The Human Gaseous Exchange System

Question 1

What are the features of the nasal cavity?

Answer 1

1. Large SA with good blood supply- warms to body temp
2. Hairy lining - secretes mucus to trap dust and bacteria - protects delicate lung tissue
3. Moist surfaces - increases the humidity of air incoming to reduce evaporation from exchange surfaces

This means the air entering the lungs is the same temp and humidity as the air already there

Question 2

What are the features of the trachea?

Answer 2

1. Wide tube supported by incomplete rings of cartilage (stops trachea from collapsing) - incomplete to allow food to pass down oesophagus which is behind
2. It and its branches are lined with a ciliated epithelium with goblet cells between and below the epithelial cells - goblet cells secrete mucus to trap dust and microbes and the cilia beat to move the mucus away from the lungs and towards the throat to be swallowed

Question 3

What are the features of the bronchus?

Answer 3

Similar structure to trachea but smaller

Question 4

What are the features of the bronchioles?

Answer 4

1. Smaller bronchioles have no cartilage rings
2. The walls contain smooth muscle - contract and relax to constrict and dilate the bronchioles - this changes the amount of air reaching the lungs
3. Lined with a thin layer of flattened epithelium - this makes some gaseous exchange possible

Question 5

What are the adaptations of the alveoli?

Answer 5

1. Large SA
2. Both the alveoli and the capillaries that surround them have walls that are only one epithelial cell thick
3. Good blood supply
4. Good ventilation
5. Inner surface is covered in a thin layer of lung surfactant - what allows the alveoli to remain inflated
   - oxygen dissolves in the water before diffusing into the blood

Question 6

What is ventilation?

Answer 6

Breathing movements causes air to be moved in and out of the lungs as a result of pressure changes in the thorax

Question 7

Describe inspiration

Answer 7

• The dome shaped diaphragm contracts causing it to flatten and lower
• The external intercoastal muscles contract, moving the ribs up and out
• The volume of the thorax has increased so the pressure has reduced
• The pressure is lover that theatmosphere so air is drawn in to the lungs to equalise the pressure

Question 8

Is inspiration an active or passive process?

Answer 8

Inspiration is an active, energy-using process

Question 9

Describe the process of expiration (normal)

Answer 9

• Muscles of diaphragm relax so it moves back up to its resting dome shape
• external intercoastal muscles relax so the ribs more down and in under gravity
• The elastic fibres in the alveoli return to their normal length
• volume of the thorax decreases, in and pressure increases
• Air moves out of rungs to equalise pressure

Question 10

Is normal expiration an active or passive process?

Answer 10

It is a passive process

Question 11

Describe expiration (forced)

Answer 11

• The internal intercoastal muscles contract, pulling the ribs down hard and fast
• abdominal muscles contract forcing the diaphragm up to increase the pressure rapidly

Question 12

What is a peak flow meter?

Answer 12

A simple device that measures the rate at which air can be expelled from the lungs

Question 13

What are vitalographs?

Answer 13

More sophisticated versions of peak flow meters, the patient being tested breathes out as quickly as they can through a mouthpiece
Produces a graph with speed and volume- forced expiratory volume

Question 14

What is a spirometer?

Answer 14

Measures different aspects of lung volume or breathing patterns

Question 15

What is tidal volume?

Answer 15

The volume of air that moves into and out of the lungs with each resting breath

Question 16

What is vital capacity?

Answer 16

The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath

Question 17

What is inspiratory reserve volume?

Answer 17

The maximum volume of air you can breathe in over and above a normal inhalation

Question 18

What is expiratory reserve volume?

Answer 18

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

Question 19

What is residual volume?

Answer 19

The volume of air that is left in your lungs when you have exhaled as hard as possible (this cannot be measured directly)

Question 20

What is total lung capacity?

Answer 20

The sum of the vital capacity and residual volume

Question 21

What is the ventilation rate?

Answer 21

The total volume of air inhaled in one minute

Tidal volume x breaths per minute