Exchange surfaces

Describe and explain how one feature of the lungs provides an efficient gas exchange surface.

many alveoli provide a large surface area for (maximum) diffusion, squamous epithelium of alveoli is only 1 cell thick to provide a short diffusion distance, good blood supply and ventilation maintains steep conc. gradient

Explain how carbon dioxide produced in the respiring body cells of worker termites is removed to the air outside the termite mound

carbon dioxide diffuses down concentration gradient out of the respiring cell (1) carried through body from cell (to tracheoles) by blood passing out via tracheoles / trachea / spiracles (1) respiration generates heat (1) hot gases expand and are less dense so rise up by convection through the mound to vents at moundtop (1)

Describe normal process of exhalation

-diaphragm muscles relax

- diaphram moves up and out

- external intercostal muscles relax

- ribs move down and in

- volume of thorax reduces

- pressure inside thorax is now higher than outside and air is forced out

Describe forced exhalation

-active, and requires energy

- internal intercostal muscles contract

- ribs are pulled down hard

- abdominal muscles contract forcing the diaphragm up

Describe normal process of inhalation

ribcage moves upwards and outwards

- external intercostal muscles contract

- diaphragm contracts, moves down and in

- volume of thorax increases

- pressure inside lungs is less than atmospheric pressure

- air rushes into lungs

Desribe fish ventilation

• water enters through the mouth, and passes over the gills

- buccal cavity lowers when mouth is open, raises when closed and increases pressure

- water leaves through the operculum