Gas Exchange

Question 1

What are some features that gas exchange surfaces have?

Answer 1

Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster

Question 2

Describe the ribs

Answer 2

Bone structure that protects internal organs such as the lungs

Question 3

Describe the intercostal muscle

Answer 3

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

Question 4

Describe the diaphragm

Answer 4

Sheet of connective tissue and muscle at the bottom of the thorax that separates the chest cavity from the abdomen and helps change the volume of the thorax to allow inhalation and exhalation.

The pressure in the thorax/chest/lung decreases;
Air moves/is drawn into the thorax

Question 5

Describe the trachea

Answer 5

Windpipe that connects the mouth and nose to the lungs

Question 6

Describe the larynx

Answer 6

Also known as the voice box, when air passes across here we are able to make sounds

Question 7

Describe the bronchi

Answer 7

Large tubes branching off the trachea with one bronchus for each lung

Question 8

Describe the bronchioles

Answer 8

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

Question 9

Describe the Alveoli

Answer 9

Tiny air sacs where gas exchange takes place

Question 10

Describe the pleural cavity

Answer 10

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

Question 11

What are the passages down to the lungs are lined with?

Answer 11

The passages down to the lungs are lined with ciliated epithelial cells.

Question 12

Describe the structure of cilia cells and their function

Answer 12

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 13

Why do cilia cells have tiny hairs on the end of them?

Answer 13

To beat and push mucus up the passages towards the nose and throat where it can be removed

Question 14

What is mucus made out of?

Answer 14

The mucus is made by special mucus-producing cells called goblet cells because they are shaped like a goblet, or cup

Question 15

What does the mucus do?

Answer 15

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 16

Fill in the blanks - Muscles are only able to - on bones, not - on them

Answer 16

Muscles are only able to pull on bones, not push on them

Question 17

How many sets of intercostal muscles are there and why?

Answer 17

There must be two sets of intercostal muscles to work antagonistically to facilitate breathing

Question 18

What are the two types of intercostal muscles and what do they do?

Answer 18

External intercostal muscles, pull the rib cage up
Internal intercostal muscles pull the ribcage down

Question 19

Explain what happens during inhalation.

Answer 19

During inhalation
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 chest cavity (thorax)
Leading to a decrease in air pressure inside the lungs relative to outside the body
Air is drawn in

Question 20

Explain what happens during exhalation.

Answer 20

During exhalation
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 chest cavity (thorax)
Leading to an increase in air pressure inside the lungs relative to outside the body
Air is forced out

Question 21

What do the external and internal muscles work as what and what does this mean?

Answer 21

The external and internal intercostal muscles work as antagonistic pairs (meaning they work in different directions to each other)

Question 22

Explain what happens during forced exhalation

Answer 22

When we need to increase the rate of gas exchange (for example during strenuous activity) the internal intercostal muscles will also work to pull the ribs down and in to decrease the volume of the thorax more, forcing air out more forcefully and quickly – this is called forced exhalation There is a greater need to rid the body of increased levels of carbon dioxide produced during strenuous activity
This allows a greater volume of gases to be exchanged

Question 23

Percentage of inspired air (Oxygen) - inspired means inhaled

Answer 23

21%

Question 24

Percentage of expired air (Oxygen) - expired means exhaled

Answer 24

16%

Question 25

Percentage of inspired air (Carbon dioxide) - inspired means inhaled

Answer 25

0.04%

Question 26

Percentage of expired air (Carbon Dioxide) - expired means exhaled

Answer 26

4%

Question 27

Percentage of inspired air (Nitrogen) - inspired means inhaled

Answer 27

78%

Question 28

Percentage of expired air (Oxygen) - expired means exhaled

Answer 28

78%

Question 29

How are the alveoli specialised for gas exchange?

Answer 29

There are many rounded alveolar sacs which give a very large surface area to volume ratio
Alveoli (and the capillaries around them) 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 30

What health conditions can smoking cause?

Answer 30

Smoking causes chronic obstructive lung disease (COPD), coronary heart disease and increased risks of several different types of cancer, including lung cancer.

Question 31

What are the chemicals in cigarettes and describe them?

Answer 31

Tar - a carcinogen (a substance that causes cancer)
Nicotine - an addictive substance which also narrows blood vessels
Carbon monoxide - reduces the oxygen-carrying capacity of the blood

Question 32

What is tar?

Answer 32

Tar - a carcinogen found in cigarettes and is linked to increased chances of cancerous cells developing in the lungs

Question 33

Describe nicotine and its effects

Answer 33

Nicotine - an addictive substance found in cigarettes which 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 34

Describe what carbon monoxide do to the circulatory system and its risk

Answer 34

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 and depth need 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 35

What health conditions does tar lead to?

Answer 35

It also contributes to COPD, which occurs when chronic bronchitis and emphysema (two different diseases which are frequently linked to smoking) occur together

Question 36

Describe Chronic bronchitis

Answer 36

Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus
It destroys cilia and mucus (containing dirt, bacteria and viruses) builds up blocking the smallest bronchioles and leading to infections
A smoker’s cough is the attempt to move the mucus

Question 37

Describe Emphysema

Answer 37

Emphysema develops as a result of frequent infection, phagocytes that enter the lungs release elastase, an enzyme that breaks down the elastic fibres in the alveoli
This means the alveoli become less elastic and cannot stretch so many burst
The breakdown of alveoli reduces the surface area for gas exchange
As it progresses, patients become breathless and wheezy - they may need a constant supply of oxygen to stay alive

Question 38

Where is the content of the blood is highest?

Answer 38

Blood exiting the lungs is the most oxygenated