Respiratory System Flashcards
What are the main functions of the respiratory system
- Gas exchange between the environment and blood
- Control of the acidity of the body
- Filtering of the air inhaled
- Vocalisation
How many lobes are in each lung
Right - 3
Left - 2
What fills the thoracic cavity
Lung tissue (with the exception of the mid-sternal line where the heart, major vessels and oesophagus are)
What is the pleural sac
A double-walled enclosure of the lungs filled with fluid (pleural fluid)
What is the role of the pleural sac
Reduces friction from movement on the surface of the lungs
Fixes lungs firmly on the thoracic wall without any physical attachments
Role of rib cage and spine
Offer rigid protection to sensitive organs (heart and lungs)
Role of the muscles (diaphragm, intercostals and abdominals)
Support the rib cage and turn the chest into a pump that drives air flow
Functions of the airways
- Warming of inspired air
- Humidification of dry inspired air
- Filtration of inhaled foreign materials
What are the turbinates (conchae)
Bony dividers that increase the SA of the nasal cavity
What is the vestibule
The entrance to the nasal cavity that is the first line of airway defence
Small hairs and mucus in the vestibule help trap inhaled particles so they can be blown back out
What is Boyle’s law
P1 x V1 = P2 x V2
What is airflow directly proportional to
The pressure difference between two points
What is airflow inversely proportional to
The resistance that is created by the airways
What factors affect airway radius
Bronchodilation - CO2, epinephrine (via b2 receptors)
Bronchosriction - parasympathetic stimulation (via muscarinic receptor), histamine
What happens to the diaphragm during inspiration
It contracts
What happens to the diaphragm during expiration
It relaxes
What is the law of LaPlace
Pressure = (2xT(surface tension))/radius
What does surfactant contain
Proteins that disrupt the forces between water molecules, the result is a reduction in the surface tension of alveolar walls
What does reduced surface tension mean
- The alveolar spaces are less prone to collapsing
- The lung is more complaint and is inflated easier
What is spirometry
Spirometry is used to measure lung volumes but also to evaluate lung function by measuring variables such as the forced expired volume in one second (FEV1)
What measures cannot be measured using a spirometer
The functional residual capacity and residual volume
What is anatomical dead space
Refers to the part of the airways where gas exchange does not take place and is a fixed volume ~150ml
What is alveolar dead space
Refers to the areas of the lungs where gas exchange can take place but that are not properly perfumed with blood (eg, apex of upright lung)
What is minute ventilation
The amount of air that is moved by the lungs in one minute
Minute ventilation values at rest and maximal exercise
Rest- 6l/min
Maximal exercise- 150l/min
What is hyperpnoea
Minute ventilation increases in proportion to metabolic rate
Hyperventilation
Minute ventilation increases more than metabolic rate
What is Dalton’s law
The pressure of a gas mixture is equal to the sum of the pressures of the individual gases
What is Fick’s law of diffusion
The greater the solubility for a particular gas means a greater rate of diffusion for that gas
Why is CO2 more soluble than O2
It diffuses across the membrane easier
Movement of gas molecules between air and liquid depends on
Temperature
Solubility
Pressure difference
How to calculate O2 consumption
(Volume of inspired O2) - (volume of expired O2)
How to calculate CO2 consumption
(Volume of inspired CO2) - (volume of expired CO2)
What is the law of mass action
When a reaction is at equilibrium, the ratio of the substrates and products will remain constant
What is haemoglobin
An oxygen binding protein contained within RBCs
How many polypeptide chains (globins) does each haemoglobin contain
4
How many haem groups does each haemoglobin contain
4
What is in the centre of each haemoglobin
A ferrous atom (Fe2+) that binds oxygen
At what point does CO2 dissolve
When CO2 is at equilibrium, because it’s more soluble than O2
Carbon dioxide and bicarbonate
~70% of all CO2 is carried in the form of bicarbonate ions (HCO-3)
Carbon dioxide and haemoglobin
~23% of all CO2 is carried bound to haemoglobin
How is ventilation involuntary
The respiratory muscle groups are controlled by the CNS
What types of ventilation are voluntary
Hyperventilation
Speaking
Breath holding
Swallowing
What are slowly adapting pulmonary stretch receptors
Located within airway smooth muscle
They are only active when tidal volume approaches the physical limitations of the lung tissue for expansion
This mechanism called the Hering-Brewer reflex protects the lungs by initiating a signal that inhibits inspiration
What are rapidly adapting pulmonary stretch receptors (irritant)
These receptors are dense in the trachea and large airways
They respond to stimuli such as cigarette smoke, inhaled particles and cold air by initiating reflexes such as coughing and sneezing by causing bronchorestriction
What causes the ventilator drive
Peripheral chemoreceptors (main stimulus is PO2)
Carotid chemoreceptors
Aortic chemoreceptors
What creates the ventilatory drive
Central chemoreceptors
