Human Alimentary Canal Structure & Functionality

The alimentary canal is the pathway for food that runs from the mouth to the anus. The canal is a long tube that helps the food to enter the mouth and moves out through the anus after digestion. (Digestion is the process of breaking large food particles into smaller particles and water-soluble particles so that the blood plasma quickly absorbs the food.) This alimentary canal plays a vital role in digestion and also termed as the digestive tract. Liver and the pancreas are also part of the digestive system.

The organs associated with the alimentary canal are:

• Mouth
• Salivary glands
• Stomach
• Oesophagus
• Pancreas, liver, gall bladder
• Small intestine (duodenum + ileum)
• Large intestine (colon +rectum)
• Anus

Now let’s discuss the functions of each organ in detail.

Mouth: 

We intake food through the mouth, and it is digested through cutting, chewing and grinding with teeth.

Salivary glands:

It makes Saliva and empties it into your mouth through openings called ducts that help in with swallowing and chewing. These glands also help in preventing the infections from developing in your mouth or throat.

Stomach:  

It is the main food storage tank of the body located at the upper left part of the abdominal cavity. The muscular walls of the stomach make the intake food into semi-liquid form and release it to the intestines to process it.

The stomach has four parts and three functions

 i) cardiac(present close to the heart), 

ii) fundus(this part is filled with air), 

iii) body (the central part of the stomach), 

iv) Pyloric (it regulates the opening of the stomach into the small intestine )

The three functions are

i)temporary storage for food 

ii)breakdown of food by contraction and relaxation iii)digestion of food

Oesophagus:

It is a muscular tube that connects the mouth and stomach. When we intake the food, the walls of the Oesophagus tube contracts and the food passes to the stomach. The length and of Oesophagus tube is between 25 to 30 centimetres and width averages 1.5 to 2 cm.

Pancreas:

The pancreas helps in converting the food into fuel for the body’s cells. There are two types of functions that pancreas undergoes i) an exocrine process ( that aids in digestion )and ii) an endocrine process (that regulates blood sugar.)

Liver: All the blood leaving the stomach and intestines passes through the liver. The primary function of the liver is to filter the blood coming from the digestive tract, before passing it to the rest of the body. The liver also helps in digesting the food and ridding the body of toxic substances. It secretes bile (a yellow-brown digestive enzyme) that ends up back in the intestines. 

Gall bladder: The gallbladder is a small pear-shaped pouch located just under the liver. It stores and controls the flow of bile produced by the liver.

Small Intestine

The small intestine (small bowel) is the longest part of the alimentary canal about 20 feet long and an inch in diameter. Its function is to absorb most of the nutrients from what we eat and drink. It comprises three parts- Ileum, Duodenum and Jejunum. 

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

Large Intestine

The function of the large intestine is to absorb salts and water from the food that has not been digested. It also gets rid of any waste products left over. Like small intestine, large intestine also has three parts- Caecum, Colon, and Rectum.

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