Final answer:
The first part of the small intestine and a common site for ulcers is the duodenum, where most chemical digestion occurs. The jejunum follows as the second section, absorbing most nutrients. The ileum, being the last part, absorbs bile salts and vitamins.
Step-by-step explanation:
The first part of the small intestine and a common location for the development of an ulcer is the duodenum. It is directly connected to the stomach and is the shortest section of the small intestine, with an average length of about 25 cm (10 in.) in adults. The duodenum plays a crucial role in chemical digestion, as most of the process occurs here with the help of digestive enzymes produced by the duodenum itself, as well as by the pancreas which secretes enzymes into this section.
Following the duodenum is the jejunum, which is the second part of the small intestine. Here, the hydrolysis of nutrients continues, and it is the primary site for the absorption of carbohydrates and amino acids into the bloodstream.
The ileum is the last and longest part of the small intestine and is responsible for the absorption of bile salts and vitamins. It joins the cecum at the ileocecal sphincter. All three sections, the duodenum, jejunum, and ileum, are framed by the large intestine and are essential in the digestive process.