Lung development and surfactant

Question 1

Name the five periods of lung development and the weeks that they occur

Answer 1

4-7 weeks embryonic period
5-17 weeks pseudoglandular period
16-25 weeks canalicular period
24-postnatal saccular period
36-8 years alveolar period

Question 2

Describe events occurring in the embryonic period

Answer 2

Lung buds arise as ventral outputting of gut tube. Produces primary bronchi, lung lobes, and bronchopulmonary segments (tertiary and segmental bronchi)

Question 3

Describe the events occurring in the psuedoglandular period

Answer 3

The respiratory tree undergoes more generations of branching resulting in the formation of bronchi, bronchioles and terminal bronchioles. Microscopically the lung resembles a gland.

Question 4

Describe the events occurring in the canalicular period

Answer 4

Terminal bronchioles give rise to two or more respiratory bronchioles which each divide into 3-6 alveolar ducts lined by cuboidal cells, a capillary network begins to be established.

Question 5

Describe the events occurring in the saccular period

Answer 5

The alveolar ducts give rise to primitive alveoli. Type 1 cells intimately involved with blood and lymph network. Type 2 cells begin to produce surfactant (surfactant production occurs from 26 weeks)

Question 6

When does surfactant production begin?

Answer 6

During the saccular period, from week 26.

Question 7

Describe the events occurring in the alveolar period

Answer 7

The number of terminal sacs increases and they mature whereby the alveoli walls thin establishing better contact with blood and lymph

Question 8

Make up of surfactant

Answer 8

95% phospholipid

5% protein

Question 9

Describe phospholipids in surfactant

Answer 9

Non-polar tail made up from carbon chain of up to 18 in length derived from glucose or glycerol. Polar head that is hydrophilic