Respiratory System Flashcards
How many lobes does the right lung have?
3: upper, middle and lower
How many lobes does the left lung have?
2: upper and lower
Functions of the lung (2)
- to transport air into and out of the lung
2. to provide an area for gaseous exchange (between alveolus and pulmonary capillary blood)
What is Compliance? what does high or low compliance mean?
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)
What is elastance? what does high or low elastance mean in relation to compliance?
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
3 basic steps of respiration (explain each)
- pulmonary ventilation: the mechanical flor or air into and out of the lungs
- external respiration: the exchange of gases between air space of the lungs
- internal respiration: the exchange of gases between blood in systemic capillaries and tissue cells
What is the rate of flow influenced by? (4)
- alveolar surface tension
- compliance of the lungs
- airway resistance
- speed and force of respiratory muscle engagement
What is ventilation? How does it occur?
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
What is perfusion?
Movement and distribution of blood through pulmonary circulation
What is the dependent lung?
Where is it located when in upright, supine and prone positions?
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
What happens to alveoli in the dependent lung?
- 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
Normal alveolar V/Q ratio
0.8 - 1.2 (approx. 0.84)
normal v/q matching = normal blood gases
What happens if V/Q is mismatched?
hypoxaemia - insufficient oxygenation of the blood
What is diffusion?
Net movement of molecules from areas of high concentrations to areas of low concentrations (a diffusion gradient) until equilibrium is reached
What is gas exchange in respiration?
Movement via diffusion of O2 and CO2 across the air-blood barrier or alveolar-capillary membrane
3 factors influencing the movement of O2 and CO2 across the respiratory membrane (diffusion)
○ 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
What is the composition of atmospheric air?
79% nitrogen
21% oxygen
0.04% Carbon dioxide
What is the composition of alveolar gas?
75% nitrogen
14% oxygen
5% water vapour
6% carbon dioxide
How is breathing controlled and modified to meet changing demands?
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)
How is oxygen transported (2)?
- bound to iron (haem) portion of haemoglobin within RBC as oxyhaemoglobin (98.5%) - SpO2
- as dissolved O2 in plasma - PaO2
What is the oxyhaemoglobin dissociation curve?
Describes the relationship between partial pressure of O2 and the degree to which Hb is saturated with O2
sigmoid shaped curve
What affects oxygen-carrying capacity?
- Hb concentration (how many RBCs)
- % Hb saturation
- PaO2
- CV competence
What is anaemia?
low concentrations of RBCs -> reduced oxygen-carrying capacity
What is hypoxia?
Low oxygen levels in end tissue -> fatigue, pallor, cold intolerance
What causes a left-ward shift of the oxyhaemoglobin dissociation curve? What does it mean?
haemoglobins affinity for oxygen increases - it holds onto oxygen (i.e. reduced offloading)
induced by:
- reduced CO2
- reduced temperature
- reduced diphosophoglycerate
- increased pH
What causes a right-ward shift of the oxyhaemoglobin dissociation curve? What does it mean?
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)
How is carbon dioxide transported in the blood (3)?
- bicarbonate ion (HCO3-) in plasma (70%) -
- chemically bound to haemoglobin (23%)
- dissolved in plasma (7%)
What is the haldane effect?
increased capacity of blood to carry CO2 under conditions of decreased haemoglobin oxygen saturation
- encourages CO2 exchange in both the tissues and lungs
