Gas exchange (humans)

Question 1

Describe the structure of the thorax.

Answer 1

The thorax includes the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli, and pleural membranes

Question 2

What is the function of the ribcage?

Answer 2

The ribcage protects internal organs, such as the lungs.

Question 3

What are intercostal muscles, and what is their function?

Answer 3

Intercostal muscles are muscles between the ribs that control their movement, aiding in inhalation and exhalation

Question 4

Explain the role of the diaphragm in ventilation

Answer 4

The diaphragm is a muscular dome at the bottom of the thorax that changes pressure to control inhalation and exhalation

Question 5

What is the trachea, and what is its function?

Answer 5

The trachea, or windpipe, is where air enters the thorax and flows to the lungs.

Question 6

Describe the structure and function of bronchi

Answer 6

Bronchi are large tubes branching off the trachea, with one bronchus for each lung, to carry air to the lungs

Question 7

What are bronchioles, and how are they related to the alveoli?

Answer 7

Bronchioles are smaller tubes formed by the splitting of bronchi in the lungs, connected to the alveoli

Question 8

Explain the structure and function of alveoli

Answer 8

Alveoli are tiny air sacs where gas exchange takes place

Question 9

What is the pleural cavity, and what is its function?

Answer 9

The pleural cavity is found on the outside of the lungs and inside of the chest cavity, lubricating the lungs to reduce friction during breathing.

Question 10

Describe the features of the lungs that make gas exchange efficient.

Answer 10

• Large surface area
• Only one cell thick
• Excellent blood supply/large capillary network

Question 11

Explain what happens in the lungs for the process of inhalation to occur

Answer 11

• Intercostal muscles contract
• Ribs move up and out
• Diaphragm contracts/flattens
• The volume inside the thorax increases
• Pressure decreases
• Air drawn in

Question 12

Adaptations to the lungs for efficient gas exchange include:

Answer 12

• Many alveoli = increased surface area
• Many capillaries = increase surface area
• Constant ventilation and blood flow = maintaining the concentration gradient
• Thin walls – only 1 cell thick = shorter distance for diffusion = faster diffusion
• Moist – to allow faster diffusion

Question 13

How is the alveoli adapted for gas exchange?

Answer 13

• Once cell thick - short diffusion distance
• Large SA - more diffusion can occur through cauliflower-like shape
• Network of capillaries to maintain concentration gradient in blood
• Moist lining on the alveolar walls - for faster diffusion of gases
• Good ventilation through constant breathing - maintains concentration gradient in lungs

Question 14

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. (5)

Answer 14

• many alveoli walls folded to provide a large SA
• Many capillaries provide a large SA
• leading to fast diffusion
• ventilation maintaining a concentration gradient leading to fast diffusion

Question 15

Using ideas about diffusion explain how oxygen gets to our cells

Answer 15

● Oxygen in the air enters our blood via diffusion through capillaries around the alveoli

● This is because the concentration of oxygen in the blood is lower than the concentration of oxygen in the air/lungs

● Oxygen is transported around the body in the blood

● Capillaries carry blood to our cells

● Oxygen passes out of the blood across the wall of the capillary into the cells via diffusion

● This happens because the concentration of oxygen in the blood is higher than the concentration of oxygen in the cells

● Diffusion across the walls of capillaries can happen because they are very thin

Question 16

What is the role of the intercostal muscles and the diaphragm in ventilation?

Answer 16

• The intercostal muscles and diaphragm help in the process of breathing.
• During inhalation, the intercostal muscles contract, and the diaphragm contracts downwards. During exhalation, they relax.

Question 17

How does the ribcage change during inhalation and exhalation?

Answer 17

During inhalation, the ribcage moves up and out. During exhalation, it moves down and in.

Question 18

How does smoking affect chronic bronchitis?

Answer 18

Smoking damages the cilia and irritates the lining of the bronchi, leading to more mucus production and a smoker’s cough.

Question 19

Describe the effects of smoking on emphysema

Answer 19

Smoking damages the alveoli walls, reducing the surface area for gas exchange and making it difficult to carry out basic tasks due to a lack of oxygen

Question 20

How does smoking affect the circulatory system?

Answer 20

Smoking damages the circulatory system by:

• increasing the risk of coronary heart disease.
• It also makes blood cells more sticky and narrows blood vessels, increasing the likelihood of clots

Question 21

Oxygen is absorbed through the alveoli in the lungs. How are the alveoli adapted for this function?

Answer 21

• Alveoli have moist lining on alveolar walls for quick diffusion of gases.
• Alveoli are thin for short diffusion distance.

Question 22

Give one function of the ribs

Answer 22

To help breathing

Question 23

Explain the role of the diaphragm when a person breathes out.

Answer 23

• Diaphragm relaxes into a dome-shape
• whilst thorax volume decreases and thorax air pressure increases

Question 24

Give two adaptations of the lungs that help the rapid absorption of oxygen into the blood

Answer 24

• Lots of Alveoli provide a large surface area
• Moist lining on the alveolar walls for faster diffusion of gases

Question 25

Describe briefly how the student could use the same apparatus to do the investigation.

Answer 25

• let a student play a sport for 30 minutes and let him breathe 3 different times into the apparatus and record readings, taking the average of each.
• Let another student who remains still and doesn’t play sports do the same and take the average of each.
• Compare both averages to see which student breathed in a larger volume of air.

Question 26

Describe one feature of the axolotl’s gills that increases the rate of diffusion of oxygen.

Answer 26

Feature: Has lots of gills

Description: Providing a larger surface area