Gas Exchange

Question 1

What is the gas exchange surface in humans?

Answer 1

The lungs.

Question 2

What are the ribs?

Answer 2

Bone structure that protects internal organs such as the lungs.

Question 3

What are the intercostal muscles?

Answer 3

Muscles between the ribs which control their movement causing inhalation and exhalation.

Question 4

What is the diaphragm?

Answer 4

Sheet of connective tissue and muscle at the bottom of the thorax that helps change the volume of the thorax to allow inhalation and exhalation

Question 5

What is the trachea?

Answer 5

Windpipe that connects the mouth and nose to the lungs.

Question 6

What are the bronchi?

Answer 6

Large tubes branching off the trachea with one bronchus (singular) for each lung.

Question 7

What are the bronchioles?

Answer 7

Bronchi split to form smaller tubes called bronchioles in the Lungs connected to alveoli.

Question 8

What are the alveoli?

Answer 8

Tiny air sacs where gas exchange takes place.

Question 9

What is pleural cavity?

Answer 9

The fluid filled space between the pleural membranes which reduces friction and allows the lungs to move freely

Question 10

What are the passages down to the lungs lined with?

Answer 10

Lined with ciliated epithelial cells.

Question 11

What are the cilia cells?

Answer 11

Cilia cells have tiny hairs on the end of them that beat and push mucus up the passages towards the nose and throat where it can be removed

Question 12

What does mucus do?

Answer 12

The mucus traps particles, pathogens like bacteria or viruses, and dust and prevents them from getting into the lungs and damaging the cells there.

Question 13

What happens in the body during inhalation?

Answer 13

• The diaphragm contracts and flattens
• The external set of intercostal muscles contract to pull the ribs up and out.
• This increases the volume of the thorax
• Leading to a decrease in air pressure inside the lungs relative to outside the body
• Air is drawn in

Question 14

What happens in the body during exhalation?

Answer 14

• The diaphragm relaxes it moves upwards back into its domed shape
• The external set of intercostal muscles relax so the ribs drop down and in
• This decreases the volume of the thorax
• Leading to an increase in air pressure inside the lungs relative to outside the body
• Air is forced out

Question 15

What does it mean when muscles work as antagonistic pairs?

Answer 15

Meaning they work in different directions to each other

Question 16

What percentage of oxygen, carbon dioxide and nitrogen is in inspired air?

Answer 16

• Oxygen: 21%
• Carbon dioxide: 0.04%
• Nitrogen: 78%

Question 17

What percentage of oxygen, carbon dioxide and nitrogen is in expired air?

Answer 17

• Oxygen: 16%
• Carbon dioxide: 4%
• Nitrogen: 78%

Question 18

How are the alveoli highly specialised for gas exchange?

Answer 18

• There are many rounded alveolar sacs which give a very large surface area to volume ratio.
• Alveoli have thin, single layers of cells to minimise diffusion distance.
• Ventilation maintains high levels of oxygen and low levels of carbon dioxide in the alveolar air space.
• A good blood supply ensures constant supply of blood high in carbon dioxide and low in oxygen.
• A layer of moisture on the surface of the alveoli helps diffusion as gases dissolve

Question 19

What chemicals are in cigarettes?

Answer 19

• Tar
• Nicotine
• Carbon monoxide

Question 20

How is nicotine dangerous?

Answer 20

• Nicotine narrows blood vessels leading to an increased blood pressure
• It also increases heart rate
• Both of these effects can cause blood clots to form in the arteries leading to heart attack or stroke

Question 21

How is carbon monoxide dangerous?

Answer 21

• Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen
• This puts more strain on the breathing system as breathing frequency needs to increase in order to get the same amount of oxygen into the blood.
• It also puts more strain on the circulatory system to pump the blood faster around the body and increases the risk of coronary heart disease and strokes

Question 22

How is tar dangerous?

Answer 22

• Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs.
• Also, Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus.
• It destroys cilia and the mucus builds up blocking the smallest bronchioles and leading to infections.

Question 23

What is a practical that can be done to understand the effect of exercise on breathing?

Answer 23

C - We will change whether the student has exercised or not
O - The students should be of the same age, gender, size and general fitness
R - We will repeat the investigation several times to ensure our results are reliable
M - We will measure the change in breathing rate
M - By measuring breathing rate before exercise and immediately after exercise and each minute for the subsequent 5 minutes.
S - The type of exercise carried out
S - The temperature of the environment