Digestive system Flashcards
What are the 6 main nutrients the cells in the body require?
Simple sugars Amino acids Fatty acids Vitamins Minerals Water
What will occur to our cells if we do not get these nutrients?
Without these things our cells and therefore body would not function properly!
Where do the 20 amino acids come from?
Essential amino acids– from foods directly (9)
Non Essential amino acids– synthesised from foods (11)
What bond holds the amino acids?
Amino acids are joined by a peptide bond.
What are 4 functions of lipids?
High energy source (energy reserves)
Insulation
Protection of organs
Structural (cell membrane)
What is digestion?
The process in which carbohydrate, protein and fat molecules are broken down to products small enough to be absorbed into the blood and into the cells
What are the 6 steps of digestion in the digestive system?
Ingestion of food
Mechanical digestion of food (physical)
Chemical digestion of food (involves enzymes)
Movement of food along the alimentary canal
Absorption of digested food and water into lymph and blood
Elimination of material that is not absorbed
What is the alimentary canal?
Most of the parts of the digestive system are arranged to form a continuous tube running from the mouth to the anus
What are the organs called that are not part of the alimentary canal, but still help with digestion?
There are also other organs called accessory organs that help with digestion.
What are carbohydrate enzymes called?
amylase
What are protein enzymes called?
Protease
What are lipid enzymes called?
lipases
What happens in ingestion of food: Digestion in the Mouth? Mechanical and chemical
Mechanical: Action of jaw and teeth breaks food into smaller particles.
Canines(2)- tearing
Incisors(4)- bite
Premolars(4)/Molars(6)- crushing and grinding
Chemical: Salivary glands secrete saliva which contains mucus and salivary amylase (begins starch breakdown)
What happens in ingestion of food (physical): chewing and swallowing?
After chewing in the mouth, the food is formed by the tongue into a rounded lump called a bolus. Swallowing then occurs, the tongue moves upwards and backwards to push the bolus into the back of the mouth, the pharynx.The pharynx leads to the oesophagus
What happens in ingestion of food: Peristalsis?
The wall of the oesophagus has a double layer of muscle, circular and longitudinal
As food enters the oesophagus the circular muscle behind it contracts to form a constriction. The contraction of successive bands of muscle moves the food along.
What is peristalsis?
A wave of muscular contraction that pushes food along
What is the stomach lining?
The stomach lining (mucosa) is specialised for the secretion of gastric juice which contains hydrochloric acid, mucus and digestive enzymes
What happens in Mechanical digestion of food (physical)?
Mechanical: waves of muscular contraction that move along the stomach wall.
Circular, longditudinal and oblique muscles (muscle contracts in a variety of ways to churn food and mix it with enzymes)
What happens in Chemical digestion of food in the stomach?
Chemical: Gastric juice secreted by gastric glands located in tube-like structures called gastric pits.
Starts protein digestion Gastric Protease
What occurs in the stomach when food comes?
Lower end of the stomach muscle constriction
Pyloric sphincter: prevents movement of food too early
The food is converted into a thick, soupy liquid called chyme
After 2-8 hours the stomach contents are pushed into the next part of the alimentary canal, the small intestine.
What occurs in the first part of the small intestine?
called the duodenum, Food enters the small intestine from the stomach is only partially digested. Most of the organic molecules are still too large to be absorbed into the blood and must be further broken down.
What are the three main fluids that helps digest the food in the small intestine?
There are three main fluids that help digest the food in the small intestine.
Pancreatic juice (from the pancreas) Bile (from the liver/gall bladder) Intestinal juice (from the small intestine)
What enzymes are in the Pancreatic juice (from the pancreas) ?
Pancreatic amylase: breaks down starch (polysaccharides) to disaccharides
Pancreatic protease (trypsin): breaks down proteins to small peptide chains
Pancreatic lipases: breaks down fats into fatty acid and glycerol
Nucleases: breaks down RNA and DNA
What is bile (from the liver/gall bladder)?
Produced by the liver stored and secreted by the gall bladder
No digestive enzymes
Contains bile salts
Emulsify fats, breaking them down into tiny droplets
MECHANICAL DIGESTION
Increases surface area for fat chemical breakdown.
What enzymes are in Intestinal juice (from the small intestine)?
Amylases: disaccharides to monosaccarides simple sugars
Peptidases: small peptides to amino acids
Lipases: Lipids to fatty acids and glycerol
Where does Absorption of digested food and water occur?
Through the wall of the small intestine into the blood
Why does absorption occur in the small intestines?
Large surface area needed
Long (6m)
Mucosa has folds
Small finger-like projections called villi (1mm)
Cells covering the outside of the villi have tiny microscopic projections called microvilli
Describe the process of absorption
Inside Villus is a lymph capillary called a lacteal, which is surrounded by a network of blood capillaries.
Continual movement of villi enhance absorption
Nutrients move via simple diffusion and active transport
Simple sugars, amino acids, water and water-soluble vitamins into blood capillaries
Fatty acids and glycerol into lacteals
What occurs in the large intestine?
Remaining water is absorbed
Bacteria in the Large intestine break down much of the remaining organic compounds. Some bacteria produce vitamins, which are absorbed through the walls into the blood.
Minerals are absorbed
Stores faeces (water, undigested food material (cellulose), bacteria, bile pigments, remains of cells of the internal lining of the alimentary canal)
Defecation
What is the large intestine?
No Villi
No digestive juices secreted
Slow movement 18-24 hours
What the 13 main structures of the digestive system?
Mouth
Salivary glands
Oesophagus
Stomach
Liver
Pancreas
Gall bladder
Duodenum
Small intestines
Large intestine
Appendix
Rectum
Anus
What happens when nutrients enter the body?
Water, vitamins and minerals are small molecules and don’t need to be broken down by the body, they just enter the cells.
The remaining body requirements need to be broken down because they are eaten as larger more complex molecules that cannot enter the cells as they are.
What 3 parts of the digestion system have mechanical digestion?
Mouth: chewing
Stomach: grinding
Duodenum: Bile-breaks down fat
What 4 parts of the digestion system have chemical digestion? State the enzymes.
Mouth: salivary amylase - starch
Stomach: Gastric protease - proteins
Duodenum-(from pancreas) pancreatic amylase, protease and lipase
Small intestines - intestinal amylase, protease and lipase
What absorption occurs in the stomach?
No nutrients are absorbed in the stomach due to thick mucus layer
Some alcohol and a few other drugs are absorbed
