Exchange surfaces

Question 1

Why do multicellular organisms require speacalised gas exchange surfaces?

Answer 1

Their smaller SA:V ratio means the distance needing to be crossed is larger and substances can’t easily enter the cells as in a single-celled organism

Question 2

How is SA to V ratio calculated?

Answer 2

surface area ÷ volume

Question 3

Name 3 features of an efficient gas exchange system?

Answer 3

• large surface area
• thin/short diffusion pathway
• steep concentration gradient (good blood supply)

Question 4

Describe the structure trachea?

Answer 4

• wide tube supported by c shaped cartilage to keep air passage open during pressure change
• lined by ciliated epithelium cells moving mucus created by goblet cells towards the throat

Question 5

What is the function of the trachea?

Answer 5

carries air to bronchi

Question 6

Describe the structure of the bronchi?

Answer 6

• supported by rings of cartilage
• lined by ciliated epithelium cells and goblet cells
• narrower than trachea and branch of into 2

Question 7

Describe then function of the bronchi?

Answer 7

allow passage of air into the bronchioles

Question 8

Describe the structure of the bronchioles?

Answer 8

• narrower than bronchi
• mostly made up of smooth muscle and elastic fibres (can contract and relax during ventilation)

Question 9

Describe the function of bronchioles?

Answer 9

allow passage of air into alveoli

Question 10

Describe the structure of the alveoli?

Answer 10

• mini air sacs lined with epithelium cells (site of gas exchange)
• 1 cell thick walls covered with a capillary network

Question 11

Describe the function of the alveoli?

Answer 11

facilitate gas exchange

Question 12

Explain the process of inspiration in the lungs?

Answer 12

• external intercostal muscles contract (internal relax)
• the ribs are pulled up and out
• diaphragm contracts and flattens
• volume of the thorax increases and pressure decreases
• air pressure outside the lungs is higher meaning air moves into the lungs

Question 13

Explain the process of expiration in the lungs?

Answer 13

• internal intercostal muscles contract (external relax)
• the ribs move down and in
• diaphragm relaxes and domes
• volume of the thorax decreases (pressure increases)
• air pressure inside the lungs is higher meaning air moves out the lungs

Question 14

Explain how a spirometer works?

Answer 14

Measures lung volume when a person breathes into a air tight chamber leaving a trace on a graph which shows the volume of the breaths

Question 15

Define vital capacity?

Answer 15

Maximum volume of air that can be taken in or expelled from the lungs in one breathe

Question 16

Define tidal volume?

Answer 16

Volume of air we breathe in and out during each breathe

Question 17

Define breathing rate?

Answer 17

Number of breathes taking per minute

Question 18

How can vital capacity, tidal volume and breathing rate be calculated by using a spirometer?

Answer 18

vital capacity = calculated by finding the maximum amplitude

tidal volume = by finding the amplitude at rest

breathing rate = counting the number of peaks in 1 minute

Question 19

Describe the gills in the fish’s gas transport system?

Answer 19

supported by arches along which are multiple projections of gill filaments (stacked up in piles)

Question 20

Describe the lamelle in the fish’s gas transport system?

Answer 20

• at a right angle to the gill filaments
• increase surface area
• blood and water flow across them in opposite directions (countercurrent)

Question 21

Explain the process of gas exchange in fish?

Answer 21

• buccal cavity volume increases enabling water to flow in (reduced to increase pressure)
• water is pumped over the lamellae by the operculum (O2 diffuses into the blood stream)
• waste CO2 diffuses into the water and flows back out of the gills

Question 22

How does the countercurrent exchange system maximise oxygen absorbed by the fish?

Answer 22

• maintains a steep conc gradient as water is always next to blood of a lower O2 conc
• keeps diffusion rate constant enabling oxygen absorbtion