
Epithelial cells → a large proportion of
↓ fatty acid + glycerolcapillaries (bloodstream ) ↓
↓ form fats againveins veins ↓
↓ pass to lactealsHepatic Portal Vein
↓ ↓ lymphatic systemLIVER
↓General circulation (vena cava)
LARGE INTESTINEColon and rectum
• Material that reaches it contains:
i) water with undigested matter
ii) cellulose
iii) fibre: digested partly by bacteria
iv) mucus
v) dead cells from the lining of the alimentary canal
• Function: absorption of water.
semisolid waste → faeces → rectum → anus (EGESTION)
ASSIMILATION
• Glucose
Respiration energy
• Fats
-Are built into cell membranes and other cell structures
- Source of energy
• Amino acids- Built up into proteins. Functions??
STORAGE OF DIGESTED FOOD
• Glucose
- Changed in the liver to glycogen
- Some of the glycogen is stored in liver(short- term store) and muscles.
- LIVER: If ↓ blood sugars Glycogen → glucose → circulation
- MUSCLES: glucose: for muscular activity
- Excess of glucose: converted to fat and stored in fats depots
STORAGE OF DIGESTED FOOD
• Fats
- There is no limit to storage of fats
- Long- term store as fat depots in:
-abdomen
- round the kidneys (adipose tissue)
- under the skin
STORAGE OF DIGESTED FOOD
• Amino acids
- They are not stored in the body
- Those not used in protein formation are deaminated (in the liver)
LIVERFunctions
• Regulation of blood sugars.
• Production of bile.
• Deamination
• Storage of iron.
• Manufacture of plasma proteins.
• Detoxication.
• Storage of vitamins