Overview of the Pulmonary System/Lung Development

Question 1

What are the conducting airways of the lung?

Answer 1

• trachea
• bronchi
• bronchioles

Question 2

What are the gas exchange units of the lung?

Answer 2

• respiratory bronchioles
• alveolar ducts
• alveoli

Question 3

on average there are _____ generations of airways in the lungs (everytime they branch). The first ____ are the conducting airways (or conducting zone) and end with the ______. Beginning with the next generation which are called ______, these generations until the end of the lung airways constitute the ______ zone.

Answer 3

• 23
• 16
• Terminal bronchioles
• Respiratory bronchioles
• respiratory (also includes the transitional zone whatever that is)

Question 4

How do we note anatomically the change from bronchi to bronchiole?

Answer 4

loss of cartilage in the outer tissue layer.

So, Brochitis and brochiectasis refer to airways with cartilage while brochiolitis refers to non-cartilagenous airways

Question 5

Why are the conducting airways known as “anatomic deadspace?”

Answer 5

they do not exchange gas

Question 6

The simple epithelium of the bronchioles gives way to two different types of alveolar epithelial cells. What are they and what do they do?

Answer 6

• squamos lining cells (type I or pneumocytes)- these account for most of the alveolar lining and fuse with capillary endothelium to create a thin membrane for gas exchange.
• secretory cells (type II cells)- these are responsible for repairing and replacing type I pneumocytes and for secreting surfactant.

Question 7

_____ (vessels) run with the bronchi while ______ (vessel) do not

Answer 7

• pulmonary arteries and arterioles

- pulmonary veins (these are more peripheral).

Question 8

production of surfactant begins at the end of the _______ stage at about weeks ____ to _____. Why is this significant?

Answer 8

-canalicular
-26, 28
If a premature infant is born around this time there is a reasonable chance of survival. Without surfactant the lungs don’t work.

Question 9

The saccular phase ends at _______ wks. Why is this important?

Answer 9

36. This helps us understand why a child born after 36 weeks gestation rarely has respiratory distress.

Question 10

The embryonic stage of development is from ______ days to ______ weeks. It includes what important events?

Answer 10

26 days to 6 weeks.

• foregut endoderm extends into surrounding mesenchyme
• 3 rounds of branching establish lung lobes

Question 11

The pseudoglandular stage of development is from ______ to ______ weeks. It includes what important events?

Answer 11

6-16 weeks

-14 rounds of branching form the terminal bronchioles

Question 12

The canalicular stage of development is from ______ to ______ weeks. It includes what important events?

Answer 12

16-28 weeks

• terminal bronchiole divides into 2+ respiratory bronchioles
• Surfactant production begins and increases as weeks progress

Question 13

The saccular stage of development is from ______ to ______ weeks. It includes what important events?

Answer 13

28-36 weeks

-respiratory bronchioles subdivide to produce terminal sacs (these continue to develop well into childhood).

Question 14

The alveolar stage of development is from ______ to ______ . It includes what important events?

Answer 14

36 weeks to early childhood (4-6 yrs).

-lung grows and alveoli mature: septa thin, single capillary network in alveolar wall, gas exchange unit established.

Question 15

How do I remember all the embryo stuff?

Answer 15

Every Person Can Say Applebees

EPCSA - embryonic, pseudoglandular, canalicular, saccular, alveolar.

Then remember the lung gets more defined and detailed as time goes on (lung lobes established first, alveoli last, terminal bronchioles become respiratory bronchioles somewhere in the middle). Surfactant begins to be produced at the end of the canalicular phase (26-28 wks). Thats pretty good.