First breath Flashcards
What do lungs develop from?
Respiratory diverticulum
Foregut
What time period do lungs develop?
Week 4-5
Define atresia?
Failure trachea and oesophagus to seperate
What occurs during the pseudoglandular phase (5-17 wks)?
Development of conducting airways
What occurs during the cannalicular phase (16-25 wks)?
Capillaries, vasculature and alveoli form
Alveoli develop until 5
What reduces surface tension in alveoli?
Surfactant
What is the function of surfactant?
Reduce surface tension
Allow equal aeration alveoli
What cell secretes surfactant?
Type 2 pneumocytes
What is more numerous type 1 or type 2 pneumocytes?
Type 1- 70%
Function type 1 pneumocytes?
Responsible for gas exchange between alveoli and capillaries
What is blood flow in utero?
RA-FO-LA-LV-AORTA-DA
What is the purpose of having different blood flow in utero?
Bypass lungs and liver- not fully developed
What allows lung to be bypassed
Foramen ovale
What allows pulmonary circulation to be bypassed
Ductus arteriosus
What does failure of foramen ovale lead to?
Persistent hypertension- lead hypoxia
What is Eisenmenger’s syndrome?
Ventricular septum defect cause intracardiac shunt
Blood continues bypass pulmonary circ. after birth
Causes cynosis, clubbing, polycythemia (raised haematocrit)
At birth what occurs?
Closure placenta- clamp umbilical vein and arteries
1) Increase systemic circulatory pressure 11.5lPa
2) Amniotic fluid in lungs expelled
3) Entry O2 into lungs cause pulmonary circulation pressure decrease- increases flow
4) Reduced pressure prevents cardiac shunting
5) Foramen ovale closes, ductus arteriosus constricted
