How Your Digestive System Works

The digestive system is a long tube that runs from your mouth to your bottom (anus). Its many organs break down food, extract nutrients from it, and move those nutrients into the bloodstream. It also removes waste materials and stores energy for future use.

How It Works
Your digestive system has several parts, including your stomach and small intestine. Each part performs a different function to break down food.

Stomach
The stomach is a sac-like organ with muscular walls that mix up food, liquid, and digestive juice as it moves through the body. Its lining contains glands that secrete acid and enzymes to break down proteins and fats. A thick layer of mucus covers the lining to keep the acidic digestive juice from dissolving tissue inside the stomach. The pylorus, a muscular valve in the stomach, opens when the food is ready to leave.

Small Intestine
The small intestine is the next step in breaking down food. It makes digestive juice, which mixes with bile and pancreatic juice to complete the breakdown of carbohydrates, proteins, and fats. The intestine also absorbs water from the bloodstream and makes vitamin K.

Bacteria in the small intestine make some of the enzymes you need to digest carbohydrates, and they also help you absorb vitamins A, B6, C, and E. The intestines also take in minerals such as calcium, iron, and zinc.

Glands in your cheeks and under your tongue secrete saliva, which coats the food you eat and helps it chew easily. Saliva also contains substances that help begin the chemical digestion of carbohydrates, including lingual lipase.

Oesophagus
After food leaves the mouth, it travels to the oesophagus through the pharynx. The oesophagus is a muscular tube that carries food from the mouth to the stomach. The oesophagus contracts to squeeze food down, and then relaxes to let it go back up again.

Segmentation
The small intestine has circular muscles that divide it into sections, moving the foods back and forth while subdividing and mixing them with digestive juices. These contractions, called segmentation, are controlled by nerves that run down the wall of the GI tract.

Mouth
The mouth is the first place you eat, and it plays an important role in your digestive system. It's where you taste the food you eat and smell it. It's also where you begin to chew it, which breaks down the food into smaller chunks.

This mechanical action causes the teeth to grind food into small pieces, and it helps your oesophagus carry it down the throat to your stomach. Your mouth also produces saliva that lubricates your oesophagus and moistens your food for easier swallowing.

In the mouth, saliva contains digestive enzymes such as amylase, which is involved in the first stage of carbohydrate digestion, and lingual lipase, which breaks down lipids in fats.

Serous and minor salivary glands are found on the palate, tongue, and floor of the mouth. They produce about 1.0 to 1.5 liters of saliva each day.