Mammalian Gas Exchange System

Question 1

Why is diffusion across the outer membranes too slow in multi-cellular organisms?

Answer 1

• Some organisms are deep within the body (a big distance)
• Large animals have a slower SA:V ratio (as it is difficult to exchange substances)
• They have a higher metabolic rate than single-celled organisms (they use up oxygen and glucose faster)

Question 2

How does SA:V and the size of organism correlate?

Answer 2

• The larger the organism, the smaller the SA:V ratio.
• takes longer for substances to reach the cells.
• it is impossible to absorb enough oxygen through the surface area to meet the needs of the body

Question 3

How are gas exchange surfaces adapted to be efficient?

Answer 3

• Increased SA:V: gas exchange takes place quicker.
• Thin layers: short diffusion distances
• Good blood supply: steeper the concentration gradient, the faster diffusion takes place.
• Ventilation - maintains diffusion gradient and makes the process more efficient

Question 4

how does gas exchange system occur in mammals?

Answer 4

• consists of lungs which air is carried in and out.
• lungs: inflatable sacs in the chest cavity.
• air passes through the nose along the trachea, bronchi and bronchioles.
• It then reaches the alveoli (gas exchange takes place)
• lungs are protected by the ribcage.
• Ribcage are held by intercostal muscles.
• action of these muscles and the diaphragm help with ventilation