Process of Digestion
Essay by Ty Turner • November 10, 2015 • Coursework • 473 Words (2 Pages) • 974 Views
Page 1 of 2
- The process of digestion begins with the mouth.
- While chewing, the teeth break the larger pieces of food into smaller ones. This process is known as mastication. Fluid, aka saliva, is also helping to dissolve the food particles.
- When the food gets swallowed, it then passes through the pharynx. In order for the food to bypass the entrance to the lungs, the epiglottis closes off the airway. After the food has been chewed and swallowed it is now a bolus.
- The food then travels down the esophagus.
- The esophagus has a sphincter muscle at each end. During a swallow, the upper esophageal sphincter opens. The bolus then goes down the esophagus, which passes through a hole in the diaphragm. The lower esophageal sphincter at the beginning of the stomach closes behind the bolus so it can proceed and won’t slip back into the esophagus.
- The stomach then holds the bolus for a while.
- Food that enters the stomach stimulates cells in the stomach wall to release gastrin. The gastrin then in turn stimulates the stomach glands to release HCL.
- At little pieces at a time, the stomach transfers food to the lower portion. It adds juices to it and churns it into a semiliquid called chyme. The stomach then releases the chyme through the pyloric sphincter, which opens into the small intestine and then closes behind the chyme.
- The small intestine secretes enzymes that digest all energy-yielding nutrients into smaller nutrient particles.
- In the beginning of the small intestine, the chyme bypasses the opening from the common bile duct, which drips fluids into the small intestine from two organs (the gallbladder and pancreas). The chyme then moves on down the small intestine through its three segments (the duodenum, the jejunum, and the ileum).
- The presence of chyme stimulates the cells of the duodenal wall to release secretin into the blood. When secretin reaches the pancreas, it stimulates the pancreas to release bicarbonate juices.
- When there is fat or protein in the small intestine, the intestinal wall releases cholecystokinin (CCK). CCK then travels to the pancreas and stimulates it to secrete its juices , which releases bicarbonate and enzymes into the small intestine.
- After traveling the long passage of the small intestine, the contents reach at another sphincter (the ileocecal valve). This is at the beginning of the large intestine.
- The large intestine absorbs water and passes waste to the rectum.
- Until it’s time to defecate, the muscles of the rectum and anus hold the waste in.
- The rectal muscles will then relax, and the two sphincters of the anus will open for the elimination of waste.
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