Question

Describe in your own words, using full sentences, 3 events that occur in the duodenum of the small intestine to allow this to be the major organ "spot" where digestion occurs. *Hint - what other organs open directly into this space or have ducts that open into this space?

1.

2.

3.

Answer 1

Digestion in Duodenum:

Duodenum is the first part of small intestine. It is 25-30 cm long tube and directly connected to stomach by pyloric sphincter on superior end and attached to Jejunum( next part of small intestine) to its inferior end.

Duodenum recieves partially digested food ( Chyme ) from stomach and help in digestion of chyme. It receives ducts from Liver, Gall bladder, Pancreas whose secretions mix with chyme to facilitate digestion.

Liver, Gall bladder, Pancreas all deliever thier secretions into Duodenum through an orifice called Ampulla of Vater, which is present on middle of Duodenum.

Events that occur in Duodenum:

1) Chyme after mixing with HCl in stomach enters into Duodenum through Pyloric sphincter. Now, Brunner's glands which are present in Duodenum secreates alkaline mucus having bicarbonate ions which neutralize HCl of chyme to facilitate digestion. This mucus also prevents walls of Duodenum from acidic pH of HCl.

2) When Chyme reachea Ampulla of Vater, it got mixed with Pancreatic juice from Pancreas and with Bile juice from Liver and Gall bladder. These secreations break complex molecules of Chyme into simpler units to complete digestion. Bile juice break Lipids into smaller globules and Pancreatic juice break Proteins, Carbohydrates, Lipids into their simple units. These secreations mixes completely with Chyme by Duodenum contraction until completion of digestion.

3) Smooth muscle contraction called Peristalsis flow down to gastrointestinal tract which pushes Chyme through complete length of Duodenum. Each wave starts from Stomach and pushes Chyme towards next part of Intestine ( called Jejunum ). Small contraction of Intestine called Segmentation, helps in completely mixing of Chyme with digestive secreations and increase rate of digestion. This food now enters into Jejunum.

Hence, secreations of Liver, Gall bladder, Pancreas helps in digestion in Duodenum of Small Intestine.