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A Level Biology > Exchange Surfaces > Flashcards

Exchange Surfaces Flashcards

1
Q

Why do multicellular organisms need exchange surfaces

A
  • small SA:Vol ratio
    Their outer surface is not large enough to enable oxygen to exchange fast enough into the body and keep all cells alive
  • more active so have higher metabolic demands for oxygen
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2
Q

Exchange surface

A

A specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other

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3
Q

SA:Vol ratio

A

Surface area (cm2)
Volume (cm3)

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4
Q

Cartilage

A
  • rings of cartilage hold the trachea and bronchi open
  • tough elasticated tissue
  • strong and flexible
  • C shaped rings of connective tissue
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5
Q

Ciliated epithelium

A

• provides the beating force that transports mucus along the airways
• Long thin hair like structures
• Layers of cells that form cover or lining
• Contains cilia on surface

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6
Q

Goblet cells

A

• contain specialised structure that enables them to carry out their function in producing and secreting components of mucus
• They line the airways and secrete mucus in order to trap any microorganisms and dust partiales which have been inhaled and prevent them from reaching the alveoli
• Found between the ciliated cells in the epithelium

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7
Q

Smooth muscle and elastic fibres

A

helps with the process of exhaling

• Elastic fibres are in the walls of the trachea, bronchi, bronchioles and alveoli
• The lungs inflate and the elastic fibres stretch in order to breathe out
• The fibres recoil to push air out

• smooth muscle is able to control the diameter of the trachea, bronchi, bronchioles
• They relax during exercise to expand the tubes, giving less resistance to airflow, letting it move in and out of the lungs
• Maintain tone

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8
Q

Trachea

A

• cartilage rings stop it from collapsing
• surrounded by ciliated epithelium and goblet cells secrete mucus, trap dust and microbes, and move them towards the stomach

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9
Q

Bronchi

A

• similar structure to the trachea
• Smaller diameter and thinner walls than trachea
• The rings of cartilage are complete, rather than c-shaped like trachea

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10
Q

Bronchioles

A

smooth muscle allows air to move in and out, and maintains high concentration gradients of oxygen and carbon dioxide

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11
Q

Alveoli

A

arranged in groups at the end of the smallest bronchioles
• Wall of an alveolus consists of single layer of epithelium, but there is also an extracellular matrix that contains elastic fibres, which allows the alveoli to expand during inspiration and recoil during expiration
• Capillaries surround the alveoli for gas exchange to take place

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12
Q

Surfactant

A

there is a water film in the alveoli
• As we breathe out, it evaporates and leaves the lungs
• The cohesion between water molecules would cause the alveoli to collapse
• A compound called surfactant produced in the alveoli lines them. This reduces surface tension and cohesion, and stops the alveoli collapsing

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13
Q

Inspiration

A

diaphragm contracts, flattens and moves downwards
• Intercostal muscles contract and move ribs up and out
• This increases the volume inside the thorax and lungs
• This reduces the pressure inside the thorax and lungs below atmospheric pressure
• Air move into the lungs, down a pressure gradient

diaphragm contracts
volume⬆️
pressure⬇️

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14
Q

Expiration

A

• diaphragm relaxes and returns to dome shape position
• Intercostal muscles relax and move ribs down and in
• This decrease the volume inside the thorax and lungs
• This indues the pressure inside the thorax and lungs above atmospheric pressure
• Air move out of lungs and down pressure gradient

diaphragm contracts
volume⬇️
pressure⬆️

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15
Q

Pathway of water in fish

A
  1. Mouth opens (operculum is closed)
  2. Buccal cavity floor is lowered
    • this increases volume and decreases pressure compared to outside
  3. Water rushes into mouth, down a pressure gradient
  4. Opercular cavity expands
  5. Buccal cavity floor is raised
  6. Pressure inside buccal cavity is now higher than Opercular cavity
  7. Water moves from buccal cavity over the gills into the Opercular cavity
  8. Mouth is now closed and operculum opens
  9. Sides of the Opercular cavity move inwards, increasing pressure
  10. Water rushes out of the fish through the operculum
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16
Q

Countercurrent flow

A
  • blood flows in the opposite direction the the flow of water
  • this results in the oxygen concentration gradient between the blood in the gills and the water being maintained across the entire length of the gill lamellae
  • This causes oxygen to diffuse down the oxygen conc. gradient, from water to blood
  • Even when the conc. of oxygen in water is low at the opercular cavity end of the lamella, the blood has just entered the gill lamella, therefore is even lower in oxygen concentration. This means there is still a diffusion gradient allowing the diffusion of oxygen from the water into the blood
  • With concurrent flow, the concentration of oxygen in water and blood in the gills will equalise, therefore no more oxygen exchange would take place
17
Q

Insects

A

Spiracle, tracheae, air sacs, tracheoles

  • tracheae are surrounded by rings of chitin for support

When insects are flying:
abdominal pumping- change the volume of their bodies

18
Q

Spirometer

A

When a person breathes in, they take oxygen away from the chamber causing it to go down
When they breathe out it pushes air into the chamber, causing it to go up
These movements are recorded on the trace by a data logger

19
Q

Safety when using a spirometer

A

• soda lime to absorb CO2 from chamber
• Use medical grade oxygen and ensure there is enough oxygen
• water level must not be too high and enter the tubes
• Disinfect mouthpiece
• Check health of patient e.g. no bronchitis

20
Q

Validity when using spirometer

A

• make sure everything is airtight so no oxygen is lost through leaks
• Nose clip- to ensure all air breathed comes from chamber, otherwise invalid results

21
Q

Tidal volume

A

Volume of air moved in and out of the lungs with each breath at rest

22
Q

Vital capacity

A

Largest volume of air that can moved in and out of the lungs in one breath

23
Q

Residual volume

A

Volume of air that always remains in the lungs even after the biggest possible exhalation

24
Q

Inspiratory reserve volume

A

The volume of air that can be breathed in above the normal tidal volume

25
Q

Expiratory reserve volume

A

The volume of air that can be breathed out above the normal tidal volume

26
Q

Why can’t air be completely expelled from the lungs

A
  • lungs can’t be completely compressed
  • trachea and bronchi held open by cartilage
    -Bronchioles and alveoli held open by elastic fibres
27
Q

Mean tidal volume

A
  • measure height of waves (tidal volume), at least 3 from the trace
  • calculate mean (add volumes together and divide by number of breaths)
    one breath is peak to peak / trough to trough

Measured in dm2

28
Q

Breaths per minute (breathing rate)

A

• count number of breaths taken in a set period of time
• Divide number of breaths by this time (in secs)
• Multiply by 60 to find breaths per minute

E.G.
5 breaths in 30s
5 x 60= 10 breaths min-1
30

29
Q

Measuring rate of oxygen uptake

A

• calculate the difference in volume between 2 peaks/troughs on the trace (dm )
• This will give you the volume of oxygen used
• Measure the time taken to use this volume of oxygen
• Divide the volume by the time to give the rate

If your time is in seconds, to give the rate in
dm3min-1 you need to divide by the number of seconds and then multiply by 60

30
Q

How does the trace on a spirometer work

A

When you exhale into a spirometer, the carbon dioxide is absorbed by the soda lime
This decreases the volume of gas in the spirometer and causes the trace line to fall gradually
This volume of carbon dioxide removed is equal to the volume of oxygen used by the person

A Level Biology (25 decks)

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