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bio > 11.1 Gas exchange in humans > Flashcards

11.1 Gas exchange in humans Flashcards

1
Q

What is gas exchange?

A

the exchange of oxygen and carbon dioxide between the blood stream and atmosphere
* oxygen passes from the atmosphere to the bloodstream
WHILE
* carbon dioxide passes from the bloodstream to the atmosphere

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2
Q

What do gas exchange features allow?

A

These features allow the maximum amount of gases to be exchanged across the surface in the smallest amount of time (make it happen faster, increase the rate)

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3
Q

What are the 4 main features of gas exchange surfaces?

A
  1. Large surface area
  2. Thin surface (walls)
  3. Good blood supply
  4. Good ventilation with air
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4
Q

How is a large surface area useful?

Gas Exchange Surfaces

A

to allow faster diffusion of gases across the surface

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5
Q

How are thin walls useful?

Gas Exchange Surfaces

A

to ensure diffusion distances remain short (so diffuses faster)

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6
Q

How is a good blood supply useful?

Gas Exchange Surfaces

A

to maintain a high concentration gradient so diffusion occurs faster
(so Gases can be carried to/from their respective cells)

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7
Q

How is a good ventilation with air useful?

Gas Exchange Surfaces

A

so that diffusion gradients can be maintained

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8
Q

Name the 8 parts of the breathing system

A
  1. ribs
  2. (internall and external) intercostal muscle
  3. diaphragm
  4. trachea
  5. larynx
  6. bronchi (pl)
  7. bronchioles
  8. alveoli
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9
Q

how does bronchi branch into different parts?

A

bronchi (two branches) -> bronchus (only 1 branch)-> bronchiole (inidivual branch)

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10
Q

Ribs definition

A

bone structure that protects internal organs such as the lungs

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11
Q

intercostal muscle definition

A

Muscles between the ribs which control their movement causing inhalation and exhalation

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12
Q

Diaphragm definition

A

Sheet of connective tissue and muscle at the bottom of the thorax that helps change the volume of the thorax to allow inhalation and exhalation

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13
Q

Trachea definition

A

Windpipe that connects the mouth and nose to the lungs

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14
Q

Larynx definition

A

Also known as the voice box, when air passes across here we are able to make sounds

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15
Q

Bronchi definition

A

Large tubes branching off the trachea with one bronchus for each lung

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16
Q

Bronchioles definition

A

Bronchi split to form smaller tubes called bronchioles in the lungs connected to alveoli

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17
Q

Alveoli definition

A

Tiny air sacs where gas exchange takes place

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18
Q

Why must there be two sets of intercostal muscles?

A
  • Muscles are only able to pull on bones, not push on them
  • This means that there must be two sets of intercostal muscles; one to pull the rib cage up and another set to pull it down
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19
Q

Where are the external intercostal muscles found?

A

found on the outside of the ribcage

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20
Q

Where are the internal intercostal muscles found?

A

found on the inside of the rib cage

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21
Q

What structure surrounds the trachea and bronchi?

A

Rings of cartilage surround the trachea (and bronchi)

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22
Q

Why are there rings of cartilage surrounding the trachea and bronchi?

A
  • during breathing keeps airways open
  • protects (named) airways
  • prevents airways from collapsing
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23
Q

What would happen if the rings of cartilage were not present around the trachea and bronchi?

A

If they were not present then the sides could collapse inwards when the air pressure inside the tubes drops

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24
Q

What are the passages down to the lungs lined with?

A

The passages down to the lungs are lined with ciliated epithelial cells

25
Q

What do cilia do?

A

these cells have tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed

26
Q

Where is mucus made?

A

The mucus is made by special mucus-producing cells called goblet cells

27
Q

What is the role of the mucus?

A

The mucus traps particles, pathogens like bacteria or viruses, and dust and prevents them getting into the lungs and damaging the cells there

28
Q

Describe the role of cilia and mucus

(3 marks/points)

A
  1. The mucus is produced by goblet cells and traps bacteria, dust, particles
  2. The cilia beat
  3. And push the mucus away from the lungs towards the throat
29
Q

What is the diaphragm responsible for?

A

it is ultimately responsible for controlling ventilation in the lungs

30
Q

What happens during inhalation?

A
  • external intercostal muscles contract (pulls ribs), internal intercostal muscles relax, ribcage moves up and out
  • diaphragm contracts and flattens
  • volume of thorax increases
  • air pressure inside thorax decreases below atmospheric pressure.
  • air flows into the lungs down the pressure gradient.
31
Q

What happens during exhalation?

A
  • external intercostal muscles relax, internal intercostal muscles contract, ribcage moves down and in
  • diaphragm relaxes and becomes dome-shaped
  • volume of thorax decreases
  • air pressure inside thorax increases above atmospheric pressure.
  • Air is forced out of the lungs down the pressure gradient.
32
Q

In what way do the the intercostal muscles work together?

A

The external and internal intercostal muscles work as antagonistic pairs (meaning they work in different directions to each other)

33
Q

What happens when we need to increase the rate of gas exchange? What is this called

A

When we need to increase the rate of gas exchange (for example during strenuous activity) the internal intercostal muscles will also work to pull the ribs down and in to decrease the volume of the thorax more, forcing air out more forcefully and quickly – this is called forced exhalation

34
Q

Why is forced exhalation needed?

A
  • There is a greater need to rid of increased levels of carbon dioxide produced during strenuous activity and to inhale more oxygen
  • This allows a greater volume of gases to be exchanged
35
Q

Does inspired and expired air have a different amount of gases? Why?

A

YES
Air that is breathed in and air that is breathed out has different amounts of gases in it due to exchanges that take place in the alveoli

36
Q

How much oxygen does inspired air have?

A

Inspired air contains 21% oxygen

37
Q

How much oxygen is in expired air?
How much oxygen from atmospheric air do we absorb?

A

expired air contains 16% of oxygen
we only absorb around 4 – 5%,

38
Q

How much CO2 does inspired air have?

A

around 0.04%

39
Q

How much CO2 is in expired air?

A

we breathe out air containing around 4% carbon dioxide, as carbon dioxide diffuses into the alveoli from the blood

40
Q

how much water vapour do we breath in and out?

A

The air we breathe out contains more water vapour than when we breathe it in

41
Q

What is also different about expired air, apart from its gas content?

A

the temperature of exhaled air is higher than inhaled air

42
Q

Why is the oxygen content in expired and inspired air different?

A

oxygen is removed from blood by respiring cells so blood returning to lungs has a lower oxygen concentration than the air in the alveoli which means oxygen diffuses into the blood in the lungs

43
Q

Why is the carbon dioxide content in expired and inspired air different?

A

carbon dioxide is produced by respiration and diffuses into blood from respiring cells: the blood transports the carbon dioxide to the lungs where it diffuses into the alveoli as it is in a higher concentration in the blood than in the air in the alveoli

44
Q

Why is the water vapour content in expired and inspired air different?

A

water evaporates from the moist lining of the alveoli into the expired air as a result of the warmth of the body

45
Q

Why is the nitrogen content in expired and inspired air same?

A

78%
nitrogen gas is very stable (held by strong bonds) and so cannot be used by the body

46
Q

What substance can be used to test for CO2?

A

Limewater

47
Q

(Using Limewater to Test for CO2 in Exhaled Air)

What change in the limewater would you see during this experiment?

A

Lime water is clear but becomes cloudy (or milky) when carbon dioxide is bubbled through it
The lime water in boiling tube A will remain clear, but the limewater in boiling tube B will become cloudy

48
Q

Using Limewater to Test for CO2 in Exhaled Air

What does this experiment show us?

A

This shows us that the percentage of carbon dioxide in exhaled air is higher than in inhaled air

49
Q

What is the effect of exercise on breathing?

A

Exercise increases the frequency (no of breaths per min) and depth of breathing

50
Q

Why does frequency and depth of breathing increase when exercising?

A

This is because muscles are working harder and aerobically respiring more and they need more oxygen to be delivered to them and carbon dioxide to be removed to keep up with the energy demand

51
Q

What happens if, during exercise, the muscles cannot receive enough nutrients?

A

If they cannot meet the energy demand they will also respire anaerobically, producing lactic acid

52
Q

Why does lactic acid need to be removed?

A

After exercise has finished, the lactic acid that has built up in muscles needs to be removed as it lowers the pH of cells and can denature enzymes catalysing cell reactions

53
Q

How can lactic acid be removed?

A

It can only be removed by combining it with oxygen – this is known as ‘repaying the oxygen debt’

54
Q

How can the time taken for a person to repay their oxygen debt be investigated?

A

This can be tested by seeing how long it takes after exercise for the breathing rate and depth to return to normal – the longer it takes, the more lactic acid produced during exercise and the greater the oxygen debt that needs to be repaid

55
Q

What increases in amount during exercise?

A

As respiration rates increase, more carbon dioxide is produced and enters the blood

56
Q

Why is carbon dioxide harmful?

A

Carbon dioxide is an acidic gas in solution and so it can affect the working of enzymes in the cells and needs to be removed as quickly as possible

57
Q

How are high carbon dioxide levels detected?

A
  • Brain detects high concentration of CO2
  • These send impulses to the muscles of the muscles
  • causing them to contract more
58
Q

What does the lungs contracting faster and stronger do to CO2 levels?

A

This causes the frequency and depth of breathing to increase until the carbon dioxide concentration of the blood has lowered sufficiently

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