Term
| Epithelial cells are polarized. How does epithelium know where the lumen/surface is? |
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Definition
| Mesenchyme secretes epimorphin, which signals the location of the basal membrane. |
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Term
How do epithelial cells know to remain in sheets or tubes?
Why is this important? |
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Definition
Mesenchyme produces tenascin and syndecan in areas that are sheets or straight tubes - not in areas of branching or areas that are globular.
Tumors lack some or all of these organizational controls. |
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Term
| Why is birth an arbitrary point between species? |
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Definition
| A lot of animals have the same stages of lung development, but happen at different times relative to birth than in humans. |
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Term
| How many generations of branching occur before birth? |
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Definition
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Term
| When are the alveoli built? |
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Definition
| Beginning right before birth, continuing through 2-8 years. |
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Term
| How many branching generations occur after birth? |
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Definition
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Term
| List the stages of lung development in order. |
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Definition
| Embryonic -> Pseudoglandular -> Canalicular -> Saccular -> Alveolar |
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Term
| What major events occur in the embryonic period? |
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Definition
| Lung buds arise from foregut and branch 3 times, forming 2 lungs, 5 lobes, & the bronchopulmonary segments. |
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Term
| What major events occur in the pseudoglandular period? |
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Definition
| 14 more branches to form terminal bronchioles. |
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Term
| What major events occur in the canalicular period? |
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Definition
Terminal bronchioles divide into 2+ respiratory bronchioles.
Respiratory vasculature begins to develop. |
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Term
| What major events occur in the saccular period? |
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Definition
Respiratory bronchioles divide into terminal sacs produced into childhood.
Type I and Type II alveolar cells appear
Surfactant is first secreted. |
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Term
| What major events occur in the alveolar period? |
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Definition
The alveoli develop and mature.
Great increase in surface area. |
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Term
In what periods does this happen?
- formation of the major airways
- formation of the bronchial tree & portions of the respiratory parenchyma
-birth of the acinus |
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Definition
| embryonic and pseudoglandular |
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Term
In what period does this happen?
-last generations of the lung periphery formed
-epithelial differentiation
-air-blood barrier formed |
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Definition
| end of pseudoglandular and most of canalicular |
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Term
In what period does this happen?
- expansion of air spaces
- surfactant detectable in amnionic fluid |
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Definition
| end of canalicular and most of saccular |
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Term
In what period does this happen?
- secondary septation |
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Definition
| end of saccular and most of alveolar |
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Term
| What is the critical factor in species selection for models of the human pediatric lung? |
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Definition
| Timing of alveolar development. |
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Term
| Where is the lung bud located? |
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Definition
| Anterior end of the foregut. |
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Term
| What does the tracheo-esophageal septum give rise to? |
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Definition
Trachealis muscle
Anterior end of the esophagus |
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Term
| Malformation of the tracheoesophageal septum leads to ________. |
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Definition
Esophageal atresia
Tracheoesophageal fistula |
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Term
During branching of the bronchial tree...
The epithelium produces _______.
The mesenchyme produces ________.
Describe how each of the secretions influence branching. |
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Definition
The mesenchyme produces FGF-10, which stimulates mitosis of epithelium.
The epithelium produces Shh and BMP-4, which stop FGF-10 when they reach a threshold. They also stimulate mesenchyme to secrete TGF-B (promote ECM) and VEGF (promote capillaries). |
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Term
| Discuss the changes in the lung that occur during the perinatal period. |
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Definition
Alveoli mature
Capillaries develop
Wall thickness and mesenchyme go down |
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Term
| What might cause hypoplasia of the lung in a newborn? |
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Definition
Post natal hernia could be formed if the colon moves into the left lung space.
Repair does not guarantee survival. |
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