Embryology Of The Respiratory And Cardiovascular Systems Flashcards
What occurs during early lung development?
Development of the lung primordium and primary lung bud formation.
What occurs during late lung development?
Bronchial branching and cytodifferentiation.
When does development of the respiratory system begin?
Week 4.
The laryngeotracheal diverticulum is first created.
What gene positions specifies the respiratory diverticum and also positions the lung on the esophagus?
TBX4
What dermal layer is the lining of the lungs composed of?
Endoderm.
The outgrowth of the foregut spreads to what dermal layer?
Splanchnic mesoderm
What divides the trachea and the esophagus?
Tracheoesophageal septum.
The laryngeotracheal diverticulum grows distally and is separated from the esophagus dorsally by this septum.
What is the most common formation of the tracheoesophageal septum?
Teachoesophageal fistula.
It results from an abnormal communication between the trachea and esophagus.
What causes a tracheoesophageal fistula?
Improper formation of trachoesophageal septum.
Polyhydramnios (too much amniotic fluid) can be a sign that there is a tracheoesophagel fistual or esophagel atresia. How is this so?
Because the fetus is not swallowing amniotic fluid.
Why is polyhyramnios?
A high volume of amniotic fluid.
It is associated with esophageal atresia and TEF
What are signs and symptoms of tracheoesophageal fistula?
Infants with excessive drooling, choking (especially when fed), coughing and sneezing.
The infant may become cyanotic and may stop breating as the overflow of fluid from the blind pouch is aspirated fom the trachea and lungs.
How is tracheoesophageal fistula treated?
The region of the esophagus with the fistula is surgically removed. The two ends of the esophagus are then sutured back together.
When does the bronchi divide into 2 bronchial buds?
During week 5.
They will become the main or primary bronchi.
Secondary bronchial buds are formed how?
By undergoing a long series of branchings to form respiratory bronchioles.
True or false: each bronchopulmonary segment is a discrete anatomical and functional unit.
True.
This means that a bronchopulmonary segment can be surgially removed without affecting the function of the others.
What does the splanchnic mesoderm differentiate into?
Smooth muscle
Nerves
Blood vessels of the lungs.
What are the stages in lung development?
Embryonic (weeks 4 - 7)
Pseudoglandular (weeks 8 - 16)
Canalicular (weeks 17 - 26)
Terminal sac (weeks 26 - birth)
Postnatal (alveolar)
What occurs during the embryonic stage of lung development?
The initial formation of respiratory diverticulum up to formation of all major bronchopulmonary segments.
Lungs grow into pleural cavities.
Pleura differentiate.
What occurs during pseudoglandular stage of lung development?
Major formation and growth of duct systems within bronchopulmonary segments.
Histologically, the structures resemble a gland.
No gas exchange occurs yet.
What occurs during the canalicular stage of lung development?
The formation of respiratory bronchioles and terminal sacs
Increased vascularization
Capillaries found in walls.
What is found in the terminal sacs?
Epitheilium lining the alveoli, which have developed from respiratory bronchiles.
They differentaiate into two cells types.
What is needed for functioning lungs?
Capillaries
Alveoli
Surfactant of lungs
What is the function of type I pneumocytes?
They form part of the blood-air barrier.
What is the function of type II pneumocytes?
They are secretory cells that produce surfactant. They reduce surface tension and facilitate alveolar expansion.
When are most of the alveoli formed?
After birth.
The primary mechanism is septation of pre-existing alveoli.
When are fetuses generally viable (e.g. They have lungs developed enough to survive)?
Around 22 weeks.
What is infant respiratory distress syndome?
A deficiency or absence of lung surfactant. It results in a collpse or incomplete expansion of a whole lung.
It occurs mostly in infants less than 37 week’s gestation and can be treated with artificial surfactant.
What is pulmonary agenesis?
A complete absence of lungs, bronchi and vasculature.
It can occur bilaterally or unilaterally.
What is pulmonary hypoplasia?
A poorly devloped bronchial tree.
It may be a partial (small segment) or total (entire lung) that is poorly developed.
What is congenital diaphragmatic hernia?
When the septum by the diaphragm does not fully form and the abdominal contents are herniated into the thoracic cavity.
The absence or poor development of what membrane near the diaphragm results in congenital diaphragmatic hernia?
Pleuroperitoneal membranes.