6. Cardiorespiratory System- Gas Exchange Systems (alveoli/muscles)

Question 1

Define diffusion

Answer 1

Is the movement of gas molecules from an area of high concentration or partial pressure to an area of low concentration or partial pressure

Question 2

Define partial pressure

Answer 2

Is the pressure exerted by an individual gas when it exists within a mixture of gasses.

Question 3

Gaseous exchange at the alveoli

Answer 3

The structure of the alveoli is designed to help gaseous exchange by:

• thin walls create a short diffusion pathway
• extensive capillary network surrounding the alveoli result in an excellent bloody supply
• a huge surface area, as a result of the millions of alveoli in each lung, allows for a greater oxygen uptake

Question 4

The partial pressure of oxygen (pO2)

Answer 4

The partial pressure of oxygen in the alveoli is higher than the partial pressure of oxygen in the capillary blood vessels. This is because the oxygen had been removed by the working muscles, so it’s concentration in the blood is lower and therefore so is it’s partial pressure. The difference in partial pressure is referred to as the concentration/diffusion gradient; the bigger it’s gradient the faster diffusion will be.

Oxygen will diffuse from the alveoli into the blood until the the pressure is equal in both. The movement of carbon dioxide occurs in the same way, but in the reverse direction. This time the partial pressure of carbon dioxide (pCO2) in the blood entering the alveolar capillaries is higher than I. The alveoli, so CO2 diffuses into the alveoli from the blood until the pressure is excuse in both

Question 5

Gaseous exchange at the muscle

Answer 5

In the capillary membranes surrounding the muscle the partial pressure of oxygen is higher than in the muscle, which allows oxygen to diffuse from the blood into the muscle until equilibrium is reached. Conversely, the partial pressure of CO2 in the blood is lower than in the muscle, so again diffusion occurs and CO2 moves into the blood to be transported to the lungs

Question 6

Impact of physical activity on the respiratory system

Answer 6

Positive effects to promote a healthy lifestyle:

• improves the efficiency of the respiratory system due to an increase in the surface area of alveoli and capillary density at the alveoli, so the body can supply muscles with more oxygen.
• respiratory muscles are strengthened, resulting in deeper breathing
• greater gaseous exchange takes place so more oxygen diffuses into the blood and more carbon dioxide diffuses from the blood
• tidal volume and minute ventilation will increase, allowing more oxygen to diffuse into blood and more carbon dioxide to diffuse into the blood and more CO2 to diffuse into the alveoli