Exchange surfaces

Question 1

what are the features of effective exchange surfaces

Answer 1

increased surface area
thin layers
good blood supply
ventilation to maintain diffusion gradient

Question 2

how are alveoli adapted for gas exchange

Answer 2

• large SA
  -barrier is cell membrane of squamous epithelia, they are permeable to gasses, moisture
• low diffusion gradient as squamous epithelia are thin and flat
  -steep diffusion gradient maintained: blood flow brings more CO2 from tissues

Question 3

what happens during inspiration

Answer 3

intercostal muscles contract
ribs are pulled upwards and outwards
diaphragm contracts and flattens
- increased volume in thorax
- reduced air pressure
air is forced into lungs

Question 4

what happens during expiration

Answer 4

the intercostal muscles relax
ribs move downwards and inwards
diaphragm relaxes and moves up
- decreased volume of the thorax
-increased air pressure
air forced out of lungs

Question 5

what are the structures within trachea

Answer 5

• has c-shaped rings of cartilage for support and to ensure the trachea does not collapse
• has goblet cells to release mucus to trap dust and pathogens which is then swept up by the ciliated epithelial cells
• there is smooth muscle within the tracheal wall, which contracts if there are harmful substance detected in the air, this reduces air flow
• there are also elastic fibres, this enables the lumen to dilate when the smooth muscle relax

Question 6

How does having a large surface area aid exchange surfaces?

Answer 6

Allows more substances to travel across at a time, increasing exchange rate

Question 7

How does being thin aid exchange surfaces?

Answer 7

Allows substances to travel across them more quickly, increasing exchange rate

Question 8

How does having a good blood supply aid exchange surfaces?

Answer 8

Allows optimal concentration gradient to be maintained by bringing/taking away substances quickly

Question 9

How does having good ventilation aid exchange surfaces?

Answer 9

Allows a steep concentration gradient to be maintained

Question 10

What are the walls of alveoli made up of?

Answer 10

Squamous epithelial cells, some collagen and elastic fibres made from elastin

Question 11

What is the purpose of the elastic tissues in alveoli?

Answer 11

They allow the alveoli to stretch when air enters, and recoil in order to help force air out

Question 12

what are two methods of measuring volume of gas drawn in and out of lungs

Answer 12

1- peak flow meter
2- a spirometer

Question 13

define tidal volume

Answer 13

it is the volume of air that moves into and out of the lungs with each resting breath

Question 14

define vital capacity

Answer 14

Maximum volume of air that can be inhaled and exhaled

Question 15

why does a spirometer contain sodalime

Answer 15

to absorb the CO2 from the users air supply

Question 16

What is the inspiratory reserve volume?

Answer 16

The amount of air you can breathe in over and above a normal inhalation

Question 17

What is expiratory reserve volume?

Answer 17

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

Question 18

What happens when a fish opens its mouth?

Answer 18

The operculum closes over the gills, the buccal cavity expands and the opercular valve (to the outside) is closed. This means that the pressure in the mouth drops, and water rushes in

Question 18

What is residual volume?

Answer 18

The volume of air left in your lungs when you have exhaled as hard as possible

Question 19

name the structures involved in gas exchange in insects

Answer 19

spiracles
tracheae
tracheoles
muscle tissues

Question 20

What happens when a fish closes its mouth?

Answer 20

The cheeks move inward, causing pressure in the mouth to increase and forcing water over the gills, also causing the opercular valve and operculum to open

Question 20

What is the counter-current flow system and why is it used by fish?

Answer 20

It is where fish have blood flowing one way and water flowing the other. This is so that the concentration gradient of CO2 and oxygen is maintained throughout the gill, thus maximising the efficiency of diffusion

Question 21

explain challenges insects face with gas exchange

Answer 21

• exoskeleton made of chitin is impermeable to gases
• no blood pigments, gases cannot be carried in blood
• high energy needs

Question 22

describe how spiracles are involved in gas exchange

Answer 22

opening in the body surface that can be opened and closed by sphincter muscles.
-when inactive, the insects oxygen demands are low so the spiracles are closed
- when oxygen demands are raised or CO2 levels build up then spiracles open

Question 23

explain how the tracheae is involved in gas exchange

Answer 23

• these are the largest tubes that carry air into and along the boy
  -the tubes are lined with spiral of chitin, which keeps them open, and is impermeable
  -little gas exchange takes place here

Question 24

explain how tracheoles are involved in gas exchange

Answer 24

• they single elongated cells, with no chitin
• because of their small size they run between individual cells
  -this is where most of the gaseous exchange takes place

Question 24

explain how muscles cells are involved in gas exchange in insects

Answer 24

• surrounded by tracheal fluid where gases can dissolve and diffuse into muscle cells

Question 25

for larger insects what are alternative methods of increasing gas exchange

Answer 25

• mechanical ventilation of the tracheal system
• collapsible enlarged tracheae or air sacs

Question 26

outline how insects use mechanical ventilation

Answer 26

-air is actively pumped into the system by muscular pumping movements of the thoraw and or the abdomen
- this changes the volume of the body cavity creating pressure differences
- happens via wing movements

Question 27

outline how insects use air sacs in gas exchange

Answer 27

• the collapsible enlarged trachea or air sacs act as reservoirs
• they inflate and deflate with pumping movements
• have thin collapsible walls

Question 28

Apart from counter-current flow system, what is another adaption in fish which helps maximise gas exchange effectiveness?

Answer 28

The tips of their gill filaments overlap, increasing the resistance to the flow of water and slowing down water movement, helping maximise the time that diffusion can occur for

Question 29

As well as increasing surface area, what is the secondary purpose of a fish’s lamallae?

Answer 29

To direct the flow of water in the gills

Question 30

Why can’t fish breathe in and out by ventilation?

Answer 30

Because water is much denser and more viscous than air, and has a much lower oxygen content, so it saves energy for them to move water in 1 direction only