Review Question - QID 210369

A 6-month-old girl is brought to the pediatrician by her father for a scheduled check-up. She was in her usual state of health until 6 weeks ago when she was hospitalized for bacterial pneumonia. She received amoxicillin and had a resolution of her symptoms. Her father reports that she seems “back to normal.” She can roll over by herself and can sit up without support. She often babbles but sometimes does make identifiable sounds like “dada” and “baba.” They recently started feeding her mushy cereal, which she seems to like but occasionally spits up. She has started teething and sometimes becomes “fussy.” Vital signs are within normal limits. A physical examination is unremarkable. The patient’s father brought a 4-week follow-up chest radiograph taken at the hospital, as shown in Figure A. Which of the structures labeled in Figure A would be most likely to change in response to another infectious illness?