In humans, the ileum is the final and longest segment of the small intestine. The ileum is approximately 11.5 feet (3.5 meters) long and accounts for approximately 3/5 of the length of the entire small intestine. It runs from the small intestine’s middle section (jejunum) to the ileocecal valve, which drives into the large intestine.The ileum’s main function is to receive nutrients from digested food (chyme). (Cunha, n.d)

The gallbladder is a small sac beneath the liver. Bile from the liver is stored in the gallbladder. The gallbladder, like a deflated balloon, is empty and flat after meals. The gallbladder may be stuffed with bile and the equivalent of a small pear prior to the scheduled meal. (Hoffman, 2009)
The gallbladder squirts kept bile into the small intestine in response to stimulation via a system of tubes known as ducts. Bile aids fat digestion, but the gallbladder is not required. In an otherwise healthy person, gallbladder removal usually causes no noticeable problems with health or digestion, but there is a slight possibility of diarrhea and fat impaired absorption. (Hoffman, 2009)

According to Christiansen (n.d), The duodenum is a vital organ in the digestive system. It is the first and shortest section of the small intestine. The small intestine’s primary function is to metabolize nutrients and transport them to bloodstream situated in the intestinal lining for absorption in the small intestine. The digestive system of the body is comprised of the duodenum and other organs of the alimentary tract. It is the pathway through which food penetrates and solid wastes are ejected.

References:

Cunha, J. P. (n.d.). What is the purpose of the ileum in the small intestine? eMedicineHealth. https://www.emedicinehealth.com/what_is_the_purpose_of_the_ileum/article_em.htm

Digestive system. (2021, June 4). Trusted Health Advice | healthdirect. https://www.healthdirect.gov.au/digestive-system

Hoffman, M. (2009, May 19). Gallbladder: Problems, picture, definition, tests & function. WebMD. https://www.webmd.com/digestive-disorders/picture-of-the-gallbladder

Christiansen, S. (n.d.). The anatomy of the duodenum. Verywell Health. https://www.verywellhealth.com/duodenum-anatomy-4780308