Collated Notes Flashcards
What is internal respiration?
Intracellular mechanism which consumes 02 and produces CO2
What is external respiration?
Events that lead to exchange of O2 and CO2 between the external environment and the cells of the body
How many steps in external respiration?
4 steps
4 steps of external respiration?
1- Ventilation = Mechanical process of moving gas in and out of the lungs 2- Gas exchange between alveoli and blood = exchange of 02 and CO2 between air in alveoli and blood in pulmonary capillaries 3- Gas transport in the blood= Binding/transporting of O2 and CO2 in blood 4- Gas exchange at tissue level= Exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells
Describe ventilation?
Mechanical process of moving gas in and out of the lungs
Describe gas exchange between alveoli and blood?
Exchange of CO2 and O2 between air in alveoli and blood in pulmonary capillaries
Describe gas transport in the blood?
Binding and transporting of O2 and CO2 in the blood
Describe gas exchange at tissue level?
Exchange of O2 and CO2 between blood in systemic capillaries and the body cells
What must the pressures be like for air to flow into the lungs during inspiration?
Intra alveolar pressures must be less than atmospheric pressures
What is Boyles law?
As volume of gas increases the pressure exerted by the gas decreases
Forces holding the thoracic wall and lungs in close opposition?
Intra-plural fluid cohesiveness Negative intra-pleural pressure (sub-atmospheric pressure forces lungs to expand outwards)
3 pressures important in ventilation?
Atmospheric Intra-alveolar Intra-pleural
What type of process is inspiration? Compare this to normal resting expiration?
Active = inspiration passive = Expiration
What muscles are used in normal resting breathing?
Diaphragm - increases thorax vertically by contraction External intercostal muscle- Contraction lifts ribs and moves out sternum
How lungs recoil during expiration?
Elastic connective tissue Alveolar surface tension (Most important)
Law of laplace?
Smaller alveoli have a higher tendency to collapse (P= 2T/r)
What does pulmonary surfactant do?
Lowers the surface tension of smaller alveoli thus preventing their collapse
What does pulmonary surfactant consist of?
Lipids and proteins
Fact about respiratory distress syndrome?
It is caused by premature babies not producing enough pulmonary surfactant
Muscles of active expiration?
Internal intercostal muscles Abdominal muscles
Accessory muscles of inspiration?
Sternocleidomastoid Scalenus (runs deep to^)
Inspiratory capacity definition?
Max vol. of air that can be inspired at end of normal quiet expiration (IC = IRV + TV)
Equation for inspiratory capacity?
IC= IRV + TV
What does IRV stand for?
Inspiratory reserve volume
Tv stands for?
Tidal volume
Look wow
What is the vital capacity?
Max vol. of air that can be moved out during single breath following max. inspiration (VC = IRV + TV + ERV)
Equation for vital capacity?
VC = IRV + TV + ERV
VC= vital capacity
IRV= Inspiratory reserve volume
TV= Tidal volume
ERV= Expiratory reserve volume
Equation for total lung capacity?
Vital capacity + residual volume
You can measure total lung capacity with spirometry. True or false?
False
What disease makes residual volume increase?
Emphysema
Elastic recoil of the lungs is lost
Lung diseases and spirometry diagram?
Equation for flow and pressure and radius?
Flow= Change in pressure/resistence
What is compliance of the lungs?
Measure of effort that has to go into stretching or distending the lungs.
Diseases which have decreased lung compliance?
Pulmonary fibrosis
Oedema
Collapse
Pneumonia
Absence of surfactant
Diseases with increased compliance?
Emphysema
Lungs are hyper-inflated
patients have to work harder to get air out
What increases the work of breathing?
Pulmonary compliance is decreased
Airway resistence is increased
Elastic recoil is decreased
Need for increased ventilation
Definition of pulmonary ventilation?
Volume of air breathed in and out per minute
Equation for pullmonary ventilation?
Tidal volume x resp rate
Definition of alveolar ventilation?
Volume of air exchanged between the atmosphere and alveoli per minute
Equation for alveolar ventilation?
(Tidal volume - dead space) x resp rate
What is ventilation perfusion matching dependant on?
Ventilation (rate gas passes through lungs)
and
Perfusion (Rate which blood is passing through lungs)
What is alveolar dead space?
Ventilated alveoli which are not adequately perfused with blood
What is physiological dead space?
Anatomical dead space + alveolar dead space
When can alveolar dead space increase?
In disease
Local controls which operate to match perfusion and ventilation in the lungs?
1) When ventilation is larger than perfusion
2) When perfusion is larger than ventilation
1) Decreased C02 constriction of airways
Increased 02 dilation of blood vessels
2) Increased CO2 dilation of airways
Decreased 02 constriction of blood vessels
4 factors which affect gas transfer across the alveolar membrane?
- Partial pressure gradient of O2 and CO2
- Diffusion coefficient for O2 and CO2
- Surface area of alvelar membrane
- Thickness of alveolar membrane
Dalton’s law of partila pressure?
Total pressure= Sum of each indiviudal component in a gas mixture
PA02?
Partial pressure of O2 in alveolar air
PiO2?
Partila pressure of O2 in inspired air
Alveolar gas Equation?
PA02= PiO2 - [PaCO2/0.8]
What would a big gradient between PAO2 (alveolar) and PiO2 (arterial) suggest?
Indicate problems with gas exchange in the lungs
Or
A right to left shunt in the heart
Diffusion coefficient (solubility of gas in membrane) of CO2 compared to O2?
20 x that of O2
Ficks law of diffusion?
The amount of gas that moves across a tissue is proportional to the area of the sheet BUT inversely proportional to its thickness. (so thicker = less exchange)
