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Flashcards in Embryology Deck (17)
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What gives rise to the larynx, trachea, bronchi, bronchioles, alveoli?

Lung bud


The lung bud develops during week 4 as a ventral diverticulum of the foregut.  What is it lined by?  What is on the outside?

  1. Endoderm
  2. External Lateral plate mesoderm


What does the endoderm of the lung bud give rise to?

all epithelia and glands of the respiratory tract.


External layer of lateral plate mesoderm which will give rise to?

 cartilages, muscles, connective tissues of airways


When does a tracheoesophageal fistula result?

What is it most likely caused by?


Likely on exam - be sure to know all aboot.

When there is abnormal partitioning of the cranial part of the foregut into tracheal and esophageal portions.  

This condition is most likely caused by a spontaneous deviation of the tracheoesophageal septum.


Tracheoesophageal fistula are often associated with what?

esophageal atresia (blind-ending esophagus) - essentially the opposite of a fistula


What is shown here?  Which type is mot common?

Tracheoesophageal fistula (and esophageal atresia.

Type A is the most common - 90%


For 500 points, what is the condition...

a rare, life threatening anomaly resulting from failure of larynx to recanalize

Laryngeal atresia


What are the four main stages of lung development?

  1. psuedoglandular stage
  2. canalicular stage
  3. terminal sac stage
  4. alveolar stage


Describe the first step of lung maturation

Pseudoglandular stage (5-16 weeks)

Terminal bronchioles are formed, no respiratory bronchioles.
Respiration not possible; fetuses born during this time are not viable.
Fetal breathing movements typically start during 12th week of development.

Strengthen thoracic muscles.
Vital for lung development as amniotic fluid is breathed in.


What is the clinical correlation associated with the 5-16 week period of lung maturation?

Oligohydramnios (low level of amniotic fluid) often results in severe lung hypoplasia.


Describe the canalicular stage of lung development.  Weeks 16-26


Lung tissue becomes highly vascular.
By 24 weeks, respiratory bronchioles and alveolar ducts have formed.
Type II alveolar cells begin forming surfactant at 20 weeks, but surfactant levels do not reach adequate amounts until about 26-28 weeks.
Surfactant reduces surface tension in alveoli, facilitating expansion during inhalation.
Fetuses born during this time may be viable (~50% or less chance) with intensive care, but often are not viable due to underdevelopment of alveoli at this stage (as well as underdevelopment of other systems).


What forms during the terminal sac stage?

Primitive alveoli


What are the odds a fetus delivered during the 26-32 week stage will make it?

may survive (80-95% chance); but still require intensive care.

Sufficient surfactant production and adequate 


What are the critical factors determining survivability during the 26-32 week period?

Sufficient surfactant production and adequate pulmonary vasculature are the most critical factors in determining survival and growth of premature infants.


What is the survivability outlook for a fetus born at the alveolar stage?

Fetus born during this period are almost as likely as full-term babies to survive.


How long do alveoli continue to form?

Up to 8 years of life.