embryology of respiratory system Flashcards
how does the primitive gut tube form?
from the folding of the endoderm of the embryo
3 things formed from gut tube
foregut, midgut, hindgut
when and where do the trachea and lung buds form from
4 weeks from the ventral wall of the primitive gut tube
what seperates the trachea and oesophagus?
oesophagotracheal septum seperates them into ventral trachea and dorsal oesphagus
what 2 things happen if the oesophagus and trachea don’t separate?
tracheoesophageal fistula and oesophageal atresia
what is a fistula
abnormal passage between 2 epithelial tubes
what is an atresia
a passage in the body that is closed off or absent
what does splanchnic mesoderm form?
visceral pleura
what does somatic mesoderm form?
parietal pleura
what is the space called between the 2 layers of mesoderm?
p…c…p
pericardioperifoneal cavity
(later called pleural cavity)
how does the pleural cavities close off from the heart?
pleuropericardial (somatic mesoderm) folds
-> pericardium of the heart
what are the 5 stages of lung development? and when do they happen?
e, f- p c s, pn
embryonic (4 weeks)
- lung buds, foregut, trachea form
foetal period
pseudo glandular (7-17 weeks)
- all lung structures develop, except the respiratory part
- no gas exchange
canalicular (17-27 weeks)
- respiratory part and alveolar duct forms
- epithelium differentiates to type l and type ll pneumocytes
- no gas exchange
saccular (27-40 weeks)
- gas exchange begins
- alveolar sacs, primitive alveoli and surfactant is 5% complete
post natal period (32 weeks - 8years)
- proliferation of alveoli from alveolar sacs, complete
- 300 million alveoli in an adult
What are 2 congenital lung conditions that involve neonatal?
NRDS and LA
neonatal respiratory distress syndrome (hyaline membrane disease)
- affects 2% of neonates, makes up 30% of neonatal disease
- surfactant deficiency -> partial collapse of alveoli
-> debris of blood elements accumulate
-> glassy hyaline appearance.
lung agenesis
- failure of lung bud to develop in embryo
- insufficient mesoderm to form pleura
- teratogens (poison)
what closes off pleural cavities from the peritoneal cavity of the abdomen?
Diaphragm
What are the four mesodermal structures that the diaphragm develops from?
1 .septum transversum -> central tendon
- pleuroperitoneal folds
-> somatic mesoderm folds grow from the periphery to fuse with septum transversum - skeletal muscle ingrowth from the peripheral body wall
-> grows inwards to cover pleuroperitoneal folds forming the muscular part - dorsal oesophagus mesentery
-> attaches embryological oesophagus to the posterior thoracic wall
-> skeletal muscle from periphery covers dorsal mesentery to form diaphragmatic crura