C7 - Mammalian Gas Exchange

Question 1

What’s a tissue?

Answer 1

A group of similar cells specialised to carry out the same function.

Question 2

Whats an organ?

Answer 2

A group of tissues working together to carry out the same function.

Question 3

What’s the purpose of cartilage?

Answer 3

It permanently holds the trachea open so it doesn’t collapse.

Question 4

What’s the purpose of ciliated epithelial cells?

Answer 4

They beat in rhythm to move mucus and any trapped dirt and bacteria up and out to the thought where it is swallowed and destroyed by stomach acid.

Question 5

What’s the purpose of goblet cells?

Answer 5

To produce mucus.

Question 6

What’s the purpose of smooth muscle?

Answer 6

To contract to adjust the diameter of the lumen (of bronchioles).

Question 7

What is the purpose of elastic fibres?

Answer 7

They recoil to change the diameter of bronchioles.

Question 8

What’s the purpose of connective tissue?

Answer 8

It anchors the trachea to surrounding soft tissues.

Question 9

What are the various organs and components of the complex mammalian gas exchange system?
(14)

Answer 9

Lungs
Bronchi
Bronchioles
Nasal cavity
Nostrils
Trachea
Cartilage
Pulmonary vein
Pulmonary artery 
Smooth muscle
Capillaries
Ciliated epithelial cells
Goblet cells
Alveoli

Question 10

What is the primary function of the gas exchange system?

Answer 10

Diffusion of respiratory gases into and out of the blood stream.

Question 11

How is the exchange system effective for its purpose?

Answer 11

Short diffusion pathway
Good blood supply
Large surface area
Moist by surfactant
Steep diffusion gradient

Question 12

Where does air move within the lungs?

Answer 12

In and down the trachea into the bronchi then branches of bronchioles then alveoli.

Question 13

What are alveoli walls made from?

4

Answer 13

Squamous epithelium cells (very thin) and elastic fibres for expansion and recoil.
The wall also contains collagen and stretch receptors which provide sensory input to help control the breathing cycle.

Question 14

What’s ventilation?

Answer 14

Breathing / the exchange of gases

Question 15

What occurs during inspiration?

Answer 15

The ribs move up and out because the external intercostal muscles between the ribs contract.

The muscular diaphragm contracts and flattens.

The lungs increase in volume so the air pressure within drops below the pressure outside the lungs, drawing air in.

Question 16

What occurs during expiration?

Answer 16

The ribs move down and in because of the contracting internal intercostal muscles.

The muscular diaphragm relaxes and reverts to it’s domed shape.

This reduces lung volume so pressure of the air rises above the pressure outside the lungs, forcing air out.

Question 17

What does a spirometer do?

Answer 17

Measure the volume of air exchanged when breathing.
The person breathes in a closed system when air is trapped in a container floating on water.
Movements are recorded in a chart known as a spirogram.

Question 18

What’s tidal volume?

Answer 18

The volume of air breathed out during a normal breath.

Question 19

What’s vital capacity?

Answer 19

The maximum volume of air that can be expired after a maximum inspiration (3-5 dm3) depending on gender and body size.

Question 20

What’s residual volume?

Answer 20

The volume of air that remains in the lungs after maximum expiration.
This prevents the lungs from collapsing.

Question 21

What’s a breathing rate?

Answer 21

The number of breaths per minute

A.k.a ventilation rate

Question 22

How is tidal volume calculated?

Answer 22

Tidal volume = vital capacity + residual volume

Question 23

What’s pulmonary ventilation?

Answer 23

The movement of gas in and out of the lungs in one minute

Question 24

How’s pulmonary ventilation calculated?

Answer 24

Pulmonary ventilation = tidal volume * breathing rate

Question 25

What is respiratory arrest?

Answer 25

When someone stops breathing

Question 26

What causes respiratory arrest?

Answer 26

An obstruction in the airway blocking the trachea or bronchi

A drug overdose that has resulted in the nervous system and breathing system being depressed sufficiently to stop altogether.

An asthma attack, severe pneumonia, severe shock or a heart attack.

Question 26

What’s surfactant?

What does it do?

Answer 26

A liquid which lines the alveoli.
It’s a detergent-like phospholipid produced by some of the cells in the alveolar walls (septal cells).
It reduces the surface tension of the water and makes it easier to inflate the lungs and stops surfaces sticking together.
It also acts as an antibacterial substance.

It enables efficient gas exchange but doesn’t change the rate of diffusion.

Question 27

What’s the pleural membrane?

Answer 27

A double membrane enclosing each of the lungs.

Between the 2 membranes is the pleural cavity filled with pleural fluid.

Question 28

What’s the pleural cavity?

Answer 28

The space between the 2 membranes of the pleural membrane which is filled with pleural fluid.

Question 29

What is pleural fluid?

Answer 29

A fluid within the pleural cavity of the pleural membrane which lubricates the lungs and adheres to the outer walls of the lungs and the thoracic (chest) cavity by water cohesion.
This enables the lungs to expand.

Question 30

How is total lung capacity calculated?

Answer 30

Vital capacity + residual volume = total lung capacity

Question 31

What is FEV1?

Answer 31

Forced expiratory volume

The volume of air that can be expelled in the first second in exhalation

Question 32

What is PEFR?

Answer 32

Peak expiratory flow rate.
It’s the maximum rate of forcing air out of the mouth by using a peak flow metre.
(For longer than a second)

(For a 25 year old)
Average male has PEFR of 570-640 dm3/min
Average female has PEFR of 420-460 dm3/min

Question 33

What are reasons for a reduced PEFR?

Answer 33

A reaction or allergen.

For males it is below 400dm3/min

For females it is below 200 dm3/min

Question 34

How is a respiratory arrest treated?

Answer 34

By EAR - expired air resuscitation

1) Call for help
2) Wear gloves and mask if available and roll victim onto their back to avoid injury.
3) Remove/sweep any visible obstruction in their mouth
4) Tilt their head back by gently pressing onto their forehead and lifting the chin to move the tongue from the back of the throats and open the airway
5) Pinch their nostrils so air doesn’t escape and seal their mouth with your mouth
6) Blow twice gently into their mouth and watch that their chest rises. (Rescue breaths) If not, repeat and check for obstructions again.
7) After 2 breaths check for pulse. If no pulse, perform CPR.

Question 35

What is soda lime?

What is its purpose in a spirometer?

Answer 35

Calcium oxide and sodium hydroxide solution.

It prevents the build up of CO2.

Question 36

How would you use a spirometer to measure a person’s vital capacity?

Answer 36

Have the individual stand up or sit up straight.
Seal the mouth around the mouthpiece and use a nose clip.
Inhale as much as possible then force out/exhale as much as possible.
The pen records the move to of the movable lid on changing water level on a chart which shows vital capacity.

Question 37

What is meant by the term tidal volume?

Answer 37

The volume of air an individual breathes out in one breath.

Question 38

Why are the trachea and bronchi supported by C-shaped rings of cartilage?

Answer 38

They support the trachea and bronchi to prevent them collapsing during exhalation.
The rings are C-shaped to allow flexibility and swallowing movements in the oesophagus.