4. Lungs

Question 0

List the parts of the human gas exchange system

Answer 0

Nasal cavity
Nostril
Trachea
bronchi
Bronchioles
Lung
Alveoli

Question 1

The volume of carbon dioxide which must be taken in and then removed from the body is large because:

Answer 1

They are relatively large organisms with a large volume of living cells

They maintain a high body temperature and therefore have high metabolic and respiratory rates

Question 2

Lungs are located inside the body because…

Answer 2

Air is not dense enough to support and protect these delicate structures
They would loose a great deal of water and dry out

Question 3

The lungs are supported and protected by a bony box called the…

Answer 3

Rib cage

Question 4

What is the structure and function of lungs?

Answer 4

They are a pair of lobed structures made up of a series of highly branched tubules called bronchioles which end in tiny air sacs called alveoli

Question 5

What is the structure and function of the trachea?

Answer 5

• flexible airway that is supported by rings of cartilage.
• The cartilage prevents the trachea collapsing as the air pressure inside falls when breathing in.
• The tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells (produces music which traps dirt which goes down the Oesophagus into the stomach).

Question 6

What is the structure and function of the bronchi?

Answer 6

Two divisions of the trachea. They have the same structure as the trachea but the amount of cartilage is reduced as the bronchi get smaller.

Question 7

What is the structure and function of the bronchioles?

Answer 7

They are a series of branching subdivisions of the bronchi. Their walls are made of muscle lined with epithelial cells. This muscle allows them to constrict so that they can control the flow of air in and out of the alveoli.

Question 8

What is the structure and function of the alveoli?

Answer 8

They are minute air sacs at the end of the bronchioles. They contain some collagen and elastic fibres and they are lined with epithelium. The elastic fibres allow the alveoli to stretch as they fill with air when breathing in. They spring back during breathing out to expel carbon dioxide rich air. The alveolar membrane is the gas-exchange surface.

Question 9

To maintain diffusion of gases across the alveolar epithelium…

Answer 9

Air must constantly be moved in and out of the lungs.

Question 10

What is breathing also know as?

Answer 10

Ventilation

Question 11

What is it called when atmospheric pressure is GREATER than the pressure inside the lungs?

Answer 11

Inspiration (inhalation) (air is forced into the alveoli)

Question 12

What is it called when pressure inside the lungs is GREATER than the atmospheric pressure?

Answer 12

Expiration (exhalation)

Question 13

The pressure changes in the lungs are bought about by two different sets of muscles.

Answer 13

The diaphragm and the intercostal muscles

Question 14

What is the diaphragm?

Answer 14

A sheet of muscle which separates the thorax from the abdomen.

Question 15

What are the two different types of intercostal muscles?

Answer 15

The internal intercostal muscles - whose contraction leads to expiration
The external intercostal muscles - whose contraction leads to inspiration

Question 16

What are the 5 steps in inspiration?

Answer 16

• external muscles contract, internal muscles relax
• the ribs are pulled upwards and outwards increasing thorax volume
• the diaphragm muscles contract causing it to flatten out - increasing volume
• increased volume of thorax = reduced pressure in lungs
• atmospheric pressure is now greater than pulmonary pressure and air is forced into the lungs

Question 17

What are the 5 steps in inspiration?

Answer 17

• Internal muscles contract, external muscles relax
• the ribs move downwards and inwards decreasing thorax volume
• the diaphragm muscles relax causing it to return to its domed position - decreasing volume
• decreased volume of thorax = increased pressure in lungs
• pulmonary pressure is now greater than atmospheric pressure and air is forced out

Question 18

Is inspiration an active process or a passive process?

Answer 18

Active

Question 19

Is expiration an active process or a passive process?

Answer 19

Passive

Question 20

The various muscles for ventilation do not play a part unless…

Answer 20

A person experiences more strenuous conditions e.g excersize. In normal quiet breathing the recoil of the elastic lungs is the main cause of air being forced out.

Question 21

What is pulmonary ventilation?

Answer 21

The total volume of air that is moved into the lungs during one minute.

Question 22

To calculate pulmonary ventilation multiply…

Answer 22

Tidal volume (volume of air taken in at each breath when the body is at rest) (normally about 0.5 dm cubed) by ventilation (number of breaths taken in one minute) (12-20 breaths in healthy adult)

Question 23

Pulmonary ventilation is measured in…

Answer 23

dm^3min^-1

Question 24

Exchange surfaces have the following characteristics to enable efficient transfer of materials:

Answer 24

• A large surface to volume ratio - speed up rate of exchange
• Very thin - to keep diffusion pathway short
• Partially permeable - allowing selected materials to diffuse easily
• movement of environmental medium e.g air to maintain a diffusion gradient
• movement of the internal medium e.g blood to maintain a diffusion gradient

Question 25

The pulmonary capillaries around each alveolus have walls that are only…

Answer 25

One cell thick

Question 26

Diffusion of gases between the alveoli and the blood will be very rapid because…

Answer 26

• red blood cells are slowed as they pass through pulmonary capillaries allowing more time for diffusion
• the distance between the alveolar air and red blood cells is reduced a the red blood cell is flattened against the capillary wall
• the walls of the alveoli and capillaries are very thin so there is a short diffusion pathway
• alveoli and pulmonary arteries have a large surface area
• ventilation is taking place constantly - maintains a concentration gradient
• blood flow maintains a concentration gradient

Question 27

In an alveolus O2 goes ____ and CO2 goes ___

Answer 27

In an alveolus O2 goes out (into blood cell in capillary) and CO2 goes in