The jejunum is the central region of the small intestine, connecting the duodenum to the ileum. The name of the structure derives from the Latin word jejunus, meaning “empty of food” or “hungry.” The term was chosen to reflect the fact that ancient physicians examining bodies after death found this section to be habitually devoid of food. In adult humans, the jejunum is approximately 8 feet long and about one inch in diameter. In order to fit in the abdominal cavity, it winds back and forth in a compact formation, as does the rest of the small intestine.

Significant mobility within the abdomen is provided to the jejunum because this region of the small intestine and the ileum are suspended by the mesentery. Part of the serous membrane lining the abdominal cavity (termed the peritoneum), the mesentery provides a link between the intestines and the back wall of the abdomen via a system of blood vessels, lymphatic vessels, and nerves. Due to the positioning of this link, the loops of the intestines are free to move against one another without friction.

A rat jejunum tissue section (presented above) was stained with Oregon Green 488 conjugated to wheat germ agglutinin, a plant-derived lectin that targets the Golgi apparatus, as well as Alexa Fluor 568 conjugated to phalloidin for cytoskeletal actin. Cell nuclei were labeled with Hoechst 33342. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.

Labeling Rat Jejunum Tissue with Fluorescent Probes Conjugated to Phallotoxins and Lectins - The jejunum functions in the absorption of nutrients as foodstuff travels along the gastrointestinal tract via peristalsis. The surface area available for such absorption is greatly increased by the presence of numerous tiny projections termed villi along the intestinal mucus membrane. Specialized goblet cells located in the epithelium secrete mucus that helps ease the movement of material through the tubular organ.