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OCR Biology > Exchange surfaces > Flashcards

Exchange surfaces Flashcards

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1
Q

what are the features of effective exchange surfaces

A

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

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2
Q

how are alveoli adapted for gas exchange

A
  • 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
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3
Q

what happens during inspiration

A

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

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4
Q

what happens during expiration

A

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

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5
Q

what are the structures within trachea

A
  • 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
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6
Q

How does having a large surface area aid exchange surfaces?

A

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

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7
Q

How does being thin aid exchange surfaces?

A

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

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8
Q

How does having a good blood supply aid exchange surfaces?

A

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

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9
Q

How does having good ventilation aid exchange surfaces?

A

Allows a steep concentration gradient to be maintained

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10
Q

What are the walls of alveoli made up of?

A

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

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11
Q

What is the purpose of the elastic tissues in alveoli?

A

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

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12
Q

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

A

1- peak flow meter
2- a spirometer

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13
Q

define tidal volume

A

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

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14
Q

define vital capacity

A

Maximum volume of air that can be inhaled and exhaled

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15
Q

why does a spirometer contain sodalime

A

to absorb the CO2 from the users air supply

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16
Q

What is the inspiratory reserve volume?

A

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

17
Q

What is expiratory reserve volume?

A

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

18
Q

What happens when a fish opens its mouth?

A

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

18
Q

What is residual volume?

A

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

19
Q

name the structures involved in gas exchange in insects

A

spiracles
tracheae
tracheoles
muscle tissues

20
Q

What happens when a fish closes its mouth?

A

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

20
Q

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

A

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

21
Q

explain challenges insects face with gas exchange

A
  • exoskeleton made of chitin is impermeable to gases
  • no blood pigments, gases cannot be carried in blood
  • high energy needs
22
Q

describe how spiracles are involved in gas exchange

A

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

23
Q

explain how the tracheae is involved in gas exchange

A
  • 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
24
Q

explain how tracheoles are involved in gas exchange

A
  • 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
24
Q

explain how muscles cells are involved in gas exchange in insects

A
  • surrounded by tracheal fluid where gases can dissolve and diffuse into muscle cells
25
Q

for larger insects what are alternative methods of increasing gas exchange

A
  • mechanical ventilation of the tracheal system
  • collapsible enlarged tracheae or air sacs
26
Q

outline how insects use mechanical ventilation

A

-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

27
Q

outline how insects use air sacs in gas exchange

A
  • the collapsible enlarged trachea or air sacs act as reservoirs
  • they inflate and deflate with pumping movements
  • have thin collapsible walls
28
Q

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

A

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

29
Q

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

A

To direct the flow of water in the gills

30
Q

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

A

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

OCR Biology (14 decks)

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