Structure of the human gas exchange system

Question 1

Why are the volumes of gases that are exchanged in mammals large?

Answer 1

-They are relativley large organisms with a large volume of living cells
- They maintain a high body temperature which is related to them having high metabolic and respitory rates

Question 1

Why are lungs located inside of the body?

Answer 1

Air is not dense enough to give support to the delicate structures
The body as a whole would otherwise lose a great deal of water and die

Question 2

Describe how the structure of the trachea relates to its function

Answer 2

• Flexible airway that is supported by rings of cartlilage preventing the trachea collapsing as the air pressure inside falls while breathing in. The trachea walls are made up of muscle, lined with ciliated epithelium and globelt cells

Question 3

Describe how the structure of the bronchi relate to its function

Answer 3

These are divisions of the trachea each leading to one lung
- Like the trachea, they produce mucus which traps dirt particles and have cilia that move the dirt laden mucus towards the throat, large bronchi are supported by cartilage

Question 4

Describe how the structure of the bronchioles relate to their functions

Answer 4

-These walls are made up of muscles lined with epithelial cells
-This muscle allows them to constrict in order to control the air flow in and out of the alveoli

Question 5

Define inspiration

Answer 5

• This is when the pressure of the air in the atmosphere is greater than that of inside the lungs so air is forced into the lungs

Question 5

Define expiration

Answer 5

-When the air pressure of the lungs is greater than that of the atmosphere, air is forced out of the lungs

Question 6

Describe the interaction of muscles which brings about inspiration

Answer 6

• External intercostal muscles contract whilst the internal intercostal muscles relax
• Ribs are pushed upwards and outwards increasing the volume of the thorax
• Diaphragm muscles contract, causing it to flatten which also increases the volume of the thorax
  -The increased volume of the thorax results in the reduction of pressure in the lungs
  -Atmospheric pressure is now greater than pulnomary pressure so air is forced into the lungs

Question 7

Describe the interaction of muscles which brings about expiration

Answer 7

• Internal intercostal muscles contract whereas the external intercostal muscles relax
• Ribs move down and in, decreasing the volume of the thorax
  -The diaphragm muscles relax and so is pushed up again by the contents of the abdomen that were compressed during inspiration, this means the thorax volume is further decreased
• Decreased volume of the thorax increases the pressure in the lungs
  -The pulnomary pressure is now greater than that of the atmosphere, so air is forced out of the lungs

Question 8

Why is gas exchange between the alveoli and blood extremely rapid?

Answer 8

• Red blood cells are slowed as they pass through pulnomary capillaries allowing more time for diffusion
• Distance between alveoli air and red blood cells is reduced as the red blood cells are flattened against the capillary walls
• The walls of both alveoli and capillaries are very thin and therefore the distance at which diffusion takes place is very short
• Alveoli and capillaries have an overall large surface area
• Heart action means blood is consistentley pumped around alveoli maintaining a steep conc gradient for exchange of gases