Page 372 - Concise Pathology for Exam Preparation ( PDFDrive )

13 The Lung 357

Terminal bronchiole Alveolar sac
Respiratory
bronchiole

Alveolar duct

FIGURE 13.1. Parts of an acinus.

Basal lamina
Red blood
cell

Type l Alveolar
pneumocyte macrophage
Air space
Air space
Type ll Capillary
pneumocyte
Surfactant
layer
Capillary

FIGURE 13.2. Schematic diagram of the structure of the alveolar septum.

Q. Write briefly on acute respiratory distress syndrome (ARDS).

Ans. ARDS is a manifestation of severe acute lung injury or ALI.

Salient Features
• Also known as diffuse alveolar damage, and shock lung
• Caused by diffuse alveolar capillary damage
• Presents with rapid onset of severe life-threatening respiratory insufficiency, cyanosis
and severe arterial hypoxaemia in the absence of cardiac failure. The respiratory insuf-
ficiency may be refractory to O2 therapy.
• May progress to extra pulmonary multisystem organ failure

Causes
• Infections
• Sepsis
• Diffuse pulmonary infections (viral, mycoplasma, pneumocystis pneumonia and
miliary tuberculosis)
• Physical injuries
• Head injury
• Pulmonary contusions
• Drowning
• Fractures and fat embolism

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