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Stomach

 

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Summary

Did you know..

..the size of a newborn baby's stomach is about the size of a small hen's egg? And the stomach of an adult can hold about a litre of food.

The stomach is a muscular pouch-like organ, shaped like the letter 'J'. It is where our food is mushed and churned to be absorbed into the bloodstream.

Oesophagus: After food is swallowed, it travels down a long tube called the oesophagus. Waves of muscular contraction push the food down. This is a process called peristalsis, and occurs throughout the entire length of the alimentary canal. At the bottom of the oesophagus is a sphincter. There are several sphincters in our bodies, and they are basically tightenings, or narrowings, of a tube.

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Stomach: After passing the sphincter (cardiac sphincter), food enters the stomach, a very muscular pouch. Here, digestive juices are secreted and mixed with the food. These juices are highly acidic, and therefore kill many of the germs that may enter with the food. The food is mashed and churned and mixed with the digestive juices, and becomes a soup-like pulp, called chyme. Only once it has become soft enough can it pass on to the duodenum, and this is because of another sphincter, the pyloric sphincter, situated at the end of the stomach. It prevents solid, undigested food from passing on to the duodenum.

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Duodenum: This is the beginning of the small intestine, and it is into this part of the stomach that the pancreatic duct (pancreas) and common bile duct (liver) secrete certain juices. These juices further aid digestion, in particular, the digestion of fats. Being alkaline, they also help neutralise the acidity of the chyme once it has left the stomach.

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Summary

So, what happens in the stomach after eating a meal?

The food we eat needs to be well-chewed before we swallow, in order to be able to pass through the cardiac sphincter at the base of the oesophagus. Once food has passed the sphincter, it enters the stomach, where it is mushed and churned by the muscular movement of the stomach. Highly acidic juices are secreted to breakdown the food, and it then becomes a soup-like substance called chyme. Once it is able to, the chyme (semi-digested food) passes onto the duodenum. This is the beginning of the small intestine, and it is here that secretions from the liver and pancreas mix with the chyme, neutralising its highly acidic quality.

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