Exchange surface and breathing 3.1

Question 1

factors affecting need for a exchange system?

Answer 1

• Size
• surface area to volume ratio
• level of activity

Question 2

Features of a good exchange system?

Answer 2

• Large surface area
• thin to reduce diffusion distance
• good blood supply for steep concentration gradient between supply side and demand side

Question 3

Lungs as an example of good exchange system

Answer 3

• large surface area due to lots of small alveoli and a thin layer of moisture to reduce cohesion of water so alveoli don’t collapse
• alveoli and capillary walls are permeable to oxygen and carbon dioxide
• thin barrier
  
  • alveoli and capillary wall are one cell thick
  • squamous cells
  • capillaries close to alveolus walls
  • capillaries are narrow meaning red blood cells are squeezed close to the wall
• goof blood supply and concentration gradient of CO2 and O2

Question 4

What’s the concentration gradient between alveoli and capillaries like?

Answer 4

High carbon dioxide concentration and low oxygen concentration in the capillaries
Low carbon dioxide and high oxygen concentration in the alveoli

Question 5

Inspiration

Answer 5

1. diaphragm contracts moving down
2. external intercostal contract to raise the ribs
3. volume of chest cavity increases
4. pressure in chest cavity drops below atmospheric pressure
5. air moves into the lungs

Question 6

Expiration

Answer 6

1. diaphragm relaxes and pushed up
2. external intercostal relax and ribs fall
3. volume of the chest cavity decreased
4. pressure in lungs increases and rises above atmospheric pressure
5. air is moved out of the lungs

Question 7

What property helps alveoli in inspiration and expiration?

Answer 7

Alveoli have elastic fibres that can stretch in inspiration and recoil in expiration

Question 8

What does mucus do?

Answer 8

Mucus traps pathogens

Question 9

How are the trachea and bronchi airways supported?

Answer 9

The airways have rings of cartilage to prevent collapse during inspiration

Question 10

What is the cartilage like in the trachea?

Answer 10

The rings of cartilage in the trachea are C shaped giving them flexibility and space for food to pass down the oesophagus

Question 11

Cartilage in the bronchioles?

Answer 11

No cartilage in the bronchioles but have walls of smooth muscle and elastic fibres

Question 12

What are the airways lined with?

Answer 12

Airways are lined with a ciliated epithelium

Question 13

Discuss smooth muscle and elastic fibres

Answer 13

Smooth muscle can contract, constricting the airways, making their lumen narrower and restricting air flow to the alveoli.
The smooth muscle cannot reverse its won contraction
Smooth muscle is elongated by elastic fibres which recoil after being deformed in contraction of the muscle . This dilates the airways

Question 14

Why might you need the airways to narrow the lumen?

Answer 14

You may need to constrict the airways if there are harmful substances in the air

Question 15

3 lung volumes

Answer 15

• vital capacity is the max volume of air that can be moved by the lungs in one breath (taking a deep breath and expiring as much as possible)
• residual volume is the amount left in the lungs after forced expiration
• tidal volume is the volume moved in and out with each breath at rest

Question 16

Measuring lung volumes

Answer 16

Use a spirometer
In inspiration air is drawn in from the chamber so the lid moves down and air moves the lid back up in expiration and the movements are recorded on a data logger to make a trace

Question 17

Precautions with spirometers

Answer 17

• subject healthy free from asthma
• soda lime fresh and functioning
• no air leaks
• sterilise mouth piece
• water chamber not overfilled
• medical grade oxygen

Question 18

Measure breathing rate

Answer 18

breathing rate can be seen by counting the number of peaks from a spirometer trace

Question 19

Calculating oxygen uptake

Answer 19

1. draw line from point a to the y axis and a line from point b to the y axis
2. find difference in time of the points along the x axis
3. divide the difference in volume by the difference in time
4. units are dm power of 3 s to power -1

Question 20

What do we assume about carbon dioxide, oxygen and soda lime

Answer 20

we assume the volume of carbon dioxide released and absorbed by he soda lime equals the volume of oxygen absorbed by the blood

Question 21

Structure of fish ventilation system

Answer 21

• gill arch
• gills covered by operculum
• opercular cavity
• each gill has two rows of gill filaments
• filaments have a folded surface of secondary lamellae
• buccal cavity

Question 22

Counter current flow in fish

Answer 22

Blood flows along the gill arch an out along the gill filaments to the secondary lamellae
Blood then flows in the capillaries in the opposite direction of the water lowing over the lamellae .
This enables maximum absorption of oxygen from the water

Question 23

Describe ventilation in bony fish

Answer 23

Floor of buccal cavity moves down drawing water into the buccal cavity. the mouth closes and the floor raises again pushing the eater through the gills .
As water is pushed from the buccal cavity the operculum moves outwards, reducing pressure in the opercular cavity helping water flow through the gills

Question 24

Describe structure of insects gaseous exchange system

Answer 24

Insects have an air filled tracheal system which supplies respiring tissues directly with air

1. air enters through a spiracle (pore in each segment)
2. Air is transported around through tracheae which divide further into tracheoles.
3. ends of tracheoles are folded with tracheal fluid and are open.
4. gaseous exchange occurs between air in tracheole and the tracheal fluid

Question 25

Discuss tracheal fluid movement and oxygen supply

Answer 25

-When insects are active tracheal fluid will be withdrawn into the body to increase surface area of tracheole wall exposed to air so more oxygen is absorbed

Question 26

3 ways insects ventilate their bodies

Answer 26

• movements of the wings alter volume in the thorax, smaller volume means air gets pushed out of the tracheae
• sections if the tracheal system are expanded and have flexible walls acting as air sacs which can be squeezed by the action of flight muscles
• locusts alter volume of abdomen by specialised breathing movements coordinate with opening and closing the valves in spiracles. As abdomen expands air enters tracheal system as spiracles at front end of . body open. Abdomen reduced the spiracles at the rear end open allowing the air to leave