Human gas exchange system

Question 1

What do all aerobic organisms require?

Answer 1

A constant supply of oxygen

Question 2

Why is CO2 removed from the body?

Answer 2

Build up of CO2 can be harmful to the body

Question 3

Why is the volume of O2 needed to be absorbed and the volume of CO2 needed to be removed so large for mammals? (2 points)

Answer 3

• large number of living cells
• maintain a high metabolic and respiratory rate

Question 4

What have mammals evolved to have because of their need for high volumes of O2?

Answer 4

Lungs

Question 5

Why are mammalian lungs located inside the body? (2 points)

Answer 5

• air is not dense enough to support and protect its delicate structure
• the body would lose a lot of water and dry out

Question 6

What are lungs supported and protected by?

Answer 6

The ribcage

Question 7

How can the ribs be moved?

Answer 7

By the intercostal muscles between them

Question 8

What is the structure of the lungs?

Answer 8

A pair of lobed structures made up of a series of highly branched bronchioles, which end in tiny air sacs called alveoli

Question 9

What is the trachea?

Answer 9

A flexible airway that is supported by rings of cartilage

Question 10

What is the function of the rings of cartilage in the trachea?

Answer 10

They prevent the trachea from collapsing as the air pressure inside the lungs falls when breathing in

Question 11

What are the tracheal walls made up of and lined with?

Answer 11

Made up of muscle. Lined with ciliated epithelial cells and goblet cells

Question 12

What are goblet cells?

Answer 12

Specialised epithelial cells that secrete mucus

Question 13

How is the structure of the bronchi related to the trachea?

Answer 13

They are the 2 divisions of the trachea, leading to one lung each
They are also supported with cartilage, but have less and less cartilage as they get smaller

Question 14

How is the function of the bronchi similar to the function of the trachea?

Answer 14

Are also lined with epithelial cells with goblet cells that produce mucus

Question 15

What are the bronchioles?

Answer 15

A series of branching subdivisions of the bronchi.

Question 16

What are the walls of the bronchioles made out of? What does this allow them to do?

Answer 16

Made out of muscle.
This allows them to constrict so they can control the flow of air in and out of the alveoli

Question 17

What are alveoli?

Answer 17

Tiny air sacs

Question 18

Where are alveoli found?

Answer 18

At the end of the bronchioles

Question 19

What are between the alveoli?

Answer 19

Collagen and elastic fibres

Question 20

What do the elastic fibres between alveoli allow them to do?

Answer 20

Allows the alveoli to stretch as they fill with air. They then spring back during breathing out to expel the carbon rich air

Question 21

What is the alveolar membrane known as?

Answer 21

The gas-exchange surface of the human gas-exchange system

Question 22

What is the process of air constantly moving in and out of the lungs?

Answer 22

Breathing or ventilation

Question 23

When the air pressure of the atmosphere is higher than the air pressure inside the lungs, so air moves in. What is this process called?

Answer 23

Inspiration

Question 24

When the air pressure in the lungs is greater than that of the atmosphere, air is forced out of the lungs. What is this process called?

Answer 24

Expiration

Question 25

Which three sets of muscles are used to change the pressure within the lungs?

Answer 25

- The **diaphragm** - The **internal** intercostals - The **external** intercostals

Question 26

Is inspiration an active or passive process?

Answer 26

Active

Question 27

What is the process of inspiration? (5 steps)

Answer 27

- External intercostals **contract**, whilst the internal intercostals **relax** - The ribs are pulled **upwards and outwards**, increasing the volume in the thorax - The diaphragm muscles **contract**, causing it to flatten, which also increases the volume - This reduces the **pressure** in the lungs - Therefore air is forced **into** the lungs

Question 28

Is expiration an active or passive process?

Answer 28

A largely passive process

Question 29

What is the process of expiration? (5 steps)

Answer 29

- External intercostals **relax**, whilst the internal intercostals**contract** - The ribs move **downwards and inwards**, decreasing the volume - The diaphragm muscles **relax** so it is pushed up by the abdomen, further decreasing the volume - The decreased volume in the lungs **increases** the pressure - Air is forced **out** of the lungs

Question 30

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

Answer 30

The recoil of elastic tissue in the lungs

Question 31

What is the site of gas exchange in mammals?

Answer 31

The **epithelium** of the alveoli

Question 32

What must be maintained to ensure a constant supply of oxygen to the body?

Answer 32

A diffusion gradient at the alveolar surface

Question 33

What must the gas exchange surface be to enable efficient transfer of materials? (3 points)

Answer 33

- Thin so short diffusion pathway - Partially permeable - Large surface area

Question 34

What must be maintained at the gas exchange surface to maintain a diffusion gradient?

Answer 34

Movement of both the **environmental** medium (eg. air) and the **internal** medium (eg. blood)

Question 35

What is around each alveolus?

Answer 35

A network of pulmonary capillaries

Question 36

How thin is the lumen of the pulmonary capillaries?

Answer 36

So narrow that red blood cells are flattened against the capillary walls in order to squeeze through

Question 37

Why is the diffusion of gases between the alveoli and the blood very rapid?

Answer 37

- Red blood cells are slowed through pulmonary capillaries, so more time for diffusion - There is a short distance between the alveolar air and the red blood cell - The alveoli and pulmonary capillaries have a very large surface area - Breathing constantly ventilates the lungs, maintaining a steep concentration gradient - Blood flow through the pulmonary capillaries maintains a concentration gradient