Exchange in lungs

Question 1

Why is the volume of oxygen and CO2 that has to be absorbed and removed in mammals large?

Answer 1

• They are relatively large organisms with a large volume of living cells
• They maintain a high body temperature which is due to them having high metabolic and respiratory rates

Question 2

What are lungs the site of?

Answer 2

Gas exchange

Question 3

What is one reason that lungs are located in the body due to their structure?

Answer 3

Air is not dense enough to support and protect these delicate structures

Question 4

What is another reason that lungs are located in the body due to the body’s needs?

Answer 4

The body as a whole would otherwise lose a great deal of water and dry out

Question 5

How are lungs supported and protected?

Answer 5

By the ribcage

Question 6

How can ribs be moved?

Answer 6

By the muscles between them

Question 7

What are lungs ventilated by?

Answer 7

A tidal stream of air, ensuring that the air within them is constantly replenished

Question 8

What kind of structures are lungs?

Answer 8

Lobed structures

Question 9

What are lungs made up of?

Answer 9

A series of highly branched tubules, bronchioles, which end in tiny air sacs called alveoli

Question 10

What is a trachea?

Answer 10

A flexible airway that is supported by rings of cartilage

Question 11

What does the cartilage do for the trachea?

Answer 11

Prevents the trachea collapsing as the air pressure inside falls when breathing in

Question 12

What are the tracheal walls made up of?

Answer 12

Muscle, lined with ciliated epithelium and goblet cells

Question 13

What are the bronchi?

Answer 13

2 divisions of the trachea, each leading to one lung

Question 14

How are bronchi similar in structure to the trachea (mucus)?

Answer 14

Also produce mucus to trap dirt particles and have cilia

Question 15

What do the cilia do in the bronchi?

Answer 15

Move dirt-laden mucus towards the throat

Question 16

How are larger bronchi supported?

Answer 16

Supported by cartilage

Question 17

What happens in terms of support as bronchi get smaller?

Answer 17

Amount of cartilage reduced

Question 18

What are bronchioles?

Answer 18

A series of branching subdivisions of bronchi

Question 19

What are the walls of bronchioles made of?

Answer 19

Muscle lined with epithelial cells

Question 20

What do the muscle walls of the bronchioles allow them to do?

Answer 20

Constrict so that they can control the flow of air in and out of the alveoli

Question 21

What are alveoli?

Answer 21

Minute air sacs at the end of the bronchioles

Question 22

What is the diameter of the alveoli?

Answer 22

Between 100 micrometer - 300 micrometer

Question 23

What is found between the alveoli?

Answer 23

Collagen and elastic fibres

Question 24

What do the elastic fibres allow the alveoli to do?

Answer 24

To stretch as they fill with air when breathing in

Question 25

What happens to alveoli when breathing out?

Answer 25

They spring back to their original shape in order to expel the CO2 rich air

Question 26

What are the alveoli lined with?

Answer 26

Epithelium

Question 27

What is the alveolar membrane?

Answer 27

The gas-exchange surface

Question 28

What is the equation for pulmonary ventilation rate?

Answer 28

Tidal wave x breathing rate = pulmonary ventilation rate

Question 29

How is the pressure change in the lungs brought about?

Answer 29

By the movement of 3 sets of muscles - Diaphragm - Intercostal muscles (there are internal and external)

Question 30

What is the diaphragm?

Answer 30

A sheet of muscle that separates the thorax from the the abdomen

Question 31

Where do the intercostal muscles lie?

Answer 31

Between the ribs

Question 32

What happens when the internal intercostal muscles contract?

Answer 32

Leads to expiration

Question 33

What happens when the external intercostal muscles contract?

Answer 33

Leads to inspiration

Question 34

What is the 1st step of inspiration?

Answer 34

The external intercostal muscles contract, while the internal relax

Question 35

What is the 2nd step of inspiration after (the external intercostal muscles contract)?

Answer 35

Ribs are pulled upwards and outwards, increasing volume of thorax

Question 36

What is the 3rd step of inspiration after (ribs are pulled upwards and outwards)?

Answer 36

Diaphragm muscles contract, causing it to flatten, which also increases volume of thorax

Question 37

What is the 4th step of inspiration after (diaphragm muscles contract)?

Answer 37

The increased volume of thorax results in reduction of pressure in the lungs

Question 38

What is the final step of inspiration?

Answer 38

Atmospheric pressure is now greater than pulmonary pressure so air is forced into lungs

Question 39

What is the 1st step of expiration?

Answer 39

Internal intercostal muscles contract, while external relax

Question 40

What is the 2nd step of expiration after (internal intercostal muscles contract)?

Answer 40

Ribs move downwards and inwards, decreasing thorax volume

Question 41

What is the 3rd step of expiration after (ribs move downwards and inwards)?

Answer 41

Diaphragm muscles relax so it is pushed up against contents of the abdomen that were compressed during inspiration Thorax volume further decreased

Question 42

What is the 4th step of expiration after (diaphragm muscles relax)?

Answer 42

Decreased thorax volume increases pressure in lungs

Question 43

What is the final step of expiration?

Answer 43

Pulmonary pressure is now greater than atmospheric, so air is forced out of lungs

Question 44

What is the main cause of air being forced out during normal, quiet breathing?

Answer 44

The recoil of the elastic tissue in the lungs

Question 45

When do the various muscles play a major part in breathing?

Answer 45

Under more strenuous conditions

Question 46

How many alveoli are there in each human lung and what is their total surface area?

Answer 46

Around 300 million and their total surface area is 70m^2

Question 47

What is each alveolus lined with?

Answer 47

Epithelial cells that are only 0.05 - 0.3 micrometers thick

Question 48

What surrounds each alveolus?

Answer 48

A network of pulmonary capillaries

Question 49

Are the pulmonary capillaries narrow?

Answer 49

Yes

Question 50

What do the red blood cells do given that the pulmonary capillaries are so narrow when exchanging gases with the alveoli?

Answer 50

They are flattened against the capillary walls in order to squeeze through

Question 51

How thin are the walls of the pulmonary capillaries?

Answer 51

One cell thick

Question 52

How does the movement of red blood cells cause diffusion of gases between alveoli and the blood to be very rapid?

Answer 52

As the pulmonary capillaries are very narrow, red blood cells are slowed as they pass though them, allowing more time for diffusion

Question 53

What is also caused by the fact that red blood cells are flattened against the capillary walls in terms of diffusion?

Answer 53

The distance between the alveolar air and the red blood cells is reduced

Question 54

Why is the distance for diffusion very short in the lungs?

Answer 54

Walls of both alveoli and capillaries are very thin

Question 55

What is the total surface area of alveoli and pulmonary capillaries like?

Answer 55

Each one has a very large surface area

Question 56

How do breathing movements and heart action cause diffusion of gases between alveoli and the blood to be very rapid?

Answer 56

- Breathing movements constantly ventilate the lungs - Heart action constantly circulates the blood around the alveoli - Together, these ensure that a steep concentration gradient of the gases to be exchanged is maintained

Question 57

What does blood flow through pulmonary capillaries maintain?

Answer 57

A concentration gradient

Question 58

What does COPD stand for?

Answer 58

Chronic obstructive pulmonary disease

Question 59

What does COPD include?

Answer 59

Emphysema and chronic bronchitis

Question 60

What are the risk factors for COPD?

Answer 60

- Smoking - Air pollution, especially in heavy industry - Genetic make-up - Infections - Occupation (e.g. working with harmful chemicals)