Q. Which one of the following is the correct sequence in the order of decreasing length of the three structural parts given below of small intestine in the human body? (UPSC Prelims 2007)
Answer: Ileum - Jejunum - Duodenum
Notes: The small intestine consists of three parts: duodenum (~25 cm), jejunum (~2.5 m), and ileum (~3.5 m). In decreasing order of length, it is ileum (longest), jejunum (middle), duodenum (shortest). Option 4 correctly sequences them as Ileum - Jejunum - Duodenum (correcting typos in spelling). This is standard human anatomy: ileum absorbs bile salts and vitamins, jejunum absorbs nutrients, and duodenum receives digestive secretions. The total small intestine length is approximately 6-7 meters in adults.