which plays a key role in the stretch and recoil of the lungs during inhala-
tion and exhalation.
184.The answer is b.(Ross and Pawlina, pp 623–625. Moore and Dalley,
pp 104, 106, 108.)The smallest functional unit of the lung is the respiratory
bronchiolar unit, which contains a respiratory bronchiole and the alveoli
associated with it. This unit allows for air conduction and gas exchange.
The alveolus (answer a)is only associated with gas exchange, and the
bronchi form part of the conduction system. The bronchopulmonary seg-
ment(answer c)is a functional unit of lung structure, but it is not the
smallest unit. Bronchopulmonary segments are particularly important in
surgical resections of the lung because they represent functional units with
connective tissue boundaries and individualized vasculature, including
pulmonary and bronchial arteries, pulmonary lymphatics, and pulmonary
nerves, all of which follow the air-conducting system of the bronchial tree
and its branches. Segmental bronchi and intrapulmonary bronchi are part
of the conduction system (answers d and e).
185.The answer is c.(Kumar, p 698. Junqueira, p 357.)The alveolar
macrophage (containing hemosiderin) has been called the “congestive
heart failure cell.” The presence of large numbers of these cells, containing
hemosiderin granules, is an indicator of edematous lung changes. During
congestive heart failure, edema results in leakage of erythrocytes into the
alveoli. Transferrin and hemoglobin are also present in the edematous fluid
released from the capillaries. These two products are phagocytosed by alve-
olar macrophages, which convert those products to hemosiderin.
186.The answer is e.(Kumar, pp 490–492. Kasper, pp 1543–1546.)Accu-
mulation of mucus in the airways is a common finding in children with cys-
tic fibrosis (CF). CF is a frequent occurrence in Caucasian children (1 in 200
births). It is a genetic disease in which the defect often occurs in the CFTR
protein that functions as a chloride channel. In the sweat glands, a decrease
in sodium transport results in increased chloride levels in the sweat [(the
original detection test for CF) answer a]. In the airways, decreased chloride
secretion (answer b)occurs in conjunction with active sodium absorption
(answer d),resulting in loss of water from the lumen as water follows
sodium(answer c).The result is increased viscosity of mucous secretions
and obstruction of the airways and other organs. The pancreas and salivary
296 Anatomy, Histology, and Cell Biology