Pulmonary development

Question 1

Two layers of pulmonary pleura

Answer 1

Parietal and visceral with a thin film of fluid in between

Question 2

How many lobes are in the lungs

Answer 2

left: superior and inferior. Right: superior, middle, inferior

Question 3

What supplies the lungs? What drains the lungs?

Answer 3

pulmonary arteries, bronchial arteries, bronchi supply lungs. Pulmonary veins and lymphatics drain the acini (gas exchange unit)

Question 4

List the progression of the airway structures

Answer 4

trachea > bronchi > bronchioles > terminal bronchioles >respiratory bronchioles > alveolar ducts > alveolar sacs

Question 5

Which parts of the airway are gas exchange regions

Answer 5

•Respiratory bronchiole, alveolar ducts and alveoli

Question 6

Which parts of the airway are conducting airway regions

Answer 6

trachea, bronchi, bronchioles

Question 7

Layers of the airway walls

Answer 7

Inner mucosal surface (epithelial cells, cilia, and goblet cells), the smooth muscle layer, and the outer connective tissue layer. Cartilage is present in the trachea and bronchi.

Question 8

Describe 2 types of cells in the gas exchange regions

Answer 8

squamous lining cells (type I cells or pneumocytes) and secretory cells (Type II cells). Type I cells comprise 95% of alveolar surface area and fuse with capillary endothelium to create a thin membrame for gas transfer. Type II cells 1) repair or replace injured Type I pneumocytes, and 2) secrete surfactant, a substance which lowers alveolar surface tension.

Question 9

Lungs develop from what embryological structure?

Answer 9

lung bud of the gut tube endoderm- an outpouching btw the 4th and 6th brachial arches

Question 10

Pulmonary circulation develops from what embryological structure?

Answer 10

Mesenchyme surrounding the lung bud

Question 11

What are the stages of development of the lungs

Answer 11

Embryonic, pseudoglandular, canalicular, saccular, alveolar

Question 12

Embryonic stage details

Answer 12

26 days to 6 weeks: Foregut endoderm extends into surrounding mesenchyme. 3 rounds of branching establish lung lobes. Branching is initially asymmetric

Question 13

During lung branching, what occurs at branch points and developing buds

Answer 13

–At branch points epithelial cell division stopped and collagen produced. At developing buds growth factors produced to induce epithelial mitosis

Question 14

pseudoglandular stage details

Answer 14

6 to 16 weeks: 14 rounds of branching form terminal bronchioles. Cartilage, smooth muscle cells and mucus glands develop from splanchnic mesenchyme

Question 15

canalicular stage details

Answer 15

16 to 28 weeks: Terminal bronchiole divides into 2+ respiratory bronchioles, Surfactant production begins and increases as weeks progress. Initial development of pulmonary capillary bed and fetal “breathing” is detected
16 to 28 weeks: Terminal bronchiole divides into 2+ respiratory bronchioles, Surfactant production begins and increases as weeks progress. Initial development of pulmonary capillary bed and fetal “breathing” is detected

Question 16

saccular stage details

Answer 16

26 to 36 weeks: Respiratory bronchioles subdivide to produce terminal sacs (these continue to develop well into childhood). Epitelial cell differentiation of type I and type II cells is hallmark

Question 17

alveolar stage details

Answer 17

36 weeks to early childhood: Lung grows & alveoli mature: Septea thin, Single capillary network in alveolar wall, Gas exchange unit established

Question 18

What embryonic structure do pulmonary arteries come from? Pulmonary veins?

Answer 18

arteries: 6th aortic arch. Veins: outgrowths from left atrium

Question 19

Pulmonary contributors to increased work of breathing (dyspnea)

Answer 19

increased elastic properties of lung tissue, resistance to airflow in airways, impaired gas exchange