Embryology 3 Flashcards
What part of the embryo does the respiratory system derive from?
Foregut part of the primitive tube
What separates primitive oesophagus and trachea as an embryo?
Oesophagotracheal septum
Lung buds enlarge to form lungs
If the oesophagus and trachea don’t separate correctly as an embryo, what can this cause?
Trachoesophageal fistula
Oesophageal atresia
What part of the embryo does the visceral pleura derive from?
Splanchnic layer of the lateral plate mesoderm
What part of the embryo does the parietal pleura derive from?
Somatic layer of the lateral plate mesoderm
In embryology, what is formed prior to the formation of the pleural cavity?
Pericardioperitoneal cavity
How is the pleural cavity formed?
The pleuro-pericardial fold closes off the pleural cavity from the heart
At what stage of the development of the respiratory system does gas exchange begin to occur?
Saccular stage (27- 40 weeks)
What is neonatal respiratory distress syndrome?
Caused by surfactant deficiency
Partial collapse of alveoli
Debris consisting of blood elements accumulate - glassy ( hyaline) membrane appearance
Affects 2% of neonates
Makes up 30% of neonatal disease
What is lung agenesis?
Failure of lung bud to develop/branch
insufficient mesoderm
Teratogens
What is pulmonary hypoplasia?
Abnormally low number/size of bronchopulmonary segments/ alveoli
What part of the embryo forms the central tendon of the diaphragm?
Septum transversum - It arises from cranial mesoderm and migrates downwards.
What part of the embryo forms the muscular part of the diaphragm?
Skeletal muscle - Grows in from body wall to cover the pleuroperitoneal folds.
What part of the embryo forms the left and right diaphragmatic crura?
Dorsal mesentery of oesophagus - Attaches embryonic oesophagus to posterior thoracic wall.
Skeletal muscle ingrowth from body wall then covers dorsal mesentery on each side.
How many mesoderm structures create the diaphragm?
4
When is the alveolar stage of development?
32 weeks - 8 years
What does folding of embryo give rise to?
Primitive gut tube formed from endoderm foregut, midgut, hundgut.
What does foregut endoderm give rise to?
Lung bud
What does lung bud give rise to?
Trachea and lungs
What does pleura arise from?
Lateral plate mesoderm surrounding the lung bud.
At 4 weeks where does the trachea and lung bud arise from?
From anterior wall of primitive foregut (endoderm)
Where does the trachea lie?
It lies anterior to oesophagus
What does a fistula mean?
An abnormal passage between 2 epithelialized tubes or surfaces. TOF is a common congenital abnormality
What does atresia mean?
A condition in which an orifice or passage in the body is closed or absent.
What is the pericardioperitoneal canal?
It is the space between splanchnic and somatic mesoderm around lungs is initially continuous with both the pericardial cavity anteriorly and peritoneal cavity/abdomen inferiorly. The continuity is called that.
What is done to maintain the correct pleural cavity negative air pressure?
The canal needs to be sealed off from the pericardial and peritoneal cavities to become a close spaced around the lungs.
Once it is sealed off, the canal then becomes the definitive pleural cavity
What does the plueropericardial folds do to seal off the pleural cavities from the pericardial cavity?
It grows in from the thoracic wall, these folds also form the pericardium around the heart.
What happens if the pleuropericardial folds fail to develop?
Pleuropericardial fistula/effusion
What is hernia?
Protrusion of an organ through structure or muscle that contains it
It occurs at oesophageal hiatus and sites where structures fail to develop or fuse.
Where does primitive gut tube form from?
Endoderm
Where does trachea and lungs form from?
Foregut endoderm
Where does visceral pleura form from?
Splanchnic (inner) layer of lateral plate mesoderm.
Where does parietal pleura form from?
Somatic (outer) layer of lateral plate mesoderm
Where does diaphragm form from?
Mainly from cranial and paraxial mesoderm.
