Human Gas Exchange and Breathing

Question 1

Why are the trachea strengthened with cartilidge?

Answer 1

To provide structural support and prevent it from collapsing.

Question 2

What is the purpose of the lungs?

Answer 2

To bring a large amount of O2 into the body and remove waste products such as CO2.

Question 3

How can metabolic rates be controlled using the lungs?

Answer 3

Respiration is exothermic so heat is released. Higher respiratory rates leads to higher metabolism.

Question 4

Why are mammalian lungs found inside the body?

Answer 4

Because air is not dense enough to protect the delicate structures.
They would also dry out if in air.

Question 5

What is the purpose of the ribcage?

Answer 5

To protect the lungs.

Question 6

What is the maximum volume of air that cab be stored in the lungs called?

Answer 6

Tidal volume

Question 7

What cells are the trachea lined with and why?

Answer 7

Ciliated epithelial cells and goblet cells. This is to produce mucus and waft it out of the lungs.

Question 8

What does the trachea divide into?

Answer 8

Bronchi, bronchioles and then alveoli

Question 9

What are alveoli?

Answer 9

Small air sacs at the end of the bronchioles which are the site of gas exchange

Question 10

Why is collagen present in the alveoli?

Answer 10

The allow them to stretch and recoil.

Question 11

What are the benefits of the alveoli being surrounded by a dense capillary network?
How do red blood cells try to decrease this distance further?

Answer 11

Capillaries are 1 cell thick and pressed directly against the alveoli, giving a short diffusion distance.
Red blood cells push against capillary walls to decrease the distance further.

Question 12

What are the benefits of the alveoli having a large SA?

Answer 12

Maximum area available for diffusion

Question 13

What are the benefits of the lungs being well ventilated?

Answer 13

Ensures there is a constant airflow of gases, helping to maintain concentration gradients.

Question 14

How are concentration gradients maintained in the lungs/body?

Answer 14

The heart pumps blood around the body so no single area of blood becomes too concentrated with gases. This also means oxygen can be delivered elsewhere in the body.
Constant ventilation means that CO2 is always removed from the body.

Question 15

Why does the bronchi contain muscle?

Answer 15

Allows them to stretch.

Question 16

What do the alveoli not have that does not prevent them from collapsing?

Answer 16

Alveoli are not reinforced with cartilage.

Question 17

What is lung surfactant?

Answer 17

A phospholipid that coats the surface of the lungs to prevent them from drying out.

Question 18

Describe the mechanism of gas exchange.

Answer 18

Oxygen diffuses from the alveoli into red blood cells which are in the capillaries.
CO2 diffuses out of the blood, back into the alveoli to be exhaled.

Question 19

What is ventilation?

Answer 19

Movement of gases in and out of the lungs.

Question 20

What is inspiration?

Answer 20

When air is forced into the lungs

Question 21

What is expiration?

Answer 21

Air is forced out of the lungs

Question 22

What part of the chest enables it to change shape?

Answer 22

Intercostal muscles

Question 23

What is the diaphragm?

Answer 23

A thin sheet of muscle that separates the abdomen and thorax.

Question 24

Does contraction of the internal intercostal muscles leads to inspiration or expiration?

Answer 24

Expiration

Question 25

Does contraction of the external intercostal muscles leads to inspiration or expiration?

Answer 25

Inspiration

Question 26

1. Inspiration
   Which intercostal muscles contract and relax?

Answer 26

Internal ICM - Relax
External ICM - Contract

Question 27

2. Inspiration
   Where do the ribs move?

Answer 27

Upwards and outwards

Question 28

3. Inspiration
   How does the volume of the thorax change?

Answer 28

Increases

Question 29

4. Inspiration
   Does the diaphragm contract or relax? What shape does it change to and how does this change the volume of the thorax further?

Answer 29

Diaphragm contracts
It flattens which increases the volume of the thorax further.

Question 30

5. Inspiration
   How does pressure change in the lungs as a result of increased thorax volume?

Answer 30

Pressure drops in the lungs

Question 31

6. Inspiration
   How does atmospheric pressure compare to lung pressure now?
   What happens to air from the atmosphere as a result of this?

Answer 31

Atmospheric pressure greater than lung pressure.
This means that air is forced into the lungs.

Question 32

1. Expiration
   Which ICM contract and which relax?

Answer 32

Internal ICM contract
External ICM relax

Question 33

2. Expiration
   Where do ribs move from/to and how does this change the volume of the thorax?

Answer 33

Ribs move down and inwards.
This decreases the volume of the thorax.

Question 34

3. Expiration
   Does the diaphragm contract or relax and how does this change the shape of it? How does this affect the volume of the thorax?

Answer 34

Diaphragm relaxes, so it curves and pushes up against the lungs, decreasing volume of the thorax further.

Question 35

4. Expiration
   How does lung pressure compare to atmospheric pressure?
   What happens to air?

Answer 35

Lung pressure now greater than atmospheric pressure so air is forced out of the lungs.