3.1.1 - Exchange surfaces

Question 1

What are the features of an efficient gas exchange system?

Answer 1

• large surface area to volume ratio
• thin (short diffusion distance)
• good blood supply (maintains conc gradient)
• good ventilation

Question 2

Why are gas exchange surfaces moist?

Answer 2

it aids diffusion -oxygen dissolves in it more easily

Question 3

Describe the pleural cavity

Answer 3

• each of the lungs is enclosed in a double membrane (known as the pleural cavity)
• space between the membranes is filled by pleural fluid

Question 4

What does pleural fluid do?

Answer 4

• lubricates the lungs
• adheres to the outer walls of the thorax by water cohesion, meaning that the lungs expand with the chest when breathing

Question 5

Describe the nasal cavity (and the functions of the parts)

Answer 5

• has large SA
• has good blood supply
• has a hairy lining (traps dust and bacteria in mucus to prevent them getting into the lungs)
• has moist surfaces (increases humidity of air to reduce evaporation of water in lungs)

Question 6

Describe the trachea (and the functions of the parts)

Answer 6

• pipe supported by a ring of cartilage (holds it open + prevents it collapsing) -rings are incomplete (to allow it to bend when swallowing food down the oesophagus behind it)
• lined with ciliated epithelium and goblet cells (prevent dust and bacteria from entering by goblet cells producing mucus that cilia beat away)

Question 7

Describe the bronchus

Answer 7

• extension of trachea (split in two -one for each lung)

- smaller version of the trachea

Question 8

Describe the bronchioles (and the functions of the parts)

Answer 8

• very small (<1mm thick)
• have no cartilage, held open by smooth muscle (when muscle contracts, bronchioles contract depending on air flow)
• lined with layer of epithelial tissues

Question 9

Describe the alveoli (and the functions of the parts)

Answer 9

• small air sacs where most gas exchange occurs
• have a very large SA:V
• made from thin, flattened epithelial cells and some collagen and elastic fibres (elastic fibres cause recoil to help move air out)
• lung surfactant coats surfaces of lungs (prevents alveoli from collapsing due to surface tension)

Question 10

What is ventilation in gaseous exchange systems?

Answer 10

pressure changes in thoracic cavity

rip cage provides a cage where pressure changes facilitate breathing

Question 11

What happens in inspiration?

Answer 11

• diaphragm moves down
• intercostal muscles contract (moves ribs up and out)
• thoracic volume increases
• pressure decreases
• air flows into lungs

Question 12

What happens in expiration?

Answer 12

• diaphragm relaxes (curves and moves up)
• intercostal muscles relax (moves ribs down and in)
• thoracic volume decreases
• pressure increases
• air flows out of lungs

Question 13

What is a spirometer?

Answer 13

a device that measures the volume of gas breathed in and out

Question 14

How does a spirometer work?

Answer 14

• lower half of tank is full of water and upper half is mobile and full of oxygen
• subject has nose clip on and breathes in and out into spirometer (breathing in making the mobile half fall and breathing out makes it rise)
• trace marker is attached to mobile upper half and draws as they breathe

Question 15

What is a peak flow meter?

Answer 15

a device that measures the rate at which air can be moved in and out of lungs

Question 16

What is vital capacity?

Answer 16

maximum volume of air that can be inhaled/exhaled in one breath
(strongest exhale followed by strongest inhale)

Question 17

What is tidal volume?

Answer 17

the volume of air moving in and out of lungs (inhaled/exhaled) with each resting breath (during regular breathing)

Question 18

What is inspiratory reserve volume?

Answer 18

the maximum volume of air you can breathe in

above normal inhalation

Question 19

What is expiratory reserve volume?

Answer 19

the maximum volume of air you can force out of lungs

above normal tidal volume of air you can breathe out

Question 20

What is residual volume?

Answer 20

the volume of air left in your lungs when you have exhaled as hard as possibe

Question 21

What is total lung capacity?

Answer 21

the total potential amount of air in the lungs at any given point

Question 22

total lung capacity =

Answer 22

vital capacity + residual volume

Question 23

What are spiracles?

Answer 23

openings in insects’ waxy exoskeleten which allow gases through to go into the trachea

Question 24

What are the differences between gas exchange systems in insects and humans?

Answer 24

Insects:
-trachea held open by chitin
-trachea splits into tracheoles
-no blood in system, just gases -tracheoles penetrate directly into body cells
Humans:
-trachea held open by cartilage
-trachea splits into bronchi (and then bronchioles)
-blood in system carries gases to body cells

Question 25

How do insects ventilate their tracheal system?

Answer 25

by using air sacs, flight muscles or specialised breathing systems

Question 26

What is the operculum and what does it do? (in a fish)

Answer 26

a bony flap that covers the gills

Question 27

What is the function of the bony gill arch?

Answer 27

supports the structure of the gills

Question 28

What is the function of the gill lamella?

Answer 28

are the main site of gaseous exchange in fish

-increase SA of gills

Question 29

What are gill filaments and what do they do?

Answer 29

occur in large stacks called gill plates

site of gas exchange

Question 30

How do fish have efficient gas exchange at all times?

Answer 30

by maintaining a constant flow of water over their gills
-either by moving or opening/closing mouth and closing/opening opercular valves in order to expand/constrict buccal cavity

Question 31

What is ram ventilation? (in fish)

Answer 31

where fish need to constantly move to ventilate the gills

-only happens in some fish like sharks

Question 32

What are the adaptions of gills?

Answer 32

• good blood supply
• large SA
• thin layers
• tips of adjacent gills overlap (increases resistance of water flow so there’s more time for gas exchange)
• countercurrent exchange system (maintains steep concentration gradient)

Question 33

What is a countercurrent exchange system?

Answer 33

a system where blood and water flow in opposite directions

maintains concentration gradient

Question 34

Describe how fish ventilate the gills when they are not moving.

Answer 34

• mouth opens (operculum valve is closed)
• buccal cavity expands and its floor lowers
• this increases the volume and decreases the pressure of the buccal cavity
• water moves into buccal cavity
• opercular cavity expands
• buccal cavity constricts and floor raises
• pressure increases inside the buccal cavity
• water moves from buccal cavity over the gills into the opercular cavity
• mouth closes and operculum opens
• sides of the opercular cavity move inwards, increasing the pressure
• water leaves the fish through the operculum