First Breath/ Lung Embryology Flashcards
What layer of TLD is RT formed from?
Endoderm
What is Respiratory Diverticulum an out-pouching of? And what does it end up forming?
Foregut
Lung Buds
What purpose does the lung have in the foetus?
None
Describe the first 3 stages of Lung formation?
1) Embryonic: Lungs and Trachea develop (0-5)
2) Pseudoglandular: Trachea branches (5-16) [Cartilage, Cilia, SM, Muc glands]
3) Canalicular: RB and ADucts form (16-26)
Describe last 2 stages of Lung development?
4) Saccular: Terminal sacs form (26-B)
5) Alveolar: Alveoli mature (8MO to CHd)
What is an Tracheoesophageal fistula?
When outpouching of Lung from Oesophagus as lung abnormally connects to it
What are the 3 foetal vessels?
1) 1 X Umbilical Vein (OB)
2) 2 X Umbilical Arteries (DOB)
What are the 3 foetal shunts?
1) Ductus Venosus (Hepatic)
2) Foramen Ovale (Connect R and L atria)
3) Ductus Arteriosus (Connect A and PA)
Describe the first breath (5)
1) Fluid removed from lungs
2) Adrenaline ^ and surfactant released
3) Air inhaled
4) O2 Vasodilates pulmonary vessels
5) UA and DA constrict, as FO closes
(Function changes from Secretory to Absorptive)
What happens to Perinatal circulation at birth?
Pressure change where Aorta pressure exceeds PA
What is Laplace’s Law?
Smaller the airway, the higher the surface tension in gas exchange
What is surfactant produced and increased by?
1) T2 Pneumocytes
2) Alveoli distension, steroids, adrenaline
Why is surfactant useful? (4)
1) Virtual abolition of surface tension
2) Allows Homogenous aeration
3) Allows maintenance of functional Res Cap
4) Prevents alveoli collapse
What is O2 role?
1) Pulmonary vasodilator
2) Systemic Vasoconstrictor
What is equation of Laplace’s law and significance?
P= 2T/R
Small alveoli = ^ Pa, so air from smaller to larger alveoli (uneven aeration, so surfactant stops this)
