Question

What is the longest part of the alimentary canal.
(a)Duodenum
(b)Ileum
(c)Colon
(d)Large intestine

Answer 1

Hint: The longest part of the alimentary canal exclusively consists of Peyer's patches lying in its mucosa. It is a part of the GALT (Gut Associated Lymphoid Tissue).

Complete answer:
The alimentary canal is a long structure extending from the mouth to the anus. It carries food through different organs and allows undigested food and waste material to exit through the anus. The longest part of the alimentary canal is 'Ileum'.
The alimentary canal consists of mouth, pharynx, esophagus, stomach, small intestine, and large intestine. It also includes some accessory digestive structures such as teeth, tongue, salivary glands, pancreas, liver, and gallbladder. The small intestine is the longest organ of the alimentary canal. The small intestine consists of three parts. The first part, called the duodenum, is a short 'S' shaped part connected to the stomach. The middle part is the jejunum. The third part, ileum, attaches to the colon. Among all the three parts of the small intestine, the final section of the small intestine, Ileum is about 3 m long and is the longest part of the alimentary canal.
So, the correct answer is Ileum.

Additional Information:
-The duodenum plays an important role in the regulation of gastric emptying. When chyme enters the duodenum, it stimulates the epithelial cell walls of the duodenum to secrete secretin and cholecystokinin.
-The primary function of jejunum is absorption, by which sugars, amino acids, and fatty acids are absorbed.
-The ileum absorbs nutrients that did not get absorbed by the jejunum, with important nutrients being vitamin B12 and bile acids for reuse.

Note: The duodenum is short (20 to 25 centimeters long) and wider anterior part into which the stomach empties. The jejunum is the coiled middle part which is 0.8 to 1.5 meters in length while ileum is the longest terminal part with 3 to 3.5 meters in length.