DIGESTION

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...

THE DIGESTIVE SYSTEM MOUTH STOMACH OESOPHAGUS LIVER SMALL INTESTINES PANCREAS

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

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

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

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...

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...

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) ...

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

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.

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

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...

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

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

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...

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

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

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 .

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.)

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

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

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

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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