Plica circularis is absent in:
Luminal surface of small bowel reveals mucosal folds called plicae circulares Numerous in the proximal jejunumIt decreases in distal small bowelAbsent in terminal ileum Aggregates of lymphoid follicles are highest in the ileum (Peyer's patches)Peyer's patches are more prominent during infancy and childhood. Ref: Sleisenger, E - 9, P-1615
Duodenum
Jejunum
Proximal ileum
Distal ileum