Exchange surfaces and breathing

Question 1

Why are exchange surfaces necessary and what are three factors affecting need?

Answer 1

supply nutrients and remove waste, large organisms need exchange surfaces for more and efficient exchange

Question 2

What are three factors affecting need for exchange surfaces?

Answer 2

sa:v ratio - cant supply enough nutrients from surface alone, diffusion pathway too far
level of activity - higher level requires more energy and oxygen
size - small animals diffusion through the surface can supply the whole body

Question 3

Features of a good exchange surface (3)

Answer 3

Large surface area for more space for diffusion
Thin barrier which reduces diffusion distance
A good blood supply to maintain concentration gradient

Question 4

Describe the pathway of air into the lungs

Answer 4

Through nose, along trachea, bronchi and bronchioles to the alveoli

Question 5

What muscles/tissues protect and ventilate the lungs?

Answer 5

protected by ribcage, which is held together by intercostal muscles, and the diaphragm helps produce breathing movements

Question 6

Describe gas exchange in the lungs

Answer 6

in the alveoli, oxygen passes into the blood and carbon dioxide diffuses out of blood into alveoli to be exhaled

Question 7

State and explain the adaptations of the lungs for gas exchange (6)

Answer 7

Millions of alveoli give surface area
surfactant which counters cohesive forces preventing collapse and dissolves gases
Barrier permeable to carbon dioxide and oxygen
Diffusion distance reduced, capillary close to alveoli, rbcs squeeze through capillary, both have one cell thick walls which are squamous (flattened)
Good blood supply to maintain concentration gradient
Well ventilated maintaining concentration gradient

Question 8

What is the role of the layer of surfactant in the alveoli?

Answer 8

counters cohesive forces preventing collapse, dissolves gases

Question 9

How is the diffusion distance reduced in the alveoli?

Answer 9

capillaries close to alveoli, rbcs squeezed through capillary, walls one cell thick and squamous

Question 10

How is the concentration gradient maintained in the alveoli?

Answer 10

good blood supply, always deoxygenated blood, good ventilation

Question 11

Describe the process of inspiration (5)

Answer 11

inhaling -
diaphragm contracts, lowers and flattens, displacing digestive organs;
external intercostal muscles contract raising ribs;
volume of chest cavity increases;
pressure drops below atmospheric pressure;
air moves into lungs

Question 12

Describe the process of expiration

Answer 12

exhaling -
diaphragm relaxes, digestive organs push up;
external intercostal muscles relax and ribs move down;
volume of chest cavity decreases;
pressure rises to above atmospheric levels;
air moves out of lungs;
internal intercostal muscles contract during exercise/coughing/sneezing to push air out

Question 13

Describe the tissues in the lungs

Answer 13

alveoli comprised of squamous epithelium, surrounded by blood capillaries, walls contain elastic fibres, stretch during inspiration and recoil to help push air out during expiration

Question 14

What is the role of elastic fibres in the alveoli?

Answer 14

stretch during inspiration and recoil to push out air during expiration

Question 15

Describe the role of ciliated epithelium and goblet cells

Answer 15

line airways, goblet cells release mucus, traps pathogens, cilia wafts mucus to top of airway where swallowed and pathogen killed

Question 16

Three requirements of the airways

Answer 16

large enough for sufficient air flow;
supported to prevent collapse
flexible to allow movement

Question 18

Structure of trachea and bronchi

Answer 18

similar but bronchi narrower;
contain rings of c-shaped cartilage, allows flexibility and room for food to pass down the oesophagus

Question 19

Structure of the bronchioles

Answer 19

Much thinner, some cartilage but mostly smooth muscle and elastic fibres

Question 20

Role of smooth muscle and elastic fibres in the airways

Answer 20

smooth muscles can contract to restrict air flow, can be important when harmful substances in the air, elastic fibres recoil, dilating the airway

Question 21

When would airways be constricted?

Answer 21

when harmful substance in air, during allergic reaction, during asthma attack

Question 22

What is a spirometer and how is this used?

Answer 22

float chamber on top of water trough, moves up/down as person breathes, soda lime absorbs carbon dioxide and vol. of air slowly falls

Question 23

What does a spirometer measure?

Answer 23

lung volume

Question 24

Precautions for using a spirometer (5)

Answer 24

Subject healthy and asthma free;
soda lime fresh;
no air leaks for accurate results;
mouthpiece sterilised;
water chamber not overfilled

Question 25

What is soda lime?

Answer 25

absorbs carbon dioxide in spirometer

Question 26

What is the vital capacity of the lungs?

Answer 26

max. volume of air that can be moved by lungs in deepest possible breath

Question 27

What factors affect the vital capacity of the lungs?

Answer 27

size, age, gender, exercise level

Question 28

What is the residual volume?

Answer 28

Volume of air always remaining in the lungs

Question 29

What is the usual residual volume of lungs?

Answer 29

around 1.5dm^3

Question 30

What is the tidal volume?

Answer 30

Volume of air moved in and out with each breath at rest

Question 31

What is the typical tidal volume of the lungs?

Answer 31

0.5dm^3

Question 32

Calculating oxygen uptake from spirometer trace

Answer 32

Gradient of decline is rate of oxygen uptake, as carbon dioxide is absorbed by the soda lime, so decrease in volume of air proportional to oxygen intake

Question 33

Calculating breathing rate from a spirometer trace

Answer 33

count number of peaks (breaths) in a minute on spirometer trace. Usually about 12-14 breaths.

Question 34

Increased oxygen uptake is caused by… (2)

Answer 34

increased breathing rate
deeper breaths

Question 35

Describe gas exchange in fish

Answer 35

exchange dissolved oxygen in water with carbon dioxide, occurs in gills
oxygen concentration in water typically far less than in air

Question 36

Describe the structure of the gills

Answer 36

gill filaments protrude from gill arc, secondary lamellae increase surface area, covered by plate called operculum

Question 37

Name some adaptations of fish for gas exchange

Answer 37

Large SA of gills, rows filaments and secondary lamellae
Blood capillaries run close to surface of gill plates
Counter current flow
Ventilation by buccal-opercular pump

Question 38

What is countercurrent flow?

Answer 38

blood flows through the lamellae in the opposite direction to water flowing over lamellae,
maintains concentration gradient and absorbs max. amount of oxygen all the way across the gills

Question 39

How are fish ventilated? (4)

Answer 39

buccal-opercular pump;
floor of mouth move down, increase volume/reduce pressure in buccal cavity;
water moves in and mouth closes, floor raising pushing water through gills;
operculum opens when water pushed through;
reduces pressure in opercular cavity and helps water flow through gills

Question 40

What is the buccal-opercular pump?

Answer 40

ventilates fish, causes water flow over the gills

Question 41

Transport of oxygen in insects (3)

Answer 41

open circulatory system;
body fluid acts as tissue fluid and blood;
circulation slow and affected by body movements

Question 42

Ventilation and gas exchange in insects (2)

Answer 42

Air enters through spiracles, travels down trachea and tracheoles
gas exchange occurs with tracheal fluid and walls at ends of tracheoles, oxygen dissolves

Question 43

Three ways insects are ventilated by body movements

Answer 43

• Air sacs in tracheal walls squeezed by flight muscles, pumps air through airways
• Movements of wings alter volume of the thorax
• Alter volume of abdomen by breathing movements coordinated with spiracle valve

Question 44

How do breathing movements help ventilate insects?

Answer 44

coordinate with spiracle valves, alter volume of abdomen, expands as valves at front body open, reduces volume as valves at back of body close

Question 45

How do flight muscles help ventilate insects?

Answer 45

air sacs in squeeze tracheal walls, pumps air through airways

Question 46

How do wing movements increase ventilation in insects?

Answer 46

volume of thorax decreases and increases, pumping air out and in

Question 47

When insects are active, what happens to increase absorption of oxygen?

Answer 47

tracheal fluid retracts to increase SA of tracheal wall exposed to air, more oxygen can be absorbed