EXCHANGE SURFACES

Question 1

What are the problems of scale?

Answer 1

• as organisms increase, so does their SA:V
• however SA doesn’t increase as much as its volume
• large organisms need to find ways to increase their SA for gas exchange

Question 2

How does a large surface area provide a perfect exchange surface?

Answer 2

The larger the area across which a substance can diffuse, the more substances can cross in a given time

Question 3

How does the exchange surface being thin benefit exchange?

Answer 3

Shorter the distance for a substance to diffuse the less time it takes

Question 4

How does a diffusion gradient provide a perfect exchange surface?

Answer 4

Concentration of substances must be higher on one side than the other fo diffusion to occur down a concentration gradient

Question 5

How does protection from drying out lead to a perfect exchange surface?

Answer 5

In terrestrial animals water vapour diffuses out of cells on the surface, if too much water is lost the plasma membrane will lose its structure and the cell will die

Question 6

What are surfactants?

Answer 6

Reduces surface tension of fluid in lungs and helps to make alveoli more stable, prevents exhalation collapsing alveoli

Question 7

What is the role of macrophages in the lungs?

Answer 7

Engulf pathogens that are inhaled into the lungs to prevent any diseases/infections from occurring in the lungs

Question 8

What is the function of cartilage?

Answer 8

C shape rings hold the trachea and bronchi open, yet allows them to expand

Question 9

What is the function of the smooth muscle?

Answer 9

Contracts to narrow the lumen and force air out

Question 10

What is the function of elastic fibres?

Answer 10

Recoil of elastic tissue widens airways and forces air out of alveoli

Question 11

What is the function of goblet cells?

Answer 11

Produces and secretes mucus and surfactants

• which traps dust and pathogens to prevent disease
• surfactants prevent lungs drying out

Question 12

What is the function of ciliated epithelium cells?

Answer 12

Cilia wafts the mucus

Then it is swallowed and killed by Hcl in stomach

Question 13

What are the stages for inspiration?

Answer 13

1. contraction of external intercostal muscles, causing rib cage to move up and out
2. muscles in diaphragm contract
3. increases vol in thoracic cavity
4. pressure in cavity is lowered, below pressure outside body
5. air flows down pressure gradient and into the thorax

Question 14

What are the stages for expiration?

Answer 14

1. intercostal and diaphragm muscles relax
2. elastic fibres between alveoli recoil back to normal length
3. vol decreases, pressure increases= air forced out

Question 15

What is the difference between breathing out normally and forced breathing out?

Answer 15

• more air can be forced out by contracting internal intercostal muscles moving diaphragm down
• contraction of abdominal muscles raises diaphragm

Question 16

Define tidal volume

Answer 16

The volume of air moved in and out of the lungs with each breath when you are at rest
-approx 0.5dm3

Question 17

Define vital capacity

Answer 17

The largest possible volume of air that can be moved into and out of the lungs in one breath
-approx 5dm3

Question 18

Define inspiratory reserve volume

Answer 18

How much air can be breather in over and above tidal volume

Question 19

Define expiratory reserve volume

Answer 19

How much air can be breathed out over and above tidal volume

Question 20

What is the formula for vital capacity?

Answer 20

Tidal vol + inspiratory reserve vol + expiratory reserve vol

Question 21

Define residual volume

Answer 21

The volume of air that always remains in the lungs after largest exhalation
-approx 1.5dm3

Question 22

Define dead space

Answer 22

The air in the bronchioles, bronchi and trachea

No gas exchange between air and the blood

Question 23

How does the spirometer work?

Answer 23

1. person breathes into enclosed air chamber
2. as person breathes in, vol inside chamber decreases making float drop down
3. vice versa for breathing in
4. float attached to a pen which maps movement (attached to a revolving drum)

Question 24

What are precautions that should be taken when using a spirometer?

Answer 24

1. container must be filled with soda lime to absorb carbon dioxide
2. medical grade oxygen needs to be present in chamber, especially if used for a long duration
3. glen the mouthpiece

Question 25

What is the function of soda lime in the container?

Answer 25

1. absorbs carbon dioxide, so it doesn’t go into the air chamber
2. useful to measure the volume of oxygen that has been consumed over a period of time

Question 26

Define breathing rate

Answer 26

Amount of breaths taken in a minute

Question 27

Define ventilation rate

Answer 27

-breathing rate x tidal vol

Total vol breathed in or out per minute

Question 28

How do you calculate oxygen consumption?

Answer 28

• chamber must be filled with oxygen
• soda lime in container
• breathe back out= CO2 in expired air absorbed by soda lime
• total vol going back in chamber is less
• traces go down and down
• over a period of time tells you how much O2 vol has been used

Question 29

What are examples of adaptions to gills?

Answer 29

• large S= increased area for diffusion
• rich blood supply= maintains a high conc gradient
• thin layers= short diffusion pathway
• tips of adjacent gill filaments overlap= increased resistance to flow of water over the gills, water movements slows to allow more time for diffusion