3.1.1 - Exchange Surfaces Flashcards
1
Q
The need for specialised exchange surfaces ( Multicellular organisms)
A
- Low SA:V ratio - Large diffusion distance
- High metabolic activity - High oxygen demand
- Therefore specialised exchange surface is need to increase diffusion and meet oxygen demands
2
Q
Why do unicellular organisms not need exchange surfaces?
A
- Metabolic activity low, so relatively low oxygen needed and carbon dioxide produced
- Large SA:V ratio, so small diffusion distance
- Therefore diffusion alone is sufficient to meet the demands.
3
Q
Features of specialised exchange surfaces
A
- Increased surface area : Provides the area needed for exchange. Overcomes the limitation of the small SA:V ratio of larger organisms.
- Thin layers : This means the distance the substances have to diffuse is short
- Good blood supply : The steeper the concentration gradient, the faster diffusion takes place
- Ventilation: Maintains concentration gradient
4
Q
Surface area , volume equations
A
Ratio = Surface area / Volume - Cuboids : V = l x W x h SA = (4 x l x h) + (2 x h x w) - Cylinder : V =Pi x r^2 x h SA = (2 x Pi x r x h) + 2 x Pi x r^2 - Sphere : V = 4/3 x Pi x r^3 SA = 4 x Pi x r^2
5
Q
Ficks Law
A
Rate of diffusion = SA x Concentration difference / Thickness of membrane
- SA & cd proportional to rate of diffusion
- Thickness of membrane inversely proportional to rate of diffusion
6
Q
Why do gas exchange surfaces need to be moist?
A
So that oxygen and carbon dioxide can dissolve in it and easily diffuse.
7
Q
Nasal cavity
A
- Large SA with rich blood supply which warms the air
- Hairy lining which secretes mucus to trap dust and bacteria.
- Moist surfaces to increase humidity of incoming air to prevent water loss at alveoli
8
Q
Trachea
A
- Carries humid air down to the lungs
- Itis supported by a layer of cartilage that holds the trachea open and prevents it from collapsing.
- The rings are incomplete to allow it to bend when food is swallowed down the oesophagus.
- Ciliated epithelium
- Goblet cells
- Smooth muscle and elastic fibres
9
Q
Bronchus
A
- Bronchus are extensions of the trachea that split into two for the left and right lung
- Ciliated epithelium
- Goblet cells
- Smooth muscle and elastic fibres
10
Q
Bronchioles
A
- Bronchus divide to form bronchioles
- No cartilage , but do have smooth muscle, this can contract to cause them to constrict.
- Ciliated epithelium
- Elastic fibres
- Goblet cells
11
Q
Alveoli
A
- Little air sacs, this is where most of the gas exchange occurs
- They are made up of a thin layer of flattened epithelial cells, as well as some collagen and elastic fibres
- The elastic fibres causes recoil which helps move air out of the alveoli
- Surfactant - Holds alveoli open
12
Q
Goblet cells
A
- Goblet cells secrete mucus
- This traps dirt and microorganisms
13
Q
Ciliated epithelium
A
- Hair- like structure, called cilia move the mucus away from the lungs, so that it can be swallowed
14
Q
Cartilage
A
- Holds the trachea open and prevents it from collapsing
- Provides strength
15
Q
Smooth muscle
A
- Allows the airway to constrict
- Control flow of air
16
Q
Squamous epithelium
A
Provide thin diffusion distance
17
Q
Elastic fibres
A
Allow them to expand and contract
18
Q
Inhalation
A
- Diaphragm contracts and flattens
- The external intercostal muscles contract
- The ribs move upwards and outwards
- The volume of the thorax increases
- The pressure of the thorax decreases
- It is now lower than the pressure of the atmospheric air
- Air is drawn in to equalise the pressure inside and outside
19
Q
Exhalation
A
- The diaphragm relaxes, so it moves up to its resting domed shape
- The external intercostal muscles relax
- Ribs move down and inwards
- The volume of the thorax decreases
- The pressure inside the thorax increases.
- The pressure inside the thorax is greater than the pressure of the atmospheric air
- Air moves out of the lungs, to equalise the pressure inside and outside.
20
Q
Peak flow meter
A
- Measures the rate at which air can be expelled from the lungs
- Blow into it the scale moves to show rate
21
Q
Spirometer
A
- The patient is asked to take the deepest breath they can, and then exhale into the sensor as hard as possible, at least 6 seconds.
- Sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway obstruction.
- Testing can be preceded by a period of quiet breathing in and out from the sensor (tidal volume), or the rapid breath in (forced inspiratory part) will come before the forced exhalation.
22
Q
Tidal volume
A
Volume of air that moves in or out of the lungs with each resting breath
23
Q
Vital capacity
A
Volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath
24
Q
Inspiration reserve volume
A
Maximum volume of air you can breathe in over and above a normal inhalation
25
Expiration reserve volume
Extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.
26
Residual volume
Volume of air that is left in your lungs when you have exhaled as hard as possible.
27
Total lung capacity
Sum of the vital capacity and residual volume
28
Breathing rate
Number of breaths taken per minute
29
Ventilation rate
= Tidal volume x Breathing rate
30
Oxygen uptake
- The trace slopes downwards because the oxygen is being used up. Although they are breathing out carbon dioxide it is absorbed by the soda lime.
- To measure oxygen uptake measure the drop in the slope.
31
Why should the subject wear a nose clip when using the spirometer
To stop air moving through the nose.
32
Why is there soda lime in the spirometer
- It absorbs the carbon dioxide they breathe out to prevent them breathing in carbon dioxide
33
How does the drum move as the subject breathes?
- It moves up as the subject breathes out
| - Down as they breathe in
34
Ventilation in bony fish
1. Mouth opens (operculum is closed)
2. The buccal cavity floor is lowered
3. This increases the volume and decreases the pressure of the buccal cavity compared to
outside
4. Water rushes into the mouth down a pressure gradient
5. Opercular cavity expands
6. The buccal cavity floor is raised
7. The pressure inside the buccal cavity is now higher than in the opercular cavity
8. Water moves from buccal cavity over the gills into the opercular cavity
9. The mouth is now closed and the operculum opens
10. The sides of the opercular cavity move inwards, increasing the pressure
11. Water rushes out of the fish through the operculum
35
Countercurrent flow
- Blood flows in the opposite direction to the flow of water
- This results in the oxygen concentration gradient between the blood and the water being maintained across the entire length of the Gill lamellae.
36
Operculum
- The bony flap covering the gills of the fish
| - Protects the gills
37
Gill lamellae
- They go across the gill filaments
- Large SA
- Good blood supple
- Thin membrane
38
Gill filaments
- Gills have large stacks of gill filaments
- In water the gill filaments spread out to increase the SA
- Oxygen can be exchanged efficiently
39
Tracheoles
Where gas exchange occurs
- No chitin
- Increases SA
- Tracheal fluid limits the penetration of air for diffusion
- Walls are moist for oxygen to dissolve in
40
Tracheae
Carries air into the body
| - Lined with chitin : Impermeable to gases, support tracheae and keep it open
41
Spiracle
Allows gas and water vapour to enter or leave
- The spiracles can be opened or closed by sphincters
- The spiracle is kept closed when the insect is at rest to reduce water loss
42
Gas exchange problems with exoskeleton
- Insects have a waxy exoskeleton which helps them with protection and water retention
- The exoskeleton is hard and it is impermeable to gases, so oxygen can’t diffuse right through
- Insects do not have a gas exchange system, substances have to diffuse right through
43
Gas exchange when the insect is at rest
- Air moves along the tracheae and tracheoles by diffusion
- Oxygen dissolves in moisture on the walls and diffuse into surrounding cells
- The tracheal fluid limit penetration of air for diffusion
- However they do not need a lot of oxygen as they are resting
44
Gas exchange when insect is active
- When the insect is active, more respiration occurs in the cells, as there is a small amount of oxygen anaerobic respiration takes place and lactic acid is produced
- As lactic acid is produced, the water potential in the cells decrease
- The tracheal fluid move by osmosis into the cells as there is a higher water potential in the tracheoles.
- This exposes more surface area for diffusion and oxygen diffuses into cells.
45
Thoracic and abdominal movement
- The muscular pumping movements of the thorax and abdomen cause the volume of the body to change and can draw air in or pump air out.
