⭐️Exchange: The Human Gas Exchange System

Question 1

Give two reasons why lungs are located inside the body

Answer 1

• air isn’t dense enough to support and protect them

- the body as a whole would otherwise loose a great deal of water and dry out

Question 2

How are the lungs ventilated?

Answer 2

A tidal stream of air and so ensuring the air within them is constantly replenished

Question 3

Describe the lungs

Answer 3

A pair of lobed structures made of a series of highly branched tubules called bronchioles which end in the alveoli

Question 4

What is the trachea and what are its walls made of?

Answer 4

A flexible airway that is supported by rigs of cartilage which prevent the trachea collapsing as the air pressure falls inside when breathing.
The walls are made of muscle lined with ciliated epithelium and goblet cells

Question 5

What are the bronchi?

Answer 5

Two divisions of the trachea supported by cartilage which produce mucus to trap dirt particles and have cilia which move tube dirt laden mucus to the throat

Question 6

What are bronchioles? What are their walls made out of and so what does this allow them to do?

Answer 6

A series of branching subdivisions of the bronchi. Their walls are made of muscle lined with epithelial cell and the muscle allows them to constrict in order to control the flow of air in and out of the alveoli

Question 7

What are the alveoli?

Answer 7

Tiny air sacs lined with epithelium and have collagen and elastic fibres between them which allow the alveoli to stretch as they fill with air when breathing in and spring back when breathing out to expel the co2 rich air.

Question 8

What part of the lungs is the gas exchange surface?

Answer 8

The alveolar membrane in the alveoli

Question 9

Give 2 reasons why mammals require a large amount of oxygen

Answer 9

• there are many cells that need it for respiration to support metabolic processes
• they need to generate lots of heat in order to maintain body temp

Question 10

What is ventilation?

Answer 10

The continual movement of air in and out of the lungs

Question 11

What is inspiration?

Answer 11

When the air is forced into the lungs because the air pressure of the atmosphere is greater than that in the lungs

Question 12

What is expiration?

Answer 12

When the air is forced out of the lungs because the air pressure of the atmosphere is less than the air pressure in the lungs

Question 13

What three muscles cause pressure changes in the lungs?

Answer 13

• The diaphragm
• external intercostal muscles
• internal intercostal muscles

Question 14

What is the formula for pulmonary ventilation rate?

Answer 14

Pulmonary ventilation rate / dm^3 min^-1 = tidal volume / dm^3 x breathing volume / min^-1

Question 15

Go through the process of inspiration in terms of the muscles involved

Answer 15

1. The external intercostal muscles contract while the internal intercostal muscles relax
2. The ribs are pulled upwards and outwards increasing the volume of the thorax
3. The diaphragm muscles contract causing it to flatten increasing the volume of the thorax
4. The increased volume of the thorax results in reduced pressure in the lungs
5. Atmospheric pressure is now greater than pulmonary pressure so air is forced into the lungs

Question 16

Go through the process of expiration in terms of the muscles involved

Answer 16

1. The internal intercostal muscles contract while the external intercostal muscles relax
2. The ribs move downwards and inwards decreasing the volume of the thorax
3. The diaphragm muscles relax so it’s pushed up again by the contents of the abdomen that were compressed during respiration and so the volume of the thorax is further decreased
4. The decreased volume of the thorax increases the pressure in the lungs
5. The pulmonary pressure is now greater than that of the atmosphere so air is forced out of the lungs

Question 17

What is the usual tidal volume and breathing rate of a healthy adult?

Answer 17

Tidal volume = 0.5 dm^3

Breathing rate = 12 - 20 min^-1

Question 18

How are the intercostal muscles in the thorax antagonistic?

Answer 18

Because when the external intercostal muscles contract, the internal intercostal muscles relax and vice versa (the do the opposite of each other)

Question 19

Where is the site of gas exchange in mammals?

Answer 19

The epithelium of the alveoli

Question 20

Give 6 reasons why diffusion between the alveolar and the blood is very rapid

Answer 20

• Because the very narrow capillary that surround the alveoli means red blood cells are slowed down as they pass through pulmonary capillaries and so allowing more time for diffusion
• the distance between the alveolar air and the red blood cells is reduced as the red blood cells are flattened against the capillary walls
• the walls of both alveoli and capillaries are very thin and therefor the distance over which diffusion takes place is very short
• alveoli and pulmonary capillaries have a very large total surface area
• breathing movements constantly ventilate the lungs and the action of the heart constantly circulates blood around the alveoli, ensuring a steeply concentration gradient of gases to be exchanged is maintained
• blood flow through the pulmonary capillaries maintains a concentration gradient

Question 21

Why is the alveolar surface moist?

Answer 21

Because this helps to dissolve gases helping them to diffuse p across the gas exchange surface more efficiently

Question 22

What are the risk factors of a COPD?

Answer 22

• Smoking
• air pollution
• genetics
• infections
• day to day occupation

Question 23

Where can you find information on the correlations, causal relationships and risk factors for lung disease?

Answer 23

• textbook pg 148-149
• YouTube
• past papers?