a. T
b. F
c. T
d. T
e. T
Composition of Surfactant
- Dipalmitoylphosphatidylcholine ( DPPC) 62 %
- Phosphatidylglycerol 5%
- Other phospholipids 10%
- Neutral lipids 13%
- Proteins 8 %
- Charbohydrate 2%
b. Formation of Surfactant
Surfactant is synthesized by type II alveolar epithelial cells and stored in lamellarbodies. Lamellar body secretes surfactant into alveolar space by exocytosis.
c. Inspiration is an active process and needs energy to 1. Expand lung against the lung and chest elastic forces (compliance work, elastic work) 2. Overcome the viscosity of the lung and chest wall structure (tissue work) 3. Overcome resistance to the movement of air into the lungs Pulmonary surfactant reduce surface tension and increase compliance (compliance is the ability of the lung and thorax to expand). Therefore it reduces the work of breathing.
d. When alveoli increase in size, the surfactant spread all over the alveolar surface and it increases surface tension. This increase surface tension reduces the rate of expansion of the alveoli. Therefore it keeps all alveoli expand at the same rate. When alveoli shrink, surfactant concentrated inside alveoli and reduces surface tension. This keeps all alveoli shrink at the same rate. Therefore all alveoli stabilize in same size.
e. Normally Surface tension force draws fluid into the alveoli. But presences of surfactant reduce fluid accumulation because surfactant reduces surface tension.