What is the major problem at the cellular level in cystic fibrosis?

A. Emphysema, a type of chronic obstructive pulmonary disease (COPD), is the most common cause of a barrel chest. It occurs due to the destruction of the alveoli, leading to air trapping and overinflation of the lungs, which causes the chest to take on a rounded, barrel-like appearance.

B. Pneumonia typically causes acute symptoms like fever, cough, and difficulty breathing, but it does not cause the chronic lung changes that result in a barrel chest.

C. Tuberculosis can cause lung damage, but it does not typically result in the barrel chest shape. It is more associated with symptoms like cough, hemoptysis, and weight loss.

D. Acute respiratory distress syndrome (ARDS) is an acute condition involving rapid onset of severe respiratory distress, often due to trauma or infection. It does not cause the chronic structural changes seen in a barrel chest.

A. While Crohn disease can affect any part of the gastrointestinal tract, it often affects the small intestine, particularly the ileum. However, the location alone does not explain the increased risk of obstruction.

B. Certain foods, such as spicy foods, may exacerbate symptoms of Crohn disease, but this is not the primary reason it causes intestinal obstruction.

C. Crohn disease causes inflammation that can lead to the formation of granulomas, particularly in the submucosal layers. These granulomas contribute to fibrosis and narrowing of the bowel, which can lead to intestinal obstruction. This is a key feature of Crohn disease that makes it more likely to cause obstruction compared to ulcerative colitis.

D. Abdominal pain and watery diarrhea are common symptoms of both Crohn disease and ulcerative colitis, but they are not directly related to the increased risk of obstruction in Crohn disease.