Embryology Flashcards
What does the lung bud form from?
The respiratory diverticulum - an out pouching of the foregut
What are the five stages of respiratory tract development?
- Embryonic
- Pseudo-glandular
- Canicular
- Saccular
- Alveolar
What happens in the embryonic phase of respiratory tract development and when does it occur?
0-5 weeks
Lungs and trachea develop
What happens in the pseudo-glandular phase of respiratory tract development and when does it occur?
5-16 weeks
Branching of the trachea
What happens in the canicular phase of respiratory tract development and when does it occur?
16-26 weeks
Respiratory bronchioles form
What happens in the saccular phase of respiratory tract development and when does it occur?
26w - birth
Terminal sacs form
What happens in the alveolar phase of respiratory tract development and when does it occur?
8m-childhood
Alveoli mature
Describe the first breath.
Fluid removed from the lungs
Adrenaline - increases surfactant release
Air inhaled
O2 vasodilates the pulmonary vessels
Umbilical arteries and ductus arteriousus constricts.. Foreamen ovale closes.
What separates the lung bud from the oesophagus in the embryo?
Transoesophageal septum
From what layer of the tri-laminar disc is the pleura derived from?
Mesoderm
From what layer of the tri-laminar disc is the respiratory tract derived from?
Endoderm
Do the lungs function in the embryo?
NO! They are of no use. Gas exchange occurs via the placenta.
What is the PaO2 equal to in the foetus?
3.2 KPa (equivalent to 31,000 feet)
In what direction does blood shunt in the foetus?
Right to Left: due to high vascular resistance in the lungs
meaning the pressure is higher in the right of the heart (supplies the lungs) than the left, thus blood will shunt through to the left via the foramen ovale
When is surfactant first produced?
At 34 weeks of gestation and production increased rapidly 2 weeks prior to birth.
Surfactant deficiency in premature babies can result in respiratory distress syndrome of the newborn. What are the implications of this?
Since low surfactant decreases lung compliance means that the baby can only inspire by the most strenuous of effort which may ultimately result in complete exhaustion, inability to breather, lung collapse and death
What does the ductus arteriosus do?
Shunts blood from aorta to left pulmonary artery
What does the ductus venosus do?
Shunts blood from umbilical vein to IVC
What does the foreamen ovale do?
Shunts oxygenated blood from RA to LA
Where does the foregut begin and end in the embryo?
Oropharyngeal membrane to the liver bud
Where does the midgut begin and end in the embryo?
Liver bud to 2/3 along TC
Where does the hindgut begin and end in the embryo?
Distal 1/3 of TC to cloacal membrane
Why are the foregut, midgut and hindgut divisions different in the adult compared to in the embryo?
It changes due to the formation of the ampulla of vater.
Are the pharyngeal clefts formed in the endoderm or ectoderm?
Ectoderm.