DESCRIBE THE DIGESTION OF A BUTTERED PIECE OF BREAD FROM THE TIME IT IS INGESTED UNTIL IT IS ABSORBED IN THE BODY. (20MKS)

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Describe the digestion of a buttered piece of bread from the time it is ingested until it is absorbed in the body. (20mks)
Mouth
Ø  Mechanical digestion where food is chewed and broken into small pieces. This increases the surface area of the food for efficient enzymatic action and makes swallowing easy.
Ø  Food is mixed with saliva which has salivary amylase; salivary amylase breaks down some starch into maltose.
Ø  The bolus is then swallowed through the oesophagus/gullet to the stomach.
Stomach
Ø  In the stomach, the presence of the bolus in the stomach stimulates the gastric glands to secrete gastric juice; which contains dilute hydrochloric acid; Pepsin and rennin;
Ø  Dilute HCl creates an acidic medium for pepsin enzyme; also kills; germs present in the food bolus.
Duodenum
Ø  In the duodenum; the pancreas; produces pancreatic juice; which contains pancreatic amylase; pancreatic lipase; and Trypsin enzymes;
Ø  Pancreatic amylase breaks down the remaining starch to maltose.
Ø  Pancreatic lipase breaks down the lipids into fatty acids and glycerol.
Ø  Trypsin breaks down proteins to peptides
Ø  The liver produces bile; that contains bile salts; which emulsify; fats into small fatty droplets; increasing their surface area for action of lipase.
Ø  Bile salts also neutralise the HCl and create an alkaline medium for pancreatic enzymes action.
Jejunum
Ø  In the second part of ileum, intestinal glands have secretory cells which secrete intestinal juice; which contains maltase, sucrase lactase, peptidase and lipase;
Ø  Maltase breaks down maltose to glucose and lipase breaks down Lipids and oils to fatty acids and glycerol. Sucrose is broken down to glucose and fructose.
Ø  Glucose and Fructose are absorbed in the ileum into the blood capillaries; to the blood stream;
Ø  Fatty acids and glycerol are absorbed by the lacteals.


20 marks

Comments

  1. UnknownMay 26, 2020 at 7:23 AM

    Plssss I won't to know what happens to a bread when it reaches the duodenum

    ReplyDelete

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