, Chapter 1: Fetal Lung Development Test Bank $i $i $i $i $i $i
MULTIPLE CHOICE $i
1. Which of the following phases of human lung development is characterized by the
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formation of a capillary network around airway passages?
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a. Pseudoglandular
b. Saccular
c. Alveolar
d. Canalicular
ANS: D $i
The canalicular phase follows the pseudoglandular phase, lasting from approximately 17 weeks t
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o 26 weeks of gestation. This phase is so named because of the appearance of vascular channels,
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or capillaries, which begin to grow by forming a capillary network around the air passages.
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During the pseudoglandular stage, which begins at day 52 and extends to week 16 of gestation, t
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he airway system subdivides extensively and the conducting airway system develops, ending wit
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h the terminal bronchioles. The saccular stage of development, which takes place from weeks 29
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to 36 of gestation, is characterized by the development of sacs that later become alveoli.
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During the saccular phase, a tremendous increase in the potential gas-
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exchanging surface area occurs. The distinction between the saccular stage and the alveolar stag
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e is arbitrary. The alveolar stage stretches from 39 weeks of gestation to term. This stage is repr
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esented by the establishment of alveoli.
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REF: pp. 3-5 $i $i
2. Regarding postnatal lung growth, by approximately what age do most of the alveoli that
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will be present in the lungs for life develop?
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a. 6 months $i
,b. 1 year $i
c. 1.5 years $i
d. 2 years $i
ANS: C $i
Most of the postnatal formation of alveoli in the infant occurs over the first 1.5 years of life. At 2
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years of age, the number of alveoli varies substantially among individuals. After 2 years of age,
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males have more alveoli than do females. After alveolar multiplication ends, the alveoli continue
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to increase in size until thoracic growth is completed.
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REF: p. 6 $i $i
3. The respiratory therapist is evaluating a newborn with mild respiratory distress due to
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tracheal stenosis. During which period of lung development did this problem develop?
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a. Embryonal
b. Saccular
c. Canalicular
d. Alveolar
ANS: A $i
The initial structures of the pulmonary tree develop during the embryonal stage. Errors in develop
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ment during this time may result in laryngeal, tracheal, or esophageal atresia or stenosis. Pulmonar
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y hypoplasia, an incomplete development of the lungs characterized by an abnormally low number
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and/or size of bronchopulmonary segments and/or alveoli, can develop during the pseudoglandula
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r phase. If the fetus is born during the canalicular phase (i.e., prematurely), severe respiratory distre
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ss can be expected because the inadequately developed airways, along with insufficient and immat
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ure surfactant production by alveolar type II cells, gives rise to the constellation of problems know
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n as infant respiratory distress syndrome.
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, REF: p. 6 $ i $i
4. Which of the following mechanisms is (are) responsible for the possible association
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between oligohydramnios and lung hypoplasia?
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I. Abnormal carbohydrate metabolism $i $i
II. Mechanical restriction of the chest wall $i $i $i $i $i
III. Interference with fetal breathing $i $i $i
IV. Failure to produce fetal lung liquid $i $i $i $i $i
a. I and III only
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b. II and III only
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c. I, II, and IV only
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d. II, III, and IV only
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ANS: D $i
Oligohydramnios, a reduced quantity of amniotic fluid present for an extended period of time, wi
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th or without renal anomalies, is associated with lung hypoplasia. The mechanisms by which am
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niotic fluid volume influences lung growth remain unclear. Possible explanations for reduced qu
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antity of amniotic fluid include mechanical restriction of the chest wall, interference with fetal bre
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athing, or failure to produce fetal lung liquid. These clinical and experimental observations possi
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bly point to a common denominator, lung stretch, as being a major growth stimulant.
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REF: pp. 6-7 $i $i
5. What is the purpose of the substance secreted by the type II pneumocyte?
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