jejunum

This term refers specifically to the central portion of the small intestine. It is characterized by a high density of plicae circulares, which are circular folds that increase the surface area for nutrient absorption. In clinical settings, it is often discussed in the context of malabsorption syndromes or surgical bypasses. As a biological term, it is a countable noun, though it is typically used in the singular when referring to the specific anatomical region of a single organism.