Exchange surfaces

Question 1

Why don’t single celled organisms need a specialised exchange surface?

Answer 1

They have a large surface area to volume ratio
They are small so the demand for O2 / CO2 removal is low
Diffusion alone is adequate to meet their needs

Question 2

Why do multicellular organisms need a specialised exchange surface?

Answer 2

They have a higher demand for oxygen and a greater need to remove CO2
They have a smaller surface area to volume ratio (SA:V)
Their surface area is too small and the distance to cells too large to supply their needs. Diffusion just takes too long

Question 3

How do Alveoli provide an efficient exchange surface?

Answer 3

-thin (epithelial) wall, reduces
diffusion distance
-collagen / elastic fibres, elastic
recoil to help squeeze air out
during exhalation
-large number / provide large
surface area, to increase rate of
diffusion
-good blood supply / capillaries,
-maintains high concentration
gradient
- surfactant, allows gases to
dissolve

Question 4

How does nasal cavity provide an efficient exchange surface?

Answer 4

• large surface area and good blood
  supply, warms air
• mucus secreting cells, trap dust
  and microbes
• moist surfaces, increase humidity
  and reduce evaporation from
  surfaces in lung

Question 5

How does trachea provide an efficient exchange surface?

Answer 5

-cartilage rings, stop it from
collapsing
- ciliated epithelium and goblet cells
secrete mucus, trap dust and
microbes and move them towards
stomach

Question 6

How does bronchi/bronchioles provide and efficient exchange surface?

Answer 6

-smooth muscle, allows air to move
in and out and maintains high
concentration gradient of O2 / CO2

Question 7

How do diaphragm and ICM provide efficient exchange surface?

Answer 7

-contract to increase volume in
lungs, reduce pressure and cause
inspiration

Question 8

What are goblet cells?

Answer 8

Cells lining airways that secrete mucus, which traps microorganisms and dust particles in inhaled air, stopping it from reaching alveoli.

Question 9

Function of elastic fibres:

Answer 9

in walls of trachea, bronchi, bronchioles and alveoli and help with the process of expiration. Elastic fibres stretched on inspiration and recoil when expiration occurs.

Question 10

Function of smooth muscle:

Answer 10

In walls of trachea, bronchi and bronchioles, allowing their diameter to be controlled. During exercise, smooth muscle relaxes, making tubes wider = less resistance to air flow and air can move in and out of lungs easier.

Question 11

What is found in trachea?

Answer 11

1- large c shaped rings of cartilidge
2- smooth muscle
3- elastic fibres
4- goblet cells
5- ciliated epithelium

Question 12

What is found in bronchi?

Answer 12

1- small rings of cartilidge
2- smooth muscle
3- elastic fibres
4- goblet cells
5- ciliated epithelium cells

Question 13

What is found in largest bronchiole?

Answer 13

1- no cartilidge
2- smooth muscle
3- goblet cells
4- elastic fibres
5- ciliated epithelium

Question 14

What is found in medium size bronchiole?

Answer 14

1- no cartilidge
2- smooth muscle
3- elastic fibres
4- ciliated epithelium

Question 15

What is found in smallest bronchiole?

Answer 15

1- no cartilidge
2- elastic fibres
3- no cilia

Question 16

What is found in alveoli?

Answer 16

1- no cartilidge
2- elastic fibres
3- no cilia

Question 17

Process of inspiriation:

Answer 17

1. Diaphragm contracts to becoming flatter, pushing digestive muscles down
2. External intercostal muscles contract to raise ribs
3. Volume of thorax increases
4. Pressure in thorax drops below atmospheric pressure
5. Air moves into lungs

Question 18

Process of expiration:

Answer 18

1. Diaphragm relaxes and is pushed up by displaced organs underneath
2. External intercostal muscles relax and ribs fall
3. Volume of thorax decreases
4. Pressure in thorax increases and rises above atmospheric pressure
5. Air moves out of lungs

Question 19

Tidal volume:

Answer 19

The volume of air moved in and out of the lungs during breathing when at rest

Question 20

Vital capacity:

Answer 20

The largest volume of air that can be moved into and out of the lungs in any one breath

Question 21

Ventilation (inspiration) in bony fish:

Answer 21

The ventilation mechanism in fish constantly pushes water over the surface of the gills and ensures they are constantly supplied with water rich in oxygen (maintaining the concentration gradient)
When the fish open their mouth they lower the floor of the buccal cavity. This causes the volume inside the buccal cavity to increase, which causes a decrease in pressure within the cavity
The pressure is higher outside the mouth of the fish and so water flows into the buccal cavity

Question 22

Ventilation (expiration) in bony fish:

Answer 22

fish raises the floor of the buccal cavity to close its mouth, increasing the pressure within the buccal cavity
Water flows from the buccal cavity (high pressure) into the gill cavity (low pressure)
As water enters pressure begins to build up in the gill cavity and causes the operculum (a flap of tissue covering the gills) to be forced open and water to exit the fish
The operculum is pulled shut when the floor of the buccal cavity is lowered at the start of the next cycle

Question 23

Gas exchange in insects:

Answer 23

Very active, flying insects need a more rapid supply/intake of oxygen. They create a mass flow of air into the tracheal system by:
Closing the spiracles
Using abdominal muscles to create a pumping movement for ventilation
Also, during flight the fluid found at the narrow ends of the tracheoles is drawn into the respiring muscle so gas diffuses across quicker (due to the diffusion distance being shorter)