First Aid USMLE STEP 1: Exam Test Questions and
Correct Answers (Verified) | Graded A+ | Newest
Update 2026/2027 | Guaranteed Success.
Quiz: How many periods does it take to develop the lung?
What are they?
Ans: 5
1) Embryonic (weeks 4-7)
2) Pseudoglandular (weeks 5-16)
3) Canalicular (weeks 16-26)
4) Saccular (weeks 26-birth)
5) Alveolar (weeks 32-8 years)
Quiz: Describe the embryonic stage
ns: Lung bud-> trachea-> mainstem bronchi-> secondary (lobar) bronchi-> tertiary
(segmental) bronchi
,**Errors at this stage can lead to TE fistula
Quiz: Describe the Canalicular stage
Ans: Terminal bronchioles-> respiratory bronchioles-> alveolar ducts.
Surrounded by prominent capillary network
Quiz: Describe the Saccular stage
Ans: Alveolar ducts-> terminal sacs.
Terminal sacs separated by primary septae. Pneumocytes develop.
Quiz: Describe the Alveolar stage
Ans: Terminal sacs-> adult alveoli (d/t secondary septation).
In utero, "breathing" occurs via aspiration and expulsion of amniotic fluid-> increase in
vascular resistance through gestation. At birth, fluid gets replaced w/ air-> decrease in
pulmonary vascular resistance
**At birth: 20-70 million alveoli
**By 8 years: 300-400 million alveoli
,Quiz: What are the 2 congenital lung malformations & describe them
Ans: 1) Pulmonary hypoplasia= poorly developed bronchial tree w/ abnormal histology
usually involving the right lung. Associated w/ congenital diaphragmatic hernia, bilateral
renal agenesis (Potter Syndrome)
2) Bronchogenic cysts= Caused by abnormal budding of foregut & dilation of terminal or
large bronchi. Discrete, round, sharply defined & air-filled densities on CXR. Drain poorly &
cause chronic infections.
Quiz: Describe the Pseudoglandular stage
Ans: Endodermal tubules-> terminal bronchioles. Surrounded by modest capillary
network
**Respiration impossible, incompatible with life
Quiz: What are Type I pneumocytes?
Ans: thin squamous cells present in the alveoli, functioning in optimal gas diffusion
Quiz: Where are Type I pneumocytes found?
Ans: 97% of alveolar surfaces. (line the alveoli)
Quiz: Role & epithelium of Type I pneumocytes
, Ans: squamous. Thin for optimal gas diffusion
Quiz: How is collapsing pressure calculated?
Ans: P = (2 x surface tension) / radius
Quiz: What is the function of Type II pneumocytes?
Ans: secrete pulmonary surfactant --> decrease alveolar surface tension; prevent alveolar
collapse, decrease lung recoil & increase compliance
Quiz: When do Type II cells proliferate?
Ans: in LUNG DAMAGE
Quiz: What is the Law of Laplace?
Ans: As the radius decreases upon expiration, alveoli have an increased tendency to
collapse.
Quiz: What does "atelectasis" mean, and how is it caused?
Ans: DEFINITION collapse of alveoli
CAUSES obstruction, compression, or contraction
--> damage to Type II pneumocytes --> loss of surfactant
NOTE Even reinflation may not return full function due to the loss of surfactant.
Correct Answers (Verified) | Graded A+ | Newest
Update 2026/2027 | Guaranteed Success.
Quiz: How many periods does it take to develop the lung?
What are they?
Ans: 5
1) Embryonic (weeks 4-7)
2) Pseudoglandular (weeks 5-16)
3) Canalicular (weeks 16-26)
4) Saccular (weeks 26-birth)
5) Alveolar (weeks 32-8 years)
Quiz: Describe the embryonic stage
ns: Lung bud-> trachea-> mainstem bronchi-> secondary (lobar) bronchi-> tertiary
(segmental) bronchi
,**Errors at this stage can lead to TE fistula
Quiz: Describe the Canalicular stage
Ans: Terminal bronchioles-> respiratory bronchioles-> alveolar ducts.
Surrounded by prominent capillary network
Quiz: Describe the Saccular stage
Ans: Alveolar ducts-> terminal sacs.
Terminal sacs separated by primary septae. Pneumocytes develop.
Quiz: Describe the Alveolar stage
Ans: Terminal sacs-> adult alveoli (d/t secondary septation).
In utero, "breathing" occurs via aspiration and expulsion of amniotic fluid-> increase in
vascular resistance through gestation. At birth, fluid gets replaced w/ air-> decrease in
pulmonary vascular resistance
**At birth: 20-70 million alveoli
**By 8 years: 300-400 million alveoli
,Quiz: What are the 2 congenital lung malformations & describe them
Ans: 1) Pulmonary hypoplasia= poorly developed bronchial tree w/ abnormal histology
usually involving the right lung. Associated w/ congenital diaphragmatic hernia, bilateral
renal agenesis (Potter Syndrome)
2) Bronchogenic cysts= Caused by abnormal budding of foregut & dilation of terminal or
large bronchi. Discrete, round, sharply defined & air-filled densities on CXR. Drain poorly &
cause chronic infections.
Quiz: Describe the Pseudoglandular stage
Ans: Endodermal tubules-> terminal bronchioles. Surrounded by modest capillary
network
**Respiration impossible, incompatible with life
Quiz: What are Type I pneumocytes?
Ans: thin squamous cells present in the alveoli, functioning in optimal gas diffusion
Quiz: Where are Type I pneumocytes found?
Ans: 97% of alveolar surfaces. (line the alveoli)
Quiz: Role & epithelium of Type I pneumocytes
, Ans: squamous. Thin for optimal gas diffusion
Quiz: How is collapsing pressure calculated?
Ans: P = (2 x surface tension) / radius
Quiz: What is the function of Type II pneumocytes?
Ans: secrete pulmonary surfactant --> decrease alveolar surface tension; prevent alveolar
collapse, decrease lung recoil & increase compliance
Quiz: When do Type II cells proliferate?
Ans: in LUNG DAMAGE
Quiz: What is the Law of Laplace?
Ans: As the radius decreases upon expiration, alveoli have an increased tendency to
collapse.
Quiz: What does "atelectasis" mean, and how is it caused?
Ans: DEFINITION collapse of alveoli
CAUSES obstruction, compression, or contraction
--> damage to Type II pneumocytes --> loss of surfactant
NOTE Even reinflation may not return full function due to the loss of surfactant.
