Respiratory System

Question 1

How many lobes does the right lung have?

Answer 1

3: upper, middle and lower

Question 2

How many lobes does the left lung have?

Answer 2

2: upper and lower

Question 3

Functions of the lung (2)

Answer 3

1. to transport air into and out of the lung

2. to provide an area for gaseous exchange (between alveolus and pulmonary capillary blood)

Question 4

What is Compliance? what does high or low compliance mean?

Answer 4

How much effort is required to stretch the lungs and the chest wall
(ease of expansion)

High = lungs and chest wall expand easily
Low = lungs and chest wall resist expansion (difficult)

Question 5

What is elastance? what does high or low elastance mean in relation to compliance?

Answer 5

the quality of recoiling or returning to an original form after the removal of pressure
(contraction)

reciprocal to compliance

Low elastance = high compliance
high elastance = low compliance

Question 6

3 basic steps of respiration (explain each)

Answer 6

1. pulmonary ventilation: the mechanical flor or air into and out of the lungs
2. external respiration: the exchange of gases between air space of the lungs
3. internal respiration: the exchange of gases between blood in systemic capillaries and tissue cells

Question 7

What is the rate of flow influenced by? (4)

Answer 7

• alveolar surface tension
• compliance of the lungs
• airway resistance
• speed and force of respiratory muscle engagement

Question 8

What is ventilation? How does it occur?

Answer 8

Movement of air into the lungs - bulk gas flow

Gas flow between the atmosphere and lung alveoli. Air flows principally due to pressure differentials created by contraction and relaxation of respiratory muscles

Question 9

What is perfusion?

Answer 9

Movement and distribution of blood through pulmonary circulation

Question 10

What is the dependent lung?

Where is it located when in upright, supine and prone positions?

Answer 10

area that receives a higher proportion of ventilation and perfusions (= V/Q is best matched)

part of the lung in the lowest part of the gravitational field

• upright = base
• supine = posterior
• prone = anterior

Question 11

What happens to alveoli in the dependent lung?

Answer 11

• alveoli in the dependent lung are squashed by the weight of non-dependent segments
  = more room for movement from a squashed position
  => larger changes in volume and airflow = optimal ventilation

Question 12

Normal alveolar V/Q ratio

Answer 12

0.8 - 1.2 (approx. 0.84)

normal v/q matching = normal blood gases

Question 13

What happens if V/Q is mismatched?

Answer 13

hypoxaemia - insufficient oxygenation of the blood

Question 14

What is diffusion?

Answer 14

Net movement of molecules from areas of high concentrations to areas of low concentrations (a diffusion gradient) until equilibrium is reached

Question 15

What is gas exchange in respiration?

Answer 15

Movement via diffusion of O2 and CO2 across the air-blood barrier or alveolar-capillary membrane

Question 16

3 factors influencing the movement of O2 and CO2 across the respiratory membrane (diffusion)

Answer 16

○ Partial pressure gradients
○ Matching of alveolar ventilation and pulmonary blood perfusion (i.e V/Q)
○ Structural characteristics of the respiratory membrane - functional surface area & membrane thickness

Question 17

What is the composition of atmospheric air?

Answer 17

79% nitrogen
21% oxygen
0.04% Carbon dioxide

Question 18

What is the composition of alveolar gas?

Answer 18

75% nitrogen
14% oxygen
5% water vapour
6% carbon dioxide

Question 19

How is breathing controlled and modified to meet changing demands?

Answer 19

Homeostatic mechanisms (influenced by a variety of sensors/feedback loops) ensure equilibrium between rates of O2 and CO2 delivery and removal

• changes in V and Q are regulated at the local level
• variations in the rate and depth of breathing under the control of the respiratory centre in the brain (medulla sets the rhythm)

Question 20

How is oxygen transported (2)?

Answer 20

1. bound to iron (haem) portion of haemoglobin within RBC as oxyhaemoglobin (98.5%) - SpO2
2. as dissolved O2 in plasma - PaO2

Question 21

What is the oxyhaemoglobin dissociation curve?

Answer 21

Describes the relationship between partial pressure of O2 and the degree to which Hb is saturated with O2

sigmoid shaped curve

Question 22

What affects oxygen-carrying capacity?

Answer 22

• Hb concentration (how many RBCs)
• % Hb saturation
• PaO2
• CV competence

Question 23

What is anaemia?

Answer 23

low concentrations of RBCs -> reduced oxygen-carrying capacity

Question 24

What is hypoxia?

Answer 24

Low oxygen levels in end tissue -> fatigue, pallor, cold intolerance

Question 25

What causes a left-ward shift of the oxyhaemoglobin dissociation curve? What does it mean?

Answer 25

haemoglobins affinity for oxygen increases - it holds onto oxygen (i.e. reduced offloading)

induced by:

• reduced CO2
• reduced temperature
• reduced diphosophoglycerate
• increased pH

Question 26

What causes a right-ward shift of the oxyhaemoglobin dissociation curve? What does it mean?

Answer 26

haemoglobin affinity for oxygen decreases - it offloads oxygen (i.e. increased off-loading)

induced by:

• increased CO2
• increased temperature
• increased diphosphoglycerate (due to increased metabolic activity)
• reduced pH (Bohr effect)

Question 27

How is carbon dioxide transported in the blood (3)?

Answer 27

1. bicarbonate ion (HCO3-) in plasma (70%) -
2. chemically bound to haemoglobin (23%)
3. dissolved in plasma (7%)

Question 28

What is the haldane effect?

Answer 28

increased capacity of blood to carry CO2 under conditions of decreased haemoglobin oxygen saturation

• encourages CO2 exchange in both the tissues and lungs