B8.1 - Gas Exchange

Question 1

what is gas exchange? definition

Answer 1

Gas exchange (in humans) is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs.

Question 2

what are the different structures in the gas exchange system?

Answer 2

Lungs 
Diaphragm 
Ribs 
Intercostal muscles 
Larynx
Trachea 
Bronchi 
Bronchioles 
Alveoli

Question 3

Lungs: location/ characteristics on a diagram and basic function

Answer 3

→ there are two lungs (right and left)

→ lungs transfer oxygen from the air into the bloodstream

Question 4

Diaphragm : location/ characteristics on a diagram and basic function

Answer 4

→ strip underneath the lungs

→ helps draw air in and out of the lungs

Question 5

Ribs : location/ characteristics on a diagram and basic function

Answer 5

→ surrounds the lungs
→ acts as a protective barrier
→ plays a vital role in ventilation (inhalation and exhalation)

Question 6

Intercostal muscles : location/ characteristics on a diagram and basic function

Answer 6

→ surrounds our lungs

→ helps move the ribs during breathing

Question 7

Larynx : location/ characteristics on a diagram and basic function

Answer 7

→ the top of the trachea

→ known as the voice box

Question 8

Trachea : location/ characteristics on a diagram and basic function

Answer 8

→ also known as windpipe, it is the tube which oxygen passes through to enter the lungs
→ it has cartilage rings used to support and strengthen the trachea

Question 9

Bronchi : location/ characteristics on a diagram and basic function

Answer 9

→ is the further branch of the trachea (split into two branches into the lungs)
→ located as the large branch inside of the lungs (tube for gases to continue to pass through)

Question 10

Bronchioles : location/ characteristics on a diagram and basic function

Answer 10

→ is the further division of the bronchi (smaller tubes)

→ further in the lungs carries gases in smaller tubes

Question 11

Alveoli : location/ characteristics on a diagram and basic function

Answer 11

→ air sacs at the end of the bronchioles
→ where gas exchange takes place
→ increase the surface area of the lungs
→ very thin wall so path for diffusion of gases is short
→ good blood supply around it
→ microscopic size
→ good ventilation (from the capillaries)

Question 12

What are the characteristics of gas exchange in the alveoli?

Answer 12

• large surface area
• thin surface (layer)
• good blood supply (surrounded by capillaries, diffusion of oxygen into blood and carbon dioxide diffusion out of capillaries into alveoli)
• good ventilation

Question 13

Capillaries : location/ characteristics on a diagram and basic function

Answer 13

→ on top of the alveoli (wrapped around)

→ helps gasses diffuse in and out of the bloodstream

Question 14

How is the rate of gas exchange increased?

Answer 14

→ widening of airways

→ increasing the amount of air being breathed in and out (exercise can have this affect)

Question 15

How is the rate of gas exchange decrease?

Answer 15

→ air sacs becoming larger and fewer
→ making too much mucus
(smoking and asthma can have this affect)

Question 16

Oxygen: How much is inhaled, How much is exhaled and what is the test?

Answer 16

inhaled: 21%
exhaled: 16% (need oxygen for respiration which is why we take in more and exhale less)
test: Splint glowing test

When a splint is lit and the fire stops, in oxygen gas the splint should relight. It will relight showing a glowing splint

Question 17

Carbon Dioxide : How much is inhaled, How much is exhaled and what is the test?

Answer 17

inhaled: 0.04% (toxic waste product)
exhaled: 4% (we breathe out more because it is not used in our body process and is a product)
test: Limewater test

In the presence of CO2, limewater will go cloudy - more will be explained later (u need to know this test)

Question 18

Water : How much is inhaled, How much is exhaled and what is the test?

Answer 18

inhaled: less
exhaled: more (because of respiration we produce water) (glucose + oxygen → carbon dioxide + water)
test: Cobalt chloride paper test

When it is dry the paper is blue but in the presence of water the paper will turn pink (test for water vapour)

Question 19

Nitrogen : How much is inhaled, How much is exhaled and what is the test?

Answer 19

inhaled: 78%
exhaled: 78% ( we don’t use nitrogen for any bodily processes)
test: n/a

Question 20

what is the limewater test for CO2?

Answer 20

→ When you exhale through a straw in lime water it will turn a cloudy/ milky white colour.
→ Limewater is an aqueous solution of calcium hydroxide dissolved in water.
→ In this experiment the gas in the test tube can be drawn through using a pipette
→ we can bubble the gas through the lime water and if the lime water turns cloudy. The gas is carbon dioxide.

Question 21

what way will air always move?

Answer 21

Air will always move from high pressure to low pressure

Question 22

how does thoracic volume impact air pressure?

Answer 22

→ when the thorax volume increases, it reduces the air pressure inside of the thorax, it is less than the atmospheric pressure, therefore, air travels inside the body
→ this is known as inhalation

→ when the thorax volume decreases, it increases the air pressure inside of the thorax, it is higher than the atmospheric pressure, therefore, air leaves the body
→ this is known as exhalation

Question 23

what happens during inhalation?

Answer 23

→ thoracic volume increases which reduces the air pressure inside of the thorax
→ the air pressure inside the thorax is less than the atmospheric pressure, therefore, air travels inside of the body
→ the increase in the thoracic volume is due to the contraction of external intercostal, this causes the ribs to move up and out
→ the diaphragm causes it’s dome shape to flatten.

Question 24

what happens during exhalation?

Answer 24

→ the thoracic volume decreases so the air pressure inside of the thorax increases
→ air pressure inside of the thorax is higher than the atmospheric pressure, therefore, air leaves the body.
→ the decrease in thoracic volume is due to the relaxation of the intercostal muscles which results in the ribcage moving down and in
→ the diaphragm relaxes returning to it’s dome like shape

Question 25

how does exercise impact the body (general)?

Answer 25

Exercise means that body cells will respire more rapidly. More carbon dioxide is produced as a result of respiration and there is an increase of carbon dioxide concentration in the blood which leads to an increase in blood acidity i.e decreased blood pH.

The brain detects the increased blood acidity and signal for the increase in breathing rate and depth to allow carbon dioixde to be excreted faster. It also of course allows oxygen to get to the respiring cells faster as well.

Question 26

how does exercise impact the depth of breathing?

Answer 26

→ The volume of air breathed in and out during breathing at rest is about 0.5 litres
→ The breathing rate is about 12 breaths per minute
→ During exercise, the volume inhaled increases to about 5 litres ( depending on the age, sex, size and fitness of the person)
→ The breathing rate can increase to over 20 breaths per minute
→ The total lung volume is greater than the vital capacity because some air always remains in the lungs (otherwise the lungs would collapse and the alveoli walls would stick together)

Question 27

how does exercise impact the breathing rate?

Answer 27

→ during exercise muscle cells respire more than they do when the body is at rest
→ the rate of breathing and the depth of breathing both increase
→ this is to make sure that more oxygen is absorbed into the blood and more carbon dioxide is removed from it.
→ an increase in heart rate and depth allows carbon dioxide to be excreted more rapidly and allows oxygen to get to the cells quicker

Question 28

what are the adaptations of alveoli?

Answer 28

→ large surface area- this allows more efficient diffusion
The alveoli allow the lungs to have a huge surface area
→ thin surface- this means that there is a short diffusion distance, thus exchange can occur more rapidly
→ good blood supply - maintains concentration gradient by carrying away substances which have diffused across already
→ good air ventilation- this means that waste gasses can diffuse out of the blood into the air in the lungs whilst oxygen diffuses into the blood
→ moist- allows gases to dissolve before diffusing across the membrane.

Question 29

what are the specialised cells in the gas exchange system?

Answer 29

goblet cells and ciliated cells

Question 30

what is the function of the goblet cell, where is it located etc?

Answer 30

→ lines the trachea
→ produce mucus
→ role of mucus: trap bacteria and dust particles and other pathogens

Question 31

what is the function of the ciliated cells, where is it located etc?

Answer 31

→ lines the trachea
→ has tiny microscopic hairs called cilia
→ role of the cilia: sweep the mucus upwards towards the back of the throat

Question 32

what happens to mucus once it reaches the back of the throat?

Answer 32

Once mucus is at the back of the throat it is then swallowed and the pathogens are destroyed in the acidic conditions of our stomach.

Question 33

how is the gas exchange system ruined or damaged?

Answer 33

smoking is an example of a process which will ruin the gas exchange system.

→ smoking tobacco can cause COPD (Chronic obstructive pulmonary disease), lung cancer and coronary heart disease.

Question 34

what are gases or substances which have a negative effect on the gas exchange system?

Answer 34

carbon monoxide, tar and nicotine

Question 35

what is the effect of carbon monoxide on the gas exchange system?

Answer 35

→ poisonous gas
→ combine with haemoglobin
→ prevents them from transporting oxygen

Question 36

what is the effect of tar on the gas exchange system?

Answer 36

→ Addictive

→ increases heart rate & blood pressure

Question 37

what is the effect of nicotine on the gas exchange system?

Answer 37

→ increases the risk of lung cancer
→ lines the air passages
→ increases mucus production
→ paralyses and damages cilia causing bronchitis