gas exchange

Question 1

Describe the counter current flow system.

Answer 1

Blood flows through lamellae and water flows over lamellae in opposite directions

Always a higher concentration of oxygen in water than the blood it is near

Hence, a concentration gradient of oxygen between the water and blood is
maintained along the whole length of lamellae (/gill plate) → equilibrium
not met

Maximising diffusion of oxygen

Question 2

Describe the process of gas exchange in the alveoli.

Answer 2

Oxygen diffuses from alveoli. Down its concentration gradient. Across the alveolar epithelium, Across the capillary endothelium into the blood (in haemoglobin)

Carbon dioxide diffuses from capillary

Down its concentration gradient

Across the capillary endothelium

Across the alveolar epithelium

Into the alveoli

Question 3

Describe how the lungs are adapted for efficient/rapid gas
exchange

Answer 3

Many alveoli/capillaries

Large surface area → fast diffusion

Alveoli/capillary walls are thin / short distance between alveoli and blood

Short diffusion distance → fast diffusion

Ventilation/circulation

Maintains concentration gradient → fast diffusion

Question 4

Mechanism of breathing (inspiration)

Answer 4

External intercostal muscles contract, internal intercostal muscles relax

Moving ribcage up and out

Diaphragm muscles contract → flatten diaphragm

Increasing volume in thoracic cavity

Decreasing pressure in thoracic cavity

Atmospheric pressure higher than pressure in lungs

Air moves down pressure gradient into lungs

Question 5

expiration

Answer 5

Internal intercostal muscles contract, external intercostal muscles relax
Moving ribcage down and in

Diaphragm relaxes, moves upwards

Decreasing volume in thoracic cavity

Increasing pressure in thoracic cavity

Atmospheric pressure lower than pressure in lungs

Air moves down pressure gradient out of lungs

Question 6

Importance

Answer 6

The movement of diaphragm and the organs involved in breathing are useful as they maintain concentration gradient as they provide ventilation. This allows oxygen to move from air into lungs and then allows for the movement of oxygen from alveoli to diffuse through alveolar epithelium across the capillary endothelium into the haemoglobin so it can be transported. This oxygen is used for various processes (name one and explain )