exchange surfaces

Question 1

Why do some organisms need specialised exchange surfaces?

Answer 1

• Larger organisms have a smaller SV/Vol ratio and so every cell is not in contact with the external environment and cannot get what it needs by simple diffusion
• So some organisms need specialised exchange surfaces to supply each cell with what it needs

Question 2

What are the four features of a food exchange surface?

Answer 2

1. Large surface area
2. Thin layers
3. Good blood supply
4. Ventilation

Question 3

How does a large surface area a feature of a good exchange surface?

Answer 3

• Provides the area needed for exchange and overcome the limitations of the SA/Vol ratio of large organisms
• Root hair cells and villi

Question 4

How are thin layers a feature of a good exchange surface?

Answer 4

• The diffusion pathway for the gasses are short and makes the process fast and efficient
• Alveoli and villi

Question 5

How is a good blood supply a feature of a good exchange surface?

Answer 5

• Ensures that gases are constantly delivered to and removed from the exchange surface, maintaining a steep concentration gradient for a faster diffusion rate
• Alveoli, villi, fish gills

Question 6

How is ventilation a feature of a good exchange surface?

Answer 6

• Helps maintain concentration gradient and makes the process more efficient
• Ventilation : a flow of water carrying dissolved gases

Question 7

What is the relationship between sa and volume?

Answer 7

The bigger the organism, the smaller the sa/vol ratio

Question 8

What are the four structures involved in the mammalian gaseous exchange system?

Answer 8

1. Trachea
2. Bronchi
3. Bronchioles
4. Alveoli

Question 9

What is the function of the trachea?

Answer 9

Carries air into the lungs, it branches into bronchi

Question 10

How are the tissues related to the function of the trachea?

Answer 10

• Supported by C shaped cartilage rings
• Lined with ciliated epithelium
• Goblet cells
• Contains smooth muscle and elastic fibres

Question 11

What is the function of the bronchi?

Answer 11

Carries air into both lungs, branches into bronchioles

Question 12

How are the tissues related to the function of the bronchi?

Answer 12

• Supported by full rings of cartilage
• Lined with ciliated epithelium and goblet cells
• Contains smooth muscle and elastic fibres

Question 13

What is the function of the bronchioles?

Answer 13

To carry air to the alveoli

Question 14

How are the tissues related to the function of the bronchioles?

Answer 14

• Walls made up of smooth muscle and elastic fibres
• Lined with ciliated epithelium and goblet cells

Question 15

What is the function of the alveoli?

Answer 15

Site of gaseous exchange

Question 16

How are the tissues related to the function of alveoli?

Answer 16

• Composed of squamous epithelium
• Walls contain elastic fibres

Question 17

What is the function of rings of cartilage?

Answer 17

To prevent collapse during inspiration

Question 18

What is the function of smooth muscle?

Answer 18

To control the diameter of the trachea, bronchi, and bronchioles
- Changes the amount of air reaching the lungs to prevent harmful substances from involuntary entering due to an allergic reaction

Question 19

What is the function of elastic fibres?

Answer 19

To stretch
- The alveoli as air is drawn in and squeeze as air is drawn out when returning to resting size
- Allows airways to return to original lumen size once smooth muscle relaxes

Question 20

What is the function of ciliated epithelium?

Answer 20

To waft mucus upward to the mouth to be swallowed

Question 21

What is the function of squamous epithelium?

Answer 21

Allows for rapid and efficient gas exchange

Question 22

What is the function of goblet cells?

Answer 22

To secrete mucus to trap pathogens

Question 23

Describe the active process of inspiration

Answer 23

1. The external intercostal muscles contract moving the ribcage upwards and outwards
2. The diaphragm MUSCLE contracts and moves downwards
3. The volume of the thorax is increased by these two actions
4. The pressure in the chest decreases and is lower than the atmospheric pressure, so air is drawn into the lungs

Question 24

Describe the passive process of expiration

Answer 24

1. The external intercostal muscles relax and the ribcage falls under its own weight
2. The diaphragm MUSCLE relaxes and moves upwards
3. The volume of the thorax is decreased by these two actions
4. The pressure in the chest increased and is higher than the atmospheric pressure, so air is forced out of the lungs

Question 25

Why is inspiration an active process but expiration is passive?

Answer 25

During expiration, energy is not required to push air out of the lungs and so is passive During inspiration, the muscles must contract to draw air into the body and so is active

Question 26

How are the lungs specially adapted to gas exchange?

Answer 26

1. Good blood supply 2. Thin walls - squamous epithelium cells 3. Ventilation - constant movement of co2 and o2

Question 27

How does a spirometer work?

Answer 27

1. A person breathes through a tube connected to the oxygen chamber 2. As the person breathes in and out, the lid of the chamber moves up and down 3. A trace is drawn on a rotating drum of paper - An upwards slope indicated the person breathing out as the volume in the chamber increases - A downwards slope indicated the person breathing in as the volume in the chamber decreases

Question 28

How do you ensure that the results of the spirometer are valid?

Answer 28

1. No air leaks/air tight 2. The person is wearing a nose clip

Question 29

What precautions must be taken when using a spirometer?

Answer 29

1. Patients should be healthy and free of asthma 2. Sterilised mouthpiece 3. Fresh and functioning soda lime

Question 30

What are the features of fish during gas exchange?

Answer 30

1. Operculum - covers gill, gill 2. Gill arch - cartilaginous structure that provides support for the filaments 3. Filaments - thread-like structures, composed of many lamellae, that spread out and create as much surface area as possible 4. Lamellae - disk-like structures stacked along the filaments that contain the capillaries where gas exchange takes place

Question 31

What are the challenges of gas exchange in water for fish?

Answer 31

1. Water is denser and more viscous than air, so slower diffusion of oxygen 2. Water has less oxygen than air 3. Bony fish are very active so have high oxygen demands

Question 32

How are fish adapted for gaseous exchange?

Answer 32

1. Counter current exchange system 2. Gill adaptations

Question 33

How does ventilation help gas exchange in fish when their mouth is open?

Answer 33

1. Buccal cavity volume increases 2. Pressure decreases 3. Water is sucked into the fish

Question 34

How does ventilation help gas exchange in fish when their mouth is closed?

Answer 34

1. Buccal cavity volume decreases 2. Pressure increases 3. Water is forced out across gill filament

Question 35

How are fish gills adapted?

Answer 35

1. Rich blood supply 2. Large SA 3. Thin layers 4. Adjacent gill filaments overlap - inc resistance to water - slow movement - inc gas exchange

Question 36

How do the fish have an increased surface area?

Answer 36

Gill filaments increase sa Gill filaments covered in lamellae which increase sa

Question 37

How are gill plates adapted?

Answer 37

They have a good blood supply through the capillaries and have a thin surface for efficient diffusion

Question 38

What are the two conflicting needs of insects during gas exchange?

Answer 38

1. Maximising gas exchange efficiency 2. Minimising water loss - waterproof cuticle covering exoskeleton

Question 39

What are the main structures involved in gas exchange in insects?

Answer 39

1. Tracheae - air filled tubes branching throughout the body 2. Tracheoles - fine branches of tracheae that deliver gases to cells 3. Spiracles - external openings on the exoskeleton along the abdomen and thorax

Question 40

How are the tracheae adapted?

Answer 40

1. Reinforced with spirals of chitin to prevent collapse and gas exchange 2. Multiple tracheae to increase sa

Question 41

How are the tracheoles adapted?

Answer 41

1. Penetrate directly into tissues - reduce gas diffusion distance 2. Thin walls - reduce gas diffusion distance 3. Highly branched - maximises sa 4. Not reinforced with chitin - allows gas exchange 5. Tracheal fluid at the ends - allows oxygen to dissolve to aid diffusion and reduces water loss

Question 42

How are spiracles adapted?

Answer 42

Open and close - controls gas exchange with the atmosphere and minimise water loss