Summary
Surfactant reduces alveolar surface tension, preventing collapse and easing breathing.
In depth
Compliance is the change in volume per change in pressure. Surfactant from type II alveolar cells lowers surface tension; premature babies lacking it develop respiratory distress syndrome. Fibrosis reduces compliance.
Elastic fibres and surface tension influence compliance. Surfactant is a mix of phospholipids and proteins. Low compliance increases work of breathing.
Key idea: surfactant prevents alveolar collapse.
Compliance of lungs is about 200 mL per cm of water. Elastic recoil arises from elastin fibres and surface tension at the air-liquid interface of alveoli. Laplace's law (pressure equals 2T/r) predicts small alveoli would collapse into large ones, but surfactant (dipalmitoylphosphatidylcholine, with proteins SP-A to SP-D) lowers surface tension more in small alveoli, stabilising them. It also reduces work of breathing and keeps alveoli dry.
Premature babies born before about 28 weeks have too little surfactant and develop respiratory distress syndrome, treated with antenatal corticosteroids and surfactant replacement. Fibrosis reduces compliance (stiff lungs), and emphysema raises compliance but reduces elastic recoil. ARDS involves surfactant dysfunction.
Example: the first breath of a newborn is hard because it must open fluid-filled alveoli against surface tension.
Frequently asked questions
What is Lung Compliance and Surfactant?
Surfactant reduces alveolar surface tension, preventing collapse and easing breathing.
Which area of biology covers Lung Compliance and Surfactant, and how advanced is it?
Lung Compliance and Surfactant is one of the 51 topics in Human Physiology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Gas Exchange in Alveoli, Breathing Mechanism, Respiratory System.
Can you give an example of Lung Compliance and Surfactant?
Steroids given before premature birth accelerate surfactant production.
What should I learn before Lung Compliance and Surfactant?
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Lung Compliance and Surfactant. Advanced topics assume the Intermediate vocabulary.
What topics are related to Lung Compliance and Surfactant?
The closest topics to Lung Compliance and Surfactant are Gas Exchange in Alveoli, Breathing Mechanism, Respiratory System, Respiratory Control. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Lung Compliance and Surfactant?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Lung Compliance and Surfactant. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Lung Compliance and Surfactant different from Gas Exchange in Alveoli?
Lung Compliance and Surfactant: Surfactant reduces alveolar surface tension, preventing collapse and easing breathing. Gas Exchange in Alveoli: Oxygen and carbon dioxide diffuse across thin alveolar and capillary walls down concentration gradients. Read both side by side and note what each one explains.
How should I study Lung Compliance and Surfactant step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Gas Exchange in Alveoli and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.