Mechanical digestion is when the food is broken down into smaller pieces. It is proven as a physical change because no new substance are made.
Chemical digestion is when large, complex substances in the food are broken down into simpler chemicals. New, smaller chemicals are produce so that the body can absorb.
Slide 4
The Mouth
The digestion begins in our teeth. Humans have four types of teeth: incisors, molars, premolars and canines.
Biting and chewing are both mechanical digestion.
Chemical digestion also takes place in the mouth. The food is mixed with saliva.
Saliva contains a chemical that starts to change any starch into glucose.
Oesophagus is a long muscular tube that has mouth at the end and a stomach at the other end.
Peristalsis is when the muscles of oesophagus push the bolus down the tube by contracting behind the ball.
Epiglottis closes the end of the windpipe as you swallow.
Peristalsis is the rhythmic contracting and relaxing the muscles of the oesophagus that keeps food moving through the tube and other parts of the digestive system.
Slide 6
Stomach
Food is stored in the stomach for 1-6 hours.
Gastric juice contains: hydrochloric acid, mucus, and digestive juices.
The muscular walls if the stomach contract and relax, churning up the food. This further digests the food mechanically.
Duodenum is the first part o the small intestine. This tube comes from the pancreas and liver. Liver produces bile which responsible for chemical digestion of fats. Duodenum squeezes and churn the food, breaking it down and making sure that the digestive chemicals are mixed through.
Small intestine is a very long, narrow tube. It is in the part of the small intestine that the digested food is absorbed into the body.
Villi are the fingers that greatly increased the surface area area of the intestine.
Nutrients that pass from the small intestines are: fatty acids,and glycerol produced from digestion of proteins, amino acids from the protein, and glucose from fats..
The final section of the digestive tract.
Water is reabsorbed into the body from what is left of the food, along with any remaining nutrients. The waste forms lump of faeces.
The wastes are then later expelled from body through the anus.
VomitingStress or infection can cause the muscular wall of the stomach and small intestine to contract. HeartburnA burning sensation that rises up the oesophagus from your stomach.
DiarrheoaThese cause the lining of the small intestine to become inflamed so that it can no longer absorb water from faeces.AppendicitisA blind-ended tube connected to the large intestine.
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