Question

Describe the alimentary canal of man.

Answer 1

Alimentary canal:-

The alimentary canal is mainly referred to as the pathway by which food enters our body and moves out through the anus after digestion. The main organs of the alimentary canal are:

1. Mouth and Oral cavity.
2. Oesophagus.
3. Stomach.
4. Small intestine.
5. Large intestine.

Mouth

1. The mouth is the first part of our digestive system. Food is ingested through the mouth.
2. Oral cavity: The oral cavity comprises the palate, tongue and teeth.
3. Palate : The roof of the oral cavity.
4. Tongue : Muscular and glandular structure attached to the base of the oral cavity. The upper surface of the tongue has tiny projections known as lingual papillae. Tongue mix saliva and food.
5. Teeth: Humans are diphyodont i.e. they have two sets of teeth- milk or deciduous and permanent teeth.
6. Types of teeth in humans

Type of teeth	Function
1. Incisors	Used for cutting
2. Canines	Used for tearing
3. Premolars	Used for Chopping
4. Molars	Used for Grinding and Chewing

7. The structure of the tooth is made up of three parts- the crown, neck, and root. The exposed part of the tooth is called the crown, the region where it is covered with gums is known as the neck and the root is embedded in the socket of the jaw bone (Thecodont).

8. Saliva is secreted by salivary gland in the mouth. Saliva contains an enzyme named salivary amylase (or ptyalin) which is responsible for the digestion of simple carbohydrate.

9. When saliva mix with food then it is called bolus.

Pharynx

1. It is the common passage for food and air. A flip like structure called Epiglottis is present at pharynx that prevents the entry of food into the windpipe.

Oesophagus

1. It is a muscular tube through which a small bolus of food passes from the mouth to the stomach by the process of peristalsis.
2. The gastro-oesophageal sphincter controls the movement of food into the stomach.

Stomach

1. It is a muscular bag, positioned in the upper left part of the abdominal cavity. It secretes gastric juice that contains mucus, HCl and pepsin enzyme.
2. It has four parts- cardiac, fundus, body and pyloric portion.
3. Cardiac part– It is present close to the heart. The opening of the oesophagus to the stomach is regulated by the gastro-oesophageal sphincter.
4. Fundus– It is dome-shaped and is usually filled with air.
5. Body– This is the main part of the stomach.
6. Pyloric- It opens in the first part of the small intestine, the duodenum. The opening of the stomach into the small intestine is regulated by the pyloric sphincter.

Small Intestine

1. It is the longest part of the alimentary canal and comprises three parts- Duodenum, Jejunum, and Ileum.
2. Duodenum– It is C- shaped. The pancreatic, bile and hepatic secretions are added to the food by the hepatopancreatic duct.
3. Jejunum– Middle part of the small intestine.
4. Ileum– It is highly coiled and opens into the large intestine.

Large Intestine

1. The small intestine leads into the large intestine. It has three parts- Caecum, Colon, and Rectum.
2. Caecum– It is a small sac-like structure containing symbiotic microorganisms. The vermiform appendix (vestigial organ) is attached to it.
3. Colon– It is divided into four regions- ascending, transverse, sigmoid and descending.
4. Rectum– It opens into the anus and stores waste food.