Respiratory Physiology 1 + 2 Flashcards
What are the functions of the respiratory system?
Gas exchange
Acid base balance - regulation of body pH
Protection from infection
Communication via speech
Why is gas exchange so important?
Need to produce energy
Oxygen is metabolised p and produces CO2 as a waste product
What does the ability of tissues to transform fuel stored as chemical energy to physical energy depend on?
Integration of the CVS
Respiratory systems to deliver fuel to active cells within the tissues and remove waste products
What is cellular/internal respiration?
Biochemical process that releases energy from glucose via glycolysis or oxidative phosphorylation
Oxidative respiration requires oxygen and depends on external respiration
What is external respiration?
Movement of gases between the air and the body’s cells via both the respiratory and cardiovascular systems
What is the pulmonary circulation?
Delivers CO2 to the lungs
Collects O2 from the lungs
Consists of the pulmonary artery that carries deoxygenated blood and pulmonary vein which carries oxygenated blood
What does increased energy demand by working muscle lead to?
Increased rate and depth of breathing which speeds up substrate acquisition and waste disposal
Increased rate and force of contraction of heart which speeds up substrate delivery to muscle and waste removal via blood
What is the net volume of gas exchanged in the lungs per unit time?
In steady state - 250ml/min O2: 200ml/min CO2
Equal to net volume exchanged in the tissues
What is average respiration rate?
12-18 breaths per min at rest
Can reach 40-45 at max. when exercising as an adult
What does the respiratory system consist of?
Nose
Pharynx
Epiglottis
Trachea
Larynx
Lung
Bronchus
What does the upper respiratory tract consist of?
Pharynx, nasal cavity, tongue, vocal cords, oesophagus and larynx
What does the lower respiratory system consist of?
Trachea, left lung, right lung, left bronchus, right bronchus and diaphragm
It is enclosed in the thorax, bounded by the ribs , spine and diaphragm
What does right lung consist of?
Superior lobe
Horizontal fissure
Middle lobe
Oblique fissure
Inferior lobe
What does the left lung consist of?
Superior lobe
Oblique fissure
Inferior lobe
Describe the branching of airways?
The trachea branches into two bronchi. Each bronchi branches 22 more times which finally terminates in a cluster of alveoli. The trachea, primary bronchus and secondary bronchus are semi riding tubes that have c shaped rings of cartilage to maintain patency
How is patency maintained in the bronchioles and alveoli?
There is no cartilage so it is maintained by physical forces in the thorax
What is different between the left and right bronchi?
The right bronchi is wider and more vertical so more common for aspirated foreign bodies commonly lodge here
Explain airway branching and resistance to air flow
More resistance to air flow happens in the conducting zone compared to the respiratory zone as there is more branching in the respiratory zone. It can be altered by activity of bronchial smooth muscle:
Contraction decreases diameter - resistance increases
Relaxation increases diameter. - resistance decreases
What are elastic fibres responsible for?
Elastic fibres surround the alveoli. They allow expansion and contraction when breathing and loss of the elasticity can lead to emphysema.
Explain type l alveoli cells
Responsible for gas exchange
They are in bulk of the alveolar wall
Explain type ll cells
Synthesise surfactant which makes breathing easier
What is tidal volume?
The volume of air breathed in and out of the lungs at each breath when at rest
What is expiratory reserve volume?
The max. amount of air which can be expelled from the lungs at the end of of a normal expiration
What is inspiratory reserve volume?
The max. amount of air which can be drawn into the lungs at the end of a normal inspiration
What is residual volume?
The volume of gas in the lungs at the end of a max. expiration
What is vital capacity?
Tidal volume plus inspiratory reserve volume plus expiratory reserve volume
Explain the pleural cavities of the lung
Each lung is enclosed in two pleural membranes. The pleural fluid and space is very small. There is the parietal pleura which is superficial to the visceral pleura. The visceral pleura is closest to the lungs
What does the pleural fluid between the pleural walls allow?
The pleura are able to cross each other when breathing as the fluid allows this with no friction.
It also holds the pleura together - harder to separate.
Sticks the lungs to the diaphragm
Explain the sticking of the lungs to the rib cage
Visceral pleura is stuck to the surface of the lungs
Visceral pleura is stuck to the parietal pleura via the cohesive forces of pleural fluid
Parietal pleura is stuck to rib cage and the diaphragm
The chest wall therefore leads the expansion of the lung during inspiration
Explain the Boyle’s law
States that the pressure exerted by a gas is inversely proportional to its volume
Gases move from areas of high pressure to areas of low pressure
Explain the muscles used in inspiration
Include the diaphragm, external intercostals, sternocleidomastoids and scalenes
Mainly the first two
Explain the muscles used in expiration
Expiration is passive at rest, but uses intercostal and abdominal muscles during severe respiratory load
Explain the diaphragm as a mechanism for breathing
Diaphragm contrasts, thoracic volume increases during inspiration - airways are pulled open by physical forces of inspiration
Diaphragm relaxes, thoracic volume decreases during expiration - airways are compressed by physical forces of expiration
Describe the pump motion of the intercostal muscles
Increases anterior posterior dimension of the rib cage
Describe the bucket handle motion of the intercostals
Increases the lateral dimension of the rib cage
What is the intra-thoracic (alveolar) pressure
Pressure inside the thoracic cavity - pressure inside the lungs
May be positive or negative compared to the atmosphere pressure
Inspiration is negative
Expiration is positive
What is the intra-pleural pressure?
Pressure inside the pleural cavity
Typically negative compared to the atmospheric pressure
What is the transpulmonary pressure?
Difference between the alveolar pressure and the intra-pleural pressure
Almost always positive because the Pip is negative
Pt = Palv - Pip
What is the intrapleural pressure of a normal lung at rest?
-3mm Hg which is subatmospheric
Describe the importance of the relationship between pleural membranes in pneumothorax
If sealed pleural cavity is opened to the atmosphere then air flows in
The air moves from higher Patmos to lower Pip to equalise the pressure
The relationship between the 2 membranes is lost and affected lung becomes useless
Lung collapses to unstretched size
Describe bulk flow of air between the atmosphere and alveoli
Is proportional to the atmospheric and alveolar pressures
Is inversely proportional to the airway resistance
F = (Patm - Pa)/R
How is a subatmospheric pressure intrapleural pressure created?
Between breaths at the end of unforced expiration - no air is flowing and the dimensions of the lungs and thoracic cage are stable as a result of opposing elastic forces
The lungs are stretched and are attempting to recoil whereas the chest wall is compressed and attempting to move outward
A transpulmonary pressure opposes the forces of elastic recoil
Explain airway resistance
Determines how much air flows into the lungs at any given pressure difference between atmosphere and alveoli
The major determinant of airway resistance is the radii of the airways
What is surfactant?
Detergent like fluid produced by Type II alveolar cells
Reduces surface tension on alveolar surface membrane and reduces tendency of alveoli to collapse
Increases lung compliance and makes breathing easier
Is surfactant more effective in small or large alveoli?
Smaller alveoli
Because surfactant molecules come closer together and are therefore more concentrated
Explain surface tension
Is on alveolar surface membrane and makes tendency for alveoli to collapse
Surface tension occurs where ever there is a air-water interface and refers to attraction between water molecules
What happens when there is no surfactant on alveolar membrane of a smaller and larger alveoli?
Pressure is greater in the smaller alveolus due to the law of LaPlace
The small alveoli then collapses as more effort would be required to keep inflated
Air moves into larger alveolus and now there is less surface area for gas exchange
Importance of surfactant between small and large alveoli
Surfactant reduces surface tension
Pressure us equalised in the large and small alveoli as surfactant more concentrated in smaller alveolus
Tendency to collapse is now reduced
When does surfactant production start?
Starts at 25 weeks gestation
Complete by 36 weeks (40weeks so full term)
Stimulated by thyroid hormones and cortisol which increase at end of pregnancy
What syndrome can premature babies have to do with their lungs?
Infant Respiratory Distress Syndrome (IRDS)
What us the difference between saline filled lung compared to lung inflation post-birth?
Less change in pressure is required to inflate the lungs in the uterus as do not need to overcome surface tension because no air-water interface
More pressure needed to fill lungs post birth so breathing is easier in uterus
Explain the term compliance
Change in the volume relative to change in pressure
Represents the stretchability of the lungs not the elasticity
High compliance = large increase in lung volume for small decrease ip pressure so not much effort is needed to give large volume in the thoracic cavity
