Final answer:
The jejunum's structural feature includes plicae circulares that increase surface area for absorption; it does not have numerous submucosal glands, contain Peyer's patches, or a mucosa dominated by goblet cells.
Step-by-step explanation:
The structural features of the jejunum include plicae circulares, which are circular folds that increase the absorptive surface area of the small intestine. These adaptations are most abundant in the proximal two-thirds of the small intestine, where the majority of absorption occurs. The jejunum does not contain numerous submucosal glands; instead, this characteristic is attributed to the duodenum with its specialized duodenal (Brunner's) glands. Peyer's patches, which are aggregations of intestinal MALT (mucosa-associated lymphoid tissue), are predominantly found in the distal ileum, not in the jejunum. While the mucosa of the small intestine does contain goblet cells, these are not the dominant cell type; instead, they are interspersed among enterocytes that facilitate absorption.