Exchange surfaces

Question 1

Why do large organisms need exchange systems?

Answer 1

Large organisms have small SA:Vol
Diffusion pathway is too long
Thus specialised exchange surfaces needed

Question 2

Structures involved in mammalian gaseous exchange system

Answer 2

Nasal Cavity
Large SA + good blood supply
Mucus secreting cells to trap pathogens
Moist surfaces to inc humidity

Trachea
Cartilage to prevent collapsing
Goblet + ciliated epithelium cells
Secrete mucus, trap and waft dust towards stomach

Bronchi
Smooth muscle = allow air to move in + out
To maintain high conc grad

Alveoli
Thin epithelium wall = short diffusion pathway
Elastic fibres recoil = help expel air out during expiration
Large number = large SA
Good blood supply = maintain high conc grad

Diaphragm
Contract, causing inc in vol and dec in pressure to cause inspiration

Question 3

How is respiratory system in bony fish adapted for maximum ventilation and gaseous exchange

Answer 3

Ventilation
Water enters mouth
Pressure change in buccal cavity
Water flows over gills
Water leaves via operculum
All unidirectional flow

Gaseous exchange
Gill filaments = Large SA
Thin = short diffusion distance
Good blood supply = steep conc grad
Counter-current system

Question 4

How is respiratory system in an insect adapted for maximum ventilation and gaseous exchange

Answer 4

Ventilation
= muscular movement
Abdominal pumping
Pressure change in abdomen
Thorax movement
Air drawn in or forced out
Size of spiracle changes

Gaseous exchange system
Gas diffuses along tracheae
O2 dissolves in water in tracheoles
Diffuses in surrounding cells
Many trachea so large SA

Question 5

Inspiration

Answer 5

Diaphragm contract - flatten = inc vol + dec pressure
External intercostal muscles contract = ribs rise
Ribs = up + out
= Air into lungs

Question 6

Expiration

Answer 6

Diaphragm relaxes - domes = dec in vol + inc pressure
External intercostal muscles relax = ribs fall
Ribs = down + in
= Air out lungs

Question 7

Pathway of blood in alveoli

Answer 7

Transport CO2 from tissues to lungs
O2 transported away from lungs
Maintains concentration gradient

Question 8

Why does the trace fall in spirometer

Answer 8

CO2 absorbed by soda lime so volume in chamber decreases

Question 9

Purpose of soda lime in spirometer

Answer 9

Absorbs CO2 produced

Question 10

Vital capacity

Answer 10

Largest volume of air that can be breathed in

Question 11

Tidal volume

Answer 11

Volume of air that moves into and out of the lungs with each resting breath

Question 12

Inspiratory reserve volume

Answer 12

Maximum volume of air you can breath in over and above normal inhalation

Question 13

Expiratory reserve volume

Answer 13

Maximum volume of air you can force out of your lungs over and above the normal tidal volume of air you breath out

Question 14

Residual volume

Answer 14

Volume of air that is left in your lungs when you have exhaled as hard as possible

Question 15

Total lung capacity

Answer 15

Sum of the vital capacity and the residual volume

Question 16

All exchange surfaces have similar features – what are they?

Answer 16

Increased SA
Thin layers = short distance to travel
Good blood supply = maintain conc grad
Ventilation to maintain conc grad
Alveoli ONLY
Thin walls - squamous epithelium, capillary walls
Gas exchange surface = moist = gases dissolve before diffuse

Question 17

Gill adaptations

Answer 17

thin epithelium of lamellae = short diffusion path
Large number of capillaries = maintains steep conc grad
Many filaments = increase SA for diffusion
Flow of oxygen containing blood opposite to flow of water = Maintains conc grad + diffusion can take place across full surface of lamellae