3.1 Exchange Surfaces

Question 1

Why don’t single cellar organisms need specialised exchange surfaces?

Answer 1

They have a short diffusion distance as substances can diffuse straight into cell. Have a high SA:V ratio so diffusion is quick!

Question 2

What are the features of a specialised exchange surface?

Answer 2

1. Large surface area to increase efficiency
2. Thin (one cell thick) so have short diffusion distance
3. Good blood supply creating a steep diffusion gradient
4. Moist

Question 3

how are mammals adapted for gas exchange?

Answer 3

Lungs (alveoli provide large SA:V ratio)

Question 4

Describe the structure of the mammalian gas exchange system also draw a picture.

Answer 4

The air enters the trachea and then flows down two bronchi (one into each lung). After this it travels down bronchioles that have alveoli on the end. On the outside is the rib cage and intercostal muscles and diaphragm. Check card paper for pic.

Question 5

How are alveoli adapted for gas exchange?

Answer 5

• Have large SA
• single layer of cells (squamous epithelium) makes short diffusion distance
• Has surfactant on surface to keep surface moist
• Elastic fibres to help recoil

Question 6

How are the cells and tissues adapted in mammals for gas exchange?

Answer 6

1. Goblet cells - secrete mucus and found in trachea and bronchi but stop dust and bacteria reaching alveoli
2. Cilia - the ciliated epithelium helps waft the mucus away from alveoli so stop infection.
3. Elastic fibres - in walls of trachea bronchi bronchioles and alveoli so they can recoil when breathing.
4. Smooth muscle - helps control diameter of airways

Question 7

Where is cartilage located in the mammal gas exchange system?

Answer 7

In the trachea and bronchi only.
trachea in c shaped rings to allow food to pass down oesophagus behind.
bronchi in irregular blocks

Question 8

Why does the trachea and bronchi have cartilage?

Answer 8

To stop the bronchi and trachea from collapsing when the pressure drops whilst breathing.

Question 9

What is ventilation?

Answer 9

Consists of inspiration and expiration and is controlled by the movements of the diaphragm, intercostal muscles and rib cage.

Question 10

Describe stages of inspiration.

Answer 10

• External intercostal and diaphragm muscles contract.
• Causes ribcage to move up and out and diaphragm flattens.
• Volume of thorax increases.
• Lung pressure decreases.
• Air flows into lungs.
• Active process requires ATP.

Question 11

Describe stages of expiration normal.

Answer 11

• External intercostal muscles and diaphragm relax.
• Ribcage moves down and in and diaphragm curves.
  -Volume of the thorax decreases.
• Increases pressure in the lungs.
• Air is forced out of the lungs.
• Passive process no ATP needed.

Question 12

Explain forced expiration stages.

Answer 12

• Internal intercostal muscles contract too pulling the ribcage down and in further.

Question 13

What is a spirometer?

Answer 13

A machine that can be used to investigate breathing.

Question 14

What readings does the spirometer give?

Answer 14

• Tidal volume
• Vital capacity
•Breathing rate
• Oxygen uptake

Question 15

What gas exchange surface do fish have?

Answer 15

Gills

Question 16

Describe the structure of gills.

Answer 16

Gill is made of gill arch which supports it and then thin plates called gill filaments that provide a large surface area. The gill filaments are covered in tiny gill plates which further increase the surface area. Gill plates have lots of capillaries and thin layer of cells for efficient diffusion.

Question 17

Why do fish need gills?

Answer 17

As there’s a lower concentration of oxygen in water than in the air so they have adapted to this with gills.

Question 18

What is the counter current system and what does it maintain?

Answer 18

Where blood flows in one direction and water flows in the opposite direction across gill plates.
Maintains a steep concentration gradient so as much 02 as possible can diffuse into blood.

Question 19

How does ventilation in fish work describe the steps involved.

Answer 19

1. Fish opens mouth and this lowers floor of buccal cavity.
2. The volume of buccal cavity increased and this decreases the pressure.
3. Water is then sucked into cavity.
4. Fish closes mouth and floor of buccal cavity is raised and volume decreases.
5. Pressure inside buccal cavity increases and this forces the operculum (bony flap) open and water is forced out across gill filaments.

Question 20

How do insects ventilate?

Answer 20

By using rhythmic abdominal movements that change the volume of their bodies and move air in and out.

Question 21

What structure do insects have for ventilation?

Answer 21

Spiracles, Trachea, Tracheoles that contain fluid.