Lecture 22 Diseases of the Lung Parenchyma 1

Question 1

Which cells produce surfactant?

Answer 1

type 2 pneumocytes of the alveoli

Question 2

When does surfactant production commence?

Answer 2

late in fetal life

Question 3

what happens to surfactant to prevent its accumulation in the lungs?

Answer 3

surfactant can be recycled by type 2 alveolar cells or degraded by macrophages

Question 4

What is the major function of surfactant?

Other functions?

Answer 4

lower the surface tension of the fluid lining the alveoli to prevent complete collapse of alveoli on expiration
-some surfactant proteins are collectins that agglutinate infectious agents, bind endotoxin, and have anti-oxidant activity

Question 5

What can impair surfactant function or secretion?

Answer 5

function impaired by fibrinogen, edema fluid, or aspirated amniotic fluid within the alveoli
secretion inhibited by prolonged shallow respiration

Question 6

Which of the domestic animals have grossly obvious lobulation of the lungs? Functional significance of this anatomical feature in pulmonary disease?

Answer 6

CATTLE and pigs
poor collateral ventilation
restricted movement of fluid, cells, molecules, and microbes between lobules in disease
cattle more commonly suffer from interstitial emphysema

Question 7

In which species is congenital melanosis of the lungs seen? Significance?

Answer 7

piglets and young ruminants

entirely incidental and fade over time

Question 8

What is fetal pneumonia? Some causes?

Answer 8

Fetal hypoxia in late gestation or during parturition ->relaxation of anal sphincter-> defecation of meconium into amniotic sac->yellow/green staining or skin/fur-/+ aspiration of meconium-> bronchopneumonia
Bacterial or fungal infections of the placenta

Question 9

What is neonatal hyaline membrane disease?

Answer 9

Failure of immature type 2 pnueomocytes to secrete pulmonary surfactant-> increased surface tension and collapse of alveoli on expiration->damage to type 1 pnuemocytes and Club cells
common in full term foals

Question 10

What is meant by the term pulmonary atelectasis? what does it look like grossly?

Answer 10

collapsed or incompletely expanded lung parenchyma

dark red, depressed, rubbery, fails to float in formalin

Question 11

What are the major mechanisms responsible for atelectasis in domestic animals? (3)

Answer 11

congenital= failure of lungs to expand after birth
compression= collapse of previously aerated lung do to external compression
obstructive= collapse of previously aerated lung due to complete airway obstruction

Question 12

What happens to atelectatic lung if the cause is not removed?

Answer 12

atelectasis may become permanent due to reduced vascular perfusion of collapsed lung-> eventually fibrosis

Question 13

What is meant by the term alveolar emphysema? Cause? Why is it common in humans? Is it common in domestic animals?

Answer 13

abnormal and permanent enlargement of air sacs distal to terminal bronchioles accompanied by damage to alveolar walls

• chronic allergic or bacterial bronchitis, heaves in horses, pancreatic necrosis
• cigarette smoking
• rare in domestic animals

Question 14

What does alveolar emphysema look like grossly? What is its effect on respiratory function?

Answer 14

pale pink, look like bubble wrap- severe bubbles may coalesce to form bullous
-decreased gas exchange, increased lung compliance (floppy lung), decreased elastic recoil (bronchioles tend to close prematurely

Question 15

What is bullous emphysema? What can rupture of a bullous lead to?

Answer 15

When the air bubbles in damaged alveoli coalesce.

can lead to spontaneous pnuemothorax

Question 16

What is the difference between alveolar emphysema and hyperinflation of alveoli?

Answer 16

Hyperinflation is a common post mortem finding and there is no accompanying damage to the alveolar walls as there is with alveolar emphysema

Question 17

What is meant by the term interstitial emphysema? In which species is it most often seen and why? to where can the air in the pulmonary interstitium track?

Answer 17

air within the interstitial connective tissues and lymphatics of the lungs
Cattle because of well developed interlobular septa and poor collateral ventilation.
beneath the visceral pleura, mediastinum, or subcutis of brisket, shoulder, or dorsal chest (subcutaneous emphysema)