GI tract histology

A 24-year-old man presents with recurrent abdominal pain, diarrhea with fatty porridge-like stools and occasional blood up to 8 times per day, joint pain, and weight loss. Ileocolonoscopy shows regions of erythema, swelling, and cobblestone-like appearance of the ascending colon and terminal ileum. Targeted biopsies are taken for evaluation. One of the slides, which underwent histological assessment, is shown in the image. Which of the following best describes the histologic finding marked with the blue circle?

A 38-year-old man comes to the clinic complaining of recurrent abdominal pain for the past 2 months. He reports a gnawing, dull pain at the epigastric region that improves with oral ingestion. He has been taking calcium carbonate for the past few weeks; he claims that “it used to help a lot but it’s losing its effects now.” Laboratory testing demonstrated increased gastrin levels after the administration of secretin. A push endoscopy visualized several ulcers at the duodenum and proximal jejunum. What characteristics distinguish the jejunum from the duodenum?