Question

In which part of the alimentary canal, food is finally digested?

• A. Stomach
• B. Mouth cavity
• C. Large intestine
• D. Small intestine

Answer 1

The correct option is D Small intestine

Hint: Digestion starts from the mouth itself just after ingestion of food and continues throughout in the different organs of the alimentary canal sequentially until it finally reaches the large intestine where only absorption takes place after which undigested food will be egested through the anus.

Part 1 - Definition - Human digestive system

• In the human digestive system, there are many parts that work together to convert the food we eat into simpler forms so that your body can absorb it.
  
• The human digestive system includes the gastrointestinal tract and other accessory parts like the liver, intestines, glands, mouth, stomach, gallbladder.
• There are 6 primary functions of the human digestive system process: Ingestion, Motility, Secretion, Digestion, Absorption, Excretion.
  

Part 2 - Parts of the Digestive system

• The different organs of the alimentary canal can be explained as –

Mouth - The starting point where digestion actually starts is the mouth with the help of saliva. From the mouth, food enters the Oesophagus.

Oesophagus - It is a long and thin muscular tube that passes through the neck, thorax, and diaphragm and opens into a muscular bag-like structure called the stomach.
Stomach - It is a muscular, hollow organ, having a capacity of 1 litre. The stomach holds food and also is a mixer and grinder.
Small Intestine - The longest part of the alimentary canal, which is divided into three parts- Duodenum, Jejunum, and Ileum. The ileum opens into the large intestine. Maximum digestion and absorption take place here.
Large Intestine - It is a wide tube consists of three parts- Caecum, Colon, and Rectum. The colon is divided into four regions-ascending colon, transverse colon, descending colon, and the sigmoid colon. Through the sigmoid colon, the descending part of the colon opens into Rectum. The rectum is the distal part of the alimentary canal that opens into the anus.

Part 3 - Process of digestion

• The digestion process is a series of reactions of food with the digestive hormones and juices. This starts right from the oral cavity.
  
• When food is taken in through the mouth along with chewing and mixing, the chemical breakdown of carbohydrates because of the action of saliva from the salivary glands also takes place.
  
• When food reaches the stomach through the oesophagus, it gets mixed thoroughly with the gastric juices through the churning movements of the stomach muscle.
  
• This mass of food that is semi-digested, acidic, and pulpy is called the chyme.
• It is mostly the proteins that get digested in the stomach through the action of pepsin.
  
• In the small intestine, further digestion takes place. There are many enzymes that are secreted into the small intestine from organs such as the pancreas, liver; apart from the intestinal juices.
  
• All these react with the food particles and digest them into smaller particles that can be absorbed into the bloodstream.
  
• Any undigested and unabsorbed waste particles, called the fecal matter, are then passed to the rectum, from where it is eliminated through the anus.
  

Part 4 - Conclusion

• From the above discussion, we can conclude that digestion starts within the oral cavity and continues until it reaches the small intestine where final digestion and absorption take place.
• We excrete undigested fecal matter after final absorption in the large intestine through the anus.

Final step: Small intestine is the part of the alimentary canal where food is finally digested.