embryology of the respiratory system

Question 1

what develops before the lungs

Answer 1

cardiac tube

Question 2

what happens in embryonic stage 1

Answer 2

endoderm develops into epithelium with mucosal and submucosal glands.
splanchnic mesoderm forms smooth muscle, cartilage and connective tissue

Question 3

what happens in stage 2 - pseudoglandular

Answer 3

lungs extend, developing conducting branches of bronchial tree and vascularisation

Question 4

what happens in stage 3 = canalicular

Answer 4

airway lumens enlarge, respiratory bronchioles form, capillaries come into contact with epithelium

Question 5

what happens in stage 4 = terminal sac

Answer 5

respiratory bronchioles give off sacs lined with cuboidal epithelium which organises into type I and type II alveolar cells
production of surfactant begins

Question 6

what happens in alveolar stage 5

Answer 6

capillaries associate closely with alveolar lining
surfactant production increase
incomplete at birth - continues post natally

Question 7

how does the foetus cope with being in a state of relative hypoxia

Answer 7

higher cardiac output then adult animal
higher affinity of foetal Hb for oxygen

Question 8

5 stages of lung development

Answer 8

embryonic
pseudoglandular
canalicular
terminal sac
alveolar

Question 9

why is the pulmonary circulation before birth largely shut down

Answer 9

lung collapsed

Question 10

what stimulates the first breath at birth

Answer 10

hypoxia
hypercapnia
lowering body temperature
increased sensory stimulation

Question 11

why do premature neonates often suffer from respiratory distress

Answer 11

not producing enough surfactant so high surface tension