Neutralising the acidic environment. The stomach and bile. The stomach is very acidic due to cells in the lining producing HCl. This means that the semi digested food is very acidic entering the small intestine. Bile plays two main parts. Neutralising the acidic environment. Emulsifying fats to provide a larger surface area for lipase to work on.

Problem! The gastric juices are acidic! There could be a danger of the lining of the small intestine being digested. Luckily two substances are produced to stop this happening. The first is mucus and we have seen how this works. The second is Bile. Bile is made in the Liver. It is a yellow/green liquid that is naturally alkaline (pH > 7).

+ This means that when Bile and the Gastric Juices meet, …the result is neutralisation of the acid.   This is essential for the lipase (the enzyme that digests fat) to function properly. pH >7 + pH <7 Neutralisation

Part of the Small Intestine  

Let’s consider the process of fat digestion.  This section of the digestive system exemplifies the true idea of an organ system as a group of organs working together for a common function.   The influential organs in the digestion of fat are the: Liver Gall bladder, Pancreas Small intestine. Each organ plays its part in turning Fat into fatty acids and glycerol phosphates

Fat within the gastric juice   Liver produces Bile Fat within the gastric juice It is released from the Gall bladder and passes down through the bile duct The Bile and the fat meet within the small intestine. The Bile emulsifies the fat. This basically means the fat is physically broken into smaller pieces. Emulsification Notice that the fat has not been chemically digested, only physically. The result is a greater surface area over which the enzyme, lipase, can attack the fat.

The pancreas and the small intestine now release enzymes The pancreas and the small intestine now release enzymes. Both organs produce all three enzymes, Carbohydrase, protease and lipase. pancreas small intestine If we just consider fat, the lipase begins to break its chemical bonds.

    Lipase Glycerol Phosphate Fat Fatty Acids

Bile emulsifies the fat. Muscular action of the small intestine In summary the digestive action of the small intestine and associated organs can be represented in the following diagram.   Fat Sugar Protein Carbohydrates Amino Acids Physical Digestion Chemical Digestion Bile emulsifies the fat. Muscular action of the small intestine Lipase enzyme Protease enzyme Carbohydrase enzyme Sugar Glycerol Phosphate Amino Acids Fatty Acids