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3.1.1 exchange surfaces > the human gaseous exchange system > Flashcards

the human gaseous exchange system Flashcards

1
Q

how does oxygen dissolve into the body surfaces

A

gaseous exchange systems are moist so oxygen dissolves in the water before dissolving into the body surfaces

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2
Q

what are moist conditions ideal for

A

evaporation of water

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3
Q

how are mammals able to exchange gases efficiently

A

they have complex systems that enable them to exchange gases whilst minimising the loss of water from the body

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4
Q

why do mammals need exchange systems

A

they have a small surface area to volume ratio and a large volume of cells.

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5
Q

why do mammals have a high metabolic rate

A

they have a high metabolic rate because they are active and maintain their body temperature independant of the environment

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6
Q

what do mammals need lots of and need to get rid of

A

they need lots of oxyegn for cellular respiration and produce carbon dioxide which needs to be removed

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7
Q

where does exchange of gases take place in mammals

A

the lungs

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8
Q

what does the gaseous exchange system consist of

A

the lungs and associated airways that carry air into and out of the lungs

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9
Q

how can air pass into the lungs

A

through the nose and along the trachea, bronchi and bronchioles.

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10
Q

where does air reach to when it passes into the lungs

A

it reaches tiny air filled sacs called alveolis

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11
Q

where does exchange of gases takes place

A

alveoli

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12
Q

what protects the lungs

A

ribcage

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13
Q

how are the ribs held

A

by the intercostal muscles

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14
Q

how are breathing movements produced

A

the action of the intercostal muscles and the diaphragm

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15
Q

what are the lungs

A

pair of inflatable sacs that carry air into and out of the lungs

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16
Q

what are the bronchi and bronchioles

A

smaller airways leading into the lungs

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17
Q

what is the trachea

A

the main airway leading from the back of the mouth to the lungs

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18
Q

what is the alveoli

A

tiny folds of the lung epithelium to increase the surface area

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19
Q

what is the diaphragm

A

a layer of muscle beneath the lungs

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20
Q

what are the intercostal muscles

A

muscles between the ribs. contraction of the external intercostal muscles raises the ribcage

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21
Q

what is ventilation

A

the refreshing of the air in the lungs so there is a higher oxygen concentration than in the blood and a lower carbon dioxide concentration

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22
Q

what do all organisms require

A

nutrients and the ability to excrete wastes

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23
Q

what can many simple organisms do

A

exchange substances directly across their external surfaces

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24
Q

what do larger organisms require to exchange and transport substances efficiently

A

specialised gas exchange and transport systems

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25
Q

how do fish exchange substances

A

across gills, while insects have openings called spiracles on their surface

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25
Q

how do mammals exchange substances

A

in the lungs and in particular the alveoli

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26
Q

what are the lungs enclosed in

A

a pleural membrane (double membranes)

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27
Q

what is the space between the two membranes in the lungs called

A

the pleural cavity

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28
Q

what is the pleural cavity filled with

A

pleural fluid

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29
Q

what does the pleural fluid do

A

it lubricates the lungs and adheres to the outer walls of the lungs to the thoracic cavity by water cohesion so that the lungs expand with the chest while breathing

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30
Q

what are the features of the nasal cavity

A
  • has a large surface area with a good blood supply
  • hairy lining
  • moist surfaces which increase the humidity of the incoming air reducing evaporation from the exchange surfaces
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31
Q

what does the large surface area and good blood supply in the nasal cavity do

A

which warms the air to body temperature

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32
Q

what does the hairy lining in the nasal cavity do

A

secretes mucus to trap dust and bacteria protecting delicate lung tissue from irritation and infection

33
Q

what do the moist surface of the nasal cavity do

A

increase the humidity of the incoming air reducing evaporation from the exchange surface

34
Q

where does the air travel after passing the nasal cavity

A

the air enters the lungs

35
Q

what is the temperature of the air that enters the lungs from the nasal cavity

A

similar temperature and humidity to the air already in the lungs

36
Q

what are the adaptations of the lungs to exchange gases

A

very large surface area in close contact with the bloodstream so oxygen can diffuse in and carbon dioxide can diffuse out

37
Q

how does air enter the lungs

A

via the trachea or windpipe

38
Q

what does the trachea carry

A

clean, warm, moist air from the nose down into the chest

39
Q

describe the trachea

A

wide tube surrounded by a layer of smooth muscle supported by incomplete rings of strong, flexible cartilage which stop the trachea from collapsing

40
Q

why are the rings incomplete

A

so food can move easily down the oesaphagus behind the trachea

41
Q

what are the trachea and its branches lined with

A

ciliated epithelium and goblet cells between and below the epithelial cells

42
Q

what do the goblet cells do

A

secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining.

43
Q

what do the cilia in the trachea do

A

beat and move the mucus away along with any trapped dirt and microorganisms preventing it from reaching the lungs.

44
Q

where does most of the mucus go

A

into the throat where it is swallowed and digested

45
Q

what do epithelial cells contain

A

many mitochondria to provide energy for the beating cilia

46
Q

what do the trachea divide into in the chest cavity

A

they divide to form the left bronchus leading to the left lung and the right bronchus leading to the right lung

47
Q

describe the bronchi

A

supported by cartilage which is deposited in partial rings and irregular blocks. the rings of cartilage are smaller

48
Q

what does each bronchus divide into

A

smaller tubes -bronchioles

49
Q

what do the bronchioles divide into

A

primary bronchioles divide into terminal bronchioles then respiratory bronchioles where gas exchange takes place

50
Q

which bronchioles does gas exchange take place

A

respiratory bronchioles

51
Q

describe the bronchioles

A

they are about 1 mm or less in diameter. they have not got cartilage and are held open by smooth muscle. when this muscle contracts the bronchioles contract, this is dependant on air flow

52
Q

what are the bronchioles lined with

A

epithelial tissues making gas exchange possible

53
Q

what are on the ends of the respiratory bronchioles

A

tiny air sacs or alveoli

54
Q

what do the alveoli do

A

gives the lungs a huge surface area making gas exchange surface area

55
Q

describe an alveolus

A
  • each is about 200-300µm diameter
  • made of a thin layer of flattened epithelial cells as well as some collagen and elastin fibres
56
Q

what do the elastin fibres do

A

they cause recoil which helps air move out of the alveoli

57
Q

what is elastic recoil

A

alveoli can squeeze as air is drawn in. when they return to their resting size, they help squeeze the air out

58
Q

where do alveoli exist in

A

alveolar ducts

59
Q

what is the exchange surface of alveoli

A

each sac is 0.05mm across increasing to 0.1mm when inflated. there are over 250 million altogether giving an exchange surface of about 80m²

60
Q

what is each alveolus covered in

A

a fine network of blood capillaries

61
Q

how do the alveoli and capillary walls allow efficient gas exchange

A

they are made of squamous epithelium (flattened cells)

62
Q

what does squamous epithelium consist of

A

one layer of cells

63
Q

how do narrow capillaries allow efficient gas exchange

A

the capillaries are so narrow that blood cells must squeeze through. this slows blood flow and minimises the distance that gases have to diffuse

64
Q

what happens to the oxygen and carbon dioxide

A

oxygen diffuses continuously into red blood cells and carbon dioxide diffuses out of the blood plasma. some air is replaced with each breath maintaining the concentration gradients

65
Q

what are the features of efficient gas exchange

A

large surface area
moist
thin layers
good blood supply
good ventilation

66
Q

how do alveoli provide large surface area

A

there are 300-500 million alveoli per adult lung. the alveolar surface area for gaseous exchange in the two lungs is about 50-75m²

67
Q

how do the alveoli provide moisture

A

alveoli have a thin layer of moisture which evaporates and is lost as we breathe out. the lungs must produce a surfactant that coats the internal surface of the alevoli to reduce the cohesive forces between the water molecules as these forces tend to make the alveoli collapse

68
Q

how do the alveolis thin layers minimise the diffusion distance

A

alveoli and capillaries surrounding them have walls that are one cell thick so the diffusion distances between the air in the alveolus and the blood in the capillaries are very short. the total diffusion barrier is less than 1µm thick

69
Q

how do the alveoli use their good blood supply

A

helps maintain their steep concentration gradient so the gases continue to diffuse. the blood system transports from the tissues to the lungs ensuring the concentration of the carbon dioxide in the blood is higher than in the alveoli so that carbon dioxide diffuses into the alveoli. the blood transports the oxygen away from the lungs ensuring the concentration of oxygen in the blood is kept lower than in the alveoli so oxygen diffuses in the blood

70
Q

how are the alveoli ventilated

A

breathing moves air in and out of the alveoli helping maintain the steep diffusion gradients for oxygen and carbon dioxide between the blood and the air in the lungs

71
Q

what is the inner surface of the alveoli covered in

A

a thin layer of a solution of salts, water and lung surfactant

72
Q

what is lung surfactant

A

makes it possible for the alveoli to remain inflated

73
Q

where does oxygen dissolve before it diffuses into the blood

A

dissolves in the air before diffusing into the blood

74
Q

which adaptations help reduce water loss

A

oxygen dissolves in the air before diffusing into the blood but water can evaporate into the air in the alveoli

75
Q

what is the role of smooth tissue

A

constricts the airway making the lumen narrower.

76
Q

what can constriction of the lumen cause

A

restriction of the flow of air to and from the alveoli

77
Q

when can controlling the flow of the air to the alveoli be important

A

if there are harmful substances in the air

78
Q

when can contraction of the smooth muscle occur

A

as a result of an allergic reaction as it is not voluntary

79
Q

what happens once the smooth muscle is contracted

A

it cannot reverse the effect on its own. the smooth muscle is elongated again by the elastic fibres. when the muscle contracts, it deforms the elastic fibres

80
Q

what happens as the muscles relax

A

the elastic fibres recoil to their original size and shape. this acts to dilate the airway

3.1.1 exchange surfaces (4 decks)

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