Topic 7.2 Flashcards
What are the functions of lungs?
1) Interact with blood = exchange CO2 + O2
2) Maintain blood pH
3) Involved in heat exchange + fluid balance
4) Key element in voice production
How much air do we typically breathe?
6 L/min = 10kg per day
How much O2 do we breathe?
- Air = 20.9% O2
- Inhale 1.2 L/min = 2kg per day
What is our breathing rate?
- Men = 12/min
- Women = 20/min
- Infants = 60/min
What is the surface area of lungs?
80m2
What is the max O2 usage?
- Average fit = 2.8 L/min
- High fit = 4 L/min
Conversion between mm Hg + cm H2O
1 mm Hg = 1.36 cm H2O
What is the formula for pressure change in alveoli?
ΔP = Pin - Pout
What is the pleural sac?
- Each lung is surrounded by a sac membrane
- Filled with intrapleural fluid
Describe the structure of the lungs
- Inner wall of sac = visceral pleura = attached to outer lung wall
- Outer wall = parietal pleura = attached to thoracic wall
What keeps the lungs from collapsing?
- Lungs springiness = pulls 2 pleural membranes apart = sac pressure decrease compared to atm
- ΔP keeps lungs expanded
What is the driving force for controlling lung volume?
- Transpulmonary pressure
- Difference in pressure alveoli + around lung
How are lungs expanded + contracted?
1) Diaphram moves down = lengthen chest cavity = inspiration
2) Ribs elevated by neck muscles = increase front-back diameter of chest cavity + ribs lowered by abdominal recti = decrease chest cavity
How does movement of structures allow air to enter?
- Air inside atm
- Inspire = diaphragm down
- Negative pressure in lungs = air flows in
- Expire = relax diaphragm = air flows out
Describe pneumothorax
- Chest wall punctured = lung collapses = diaphragm lowered = chest wall expands
