Lecture 2: Respiration II

Question 1

Major contributors to lung recoil

Answer 1

1. Elastic CT (collagen, elastin)
2. Surface tension of water

Question 2

Emphysema

Answer 2

Loss of elastic tissue and alveolar walls, increasing airway resistance and causing fewer + larger alveoli. Increases compliance and lowers perfusion capacity.

Question 3

Altitude sickness

Answer 3

Composition of air does not change with altitude, but total P_atm decreases, thus less oxygen is inspired with each breath.

Question 4

Pneumothorax

Answer 4

Collapsed lung due to air in the intrapleural space (P_ip = atm)

Question 5

Surfactant

Answer 5

Amphiphilic phospholipids + protein mixture secreted by AT2 cells that interferes with air-water interface, reducing surface tension within alveoli.

Question 6

Effect of surfactant on alveoli tension

Answer 6

Surfactant reduces surface tension especially for smaller alveoli (smaller surface area = more concentrated) and maintains alveolar pressure despite size changes

Question 7

Pressure of an open sphere with surface tension

Answer 7

P = 2T / r

Question 8

Infant Respiratory Distress Syndrome (Hyaline membrane disorder)

Answer 8

Premature birth -> underdeveloped lungs -> low surfactant production -> low lung compliance, making inspiration difficult and causing alveolar collapse

Question 9

Conditions increasing lung compliance

Answer 9

Aging, emphysema

Question 10

Conditions decreasing lung compliance

Answer 10

Pulmonary edema, fibrosis, increased blood volume, increased surface tension

Question 11

Air flow equation

Answer 11

Flow = P_alv - P_atm / R; resistance depends primarily on radius (1/r^4)

Question 12

Dynamic compression

Answer 12

Compression of airways occurring during forced expiration due to friction of air flow. Fluttering occurs due to collapse + pressure build up. Amount of compression depends on starting TPP; better flow when starting at higher volume