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PSL302-Lecture 36- Respiratory System Overview:
What are the functions of the respiratory system?
Structures that make up the respiratory system?
How is blood transported to and from the lungs?
What protects the respiratory system from pathogens/foreign particles?
How is lung function measured?
•Asthma attacks- treated by steroids inhalers or lung dilators
•What lung structures are affected during an asthma attack?
•If he were to undergo a lung function test during an asthma attack, what would you expect to observe?
The respiratory system functions to
•Exchange gases between air and blood, take in oxygen for cellular respiration and put out CO2 (made
•Regulate blood pH –this is due to the CO2 levels
•Defense from inhaled pathogens/foreign particles
•Vocalization - specifically the larynx – the air moves across the vocal chords along with the movement
of the tongue and the teeth…etc
•Cellular respiration = chemical processes inside the cell
Structures in the respiratory system:
•The nasal cavity and the mouth are part of the respiratory system
•Common passage way called the pharynx, both air and food can pass –the food goes into the
esophagus towards the digestive system and the air goes to the trachea
•At the top of the trachea we have the larynx
•When you swallow food, the epiglottis covers the common area so it goes to the esophagus not the
•There has to be a shuttling mechanism so food goes to the esophagus not the lungs
•Air is going through the larynx and trachea, and the trachea branches to form the right and left
bronchus, which branch further to get all the way down to microscopic sacs called the alveoli
•Starting at the trachea, it is the lower respiratory tract
•Respiratory muscles change the volume of the cavity in which lungs are found
oMuscles of inspiration
oMuscles of expiration
•Both types of muscles are found on both sides, even though they are put each on a side on the diagram.
•To bring air into the lungs, it requires that the diaphragm contracts and pushes down so that it
expands the thoracic cavity
oWhile in forced breathing in, the external intercostals will contract and raise up the rib cage
•In the case of expiration, it can be completely passive that when you stop breathing in there is elastic
recoil that will cause air to move out of the lungs esp when the diaphragm is relaxed, but if you want to
forcefully expire air, you rely on the internal intercostals to contract which draw the rib cage inward to
make the thoracic cavity smaller and the abdominal muscles, which contract and push up on the
diaphragm, and decrease the volume of the thoracic cavity.
•You need these muscles to breathe in and for forced expiration to breathe out
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•If we look at a cross section through the body, we see how the lungs are situated in the cavity
•Lungs are surrounded by two membranes, and in between these two membranes you have the pleural
cavity – a very small cavity that is filled with fluid
•You need this cavity because it allows the lungs to be inflated against the walls of the thoracic cavity
•Think of the lungs as an air filled balloon, imagine taking a fluid filled balloon pushing on the air
balloon, and you end up with something that resembles that pleural cavity
oInhalation is created by the dome shaped muscle, the diaphragm, flattening out. The diaphragm
also seals the bottom of the cavity (the plural cavity) that contains the lungs.
As the diaphragm flattens out, it increases the volume of the pleural cavity. As the cavity
increases in size, the same amount of gas that was in your lungs/cavity a moment ago does not
increase and you have the same amount of gas filling a larger cavity which decreases the
pressure as compared to barometric pressure.
As a result, you don't pull air in, air is actually pushed into lower (negative) pressure inside of
your lungs by the area of greater pressure that is outside of your lungs.
•The air travels through the airways that branch out and are finally found in the lungs
oPrimary bronchus – divides about 22 times to terminate in microscopic structures known as
alveoli where gas exchange takes place
oAs the air moves to the lungs, it is filtered and is humidified
oBy the time it reaches to the lungs, it is 100% humidified, has moisture in it, and is at body
temperature (Even if cold when first breathed in)
oThere is filtering that takes place in the nose and along the cells that line the respiratory tract
= the respiratory cilia that helps filter
•If you look at the cells in the nose or respiratory tract, you see that it is lined with cells that are of two
types – cells with cilia and cells that secrete mucus
•The mucus that is secreted forms a layer on top of the cilia and anything that you breath in gets
trapped in the mucus and the cilia beat moves mucus up into the throat where you can cough it or
swallow it, going to the stomach since it is acidic and can destroy pathogens
•The immune system secretes antibodies on all the different epithelial surfaces on the body, those bind
to pathogens and neutralize them and prevent them from interacting with epithelium cells
oIn tutorial, the case is talking about H1N1 and how the body defends against that and what
happens to respiratory function when you have influenza
•List of the names of the different branches of the airways as we move down to the lungs
oBronchi lobar all with cartilage that maintains their open shape
oSegmental bronchi terminal bronchioles all stabilized by bronchiolar muscles (smooth
muscles that surround the passageway).
oAll of these are called CONDUCTING AIRWAYS – transport air into the lungs
They constitute an anatomical dead space- if you breath in, air goes into the lungs, the
portion that remains in this part of the system is not going to exchange with the
epithelium of the alveoli, no gas exchange, and when we breath air out, it is a dead space
The first air we breathe in is the air in this pathway which doesn’t contain a lot of oxygen
– stail air that you breathe first, this volume is about 150ml and is called the dead space.
The Primary Lobules
•Bronchioles continue to branch and you get to this region
•This region consists of the respiratory bronchioles, alveolar ducts, and alveolar sacs, and alveoli –thin
enough to allow for gas diffusion and exchange
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