Respiratory system Flashcards
What is partial pressure
The pressure exerted by an individual gas in a mixture is known as its partial pressure.
Why is knowing partial pressures important
Because gases always diffuse from high partial pressure to low partial pressure
What is gas exchange
It is also known as respiration, and involves the actions of taking O2 from the atmosphere and discharge of CO2 back into the environment from the body
What is the atmospheric pressure
It is 760 mmHg
How do you calculate specific pressures of gases given a certain pressure
Once we know the % composition of that gas in a certain environment, we can multiply that with the pressure known.
For example, O2 makes up 21% of the atmosphere. Thus the partial pressure of O2 (PO2) = 760 x 0.21 = 160 mmHg
What is the nature of gas flow
Gas flows from higher pressure into lower pressure
How does Oxygen come into the lungs
When we inhale, the diaphragm contracts and pulls downward, making our ribcages expand, thus allowing the lungs to expand. This creates a lower pressure in the lungs than outside. As a result from gas flow, the gas flows from high to low pressure thus bringing in the oxygen
Explain the mechanisms of breathing out
When we breath out, our diaphragm relaxes, thus allowing ribcages to relax and shrink, allowing lungs to get smaller. This creates a higher pressure in the lungs than outside. This thus allows the gases from the lungs to flow out into the atmosphere
Why do our lungs expand when our chest contracts
A double membrane surrounds the lungs. One side adheres to the outside of the lung, and the other to the wall of the thoracic cavity.
This membrane is filled with fluid that creates surface tension —> easily stuck together (physically) but not easily pulled apart
Does expiration require contraction of muscles
No its a passive process. The relxation of diaphragm and rib cage reduces volume of thoracic cavity (relaxation involves diaphragm moving up), driving air out of lungs
WHat is the minimal lung volume (residual volume)
Residual volume (RV) is the volume of air remaining in the lungs after maximum forceful expiration
Normal values are around 1000-1200 mL
Why is minimal lung volume important
Because we need to ensure there is enough air for continual exchange of gases in the alveoli
What is the total lung capacity
The maximum amount of air the body can have at max inhalation. Typically around 5700mL
What is the normal volume of lungs at the end of normal inspiration
2700mL
What is the normal volume of lungs at the end of normal expiration
2200mL
What is the tidal volume
Difference between end expiratory and end inspiratory volume. It is around 500mL
What is the function of alveoli
We have millions of them, and they allow O2 to rapidly diffuse across membrane into surrounding capillaries for dispersal around the body.
It also allows for CO2 to transfer back into the lungs
The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out. Oxygen breathed in from the air passes through the alveoli and into the blood and travels to the tissues throughout the body.
WHat do type 2 alveolar cells do
Coats alveoli and stops hydrogen bonds forming in alveoli as it would cause it to collapse
How is gas transported around the body
Oxygen is predominately transported around bound to haemoglobin within red blood cells (98% transported this way, 2% dissolved in plasma)
CO2 transported by 3 mechanisms:
7% dissolved in plasma
Remaining 93% within red blood cells, but via two separate mechanisms (23% bound to haemoglobin, 70% converted to bicarbonate)
How many O2 molecules can a haemoglobin molecule carry
It can carry 4 molecules each
What is the normal saturation of haemoglobin
Normally 98% saturated
What happens if diffusion of gases between alveoli and blood is impaired
Hypoxia (typically goes with hypercapnia (too much co2))
What are two general categories of dysfunction in the lungs
Obstructive lung disease
Restrictive lung disease
WHat is the difference between obstructive and restrictive lung disease
Obstructive lung diseases include conditions that make it hard to exhale all the air in the lungs. People with restrictive lung disease have difficulty fully expanding their lungs with air.
What are some more conditions which could affect respiratory function
Diseases affecting diffusion of O2 and CO2 across pulmonary membranes
Reduced ventilation due to mechanical failure
Failure of adequate pulmonary blood flow
Ventilation/perfusion abnormalities involving a poor matching of air and blood so that efficient gas exchange doesnt occur
What are some involuntary responses
Sneezing
Coughing
Hiccups
Why does sneezing occur
Receptors in nose sends signal to brain to close off mouth
Forces air out of lungs through nose to expel irritants
Why does coughing occur
Receptors in respiratory tract send signal to brain to close off glottis and vocal cords
Builds pressure in lungs where it is then forced out when muscles contract
Why do hiccups occur
Trigger leads to involuntary contraction of the diaphragm
This closes off vocal cord briefly causing air to bounce off them, creating the hic sound
Describe flow of air into the body beginning at the nose and ending at the alveoli
Air enters the body through the mouth or nose and quickly moves to the pharynx, or throat. From there, it passes through the larynx, or voice box, and enters the trachea.
The trachea is a strong tube that contains rings of cartilage that prevent it from collapsing.
Within the lungs, the trachea branches into a left and right bronchus. These further divide into smaller and smaller branches called bronchioles.
The smallest bronchioles end in tiny air sacs. These are called alveoli. They inflate when a person inhales and deflate when a person exhales.
These alveoli then transfers gases to nearby capillaries
How many lobes are there of the lung on the right and left side? WHy the difference?
Right side = 3 (superior, middle and inferior lobe)
Left side = 2 (superior, inferior lobe)
This is because left is missing the middle lobe, because of the cardiac notch that it has (allows for space for heart)
