3.1 Exchange Surfaces

Question 1

What is the need for specialised exchange surfaces?

Answer 1

Larger organisms have a relatively small surface area to volume ratio.
Oxygen cannot diffuse quickly enough (long diffusion distance) to meet metabolic needs.
Multicellular organisms have a higher metabolic activity.

Question 2

Features of an efficient exchange surface

Answer 2

Large surface area
Short diffusion distance
Steep concentration gradient

Question 3

Goblet cells

Answer 3

• Found between ciliated epithelial cells that line the trachea
  -Secrete mucus which traps dust/bacteria that enters the lungs

Question 4

Cilia

Answer 4

• Line the trachea
• Waft mucus to the back of the trachea where it is swallowed or coughed up.

Question 5

Elastic fibres

Answer 5

Recoil to their original shape to expel air and prevent the lungs from bursting.

Question 6

Smooth muslce

Answer 6

Contracts to constrict the airways by reducing then diameter of the bronchus.

Question 7

Cartilage

Answer 7

Provides strength and support
Prevents collapse during inspiration: (chest volume increases so lower pressure in trachea)

Question 8

Describe trachea

Answer 8

C shaped rings of cartilage
Elastic fibres in wall
Smooth muscle
Ciliate epithelium and goblet cells

Question 9

Describe the Bronchi

Answer 9

Plates of cartilage
Smooth muscle
Elastic fibres
Ciliated epithelium

Question 10

Describe the bronchiole

Answer 10

Smooth muslce
Elastic fibres
Squamous epithelium

Question 11

Describe alveoli

Answer 11

Elastic fibres
Squamous epithelium

Question 12

How are fish adapted for gas exchange

Answer 12

Many lamella so there is a large surface area for gas exchange.
Secondary lamella on primary lamella increase SA.
Short diffusion distance between blood and water.
Countercurrent exchange system to maintain steep concentration gradient.

Question 13

Breathing in fish

Answer 13

Mouth opens, buccal cavity expands, increase volume decrease pressure, water moves in down pressure gradient.

Opercular cavity expands (valves shut), increase opercular volume, decrease pressure, water moves into opercular cavity across gills down pressure gradient.

Buccal cavity and opercular cavity constrict, decrease volume increases pressure, water pushes valves open and leaves opercular cavity to outside down pressure gradient.

Question 14

Gas exchange in insects

Answer 14

Spiracles open when active.
When active (flying/jumping) - increases respiration.
This increases lactic acid lowering water potential.
Tracheole fluid leaves tracheoles and enters surrounding tissue via osmosis.
Air drawn in for aerobic respiration.

Question 15

Describe expiration (exhalation)

Answer 15

Diaphragm relaxes and domes.
External intercostal muscles relax, ribs move down and in.
Volume decreases, pressure increases above atmospheric pressure.
Air leaves lungs down pressure gradient.

Question 16

Describe inspiration

Answer 16

Diaphragm contracts and flattens and external intercostal muscles contract.
Ribs up and out, volume in thorax increases, pressure decreases below atmospheric, air moves in

Question 17

What is tidal volume?

Answer 17

Volume or air breathed in and out in a single breath at rest. (Approx 500cm3 at rest)

Question 18

Define vital capacity

Answer 18

Maximum volume of air which can be breathed and out in a single breath

Question 19

Define breathing rate

Answer 19

Number of breaths per minute

Question 20

Oxygen uptake in spirometry

Answer 20

Gradient of trace (steeper in exercise)
Air breathed into the spirometer has CO2 removed by soda lime, oxygen used for aerobic respiration