Lecture 15: The Lower Respiratory Tract Flashcards
What are the 5 components of the LRT?
- larynx
- trachea
- bronchi
- bronchioles
- alveoli
What are the 3 functions of the LRT?
- conducts air to and from the site of gas exchange
- completes cleaning, warming, and humidifying of air
- provides a barrier between the air and the blood, and a large area for gas exchange
Where is the larynx located?
from the hyoid bone to the trachea
What passes through the larynx?
Air only
What is the purpose of the cartilage surrounding the larynx?
To protect it and to maintain an open airway
Name 5 cartilages of surrounding the larynx?
Thyroid cartilage, laryngeal prominence, cricoid cartilage, tracheal cartilage, epiglottis
What is the function of the thyroid cartilage/laryngeal prominence?
It is a big protective layer to make sure the airway stays open
Describe the cricoid cartilage
It is a complete ring of cartilage
What is the purpose of the epiglottis?
It prevents food from entering the airway
Where is the epiglottis?
Above the larynx
Is the glottis/voice box part of the larynx?
YES
Describe the glottis
There are folds of tissue attached to cartilages. When air passes over them, there is movement and this produces sound.
What are the two folds of the glottis?
vocal folds
vesibular folds
Describe the vocal folds
- true vocal cords
- used to produce everyday sound such as speaking and singing
How does the vocal folds produce sound?
Because they are such as thin membrane, when air passes over them it produces sound
How does testosterone affect the vocal folds?
testosterone affects the cartilage and the muscle, resulting in longer, thicker folds which results in a deeper tone
What is the role of the vestibular/”false” vocal cords?
These can close over to make sure foreign objects don’t damage the other vocal cords, or go further down the airway
They also produce very deep sounds
Where is the trachea located?
anterior to the oesophagus, sitting between the larynx and the primary bronchi
What is the role of the trachea?
Keep the airway open so that air can get to the lungs
How can the trachea keep the airways open?
There are C-shaped (incomplete) rings of cartilage which hold it open.
Where is the trachealis muscle and what is its role?
It is on the posterior aspect of the trachea which spasms when foreign objects enter the trachea which stimulates a cough and this forces the objects out of the trachea
What sort of epithelium lines the trachea?
respiratory epithelia: pseudostratified ciliated columnar epithelium with goblet cells
Where is the mucociliary escalator?
in the trachea
What is the purpose of the mucociliary escalator?
It removes debris to the pharynx to be swallowed and digested
How does the mucociliary escalator work?
mucus from goblet cells coat the surfaces of the epithelium so the debris becomes trapped then the cilia move the mucus to the pharynx
How many lungs do you have?
2
How many lobes does the lung on the right have?
3
How many lobes does the lung on the left have?
2
What are the three lobes of the right lung called?
superior lobe
middle lobe
inferior lobe
What are the two lobes of the left lung called?
superior lobe
inferior lobe
Why does the left long only have two lobes?
Because the heart sits to the left so it takes up space
Where is the apex of a lung?
just beneath the clavicles
Where is the base of the lung?
it sits on the diaphragm
What is the hilum of the lung?
The part of the lung where blood vessels, nerves and lymphatics go in and out.
Where do the bronchi enter the lungs?
in the hilum
Where is the costal surface of the lungs?
right up against the ribs
How do we get to the lungs from the trachea?
the bronchial tree
Where are the primary bronchi?
When the trachea spilts into two and they enter the lungs through the hilum
Where are the secondary bronchi?
Branching off the primary bronchi, heading into each of the lobes
How many secondary bronchi are in the left lung and why?
2 because there are 2 lobes
How many secondary bronchi are on the right bronchi and why?
3 because there are 3 lobes
What is the other name for the secondary bronchi?
lobar bronchi
Where are the tertiary bronchi?
Branching off the secondary bronchi
What branches off bronchi?
Bronchioles
As the branching happens, the diameter of the bronchioles gets
Smaller
At the end of the bronchial tree, there is the _______. What does this signify?
terminal bronchioles
This signifies the end of the conducting region and the start of the respiratory region
Describe the cartilage of the primary bronchi and state why
There are complete rings of cartilage because there is no trachealis muscle
Describe the muscle of the primary bronchi and state why
There is a complete ring of smooth muscle to allow for dilation
As there is more branches, the vessels get smaller which means there is less of a need for
cartilaginous support
Describe the cartilage of the secondary and tertiary bronchi
There are individual bits of cartilage that aren’t a full ring. These are called cartilage plates. They give some support
What is the epithelium in the primary bronchi?
respiratory epithelium: pseudostratified ciliated columnar epithelium with goblet cells
What is the epithelium in the secondary and tertiary bronchi? Why is this needed?
respiratory epithelium: pseudostratified ciliated columnar epithelium with goblet cells but the columnar cells reduce in height because the vessels have a smaller diameter. There are also less goblet cells
What is the epithelium in the bronchioles?
Cubiodal epithelium with no goblet cells
Why are there no goblet cells in the bronchioles?
Because they are such as small diameter that any mucous would block up the airway
Describe the cartilage and smooth muscle of the bronchioles
There is no cartilage but there is smooth muscle
What is the purpose of the smooth muscle in the bronchioles?
for bronchoconstriction/dilation
Each terminal bronchiole supplies a
pulmonary lobule
Pulmonary lobules contain many
alveoli
What are alveoli?
air sacs
What is the epithelium of the alveoli? Why is this needed?
Simple squamous epithelium on a thin basement membrane is needed so that there is as little distance as possible for gas exchange
External surface of the alveoli are covered in a fine network of
pulmonary capillaries
The simple squamous epithelium of the alveoli is made of
pneumocytes (lung epithelial cells)
What are the two types of pneumocytes?
- type | squamous
2. type || cuboidal
What is type | squamous pneumocytes needed for?
It forms the respiratory membrane/blood-air barrier with capillary wall and shared basement membrane
Where are type || cuboidal pneumocytes and what are they needed for?
they are scattered amongst type | squamous and they secrete surfactant
What is the surfactant secreted by the type || cuboidal pneumocytes and what is their purpose?
It is a complex lipoprotein that reduces surface tension of the alveolar fluid to make sure the sac stays open so air can go in there
Apart from type | squamous and type || cuboidal pneumocytes, what is the other types of cell in the alveoli and what is its role?
Roaming macrophages that remove debris
Where is the respiratory membrane/blood-air barrier?
Where the capillary meets the alveolar wall/cell layer
The respiratory membrane/blood-air barrier is made up of what three layers?
- type | squamous pneumocytes forming the alveolar wall/cell layer
- fused basement membrane
- capillary endothelium
