Gastrointestinal Tract: Definition, Function, Diagram, Examples

What is Gastrointestinal Tract?

The gastrointestinal tract is the main canal for the human digestive system. It is a long alimentary canal with a length of about 20 to 25 feet. It comprises a row of organs starting from the mouth to the anus. It includes the mouth, oesophagus, stomach, small intestine and large intestine. The gastrointestinal tract breaks food into nutrients. The digestion starts in the mouth and continues in the stomach and small intestine. It is the site where food is enzymatically and acidically broken down into absorbable nutrients. Lastly, in the large intestine, water and electrolytes are absorbed, and solid waste is produced.

Gastrointestinal Tract Functions

The gastrointestinal tract breaks food into simple nutrients with the help of enzymes and acids. The gastrointestinal tract starts digestion in the mouth. The liver, pancreas, and gallbladder help digestion. The gastrointestinal tract keeps the body healthy. Some gastrointestinal tract functions are given below:

• Breaks food into simple nutrients.

• Absorbs vitamins, minerals, and water.

• Absorbs electrolytes and maintains balance.

• Support the absorption of digested food.

• Formation of faeces and removal of waste.

• Supports digestion with the liver, pancreas, and gallbladder.

Anatomy of the Gastrointestinal Tract

The gastrointestinal tract is made of several organs. Each organ has a special role in digestion. Together, they help in breaking down food, absorbing nutrients, and removing waste. The major components of the alimentary canal anatomy are:

Mouth

Structure:

• Made up of the oral cavity, which comprises lips, teeth, tongue and palate.

Functions:

• The point of intake of foods initiates the process of digestion.

Role of Saliva and Salivary Glands:

• Saliva from the salivary glands (parotid, submandibular, and sublingual).

• Contains amylase, which initiates the digestion of carbohydrates

• Aids in the moistening of foods for easier swallowing.

Esophagus

Structure:

• A muscular tube which connects the mouth to the stomach.

Functions:

• Helps in swallowing through the process of peristalsis.

Peristalsis:

• Swallowing is a process of moving food through the oesophagus and into the stomach through well-coordinated muscular contractions in the form of waves.

Stomach

Anatomy:

• J-shaped organ

• Regions include cardia, fundus, body, and pylorus

• Lined by the gastric mucosa.

Functions:

• The stomach mixes food with gastric juice.

• Churns and breaks it down into a paste-like substance called chyme.

Role of Gastric Juices and Enzymes:

• Proteins are acted upon by enzymes such as hydrochloric acid and pepsin and digestion occurs in an acidic medium.

Small Intestine

Parts:

• Duodenum

• Jejunum

• Ileum

Functions:

• The major site of digestion and absorption

Role of Villi and Microvilli:

• Increase the area for the absorption of nutrients at the epithelial layer.

• Facilitates nutrient absorption into the blood.

Large Intestine

Parts:

• Cecum

• Colon

• Rectum

Functions:

• Absorption of water and electrolytes.

• Formation of faeces.

Accessory Digestive Glands in the Gastrointestinal Tract

Accessory digestive glands help the gastrointestinal tract in digestion. They include the liver, pancreas, and gallbladder. Each gland has a special role in breaking down food and absorbing nutrients. Accessory digestive glands are discussed below:

Liver

• The largest gland in the body

• Destruction of toxins

• Production of bile for fat digestion

• Helps in the digestion of vitamins and fats.

Pancreas

• An elongated organ located below the stomach.

• Produces insulin for sugar control.

• Secretes substances for the small intestine example digestive enzymes.

Gallbladder

• A small pouch beneath the liver

• Stores and concentrates the produced bile.

• Reaches the small intestine, where it is of use in the digestion and absorption of fats by regurgitating bile.

Gastrointestinal Tract Common Disorders

The gastrointestinal tract can face many problems. These disorders affect digestion, absorption, and waste removal. Students must know causes, symptoms, and treatments for exams like NEET. Some common disorders related to the gastrointestinal tract are:

Constipation

• Causes: Low-fibre diet, not drinking enough water, physically inactive, or because of a certain medication or disease.

• Symptoms: Constipation, difficulty in bowel movements.

• Treatments: A diet rich in fibre, increased fluid intake and exercising, medication such as laxatives or stool softeners may be prescribed.

Irritable Bowel Syndrome (IBS)

• Causes: Gut-brain signalling problem, stress, and diet.

• Symptoms: Abdominal discomfort, pain, and or changes in bowel movements like diarrhoea, constipation or both.

• Treatments: Dietary interventions (for example, low FODMAP diet), stress reduction strategies, and medications for symptom relief.

Colon cancer

• Causes: Age, family history of colon cancer, diet rich in red or processed meats, smoking, and conditions like Crohn’s disease and ulcerative colitis.

• Symptoms: Changes in bowel habits, the presence of blood in stools, pain in the abdomen and unexplained weight loss.

• Treatments: Therapies frequently include surgery, chemotherapy, and/or radiation therapy based on the stage of the malignancy.

Haemorrhoids

• Causes: Excessive pressure on the rectal as well as anal veins, pregnancy or sitting down for long periods.

• Symptoms: Itching, pain, swelling around the anus, and even bleeding when one is defecating.

• Treatments: Dietary changes such as increasing fibre intake, use of creams and in the worst-case scenarios, surgery like hemorrhoidectomy.

Liver Disorders (Related to GI System)

• Hepatitis: Inflammation of the liver resulting from viral infections of the liver (hepatitis A, B, C), alcoholism, or other ailments.

• Cirrhosis: A state of the liver in which liver tissues are gradually replaced with fibrous tissues, and the function of the organ starts to deteriorate.

• Liver Cancer: It develops mostly from conditions like cirrhosis or hepatitis.

Preventive Measures for Gastrointestinal Tract Health

The gastrointestinal tract stays healthy with good habits. Preventive measures reduce the risk of disorders of the digestive system. Some of the preventive measures and healthy practices include:

Importance of a Balanced Diet

• Source of essential nutrients, provides energy, and maintains digestive health.

• Prevents digestive diseases.

Role of Fibre

• Used to make the stool bulky

• Relieve the individual from constipation and related complaints.

Regular Exercise

• Helps in the stimulation of bowel movements.

• Helps in keeping your weight in check.

Hydration

• Promotes the easing of bowel movement and digestion

• Prevents constipation.

Avoiding Harmful Substances

• Avoid alcohol and tobacco.

• Reduces GI diseases and cancers.

Gastrointestinal Tract NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Gastrointestinal tract anatomy

• A common disorder of the gastrointestinal tract

Practice Questions for NEET

Q1. Which of the following controls the secretion of bile from the gall bladder?

1. Secretin

2. Gastrin

3. Somatostatin

4. Cholecystokinin

Correct answer: 4) Cholecystokinin

Explanation:

Secretin stimulates the pancreas to release alkaline bicarbonate solution into the duodenum to neutralise the acidic chyme.
Secretin acts in tandem with another hormone called Cholecystokinin. It not only stimulates the pancreas but also stimulates the gall bladder to release bile.
Gastrin is secreted by g cells in response to the presence of proteins, etc. Gastrin stimulates the stomach to release hydrochloric acid.
Somatostatin stimulates the stomach to stop releasing hydrochloric acid when the need for maintaining an acidic environment in the stomach is over.

Hence, the correct answer is option 4) Cholecystokinin.

Q2. Which of the following hormones controls hyperacidity in the stomach?

1. Gastrin

2. Secretin

3. Somatostatin

4. Cholecystokinin

Correct answer: 3) Somatostatin

Explanation:

Somatostatin stimulates the stomach to stop releasing hydrochloric acid when the need for maintaining an acidic environment in the stomach is over.
Secretin stimulates the pancreas to release alkaline bicarbonate solution into the duodenum to neutralise the acidic chyme.
Secretin acts in tandem with another hormone called Cholecystokinin. It not only stimulates the pancreas but also stimulates the gall bladder to release bile.
Gastrin is secreted by G cells in response to the presence of proteins, etc. Gastrin stimulates the stomach to release hydrochloric acid.

Hence, the correct answer is option 3) Somatostatin.

Q3. Which of the following stimulates the release of Hydrochloric acid in the stomach?

1. Secretion

2. Gastrin

3. Somatostatin

4. Both b & c

Correct answer: 2) Gastrin

Explanation:

Role of Hormones in Digestion – Secretin stimulates the pancreas to release an alkaline bicarbonate solution into the duodenum, neutralizing the acidic chyme from the stomach. Gastrin, secreted by G cells in response to proteins, triggers the stomach to release hydrochloric acid (HCl), aiding digestion. In contrast, somatostatin inhibits HCl secretion once the stomach has achieved the required acidic environment, helping regulate digestive processes and maintain balance.

Hence, the correct answer is option 2) Gastrin

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