Jejunal Atresia - Apple Peel Deformity

A newborn male at 34 weeks gestation presents at 12 hours of life with bilious vomiting and abdominal distension. Antenatal ultrasound had shown polyhydramnios and dilated fetal bowel loops. Abdominal radiograph shows the classic "triple bubble sign" with air-fluid levels and paucity of distal bowel gas. At laparotomy, the proximal jejunum ends blindly, and the structure marked **B** in the diagram—the distal small bowel—is found coiled in a spiral fashion around a single vessel. What is the embryological basis for this characteristic "apple peel" appearance?