Digestion

The 5 Stages of Digestion

Digestion is a process of mechanical and chemical breaking down of food into smaller components that can be absorbed into the blood stream. The digestive tract through this process retrieves chief nutrients and converts the unused food into waste. Each organ in the digestive system has a specific function. The coordination of the functions is controlled by endocrine and nervous systems.

Stage 1: Digestion in Mouth

  • This is the first step of digestion. In the mouth, chewing of food or mastication process occurs. Saliva initiates the digestion and helps in food chewing. The food is made into soft mass called bolus.
  • Thus soft mass along with saliva becomes slippery and makes it easier to slide down into the throat and oesophagus.
  • Through the oesophageal sphincter, soft mass of food enters into the stomach.

Stage 2: Digestion in Stomach

  • The stomach is in the form of a pouch and receives the soft bolus of food from the oesophagus.
  • It contains hydrochloric acid that mixes with the food and breaks it into a liquefied substance called chyme.

Stage 3: Digestion in Small Intestine

  • The liquefied food called chyme enters into the duodenum, the first part of the small intestine.
  • The enzymes are released from gallbladder, liver and pancreas that further break the liquefied chyme into simpler elements.
  • It is in this stage the food can be easily absorbed by the body. Small intestine has finger-like projections called villi that allow the completely digested food to enter into the bloodstream.
  • The vitamins and nutrients are also well absorbed in this stage.

Stage 4: Digestion in Large Intestine

  • The liquefied chyme travels though the small intestine and enters into large intestine.
  • Before entering into large intestine, it travels through ileocecal valve.
  • An inconsiderable digestion takes place in this stage. Hence, it is considered as waste.
  • As the waste passes through the large intestine, it becomes solid as the water gets reabsorbed.

Stage 5: Digestion in Rectum

  • The waste is finally collected in the rectum, the last part of large intestine.
  • It is finally eliminated through anus when the brain signals the particular action to occur.

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