The Digestive System

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Mouth
We ingest food through our mouth or buccal cavity.
Our jaws, teeth and tongue break up our food into smaller pieces so it is easier to swallow.
Saliva from our salivary glands helps moisten our food and made it easier to swallow. It also contains enzymes
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Oesophagus
Food slides past our epiglottis and into the oesophagus or gullet.
The Oesophagus is a muscular tube that squeezes food down by muscular contractions called peristasis.
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Stomach
A muscular sac that churns our food around and starts to digest the protein in our food. Gastric juice is added which contains enzymes and hydrochloric acid.
The partially digested mush called CHYME is then ready to move to the small intestine.
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Small Intestine
Movement of food into the small intestine is controlled by the opening and closing of the pyloric sphincter.
Three parts to small intestine:
- Duodenum - continues to digest food with enzymes added from intestinal juice. Pancreatic juice. Bile is added fr
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Villi
The wall of the ileum is covered with finger like projections called villi which provide a large surface area. Villi contain blood vessels. Digested food is absorbed through the wall into the blood.
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Large Intestine or Colon
Water in the undigested food passes back into the blood forming semi-solid faeces. Bacteria feed on our undigested food providing us with vitamins such as folic acid and Vitamin K, also gases.
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Rectum and Anus
Faeces are stored in rectum before being squeezed out of the anus.
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Mechanical Digestion
Mechanical Digestion - physically breaking down food into smaller pieces. Chewing and the squeezing of the food by the muscles of the stomach are examples of mechanical digestion. Pulverising the food makes it easier for enzymes to break the food molecule
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Chemical Digestion
Chemical Digestion - changes large food molecules into simpler smaller molecules using enzymes. Happens in the mouth, stomach and small intestine.
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Enzymes - How do they work?
Enzymes are proteins that have part of them called an active site that has a specific shape. Different enzymes break down different substrates.
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Enzymes involved in digestion
Carbohydrate - Salivary Amylase - Mouth
Carbohydrate - Amylase - Duodenum
Carbohydrate - Maltase - Duodenum
Carbohydrate - Sucrase - Duodenum
Protein - Pepsin - Stomach
Polypeptides - Peptidases - Duodenum
Peptides - Peptidases - Duodenum
Fats - Lipases
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Role of Bile
Made in liver. Stored in gall bladder. Bile consists of water, sodium chloride, bile salts and bile pigments. NO enzymes. Ph=8
Functions of bile:
- dilutes contents from stomach
- creates optimum pH for pancreatic enzymes to work in duodenum
- Contains bi
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Which enzymes where?
- Mouth
Mouth - Salivary amylase in saliva starts to break down starch into maltose.
Stops as soon as the food hits the stomach as the low ph of the stomach "denatures" of the salivary amylase so it can no longer fit the starch.
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Which enzymes where?
- Stomach
The stomach produces gastric juice containing pepsin and hydrochloric acid. Pepsin needs acid conditions to work.
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Which enzymes where?
- Duodenum
The enzymes that will be added here will denature in acid conditions so when the chyme enters from the stomach it has to be neutralised. Alkaline salts are added in bile and pancreatic juice.
The pancreas and walls of the duodenum also produce more digest
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Other cards in this set

Card 2

Front

Food slides past our epiglottis and into the oesophagus or gullet.
The Oesophagus is a muscular tube that squeezes food down by muscular contractions called peristasis.

Back

Oesophagus

Card 3

Front

A muscular sac that churns our food around and starts to digest the protein in our food. Gastric juice is added which contains enzymes and hydrochloric acid.
The partially digested mush called CHYME is then ready to move to the small intestine.

Back

Preview of the back of card 3

Card 4

Front

Movement of food into the small intestine is controlled by the opening and closing of the pyloric sphincter.
Three parts to small intestine:
- Duodenum - continues to digest food with enzymes added from intestinal juice. Pancreatic juice. Bile is added fr

Back

Preview of the back of card 4

Card 5

Front

The wall of the ileum is covered with finger like projections called villi which provide a large surface area. Villi contain blood vessels. Digested food is absorbed through the wall into the blood.

Back

Preview of the back of card 5
View more cards

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