As we all know, the task of the mouth is to ‘grind’ all the food that we take into small bits.
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We do this by chewing (=masticating) the food, with our masticating muscles and with our teeth, and with saliva, secreted from the salivary glands.
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The major point of the mouth is to grind our food into such small pieces that they can easily be swallowed into our esophagus.
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The nice thing about the mouth is that we can ‘taste’ our food, something that does not happen in the rest of the GI-system.
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We are also helped with the nose that actually ‘smells’ our food much better than the tongue in our mouth.
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But the major reason why we want to taste and smell the food that we ingest is, of course, to warn us if we accidently eat something that is dangerous to us!
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In that sense, the mouse and the nose work together as a warning system. Just like the security check-in at the airport!
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After all, when the food has passed beyond the mouth, there is no ‘return’ any more. Same as in an airplane!
The task of the esophagus is very straightforward; transport the food from the mouth cavity into the stomach.
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The esophagus is a long tube that passes from the skull, through the thorax, adjacent to the lungs and the heart, runs through a hole in the diaphragm, and finally ends in the stomach.
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This is the ‘swallowing’ act that we are all familiar with. The food is transported as a sequence of boluses down the tube.
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The swallowing is actually an active process whereby the muscles inside the wall of the esophagus relax and contract in order to ‘push’ the food bolus into the stomach. This is called ‘peristalsis’.
The major function of the stomach is to digest the food that comes from the esophagus.
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All the food that has been chewed to bits in the mouth now has to be digested into a slimy substance called chyme.
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The stomach also secretes several compounds to help in this digesting process such as gastric acid and several enzymes.
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And the stomach is also a muscle that regularly contracts, just like the heart, although at a much slower rate (about 3/min), to knead and push this chyme into the small intestine.
The small intestine is not small at all! It is actually a very long tube, about 3-5 meters in a human adult.
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This is the organ where most of the foodstuff gets absorbed into the body. In a sense, this is the center, or the ‘heart’ of the GI-system.
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The chyme is pushed along this long tube by the walls of the tube that contract in a peristaltic manner; pushing the chyme in front of the contractions.
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The small intestine is divided into three segments:
the duodenum
the jejunum
the ileum
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The duodenum is relatively short, about 20-30 cm long, receives the chyme from the stomach and mixes it with digestive juices that come from the liver and the pancreas.
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The jejunum is longer, about 2 meters, and this is were a lot of the nutrients (amino acids, sugar and fatty acids) gets absorbed into the blood stream.
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The ileum is the last and longest part of the small intestine, approx. 3 meters long and absorbs mainly vitamin B12 and bile acids.
The large intestine, also called the large bowel or the colon, is the last part of the GI system.
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It is about 1.5 meters long and receives whatever chyme is left from the small intestine.
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Also here, the chyme is propelled by rhythmic contractions of the wall of the colon.
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The major function of the colon is to absorb the water that is left in the chyme. This makes the waste material more hard and into feces, ready for defecation.
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And, another major function of the colon is to keep the waste inside your body until YOU are ready to release your ‘shit’ to the outside world!
The liver is the major biochemical factory in the body!
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It produces many compounds such as proteins and hormones, regulates glycogen storage etc., etc.
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The liver also detoxifies various metabolites and produces bile. This bile, stored in the gallbladder and released into the duodenum, helps in the breakdown and the emulsification (= blending in water) of fats in the food.
The pancreas is an endocrine and an exocrine gland (endocrine = hormones and exocrine = compounds to digest the food).
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The pancreas produces several hormones that are crucial in the body such as insulin, glucagon and several compounds to help in the digestion of our food.
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The insulin, as you may know, plays a crucial role in the regulation of our sugar level. If there is something wrong in this regulation, then you may suffer from diabetes!
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All these fabricated compounds are either released into the duodenum (=exocrines) or into the blood (=endocrines).
