3.1.1 Exchange Surfaces

Question 1

Why are exchange surfaces needed?

Answer 1

• diffusion alone not enough to supply organism
• metabolic activity demands are higher
• SA:V ratio of an organism is small

Question 2

How to calculate SA:V

Answer 2

SA = 4 x pi x r squared

V = 4/3 pi x r cubed

Question 3

Features of effective exchange surfaces

Answer 3

• increased SA
• thin diffusion distance
• good blood supply
• good ventilation

Question 4

The mammalian gaseous exchange system

Answer 4

Moist surfaces – O2 dissolves
Nasal cavity – high SA, good blood supply, warms air
Trachea – cartilage rings, ciliate epithelium with goblet cells
Bronchus – left/right, rings of cartilage
Bronchioles – no cartilage, construct and dilate, lined w this layer of flat epithelium

Question 5

Mammals: Alveoli

Answer 5

Air sacs, thin flattened epithelial cells, collagen, elastic recoil
• large SA
• thin
• good blood supply 
• good ventilation

Question 6

Ventilating the lungs; inspiration

Answer 6

ACTIVE
Diaphragm contracts, flattens, lowers
External intercostal muscles contract pushing ribs up and out
Vol of thorax increases and pressure reduced=AIR IN

Question 7

Ventilating the lungs; expiration

Answer 7

PASSIVE
Diaphragm relaxes, dome shape
External intercostal muscles relax, ribs move down and in
Decreases vol in thorax, pressure increases=AIR OUT

Question 8

Measuring ventilation of the lungs

Answer 8

Peak flow meter - measures rate air is expelled from lungs

Vitalographs - breathe out quickly, graph produced

Spirometer - measures diff aspects of lung volume

Question 9

Spirometry

Answer 9

Tidal volume = vol of air with each resting breathe
Vital capacity = max vol of air, max in/exhalation
Inspiratory reserve = max vol of air you can breathe in
Exploratory reserve = max vol you can breathe out
Residual volume = vol of air left in lungs after maximum exhalation

Question 10

Ventilation rate = ?

Answer 10

Ventilation rate = tidal vol x breathing rate (min)

Question 11

Ventilation in insects

Answer 11

Trough spiracles in thorax/abdomen
Open/closed by sphincters

Spiracle-> tracheae-> trachioles

Tracheal fluid = mechanical ventilation of system, collapsible enlarged trachea

Question 12

Ventilation in bony fish

Answer 12

Gills: high SA, good blood supply, thin layers
Gill cavity protected by operculum (flap)
Water flow over gill
Mouth open = buccal cavity expands, opercular valve closes
Mouth closed = buccal cavity constricts l, opercular valve opens