Exchange surfaces and Breathing

Question 1

Do small organisms need specialised exchange surfaces?

Answer 1

No, the cytoplasm is clos to the environment so diffusion is enough

Question 2

Why do multicellar organisms need specialised exchange surfaces?

Answer 2

they need to have a long diffusion pathway as diffusion on its own is not enough and oxygen would not get to cells quick enough

Question 3

Why does a small organism have a large surface area to volume ratio?

Answer 3

they have a small surface area and a small volume, the surface area is large compared with the volume therefore they have a large surface area to volume ration

Question 4

Why does a large organism have a small surface area to volume ratio?

Answer 4

They have a large surface area and a large volume, the surface area is small compared with the volume therefore they have a small surface area to volume ratio

Question 5

What are the main factors that affect the need for an exchange system

Answer 5

• Size – the larger the animal the more need for an exchange system, this is because they are multicellular which means they have more than one layer of cells so need the diffusion pathway is too long and too slow to enable a sufficient supply to the inner cells, furthermore the outer cells will use up most the oxygen and nutrients
• Surface area to volume ratio – if you have a small surface area to volume ratio you are more likely to need and exchange system (see below)
• Level of metabolic activity – if you are more active you are more likely to need an exchange system, this is because the cells need a good supply of nutrients and oxygen for movement as well as keeping warm in mammals

Question 6

What are the features of a good exchange surface

Answer 6

1. A large surface area to provide more space for molecules to pass through – folding walls and membranes
2. Thin barrier – this reduces the diffusion distance; the barrier can also be permeable
3. Good blood supply – fresh supply of molecules to one side keeping the concentration high or remove molecules from the demand side keeping the concentration low therefore it maintains a steep concentration gradient so that diffusion can occur rapidly

Question 7

What makes an efficient gaseous exchange?

Answer 7

• large surface area
• permeable barrier
• thin barrier
• good blood supply
• ventilation

Question 8

How are the lungs adapted to maintain diffusion in the most efficient way

Answer 8

• Large surface area – individual alveoli are small but them all grouped together are large, they are lined by a thin layer of moisture this is evaporated and lost as we breath out therefore the lungs must produce a surfa ant that coats the internal surface of the lungs to stop the forces between the water moleucels otherwise the forces would make the alveoli collapse
• Barrier permeable to oxygen and carbon dioxide – molecules are small and non-polar
• Thin barrier to reduce the diffusion distance – avleoulus wall is one cell thick, the capillary wall is one cell thick, both walls consist of squamous cells, in close contact, the capillaries are narrow so that the red blood cells are squeezed against the capillary wall making the close to the air in the alveolus and reducing their rate of flow
• Good blood supply – maintain steep concentration gradient so things continue to diffuse. Blood system transports carbon dioxide from the tissues to the lungs therefore high concentration of co2 in blood which is higher than in the air in the alveoli therefore the co2 diffuses into the alveoli. Blood transports o2 away from lungs therefore concentration is lower than in alveoli so oxygen diffuses into the blood

Question 9

What is the average size of the diameter of the alveolus?

Answer 9

100-300um

Question 10

What are the alveolus lined with and why?

Answer 10

a surfactant coat on the internal surface to stop forces between the water molecules this friction would make the alveoli collapse

Question 11

What does a permeable barrier do?

Answer 11

this allows oxygen and carbon dioxide because molecules are small and non-polar

Question 12

What does a thin barrier do?

Answer 12

reduces the distance needed to travel

Question 13

What are the features of a thin barrier in the lungs

Answer 13

• alveolus and capillary wall one cell thick and squamous cells (flattened and thin)
• capillaries in close contact with the alveolus wall
• the capillaries are narrow so RBC is squeezed and moves them close to air and reduces flow rate

Question 14

Why do you want a good blood supply?

Answer 14

maintains the steep concentration gradient

Question 15

Describe how Carbon dioxide is transported to the alveoli

Answer 15

the carbon dioxide is transported from the tissue to the lung this makes the concentration of carbon dioxide higher in the blood then in the alveoli so it diffuses out
- opposite for oxygen

Question 16

What does ventilation do?

Answer 16

replaces the air and brings more oxygen and removes carbon dioxide

Question 17

How does inspiration work?

Answer 17

• Diaphragm contracts and flattens
• external intercoastal muscles contract
• ribs go up and out
• volume of chest cavity increases
• pressure decreases
• air moved in

Question 18

How does expiration work?

Answer 18

• Diaphragm relaxes and pushes up
• external intercostal muscles relax
• ribs go down and in
• volume decreases
• pressure increases
• air moved out

Question 19

What is the alveoli made out of and what is its job?

Answer 19

squamous epithelium tissue, this is surrounded by capillaries therefore diffusion distance is short they also contain elastic fibres these stretch during respiration an recoil to push air out

Question 20

How are the airways designed?

Answer 20

large enough to allow airflow, supported to stop collapse when air pressure is low
flexible to allow movement
lined with ciliated epithelium - globet cells release mucus this traps the pathogen , cilia moves it to the top of the airway and then its swallowed
glandular tissue also provides mucus this is in the loose tissue

Question 21

How are the trachea and bronchi adapted?

Answer 21

• Bronchi are narrower than the trachea
• Supported by the rings of cartilage these prevent collapse during inspiration, they are c-shaped this allows flexibility and space for food to pass down into the oesophagus

Question 22

Describe the bronchioles

Answer 22

• Narrower than the bronchi
• Larger ones have some cartilage but smaller ones do not
• Wall is made out of smooth muscle and elastic fibres
• Smallest bronchioles end in clusters of alveoli

Question 23

how does smooth muscle work?

Answer 23

the smooth muscle contracts therefore constricting the airways and narrowing the lumen this restricts the airflow to the alveoli

Question 24

why is smooth muscle important?

Answer 24

its important as it can constrict the airway therefore preventing harmful substances entering the lungs

Question 25

Is smooth muscle constricting voluntary or not?

Answer 25

not voluntary

Question 26

How does the smooth muscle return to its normal position?

Answer 26

it is elongated by elastic fibres therefore as the muscles relaxes the elastic fibres recoil to their original shape and size

Question 27

What is a spirometer used for?

Answer 27

its is used to measure lung volumes and measures the movement of air and out as the person breathes

Question 28

What happens during inspiration? (spirometer)

Answer 28

air is drawn in from the chamber and the lid moves down

Question 29

What happens during exhaliation? (spirometer)

Answer 29

air returns to the chamber and raises the lid

Question 30

What is the soda lime used for?

Answer 30

it absorbs carbon dioxide so only the oxygen is measured

Question 31

What are the precautions needed to be taken when using the spirometer?

Answer 31

• subject should be healthy and free from asthma
• soda lime should be fresh and functioning
• no air leaks
• mouth piece should be sterilised
• water chamber should not be overfilled

Question 32

what is the total lung volume?

Answer 32

the total lung volume consitis of the vital capacity which is measured and the residual capacity which is not measured by the spirometer

Question 33

What is the vital capacity?

Answer 33

the maximum volume of air that can be moved by the lungs in one breath

Question 34

What does the vital capacity depend on?

Answer 34

• size
• age
• gender
• fitness

Question 35

What is the residual volume?

Answer 35

the volume of air that remains in the lungs even after forced expiration (remains in the airways and alveoli) about 1.5dm3

Question 36

What is the tidal volume?

Answer 36

the volume of air moved in and out with each breath, measured at rest

Question 37

How does the oxygen uptake work?

Answer 37

the carbon dioxide absorbed by the soda lime this decreases the volume in the spirometer
- this decrease in carbon dioxide released equals the volume of oxygen absorbed by the blood

Question 38

How do you measure the breathing rate?

Answer 38

count the number of peaks per minute

Question 39

What does the oxygen uptake depend on?

Answer 39

exercise

Question 40

What will increasing the oxygen uptake lead to?

Answer 40

increased breathing rate

deeper breaths

Question 41

How does gas exchange happen in bony fish?

Answer 41

they use the gills to absorb dissolved oxygen and release carbon dioxide
5 pairs of gills are covered by a bony plate called operculum, each gill has two rows of gill filament (primary lamellae) which are attached to a bony arch
- the filament is thin and their surface is folded into secondary lamellae this increases surface area and are close to blood capillaries

Question 42

what is counter current flow?

Answer 42

two fluids flowing in opposite directions

Question 43

How does counter current flow work?

Answer 43

blood flows along gill arch and out along the filaments to the secondary lamellae then through the capillaries in opposite direction to the flow of water over the lamellae this allows it to absorb maximum amount of oxygen

Question 44

describe ventilation in bony fish

Answer 44

to keep water flowing over the gills they use a buccal-opercular pump, this measn the buccal cavity changes volume this is done by…

1. the floor of the mouth moves down
2. draws water in the mouth
3. mouth closes
4. floor raises and pushes the water through the gills
   - the movement of the operculum co-ordinate with movements of the buccal cavity the operculum moves outwards this reduces the pressure in the operculuar cavity helping the water goes through the gills

Question 45

How does an insect breathing system work

Answer 45

they use an open circulatory system this means there is no blood vessels, the bodily fluid acts as the blood and tissue fluid
they have an air-filled tracheal system this supplies air directly to respiratory sites, air enters via a pore in each segment called a spiracle, the air is then supported by tubes called trachea which divide into smaller tubes called tracheales. the ends of the tracheoles end with tracheal fluid

Question 46

How do insects increase gas exchange when active?

Answer 46

the tracheal fluid is withdrawn to increase the surface area of the tracheal so more oxygen is absorbed

Question 47

why is circulation in an insect slow?

Answer 47

affected by body movement

Question 48

how does ventilation in insects work?

Answer 48

• sections of the tracheal system are expanded and have flexible walls which act as air sacs and can be squeezed by the action of light muscles, contraction and expansion of sacs ventilate the system
• movement of wings alter the volume of the thorax - if the volume of the thorax decreases this increases pressure and air is pushed out, if volume of thorax increases then pressure decreases and air is forced in
• abdomen expands and spiracles at front end open this makes air open, as abdomen decreases in volume spiracles at the end open and air flows out