3.1.1 Exchange Surfaces Flashcards
1
Q
what is an exchange surface
A
- a specialised area adapted to make it easier for molecules to cross from one side of the surface to the other
2
Q
What are the reasons diffusion alone is enough to supply the needs of single celled organisms
A
- their surface area to volume ratio is large
- their metabolic activity is low so oxygen requirement and CO2 production is low
3
Q
why do multicellular organisms require specialised exchange surfaces
A
- they have small surface area to volume ratio
- they have higher metabolic activity so demand for oxygen is higher and CO2 production in high
4
Q
List the key features of an efficient exchange surface
A
- increased surface area
- thin layer
- good blood supply
- ventilation to maintain gradient
5
Q
Why is a large surface area a feature of an efficient exchange surface
A
- large surface area provides more space for molecules to pass through
6
Q
How can large surface areas on exchange surfaces be achieved + examples
A
- by folding walls of membranes involves
- examples:
> root hair cells in plants
7
Q
How do thin layers provide an efficient exchange surface
A
- reduces distance for diffusion + makes process faster and efficient
- barrier must be permeable to allow gas to dissolve
8
Q
Where are examples of thin walls in efficient exchange surfaces
A
- in the alveoli
9
Q
Why does a good blood supply contribute towards an efficient exchange surface + examples
A
- steeper conc gradient = faster diffusion rate
- good blood supply ensures substances are constantly delivered and removed from exchange surface
> this maintains the steep conc gradient for diffusion - examples are gills + alveoli
10
Q
Why is ventilation a feature of an efficient exchange surface
A
- ventilation helps maintain steep conc gradient making process more efficient
> example is alveoli and gills of fish where ventilation means flow of water carrying dissolved gases
11
Q
Where does human gas exchange happen
A
- in the alveoli of the lungs
12
Q
What are key features of the nasal cavity
A
- large SA + good blood supply warming air to body temp
- hairy lining secreting mucus that traps dust and bacteria, protecting delicate lung tissue from infection
- moist surfaces that increase humidity of incoming air, reducing evaporation from exchange systems
13
Q
What are the different levels of the airways in large to small order
A
- trachea
- 2 bronchi
- bronchioles
- alveolar duct
- alveolar sac
- alveolus
14
Q
How does air go into your lungs
A
- air passes through nose and along trachea, bronchi, bronchioles until it reaches tiny air filled sacs called alveoli
15
Q
Why is the network of capillaries on alveolus good
A
- constant flow of blood brings CO2 and takes O2
> maintains a steep conc gradient
16
Q
What are alveolar macrophages
A
- type of phagocytic white blood cell
- digests any foreign particles that reached the alveolus
17
Q
what is the role of squamous epithelial cells in the alveoli
A
- flattened cells that make up most of alveolar thin walls
> single cell thick - short diffusion distance between air in alveolus and blood in capillaries
18
Q
What are squamous epithelial cells also referred to as
A
- type 1 and type 2 pneumocytes
> type 1 are large flattened cells (make up alveolar wall)
> type 2 secrete surfactant
19
Q
Why is good ventilation a key feature of the alveoli
A
- breathing moves air in + out of alveoli
> maintains steep diffusion gradient for O2 and CO2 between blood and air in lungs
20
Q
What is surfactant + role
A
- mixture of lipids and proteins that help reduce surface tension of liquid lining inner surface of alveoli
- speeds up transport of gas between air and liquid lining alveoli
- kills bacteria
21
Q
What does connective tissue consist of
A
- fine collagen
- elastin fibres
- fibroblast cells
22
Q
What does connective tissues do
A
- allows stretch and recoil of lung tissue with breathing
> stretch stops alveoli from bursting
> recoil helps to expel the air - forms supporting layer beneath the epithelium
23
Q
What is the trachea
A
- the main airway carrying clean, warm, moist air from nose down into chest
24
Q
describe the structure of the trachea
A
- wide tube supported by incomplete C shaped rings of strong, flexible cartilage
25
what is the function of the cartilage in the trachea
- prevents trachea from collapsing
> incomplete due to food moving easily down the oesophagus behind trachea
26
what two structures of the lungs are lined with ciliated epithelium + another feature
- trachea + bronchi
> have goblet cells between + below the epithelial cells
27
what is the function of goblet cells
- secret mucus onto lining of trachea, trapping dust + microorganisms
28
how does cilia help in the trachea
- cilia beat + move mucus along with bacteria away from lungs
> most of it goes into the throat + swallowed and digested
29
what are bronchus
- in chest cavity trachea divides to form left + right bronchus leading to each lung
> similiar in structure to trachea with cartilage rings but smaller
30
what are bronchioles
- in lungs bronchi divide to form many small bronchioles
31
what is the structure of bronchiols
- small (1mm or less)
- no cartilage rings
- walls contain smooth muscle
- thin layer of flattened epithelium (makes some gaseous exchange possible)
32
what does the smooth muscle in the bronchioles do
- when smooth muscle contracts, the bronchioles constrict
- when it relaxes, the bronchioles dilate
- this changes volume of air reaching lungs
33
what are alveoli
- tiny air sacs
- main gas exchange surfaces of the body
34
what are the functions of the alveoli
- diameter around 200-300 micrometers
- thin flattened epithelial cells
- collagen + elastic fibres (made from elastin)
35
what is the function of elastic tissue in alveoli
- allows alveoli to stretch as air is drawn in
36
what are the main adaptations of alveoli for effective gas exchange
- large SA
- thin layers (shorter diffusion distance)
- good blood supply (network of capillaries)
- good ventilation
37
what is the function of the ciliated epithelium
- wafts mucus up the throat by synchronised beating
38
what is ventilation
- breathing
- the process by which air is constantly moved into + out of lungs
39
air is moved in and out of the .... as a result of .... in the thorax brought about by ....
- lungs
- pressure changes
- breathing movements
40
what is the ribcage
- a semi-rigid case within which pressure can be lowered with respect to air outside it
41
what is the diaphragm
- a broad, domed sheet of muscle making up the floor of the thorax
42
where are the external + internal intercostal muscles found
- between the ribs
43
is inspiration an active/passive process
- active
- uses energy
44
describe the process of inspiration
- diaphragm contracts, flattening and lowering
- external intercostal muscles contract moving ribs upwards + outwards
- volume of thorax increases, so pressure reduced in thorax
> pressure lower than atmospheric air so air is drawn through nasal passages into lungs
> equalises pressure inside + outside chest
45
is expiration and active/passive proccess
- passive
46
describe the process of expiration
- diaphragm muscles relax so moves up into resting dome shape
- external intercostal muscles relax so ribs move down and inwards under gravity
- elastic fibres in alveoli return to normal length
- volume of thorax decreases
> pressure in thorax greater than atmospheric air do air moves out of lungs
47
is forced expiration an active/passive process
- active
48
describe the process of forced expiraion
- internal intercostal muscles contract, pulling ribs down hard + fast
- abdominal muscles contract forcing diaphragm up to increase pressure in lungs rapidly
49
what is a spirometer used for
- to measure and read volumes of air inspired + expired over a period of time
50
what is a spirograph/kymograph
- the paper record (trace) of the volumes recorded by a spirometer
51
define tidal volume
- volume of air that moves into + out of lungs in one breath
> usually measured at rest
52
define vital capacity
- the greatest volume of air that can be breathed in when the strongest exhalation possible followed by the deepest possible intake of breath
53
define inspiratory reserve volume
- maximum volume of air that can be inspired over and above a normal inhalation
54
define expiratory reserve volume
- extra volume of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
55
define residual volume
- volume of air that is left in your lungs when you have exhaled as hard as possible (after forced expiration)
> can't be measured directly
56
define total lung capacity
- sum of the vital capacity + residual volume
57
define breathing rate
- number of breaths taken per minute
58
define oxygen uptake
- volume of oxygen absorbed by the lungs in one minute
59
define ventilation rate
- measure of total volume of air inhaled in one minute
60
how can you determine the ventilation rate
- ventilation rate (dm*3min*-1) = tidal volume (dm*3) x breathing rate (min*-1)
61
explain how to use a float chamber spirometer
- subject sits at rest + breathes normally
- as subject inspires, air is drawn in from chamber + lid moves down
- during expiration air returned to chamber + lid moves up
- movements are recorded on trace of spirograph
62
what causes spirometer lid to move
- spirometer chamber filled with medical grade oxygen + floats on water
- as air is removed lid moves down
- as air is returned lid moves up
63
what precautions must be taken regarding the subject when using a spirometer
- healthy subject
- subject at rest + breathing normally
- subject wears nose plug (prevents ventilation via nose)
64
what precautions must be taken regarding the actual spirometer when using it
- fresh soda lime to absorb CO2
- water chamber not overfilled (so subject doesn't take in water)
- no leaks to make results invalid
- sterile mouthpiece
65
why does the trace on a spirograph get lower as experiment progresses
- some oxygen will be consumed by the body
66
how can you calculate the breathing rate form a spirograph
- count how many breaths in a min
> number of peaks in min
67
how can you calculate the tidal volume from a spirograph
- measure height of a single trace / peak
68
why can't bony fish rely on diffusion for gaseous exchange
- small SA:V (diffusion not enough to supply cells with oxygen)
- scaly outer covering doesn't allow gaseous exchange
69
what are the gills to bony fish
- their organs of gaseous exchange`
70
what are some general features of gills
- large SA (diffusion)
- good blood supply (steep conc gradient for diffusion)
- thin layers (shorter distance for diffusing substances)
> all good for successful gaseous exchange
71
where are gills found
- contained in the gill cavity
- covered by protective operculum
72
what are gills made of
- many gill filaments arranged in large stacks (gill plates)
73
why do gill filaments provide a large SA
- there are many of them
- need flow of water to keep them apart and so exposes large SA needed for gaseous exchange
74
why are gill lamellae good for gaseous exchange
- have rich blood supply + large SA
- few cells thick + contains blood capillaries
75
what are gill lamellae
- main site of gaseous exchange
76
how do gill lamellae increase SA
- project at right angles from the filaments
77
what is the operculum
- bony flap that covers the gill cavity
- active in maintaining a flow of water over the gills
78
describe the steps in how water flows over the gills
- mouth opens + floor of buccal cavity lowers, inc volume + lower pressure allows water to move in
- opercular valve shut + opercular cavity containing gills expand + lowers pressure
- floor of buccal cavity moves upwards, inc pressure + water moves from buccal cavity over gills
- as mouth closes, operculum opens + sides of opercular cavity move inwards + inc pressure and forces water over gills and out of operculum
79
what happens in a counter current flow + why is it good
- blood always comes into contact with water that has a higher dissolved oxygen concentration
- diffusion gradient for oxygen is maintained along entire length of gill structure
> facilitates maximum possible gas exchange across gill lamellae
80
how is a counter current flow system maintained in bony fish
- blood flows along gill arch + out along filaments to secondary lamellae
- blood then flows through capillaries in opposite direction to flow of water over lamellae
- oxygen enters blood as CO2 diffuses out into water
81
how do gill filaments slow down movement of water
- tips of adjacent gill filaments overlap
- inc resistance to flow of water over gill surfaces + slows water movement
> as result there is more time for gaseous exchange to take place
82
what prevents gaseous exchange happening in insects
- tough exoskeleton
- no blood pigments to carry O2
83
what type of circulatory system do insects have
- open
84
what do insects have that is used for gaseous exchange
- they have an air-filled tracheal system that supplies air directly to respiring tissues
85
what are spiracle + where are they found
- small openings
- found along thorax and abdomen
86
how does air enter / leave an insect
- through the spiracles
87
what helps spiracles to open / close
- sphincters
88
why are spiracle sphincters kept as closed as possible
- to minimise water loss
89
when will the spiracles of an insect be closed
- when insects are inactive and O2 demands are very low
90
when will the spiracles of an insect be open
- when O2 demands are raised or CO2 levels build up
91
what comes after the spiracles in an insect
- trachea
92
what are trachea
- largest tubes of insect respiratory system
> up to 1mm
- carry air into body
- supported by spirals of chitin to keep them open
93
what to trachea narrow down to from
- tracheoles
- 0.6 - 0.8 micrometer
- no chitin lining
94
what is tracheal fluid + where is it found
- found towards the end of tracheoles
- facilitates gas exchange by allowing O2 to dissolve + diffuse into respiring cells
95
where is the main site of gaseous exchange in insects
- tracheoles
96
how is tracheal fluid helpful when insect tissues are active
- tracheal fluid can be withdrawn into body in order to increase SA of tracheole wall exposed to air
> more O2 can be absorbed
97
name some alternative methods of inc level of gaseous exchange in larger insects
- mechanical ventilation of tracheal system
- collapsible enlarged trachea or air sacs acting as reservoirs
- movement of wings altering volume of thorax
98
how does mechanical ventilation of tracheal system inc gaseous exchange
- air actively pumped into system by mechanical movements of thorax / abdomen
- movements change volume of body + pressure in trachea and tracheoles
- air drawn into trachea + tracheoles / forced out as pressure changes
99
how do collapsible enlarged trachea or air sacs inc gaseous exchange
- used to inc volume of air moved through gas exchange system
- usually inflated + deflated by ventilating movements of thorax + abdomen
100
how do wing movements inc gaseous exchange
- thorax vol dec - air in tracheal system under pressure and pushed out
- thorax vol inc - pressure inside drops and air pushed into tracheal system from outside
101
O2 moves ... conc gradient from ... into ...
- down
- air
- body cells
102
CO2 moves ... conc gradients from ... into ...
- down
- body cells
- air
