The First Breath Flashcards
What are the stages of lung development?
Embryonic - 4-7 weeks - foregut derivative
Pseudo glandular - 5 -17 weeks - major airways defined, angiogenesis, muscle and cartilage - down to bronchioles
Canalicular - 16-25 weeks - respiratory bronchioles from, capillary beds and alveolar ducts
Saccular - 25 weeks - alveoli sacs develop
Alveolar - 25 weeks to birth - alveolar building (type 1 and 2 pneumocytes), thinning and capilarisation
Alveolar continue to thin and increase complexity up to 5 years
What is oxygens purpose and affect on systemic circulation?
Purpose to be delivered to hypoxic tissues. There in systemic circulation oxygen is a vasoconstrictor.
This is because hypoxia — vasodilation — increased perfusion — increased O2 supplied to the area.
What is oxygens purpose and affect in pulmonary circulation?
Purpose to be picked up during gas exchange
In the lungs it is a vasodilator
Hypoxia would lead to vasoconstriction of blood vessels.
Increased oxygen in lung area means increased perfusion to area therefore more oxygen taken up = beneficial
What are the 1-2-3 features of the foetal circulation?
1 - umbilical vein - receives oxygenated blood from the placenta
2 - umbilical arteries that receive deoxygenated blood
3 - foetal shunts:
Ductus venosus
Foramen ovale
Ductus anteriosus
What is the Ductus Venosus, foramen ovale and the ductus anteriosus?
DV = a shunt that bypasses the liver taking blood from the umbilical chord to the inferior vena cava
Foramen ovale = shunts blood from the right to the left atrium becomes the fossa ovalis after birth.
Ductus anteriosus = shunts blood from the pulmonary artery to the aorta, becomes the ligaments anteriosus after birth
Why is the foetal lung not a useful organ, what features are there to ensure it remains unused…
Not useful because the blood is oxygenated by the placenta.
Shunts and high pulmonary vasoconstriction (lack of oxygen) - keeps the blood out of the lungs.
What is pulmonary hypertension of newborn?
When the lungs don’t fill with O2 (poor breath), little vasodilation of the lungs therefore there is still high pulmonary resistance, resulting in pulmonary hypertension — blue baby - lack of oxygen.
Treatment = increase O2 to the blood.
The foetus airways are distended with fluid why and how does this change?
Fluid aids lung development
The secretory channels change to absorbing channels before birth and as the baby breaths.
Airways become free for gas exchange
What is surface tension?
Is a measure of the force acting to pull a liquids surface molecules together at an air liquid interface.
How does Laplace’s law affect the filling of alveoli?
The smaller the airway radius
The larger the surface tension
Therefore gas will move into larger alveoli with lower pressure
However due to surfactant produced by the lungs the surface tension is equal in all the alveoli so they all fill equally.
What is surfactant? What produces it? What’s its job?
It is a surface active phospholipid
Produced by type 2 pneumocytes from 34 weeks gestation.
Abolishes surface tension and hence allows the lungs to fill with air.
What can a surfactant deficiency cause?
Respiratory distress syndrome
Due to premature birth not enough surfactant produced if any therefore there is a loss of lung volume.
On an X-ray lungs appear hazy due to being full of liquid this is because they cant expand du to no surfactant.
Manage - warmth, oxygen,
The first breath - overview of the whole process:
Birth causes a change of the secretory to absorptive lung fluid channels.
Adrenaline causes increased surfactant production
Air is then inhaled:
Oxygen causes vasodilation of the pulmonary arteries, decreasing pulmonary resistance and increasing pulmonary blood flow.
The umbilical arteries constrict along with the shunts…
