Gastrointestinal Tract: Definition, Types, Functions & Infections

Gastrointestinal Tract is the path from where the food enters the body, and the waste is excreted. It includes all major digestive system organs, including the esophagus, stomach, intestines, liver and pancreas.

• The gastrointestinal tract is a muscular tube that extends from the mouth to the anus.
• It is also known as the digestive tract or alimentary canal.
• Chemicals that are harmful to internal organs enter the body through the gastrointestinal (GI) tract.
• The mucosa is a delicate barrier that keeps germs out while allowing nutrients to enter and maintain equilibrium. 
• The gastrointestinal tract is also the only internal organ that contains bio-transforming and toxigenic microorganisms.
• It also contains drug-binding compounds that are inert.

As a result, when a substance is introduced into the gastrointestinal system, its ultimate toxicity is dictated by interactions with bacterial and mammalian enzymes and the level of detoxification and activation processes.

Read More: Immune System

Key Terms: Gastrointestinal Tract, Oesophagus, Intestine, Ileum, Ischium, Chyme, Mucous, Pancreas, Liver, Rectum, Digestive System

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Gastrointestinal Tract: Definition

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The gastrointestinal tract is an organ system in humans and other animals that takes in food, digest it, absorb nutrients and expel it out in the form of faeces. It passes through the pharynx, esophagus, stomach, and intestines.

• The length of the gastrointestinal tract is approximately 9 metres.
• It consists of gut microbiota that are responsible for maintaining the immunity and metabolism inside the body.
• The cells inside the GI tract will release the hormones that will control the digestive process.
• All of the gastrointestinal system's activities are contained in the gastrointestinal tract, which extends from the mouth to the anus in humans and many mammals.
• The meal is ingested and digested to receive nutrients and absorb reactive power, with wastes expelled as faeces.
• As an adjective, "gastrointestinal" refers to the gut and bowels. 
• A tract is a collection of connected anatomical structures or related body organs.

• The human Gastrointestinal Tract is divided into parts, namely Upper gastrointestinal tract and Lower gastrointestinal tract

Digestive System

Read More: Human Digestive System

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Upper Gastrointestinal Tract

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The upper portion of the gastrointestinal tract includes the mouth, pharynx, esophagus, stomach, and duodenum. The details about each part of the upper gastrointestinal tract are as follows:

Mouth

Mouth is the first part of the upper gastrointestinal tract. The functions of the mouth are as follows:

• It includes the teeth, tongue, and buccal mucous membranes, which contain the tips of the salivary glands.
• It extends to the soft palate, mouth floor, and tongue bottom.
• The tongue, cheeks, and teeth all work together to chew food, and the lower jaw and upper jaw work together also help in the process.

Salivary glands

Salivary glands produce saliva, which is a fluid found in the mouth and throat. The functions of the salivary glands are as follows:

• Saliva includes enzymes that start the digestion process.
• It also includes antibodies and other compounds that aid in the prevention of mouth and throat infections.
• The parotid, sublingual, and submandibular salivary glands are located under and behind the jaw of humans.

Teeth and Tongue

Teeth is another part of the upper gastrointestinal tract whose function is as follows:

• In the buccal cavity of an adult, there are 32 teeth.
• Food is broken down and crushed with the help of our teeth. 
• Later, it is sliced and ripped by the incisors and canines (front teeth).
• Next, it is crushed and broken into smaller bits by the bicuspid and molars (back teeth).
• The tongue is a three-lobed triangular organ with a muscular and meaty appearance. It runs the length of the floor of the buccal cavity.

Pharynx

The pharynx is a part of the digestive and respiratory systems encased in the neck and throat.

• It keeps food from getting into the trachea and lungs.
• The pharynx is responsible for the muscular propulsion of materials into the esophagus.

Esophagus

Esophagus is a muscular tube-like structure that carries food to the stomach.

• The esophagus regulates the action of swallowing after the chewed food enters the esophagus from the mouth.
• It is also known as the oesophagus.
• It is also responsible for transporting required minerals and materials to the stomach.

Stomach

The stomach is the place where majority of digestion takes place. In this, the mechanical processing of food takes place through muscular contractions.

• The stomach is a J-shaped bag-like organ.
• It temporarily stores food before breaking it down.
• The stomach is responsible for mixing and churning food with enzymes and other digestive fluids before passing it to the small intestine.

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Lower Gastrointestinal Tract

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The lower gastrointestinal tract consists of the lungs and small intestines. It extends from the pyloric sphincter of the stomach to the anus. The details about each part of the lower gastrointestinal tract are as follows:

Small Intestine

The small intestine is a 6-7 metre long coiled thin tube where the majority of nutrient absorption takes place. Its functions are as follows:

• Food is combined with liver and pancreas enzymes in the small intestine. 
• The small intestine's surfaces absorb nutrients from meals into the bloodstream, transporting them to the rest of the body.
• It is divided into three parts, namely duodenum, jejunum and IIeum. 
• The mucosal area in a human being is approximately 30 m².

Large Intestine

The large intestine is a thick tubular structure that wraps around the small intestine. Its major job is to digest waste products and reintroduce any remaining nutrients and water into the system. 

• The leftover waste is subsequently sent to the rectum, where it is expelled as a stool.
• It is also known as colon.
• The intestine is shaped like an arch, starting at the cecum and ending at the rectum.
• The appendix is also part of the large intestine.

Read More: Difference Between Small and Large Intestine

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Function of Gastrointestinal Tract

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The functions of gastrointestinal tract are as follows:

• The gastrointestinal tract will help in the ingestion and digestion of food.
• It is responsible for the secretion of water and enzymes in the body.
• The majority of nutrients are absorbed with the help of the GI tract.
• It helps in the excretion of waste products.

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Infection caused by Gastrointestinal Tract

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Gastrointestinal infections are viral, bacterial, or parasites that cause gastroenteritis, a gastrointestinal tract inflammation affecting both the stomach and the small intestine. 

• Diarrhoea, vomiting, and abdominal pain are some of the symptoms.
• The microorganisms that can cause these infections include adenovirus, campylobacter, E.coli, Staphylococcus aureus, etc.

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Diseases caused by Gastrointestinal Tract

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The disease caused by gastrointestinal tract are as follows:

Constipation

Constipation is a functional problem in which you cannot have a bowel movement (or pass stools). In this, your stools are infrequent (less than three times per week) or incomplete. Constipation is frequently caused by a lack of "roughage" or fibre in your diet and a change in your normal routine or diet.

Irritable bowel syndrome (IBS)

Irritable bowel syndrome (also known as spastic colon, irritable colon, IBS, or anxious stomach) is a functional illness in which the muscles of your colon contract more or less frequently than "normal." Certain foods, medications, and emotional stress are all known to cause IBS.

Haemorrhoids

Haemorrhoids are structural disorders caused by dilated veins in the anal canal. Your anal hole is lined with enlarged blood vessels. 

• Chronic excess pressure from straining during bowel movements, severe diarrhoea, or pregnancy might cause them. 
• Internal and external haemorrhoids are the two types of haemorrhoids.

Anal fissures

Anal fissures are a structural problem as well. They're fissures or cracks in the anal opening's lining. Passing very hard or wet faeces is the most prevalent cause of an anal fissure. 

• The underlying muscles that control the movement of stool through the anus and out of the body are exposed by the gap in the anal lining. 
• An anal fissure is one of the most unpleasant issues because exposed muscles become inflamed by faeces or air.
• It results in acute searing pain, bleeding, or spasm following bowel movements.

Read More: Gastric

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Things To Remember

• Gastroenteritis is caused by viruses, bacteria, and parasites attacking the digestive tract (inflammation of the alimentary canal). 
• Both the stomach and the intestine can be infected with them. 
• Adenovirus, campylobacter, E. coli, Staphylococcus aureus, and other microbes can cause these diseases.
• Peristalsis is the movement of food through the gastrointestinal tract.
• A valve-like structure appears when the bolus is about to enter the stomach.
• One of the major problems is the amount of water in food. 
• If we take adequate water daily, we can prevent many diseases. 

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