Unit 11 - gas exchange in humans

Question 1

What is the breathing system?

Answer 1

An organ system that allows the body to obtain oxygen for aerobic respiration and remove carbon dioxide as a waste product of respiration.

Question 2

What pathway does air travel through + short explanation of all parts of the breathing system?

Answer 2

Nose/mouth - larynx (voice box located above lungs) - trachea - bronchi (2 big pathway to each lung) - bronchioles (smaller pathways leading to different parts of each lung) - alveoli (tiny air sacks with capillaries on their walls)
Through this pathway, air reaches millions of tiny structures in the lungs called alveoli.
The intercoastal muscles are between the rib.

Question 3

Where does gas exchange in humans happen + what gases are exchanged?

Answer 3

At the surface of the alveoli, allowing oxygen to diffuse from the air to the blood in the capillaries. CO2 diffuses from the blood to the air.

Question 4

State and explain 4 ways that the alveoili (as a gas exchange surface ensure) efficient gas exchange

Answer 4

1. Have a large surface area = more space for gas to be exchanged, making the process more efficient
2. Have thin surface/walls - less distance needed for oxygen to diffuse across it makes the process faster
3. Have a good blood supply due to lots of associated capilaries on the surface of the alveoli - ensures that oxygynated blood is replaced with deoxygynated blood ( maintains high concentration gradient)
4. Have a good ventilation with air - brings/provides a lot of air to alveoli ( maintains high concentration gradient)

Question 5

State the definition and composition of inspired air vs expired air

Answer 5

Inspired air - the air you breathe in. 21% oxygen, 0.04% CO2, variable water vapour levels
Expired air - the air you breath out. 16% oxygen, 4% CO2, always high water vapour levels ( moisture evaporates from the cells of the gas exchange surface)
Therefore, inspired air has more oxygen than expired air but less CO2 and water vapour

Question 6

Describe an experiment for investigating the difference between expired and inspired air

Answer 6

1. Get 2 boiling tubes, a bing, a mouthpiece, & a delivery tube
2. Connect 2 boiling tubes using a delivery tube so that in boiling tube 1, the part of the delivery tube connected to the mouthpiece is not in the limewater while in boiling tube 2 it is; the delivery tube not connected to the mouthpiece should be in contact with the limewater in boiling tube 1 and vice versa for boiling tube 2.
3. Put the disinfected mouthpiece in your mouth and breathe in & out 10 times
4. Record the appearance of the liquid in both boiling tubes
   The limewater in test tube 2 should turn cloudy due to there being more carbon dioxide in expired air

Question 7

Describe an experiment on the effects of physical activity on the rate & depth of breathing

Answer 7

1. Measure your breathing rate at rest by counting the number of breaths/30 seconds and doubling it.
2. Assess the depth of your breathing (whether it is light, moderate, deep or gasping
3. Run on the spot for 2 minutes
4. Immediately after the exercise ends, sit down and measure your breathing rate again. Assess the depth of your breathing once more.
5. Repeat step 4 two minutes after the exercise ended and then again two minutes later
6. Record your data
   Both the rate and depth of breathing should increase after exercise and gradually return to normal resting values.

Question 8

Why do we breathe faster and deeper during physical activity?

Answer 8

The cells of the body respire more during physical activity to provide energy to the muscles. Increased rate of respiration produces more CO2 as a waste product. This increased CO2 concentration is detected by the brain, which triggers the body to respond by increasing the rate & depth of breathing to expel CO2 from the body and increase the amount of oxygen obtained to maintain aerobic respiration.

Question 9

What is the diaphragm?

Answer 9

Muscle forming at the base of the thorax