1. DIGESTION

2. The Digestion System What is digestion?
Digestion is the process of breaking down large complex food molecules into small molecules which can diffuse into our body cells
Digestion of food is helped by enzymes present in digestive juices secreted to the digestive system...

3. THE DIGESTIVE SYSTEM MOUTH STOMACH OESOPHAGUS LIVER SMALL INTESTINES
PANCREAS

4. The alimentary canal consists of all the organs through which food passes:
mouth
esophagus
stomach
duodenum
small intestine
large intestine
rectum
anus
the alimentary canal

5. IN THE MOUTH
food is masticulated and
mixed with saliva which
contains ptyalin which breaks
down starch to maltose.Food passes down the oesophagus
IN THE STOMACH
food is mixed with gastric juices
which contain HCl and enyzmes
proteins are digested here. Pepsin acts
on proteins and rennin acts on casein
IN THE SMALL INTESTINE
digestion is completed with the help of enzymes from the pancreas and those in the ileum

6. Mouth Food is cut/chewed into smaller pieces
this gives a larger surface area for enzymes to act on
food is mixed with saliva
starch maltose by ptyalin or salivary amylase
partly digested food is rolled into soft balls by tongue
swallowed into oesophagus by peristalsis

7. Stomach food is mixed with gastric juice produced by stomach
gastric juice contains hydrochloric acid(HCl) and enzymes
hydrochloric acid provides an acidic environment for the enzyme, pepsin, to work in
hydrochloric acid also kills bacteria in the food to stop decay...

8. Stomach
Enzyme renin coagulates the milk present so that it is easier to digest
another enzyme, pepsin, digests the protein
finally, food in semi-liquid form is released to the duodenum in small quantities...

9. Duodenum food here is mixed here by bile and pancreatic juice
bile is made by the liver, stored in the gall bladder
fats and oil in food are emulsified by bile to give a larger surface area for digestive juices to work on
pancreatic juice, produced by the pancreas contains enzymes(amylase, lipase, protease) ...

10. Duodenum Any undigested food is digested into small intestine:
proteases
amylase
lipase
digested food in small molecules are absorbed through wall of small intestine into bloodstream by diffusion...
proteins and peptides
peptides and amino acids
Maltose
Starch
Fatty acid and glycerol
Fats

11. Digestion in the ileum
Fats are acted upon by lipase and broken down to fatty acids and glycerol which are absorbed by the lacteal of the villi of the ileum.
Peptones are broken down by peptidases to amino acids.
Double sugars like maltose, lactose and sucrose are acted upon by maltase, lactase and sucrase respectively and changed to simple sugars.

12. Digestion of sugars in the ileum
Maltose is broken down by maltase to glucose
Sucrose is broken down by sucrase to glucose and fructose
Lactose is broken down by lactase to glucose and galactose.
All these simple sugars are absorbed in the bloodstream through the villi of the ileum

13. Duodenum Bloodstream carries the digested food to body cells
mineral salts and vitamins which need not be digested are also absorbed in the small intestine and carried by blood to the body cells...

14. Absorption
.Absorption is the process of passage of the products of digestion through the walls of the digestive tract. This takes place in the ileum
Villi of the small intestine are fingerlike projections supplied with numerous blood capillaries for
the absorption of water-soluble nutrients, amino acids, monosaccharides Vitamins B and C and other elements
It also contains a tiny tube called the lacteal for the absorption of fatty acids and glycerol

15. Large intestine
Undigested or unabsorbed food moves on to large intestine
It is a semi solid waste known as faeces
This moves on into the rectum and are later discharged through the anus...
Water in food is absorbed in the large intestine

16. digestive enzymes
Digestive enzymes are chemical substances set free by digestive organs to help in the digestion of food
enzymes speed up process of digestion but they themselves remain unchanged when food is digested
each enzyme only work on one type of food
enzymes work best in 37ºC. they are destroyed at high temperatures
enzymes function in either acidic medium or alkaline medium...

17. Enzymes in digestion Starch in the mouth - salivary amylase (ptyalin)
pancreas- pancreatic amylase
small intestines- maltase, lactase, sucrase

18. Enzymes in digestion Protein stomach rennin and pepsin duodenum
Fats
stomach
Lipase
pancreas
lipase
(liver- bile salts stored in the
gall bladder
emulsifies the fats)
duodenum and small intestine
Protein
stomach
rennin and pepsin
duodenum
trypsin
small intestine
erepsin

19. digestion of fats In the mouth, No digestion of fats
Food moves along the oesophagus
In the stomach, food is mixed with gastric juice.
No digestion but fats are melted.
Food stays in the stomach for 2-4 hours
In the duodenum , melted fats are emulsified by the bile
from the liver and the chyme is made alkaline. The enzyme lipase from the pancreatice juices splits fats into fatty acids and glycerol.
In the small intestine the enyzme lipase splits the remaining fats
into fatty acids and glycerol which are absorbed by the lacteal of the villi .

20. digestion of carbohydrates
In the mouth
food is chewed and mixed with saliva.Ptyalin
acts on starches & change them to maltose.
Food moves down oesophagus
In the stomach
food is mixed with gastric juices.
No digestion of CHO
In the pancreas, amylase is produced.
In the duodenum, this amylase acts on any starch left and changes it to maltose
In the small intestine
Intestinal glands produce enzymes –
maltase which acts on maltose, sucrase on sucrose and
lactase on lactose. These are changed to simple sugars which are absorbed into the blood vessels of the villi.)

21. DIGESTION OF PROTEINS MOUTH No chemical digestion STOMACH
Gastric juices create an acid medium for enzymes to act efficiently.
Rennin coagulates milk protein
Pepsin break down proteins into smaller parts.
DOUDENUM
Pancreas produces pancreatic juice containing trypsin which breaks down protein further.
SMALL INTESTINE
intestinal juices containing erepsin acts on the
peptones and converts them into amino acids. These are absorbed into the capillaries of the villi

22. Metabolism and storage of nutrient
Once nutrients are absorbed in the capillaries they unite to form one large vein known as the hepatic portal vein. This vein carries the absorbed nutrients from intestine to the liver

23. The liver Level of glucose is regulated
Some glucose is removed from the blood and converted to glycogen
Fat is formed when the limit is reached for the amount of glycogen that can be stored.
Level of amino acids controlled-excess is deanimated in the liver. The nitrogen is excreted as urea.
Reserves of nutrients stored-the liver stores Vitamin A, D, B12, Iron Potassium and copper

24. Metabolism
This modified blood has the correct nutrients and most living cells are able to absorb.
Amino acids-built into structural proteins
Fats broken down by enzymes in a series of chemical reactions to form carbon dioxide and water. Energy is released
Glucose is broken down by the cells to form carbon dioxide and water. Energy is released. Process is known as cellular respiration

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