6.4 gas exchange

Question 1

ventilation

Answer 1

Ventilation is the movement of air into and out of the lungs. Inspiration and expiration.

Question 2

gas exchange (simple definition)

Answer 2

Gas exchange is the movement of oxygen and carbon dioxide, via simple diffusion, between the alveoli and the blood stream.

Question 3

gas exchange

Answer 3

Gas exchange is a passive process. It involves the diffusion of CO2/O2 from a high concentration to a low concentration.
In the alveoli, oxygen must move along a concentration gradient (high to low) from the lung into the bloodstream (diffusion). Therefore, oxygen concentrations must remain high in the lungs/alveoli. Inspiration ensures a constant supply fresh air, maintaining a high concentration of O2.
Carbon dioxide, is a waste product. CO2 concentrations in the alveoli must remain lower than blood CO2 concentrations to enable the passive diffusion of CO2 into the lungs. Expiration removes excess CO2 from the lungs.

Question 4

alveoli

Answer 4

air sacs in lungs

Maximize surface area for maximal gas exchange between the lungs and the capillaries of the blood system.
One cell thick to ensure rapid diffusion of gasses.

Question 5

pneumocytes

Answer 5

Differentiated cells
AKA: Alveolar cells - they line the alveoli.
There are two types:
Type I (~95% of surface)
Type II (~5% of surface)

Question 6

Type I pneumocytes

Answer 6

Involved in gas exchange
Flattened (increase surface area to volume ratio) and extremely thin. Reduces distance of gas diffusion
Large areas of free cytoplasm* to maintain thin shape.
Unable to replicate. Type II cells can differentiate into Type I cells.

Question 7

Type II pneumocytes

Answer 7

Few.
Secrete pulmonary surfactant**. This reduces surface tension making inflation of the alveoli easier.
Divide to create new type II cells
Repair

Question 8

pulmonary surfactant

Answer 8

surfactant is like a soap. It is amphipathic. In type 2 pneumocytes, the surfactant is made up of phospholipids

Question 9

muscles of inspiration

Answer 9

1. external intercostals (flatten to expand lungs)
2. diaphragm (contracts to expand thoracic activity)

Question 10

muscles of expiration

Answer 10

1. internal intercostals (contracts to pull ribs down)
2. diaphragm (relaxes to reduce thoracic activity)

Question 11

lung cancer: risk factors & consequences

Answer 11

risk factors:
- smoking, secondhand smoke, previous radiation therapy, exposure to carcinogens, family history

consequences:
- shortness of breath, coughing up blood, pain, fluid in chest, metastasis (cancer spread)

Question 12

emphysema: risk factors & consequences

Answer 12

risk factors:
- smoking, long term exposure to lung irritants, age, genetics

consequences:
- Frequent coughing or wheezing
- A cough that produces a lot mucus
- Shortness of breath, especially with physical activity
- A whistling or squeaky sound when you breathe
- Tightness in your chest

Question 13

empysema

Answer 13

a type of COPD (chronic obstructive pulmonary disease). affects air sacs in lungs