USMLE Step 1 Respiratory Quiz with complete solutions | Latest 2023/2024

USMLE Step 1 Respiratory Quiz with complete solutions | Latest 2023/2024 What are the four developmental stages of the lungs? -- pseudoglandular, canalicular, saccular, alveolar Respiratory system development (<4 weeks) -- distal lung bud forms from distal respiratory diverticulum Respiratory development (embryonic period: weeks 4-7) -- lung bud forms trachea, bronchial buds, develop to mainstem bronchi, secondary/tertiary bronchi if an error occurs during the embyronic stage of lung development, what types of abnormalities can this cause? -- tracheoesophageal fistula Respiratory development (pseudoglandular period: weeks 5-17) -- endodermal tubules form terminal bronchioles, surrounded by modest capillary network Respiratory development (canalicular period: weeks 16-26) -- terminal bronchioles form respiratory bronchioles, alveolar ducts, surrounded by prominent capillary network, airway diamter increases Respiratory development (saccular period: weeks 26-birth) -- alveolar ducts form terminal sacs, separated by primary septae, pneumocytes develop Respiratory development (alveolar period: weeks 36-8 years) -- terminal sacs form adult alveoli via secondary septation In utero breathing mechanism -- aspiration/expulsion of amniotic fluid, vascular resistance increases throughout pregnancy changes at birth in neonatal breathing -- fluid replaced by air, decreases pulmonary vascular resistance can a developing fetus breathing during the pseudoglandular period? (weeks 5-17) -- no, incompatible with life when can an developing fetus begin breathing air? -- 25 weeks what gestational age does the embryonic period of respiratory development occur? -- 4- 7 weeks what gestational age does the pseudoglandular period of respiratory development occur? -- 5-17 weeks