Barb suffers from Crohn’s disease, a regional inflammation of the intestine that is thought to have some genetic basis, although the actual cause remains unknown. When the disease flares up, she...

Barb suffers from Crohn’s disease, a regional inflammation of the intestine that is thought to have some genetic basis, although the actual cause remains unknown. When the disease flares up, she experiences abdominal pain, weight loss, and anemia. Which part(s) of the intestine is (are) probably involved, and what might be the causes of her signs and symptoms?