7.2/7.3 Digestive system Flashcards
ka1 term3 - 2025
Main organs of digestive system
Alimentary canal: mouth, oesophagus, stomach, small intestine (duodenum + ileum) + large intestine (colon + rectum + anus)
Assotiated organs: salivary glands +pancreas + liver + gall bladder
Ingestion
taking of substances (mouth)
Digestion
breakdown of food
Chemical: breakdown of large insoluble molecules into small soluble ones (enzymes)
Physical/mechanical: breakdown of food into smaller pieces without chemical change to the food molecules
(increase the surface area of the food so that enzymes can more effectively break it down (chewing/churning)
Absorption
movement of nutrients from intestine into the blood (SI)
nutrients/digested molecules cross the wall of intestine to bloodstream
Assimilation
uptake and use of nutrients by the cell used for energy growth and repair
Egestion
removal of undigested food from body as feces (anus) - defecation (fiber, feces, etc.)
Mouth
ingestion (start of alimentary canal)
Food –> bolus of food (teeth + saliva)
has salivary glands
(Ingestion ,chem+phy digestion)
salivary glands
3 pairs; produce saliva through the salivary duct
- produces salivary amylase to break down starch
Secrete - make and release
Oesophagus
muscular tube helping food move down by peristalsis
(Chemical digestion)
Liver
Produce bile which help neutralize acidic chyme + emulsifies fats (Assimilation)
Stomach
muscular bag that stores food + mixes food with acidic digestive juice to make chyme
Churns food up with muscular wall
produces pepsin + gastric juice(with HCl) to:
kill bacteria in food and provide optimum pH for pepsin
(Chemical/physical digestion)
Gall bladder
stores bile before poured into duodenum (bile duct)
Small intestine
2 parts, where most absorption happens
1. Duodenum
2. Ileum
Pancreas
produses pancreatic juice (with enzyme + mucus + hydrogencarbonate - neutralises chyme)
It produces - protease(Trypsin), amalase and lipase –> small intestine (pancreatic duct)
Large intestine
3 parts - reabsorb excess water + vitamin/minerals
1. colon (absorption)
2. Rectum
3. Anus (egestion)
Rectum
last fart of LI, stores feces before egested
Anus
feces is egested (controlled by 2 anal sphincters)
Amalase
Breaks down starch –> maltose
Optimum = 7ph
salivary amylase
pancreatic amylase
Protease
Breaks down protein –> peptides + amino acids
Pepsin - Optimum(2pH) in stomach
Trypsin - Optimum(8pH) in pancreas
Lipase
Breaks down lipids (neutral pH) –> fatty acids and glycerol (acidic pH)
Optimum = 8pH
In pancreas, secreted to duodenum
Bile, what does it do
Slightly alkaline, released from gal bladder
1. Neutralizes the chyme
- alkaline environment for enzymes
2. Bile salts, emulsify fat and break it down
- lipid molecules attract each other and stick making it slow for enzymes to digest them
- bile salt causes emulsification
-globules –> smaller droplets
- increases SA of oil = rate of lipase activity increase
Hydrolysis
Breaking down large molecules into smaller ones by adding water.
Large insoluble molecule —enzyme+water–> small, soluble molecules
Chemical reaction where food molecules are broken down with water and catalyzed by enzymes
Benefits of chewing food
-food has a larger SA
- this increases rate of digestion
- as the enzymes can go from different angles
What is the process of muscle contraction that pushes food down
Peristalsis
Fats break down to
glycerol + fatty acids
Carbohydrates break down to
Starch –> maltose —-maltase—> glucose
Proteins break down to
Polypeptides —-peptidases—> peptide/amino acids
Hydrogen carbonate +HCl
Hydrogen carbonate - alkaline (environment for enzymes)
HCl - acidic environment for pepsin + kill bacteria
Duodenum
1st part of small intestine where food is mixed with pancreatic juice and bile
(Chem/Phys digestion)
breaks starch, protein and fats
Ileum
the longest part of SI where food is absorbed to blood (absorption) - intestinal juice from villi (maltase)
breaks maltose that wasn’t fully broken up
Villi
Finger-like projections that line the inner surface of the small intestine. (with epithelial cells)
This increases SA for absorption
Phenophthalein
Pink above 8.2 pH
colorless at lower pH
Risk assessment for
buffers, chemicals in eyes, broken glass ware, and hydrogen peroxide
- buffers - wash off with water if spilt on skin
- chemicals in eyes - wear safety goggles
- broken glass ware - ask teacher to clean up and seek medical attention
4.hydrogen peroxide - if it is on skin, wash it up
