Lung development Flashcards
Describe the pseudoglandular phase of lung development.
This takes place from 6 to 16 weeks gestation.
The lung is a mass of tissue with little channels developing within.
Describe the canalicular phase of lung development.
Airways branch and blood vessels grow alongside them.
This takes place from 16 to 26 weeks gestation.
Describe the saccular phase of lung development.
- Ongoing branching of airways.
- Alveoli counts go up
- Septae form within the alveoli to provide larger SA and more extensive blood supply
- Mesenchyme regresses, forming an air filled structure in the chest
This takes place from 26 to 32 weeks gestation.
How is hyaline membrane formed?
Injury to the thin and fragile type I pneumocytes increases permeability of airways.
Plasma from the surrounding blood vessels influx into the alveolus, forming a hyaline membrane
What is a pneumothorax?
Air leaks through and is collected outside of the lung, within the chest wall, causing collapse of the lung
What drugs can be used to close the ductus arteriosus?
NSAIDs
At what point does the fertilised egg divide to give dichorionic diamniotic?
Before 4 days
At what point does the fertilised egg divide to give monochorionic diamniotic?
4-8 days
At what point does the fertilised egg divide to give monochorionic monoamniotic
8-13 days
At what point does the fertilised egg divide to give conjoined twins?
After 13 days
If the twins are dichorionic, what is the inter twin membrane thickness?
> 2.4 mm
If the twins are monochorionic, what is the inter twin membrane thickness?
< 1.8 mm
What type of inter-twin membrane placental insertion is indicative of dichorionic twins?
Lambda
What type of inter-twin membrane placental insertion is indicative of monochorionic twins?
T sign
If there are 2 membrane layers, what type of twin is this indicative of?
Monochorionic diamniotic
The 2 membrane layers = 2 amnions
If there are 4 membrane layers, what type of twin is this indicative of?
Dichorionic diamniotic
The 4 membrane layers = 2 chorions, 2 amnions
What is the treatment of choice for twin to twin transfusion?
Fetoscopic laser technique
What is polycythaemia?
High haemoglobin
What is the difference between TAPS and TTTS
- TAPS has no oligohydramnios/polyhydramnios sequence
- TTTS occurs due to large, central artery-to-vein connections. TAPS occurs due to tiny, peripheral artery-to-vein connections.
What is selective fetal growth restriction?
Growth discordance of >20%
When should type I selective growth restricted twins be delivered?
34-36 weeks
When should type II and III selective growth restricted twins be delivered?
32 weeks
What is TRAP?
Structurally normal twin pumps blood in a retrograde manner to abnormal twin (which lacks a heart and upper structures) because there is a superficial artery-artery anastomosis in the placenta
When is cord entanglement in monochorionic monoamniotic twins seen?
Before 20 weeks gestation
What does sulindac do?
Reduces the amount of amniotic fluid production to reduce the risk of cord entanglement
When is endovascular invasion of EVT complete by?
10-12 weeks
Failed endovascular invasion
EVT invasion is limited to the decidua and does not invade into the myometrium
Where are paternal HLAs (-A, -B and -C) presented on?
Placental macrophages and chorionic villus
What is anti D prophylaxis?
Anti D destroys the anti-Rh+ve IgG so that fetal RBCs are not attacked.
