The Digestive System

A long and winding road

by Mary Treacy

age-well.org > The Digestive System

Table of Contents

This Page
The Digestive Tract
The Mouth
The Oesophagus
The Stomach
The Small Intestine
The Large Intestine

Page 2
The Intestine - Healthy Intestines for a Healthy Life

Page 3
Prevent Constipation

Other Resources
Eat Well
Benefits of Drinking Enough Water
Five Tips on Detoxing the Body
Aloe Vera Detox Program

The Digestive Tract

The digestive system consists of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and the gallbladder, pancreas and liver. Together this system break down and absorb food to fuel the body.

The digestive tract includes the mouth, esophagus, stomach, small intestine, large intestine, which comprises the colon and rectum, and the anus. The lining of the digestive tract is the mucosa. The mucosa In the mouth, stomach and small intestine, produces juices to help digest food. The digestive tract is also endowed with muscle that helps break down food and move it along the tract.

The liver and pancreas are connected to the tract by ducts through which they supply digestive juices to help the digestive system. However, overproduction of the liver's digestive juices are stored in the gallbladder until needed. Parts of the nervous and circulatory systems, not to mention the eyes and nose also play major roles in the digestive system.

Digestion is the process of breaking down food so that it's small enough to be absorbed and used by the body for energy or in other bodily functions.

The Mouth

The first stage of digestion is the stage which starts before the food enters you mouth, when the smell, anticipation, sight of the food and memory of how it tasted on other occasions starts to activate the saliva which will start breaking down the food in advance of the main digestive juices which contain enzymes which ibreak down the food.

Once the food enters the mouth, our tastebuds start to identify the chemicals within thefood sending signals to the brain to give you the taste sensations of salt, sweet, sour or bitter. As your teeth chew and grind the food, breaking it down, it becomes mixed with the enzyme containing saliva. The enzymes begin to break down the food bread, cereals, potatoes and pasta. Saliva also contains mucin, which moistens the food so it can pass easily through the digestive (gastrointestinal) tract.

The Oesophagus

The oesophagus is a muscular tube through which the food passes after it has been swallowed before it reaches the stomach. Involuntary contractions of the oesophagus push the food down to the stomach.

The Stomach

The stomach is a hollow organ with a saclike shape covered in muscle. It is located between the esophagus and the intestines.

The human stomach is a muscular, elastic, pear-shaped bag, lying crosswise in the abdominal cavity beneath the diaphragm. It changes size and shape according to is position of the body and the amount of food inside. The stomach is about 12 inches (30.5 cm) long and is 6 inches. (15.2 cm) wide at its widest point. The stomach's capacity is about 1 qt (0.94 liters) in an adult.

Food enters the stomach from the esophagus. The connection between the stomach and the esophagus is called the cardiac sphincter.

The stomach has several important roles in the digestive system. it stores, mixes and digests the food that we eat, and acts to protect us from infectious organisms we may have ingested.

The stomach is a sack made of muscle and, when it's empty, it has a volume of only 50ml but this can expand to hold up to 1.5 litres or more after a meal. The walls of the stomach are made of three different layers of muscle that allow it to churn food around and make sure it's mixed with the stomach's acidic digestive juices. The presence of hydrochloric acid in the stomach prevents the action of salivary amylase and helps to kill bacteria that might be present. The stomach also produces the enzyme pepsin, which breaks down proteins (mostly found in meat, fish, eggs and dairy products).

The hormone ghrelin is produced by cells lining the stomach. Ghrelin stimulates hunger and tends to increase before a meal and decrease after eating. This hormone forms part of the communication system between the gut and the part of the brain that controls hunger and satiety (how full you feel).

Food can stay in the stomach for a few minutes or several hours in the gastric phase where numerous acids and enzymes are released, including the hormone gastrin. When the food has been churned into a creamy mixture known as chyme, the pyloric sphincter (an opening controlled by muscle) opens and chyme passes gradually into the small intestine.

The Small Intestine

The small intestine also plays an important role in the digestive system. It absorbs fat, protein and carbohydrates but three other organs are involved in this process and also make up part of the digestive system:

The gall bladder provides bile salts that help to absorb the fats.

The pancreas provides bicarbonate to neutralise acids from the stomach, and also produces further digestive enzymes.

The intestinal wall The cells of the wall of the small intestine help to neutralise the acid and produce enzymes to digest food.

The inner surface of the small intestine is folded into finger-like structures called villi, which increase the surface area until it is equivalent to that of a tennis court in order to give more surface for absorption. Blood vessels receive the digested food from here and transport it through the blood stream to the liver via the hepatic portal vein.

Probiotics are live bacteria ften referred to as 'friendly bacteria', similar to the bacterial micro-organisms that live in the large intestine. They originate from food sources or dietary supplements. The mix of these 'friendly' bacteria and other gut microorganisms is important for health. This delicate balance can be affected by different factors such as an infection or use of antibiotics. Friendly bacteria are vital for the immune system, offering protection against disease causing micro-organisms and aiding the absorption of food and nutrients. The digestion of fat is a much longer process which cantake up to five hours. Unabsorbed residue of this process is propelled into the large intestine.

The Large Intestine

This is one of the most active organs in the digestive system and indeed the whole body. It measures about 1.5 metres and contains over 400 different species of bacteria that break down and utilise the undigested food, which is mostly dietary fibres. As the watery contents move along the large intestine, water is absorbed and the final product - faeces - is formed, which is stored in the rectum before being extreted by the anus.

Mary Treacy is the founder and contributing editor of age-well.org. She has over thirty years of experience working with non-profit, non-governmental organizations (NGOs), mainly business associations, and is an experienced writer in many sectors including co-operatives, agriculture, commmerce, housing, insurance, banking and health. You can find her on Google + and Twitter.

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