2.1 Structure and function of the ventilatory system Flashcards
What are the three main functions of the conducting airways?
- Low resistance pathway for airflow
- Defence against chemicals and other harmful substances that are inhaled
- Warming and moistening the air
Outline the function of low resistance
Nasal passages are a low resistance pathway for airflow. Allows ventilation to occur easily. Important for supplying the body with oxygen.
Outline the function of defence
The nose and throat contain tiny hairs, called cilia. They filter the air and trap particles that are present. This stops them from entering the lungs and causing infections.
Outline the function of warming and moistening the air
Air needs to be warmed to aid with thermoregulation of the body - cold air in the lungs could cause capillaries to vasoconstrict (get smaller). Environment of the lungs needs to remain moist to allow for gas exchange to take place. The nose and trachea moisten the air that is inspired.
Define pulmonary ventilation
Inflow and outflow of air between the atmosphere and the lungs (also called breathing)
Define total lung capacity (TLC)
Volume of air in the lungs after a maximum inhalation
Define vital capacity (VC)
Maximum volume of air that can be exhaled after a maximum inhalation
Define tidal volume
Volume of air breathing in and out in any one breath during normal breathing
Define expiratory reserve volume
Volume of air in excess of tidal volume that can be exhaled forcibly
Define inspiratory reserve volume
Additional inspired air over and above tidal volume
Define residual volume
Volume of air still contained in the lungs after a maximal exhalation
Draw the pulmonary ventilation diagram
Explain the mechanics of ventilation regarding inspiration
External intercostal muscles contract which makes the ribs move up and out. This lowers the pressure relative to the outside pressure. The volume increases. This all makes air move into the lungs. Air moves from high to low pressure. Diaphragm contracts which increases volume.
Explain the mechanics of ventilation regarding expiration
Internal intercostal muscles relax which makes the ribs fall. This decreases the volume in the lungs which increases the air pressure relative to the air outside. This all makes air move out of the lungs. Air moves high to low pressure. Diaphragm relaxes which decreases the volume.
What is haemoglobin?
Main protein in the red blood cells that transports oxygen around the body
Where are red blood cells produced?
Erythrocytes (red blood cells) are found i the red bon marrow (spongey bone) of long bones
Which hormone regulates the production of haemoglobin?
Erythropoetin (EPO)
In what form is oxygen transported?
Oxyhaemoglobin - the bond is unstable and reversible
How does the shape of an alveoli maximise surface area?
The air that is breathed in fills the sack. The alveoli has a large surface area which allows for a faster diffusion of gases. Balloon-like structure.
DON’T FORGET TO PRACTICE LABELLING THESE THINGS
diagram of ventilatory system
diagram of breathing patterns
how air comes in and out of the lungs
diagrams of alveolus and capillary
How does the structure of an alveolus and capillary allows for gaseous exchange to take place?
Alveolus packed with oxygen and capillaries packed with CO2. Diffusion makes O2 and CO2 want to move to a lower concentration. CO2 is unloaded into the lungs while haemoglobin takes on the O2.
Explain the concepts of diffusion (fick’s law)
‘The rate of diffusion is proportional to both the surface area and concentration difference and is inversely proportional to the thickness of the membrane’
—> rate of diffusion (weird x - is proportional to) (surface area x concentration difference)/thickness of membrane
What are the factors that make the rate of diffusion double?
- Surface area or concentration difference is doubled
- Thickness of the exchange membrane is halved
- Exchange surfaces consist of cell membranes which are thin and this allows fast diffusion (high concentration to low concentration) across membranes
What is partial pressure (Dalton’s law)?
Dalton’s law states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases
Dissolved gases always diffuse down their partial pressure gradients (high pressure to low pressure)
What is respiration?
Cell respiration is the controlled release of energy in the form of adenosine triphosphate (ATP) from organic compounds in cells
What is the difference between aerobic and anaerobic respiration?
Aerobic respiration produces ATP in the presence of oxygen whilst anaerobic respiration produces ATP without the presence of oxygen
What happens to lactic acid and H+ ions during anaerobic respiration?
Lactic acid and H+ ions accumulate faster, further decreasing the pH of the blood
What are the three neural controls of ventilation?
Lung stretch receptors
Muscle proprioceptors
Central chemoreceptors and Peripheral chemoreceptors
Where can central chemoreceptors be found?
In the medulla (brain stem)
Where can peripheral chemoreceptors be found?
In the aortic arch
What do the chemoreceptors do?
They sense changes in CO2 levels in the blood - receives info about chemicals in the blood - tells us when to breath more when we exercise
How do muscle proprioceptors help us to regulate ventilation?
During exercise they send signals to the brain to increase rate and depth of ventilation. Increase the removal of CO2. Senses movement.
How do lung stretch receptors help regulate ventilation?
When they are excessively stretched, signals are sent to the expiratory centre to shorten inspiration.
This protects the lungs by decreasing the risk of over inflation of the alveoli.
This is known as the Hering-Breuer reflex
Why does ventilation increase in regards to blood acidity levels?
Ventilation increases as a direct result of increases in blood acidity levels (low pH).
This is due to increased carbon dioxide content of the blood.
How does ventilation change in relation to the blood acidity levels?
Ventilation increases as a direct result of increases in blood acidity levels (low pH) due to increased carbon dioxide content of the blood detected by the respiratory centre. Resulting in an increase in the rate and depth of ventilation
Equation of minute ventilation
Minute ventilation = tidal volume x number of breaths per minute
What happens to minute ventilation during exercise?
It increases due to tidal volume and breaths per minute increasing (breathing depth and rate).
What do the neural controls of ventilation include?
Lung stretch receptors
Muscle proprioceptors (sensitive to pressure and tension)
Chemoreceptors (sense changes in CO2, O2, and pH
What are other factors that could change ventilation?
Partial pressures, acidity, temperature, and hormones
How can oxygen easily bind to haemoglobin in the lungs?
There is high partial pressure
How does oxygen detach from haemoglobin?
In the active muscle where partial pressure is lower, oxygen detaches and diffuses into the blood into the active tissue
How does the exchange of O2 and CO2 work in the muscle tissue?
The pressure gradient will drive O2 from blood into tissue and CO2 from tissue to blood
What happens to the pressure gradient during exercise?
It becomes greater so more O2 can be used up
Why do the lungs struggle during exercise?
They struggle to maintain resting partial pressure in the alveoli. Otherwise, exercise cannot be maintained for a long period of time.
