The path of food through the digestive system

Sunday, October 18, 2020

What is the path of food through the digestive system?

Digestion is the breakdown of food into small particles so that they can be absorbed into the blood.

The digestive system breaks food down (digestion), absorbs nutrients, and eliminates waste.

Digestion starts in the mouth.


This involves both mechanical digestion, ( the chewing of food) and chemical digestion.

Teeth chew food into smaller pieces, while saliva is mixed with the food to aid in swallowing. Amylase in saliva starts to break down starches into simple sugars. After passing through the esophagus, food enters the stomach, where it is churned into a thick liquid called chyme. Hydrochloric acid excreted by parietal cells lowers the pH in the stomach, which increases the effectiveness of pepsin—an enzyme that begins the digestion of proteins.

The chyme then passes into the first section of the small intestine, called the duodenum. Here bile which is created at the liver and stored in the gall bladder is released and enzymes created at the pancreas are added to the food. Bile helps break down fats by reducing large drops of fats to small droplets, which increases the surface area of the fats. Three pancreatic enzymes digest nutrients

lipase breaks down fat molecules into fatty acids

amylase reduces starches to simple carbohydrates and,

trypsin breaks up proteins 

digestion enzymes

The walls of the small intestine are lined with folds and tiny finger-like projections called villi, which greatly increase the surface area of the small intestine. Each villus contains capillaries and a lymphatic vessel. Nutrients diffuse through the thin walls of the villus and into either the capillaries or lymphatic vessel: fatty acids go into the lymphatic vessel, and (simple sugars), amino acids, and water flows into the capillaries.

digestion system

The capillaries and lymphatic vessels deliver the nutrients into the bloodstream, where they are transported to body cells. The small intestine is very long, measuring about 7 meters (23 feet) in length.
After the small intestine, food passes into the large intestine or colon. The large intestine is full of bacteria, some of which produce useful vitamins such as vitamin K. 

Excess water is also absorbed in the large intestine. A mixture of waste material, bacteria, and mucus are passed to the rectum, where the mixture is compacted and readied for elimination. Wastes are eliminated through an opening called the anus.

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