Final answer:
The small intestine is divided into three parts: the duodenum, the jejunum, and the ileum, each with specific roles in digestion and nutrient absorption.
Step-by-step explanation:
The small intestine is an essential organ for digestion and absorption in the human body. The structure of the small intestine is subdivided into three distinct parts. From the section closest to the stomach (proximal) to the furthest section (distal), these parts are identified as the duodenum, jejunum, and ileum.
The duodenum is the initial segment that primarily receives partially digested food known as chyme from the stomach. The jejunum follows and is about 0.9 meters (3 feet) long. The term 'jejunum' is derived from Latin meaning 'empty,' named so due to it typically being void of food at the time of death.
The ileum is the final segment of the small intestine, which leads to the large intestine. These three segments are lined with mucosa that has a tremendously folded surface populated with finger-like projections known as villi. The surface of each villus contains countless microscopic extensions termed microvilli, all combined, increase the surface area significantly for optimal absorption of nutrients.