The first breath Flashcards
What are the stages of lung development
Embryonic 0-5 weeks
Pseudoglandular 5-17 weeks
Cannalicular 16-25 weeks
Alveolar 25 weeks-term
Where do the lungs come from?
- The foregut (which are an anterior outpouching)
- This happens in the 0-5 weeks in the embryonic stage
- It is an outpouch of the oesophageal appendix
What is the pseudo glandular stage of lung development?
Where thinks start to become glandular (5-17 weeks)
- Other components of the airway start to group
- Lungs are full of fluid pretty much until term. Lungs are not being used to oxygenate you - that is through the mother
- Angiogenesis (blood vessels start to form)
What is the Cannalicular stage of lung development?
- Occurs at 16-25 weeks
- Distal architecture
- Vascularisation (formation of capillary bed)
- Respiratory bronchioles
- Alveolar ducts
- Terminal sacs
What is the alveolar stage of lung development?
- Occurs at 25 weeks to term
- Alveolar sacs
- Type 1 + 2 cells
- alveoli simple with thick
What happens to the alveolar membrane from birth to 3-5 years?
Thinning of alveolar membrane and interstitium
What can go wrong in the embryonic stage?
- Laryngeal, Tracheal and oesophageal atresia (absence or abnormal narrowing of an opening or passage in the body)
- Tracheal and bronchial stenosis (narrowing of these structures)
- Pulmonary agenesis (failure of an organ to develop)
What can go wrong in the Pseudoglandular phase?
Group of abnormalities
Bronchopulmonary sequestration
Cystic adenomatoid malformations (can occur at ant point in the this stage with any structure)
alveolar-capillary dysplasia
What can go wrong with the Alveolar phase?
Acinar Dysplasia
Alveolar capillary dysplasia
Pulmonary hyoplasia
What is the purpose of systemic vessels?
To deliver oxygen to hypoxic tissues
Is hypoxia/ CO2 a vasodilator or vasoconstrictor?
Vasodilator in systemic vessels
Vasoconstrictor in pulmonary vessels
Is oxygen a vasodilator or vasoconstrictor?
Vasoconstrictor in systemic vessels
Vasodilator in pulmonary vessels
What is the purpose of the pulmonary vessels?
Pick up oxygen from oxygenated lung
What are the lungs doing in the foetal?
- The lung is not a useful organ to the foetus
- PaO2 = 3.2kPa
- Shunting of blood right to left in heart
- High pulmonary vascular resistance (because you are hypoxic)
- Tissue resistance (fluid filled)
- Low systemic resistance (placenta)
How do the lungs fill with fluid?
- Lungs are actively being filled with fluid by a chlorine/ potassium ion pump
- So they are ready for the first breath
What does the Ductus venosus do?
- a proportion of nutrient filled blood will still pass through the liver as you need to filter it etc and then into the inferior vena cava
- BUT 1/3 diverted
- takes it directly from mother and straight into inferior vena cava
What is the ductus arteriosus?
- Connection between the pulmonary trunk and aorta
- When blood into RA, RV straight into aorta, stopping blood go into the lungs and instead straight into the aorta
- One method of a right to left shunt
- this closes after birth
What happens to the lungs as squeezed out at birth?
Lungs are given a physical squeeze as pushed out of the vagina which squeezes the fluid out of the lungs (like a sponge)
What hormone is released during first breath?
Adrenaline stress leads to increased surfactant release
- Gas is inhaled which is rich in oxygen
What happens after gas is first inhaled?
- Oxygen is a vasodilator in pulmonary vessels so pulmonary vascular resistance falls
- Right atrial pressure falls, closing the foramen ovale
What happens to the arteries after first breath?
- Umbilical arteries constrict (as it is cut)
- Ductus arteriosus constricts (due to changes in O2 levels)
What is Laplace’s Law?
P = 2T/R
T (surface area)
- Smaller alveoli may shut and bigger open when tension applied
Why is surfactant important?
- Surface active phospholipid
- Produced by type 2 pneumocytes
- Keeps alveoli open to allow aeration and gets rid of surface tension
- So premature babies will be deficient in surfactant
What diseases with a lack of surfactant?
Respiratory Distress Syndrome (HMD)
Loss of lung volume
Non-compliant lungs
Uneven aeration
