Lungs and Posterior Mediastinum Flashcards
1 bronchi divide into what structures?
lobar bronchi (aka 2 bronchi).
The branching of each secondary bronchus continues many more generations in the creation of the final bronchial tree structure
Where does the bronchi bifurcation occur?
at the level of the sternal angle
What keeps the tracheal lumen open?
C shaped cartilage
the lumen of most of the bronchial tree is kept open by cartilage, although it may not be c shaped
The tracheal cartilage at the bifurcation is called what?
carina
Does the carina sit in the absolute midline of the trachea? If not, where does it sit?
No. It sits just to the left of the midline of the bifurcation
What is the consequence of the carina sitting just to the left of the midline of the trachea near the bifurcation of the bronchi?
the right bronchus is slightly larger than the left. Thus, most aspirated bodies travel into the RIGHT bronchus (also because it descends at a more vertical plane than the left- due to the placement of the heart around the left bronchus)
What causes the cough reflex?
the carina in the trachea. it is very sensitive to aspirated bodies
Besides aspirated bodies, what else can stimulate the cough reflex?
Spread of cancer and subsequent swelling of lymph nodes inferior to the carina
How is the lumen of the bronchi kept open at different segments along their length?
C-shaped cartilage in the trachea become plate shaped cartilage in the proximal bronchi and continue until the bronchi transition to bronchioles (at which point it stops)
At the point where the cartilage ends (and with some overlap), elastic fibers, smooth muscle fibers, and musoca (and some submucosa) keep the lumen open and determine the diameter of the lumen
Near the alveoli, negative pressure inflates the most distal aspects of the bronchi
Where does cartilage end in the bronchi?
Between the bronchi and bronchioles
smooth muscle and elastic fibers are still present here
Once alveoli begin to appear in the bronchioles at increasingly distal segments of the bronchi, what are they called?
respiratory bronchi
Where do respiratory bronchioles terminate?
in alveolar ducts which lead into alveolar sacs that are clusters of alveoli around a structure called an atrium
Pathology can cause destruction of lung tissue. This is called?
emphysema. (think about what may cause emphysema- both genetically and environmentally)
What is the effect of emphysema on alveoli?
Emphysema causes a coalescence of alveoli and dissolution of large numbers of alveolar walls. This dramatically reduces the overall surface area of the respiratory membrane and this has a major effect on the acquisition of O2 and depletion of CO2.
Which diffuses through the respiratory membrane more easily, CO2 or O2?
CO2 (~10x).
Consequence: pathology causing increased respiratory membrane width will have less of an impact on CO2
What are the barrier layers of the respiratory membrane going from the lung space to the capillary?
1) surfactant
2) alveolar epithelial cells
3) capillary endothelium & their basal laminae
4) connective tissue
5) and, once inside the capillary, the plasma.
What pathologies can impair/affect the respiratory membrane?
1) cigarette smoking
2) fibrosis
3) Edema
4) infections
5) Pulmonary embolism
How does cigarette smoking affect lung function?
it increases the distance (width) of the respiratory membrane by accumulation of particles
How does edema affect lung function?
will cause fluid build-up and increase the distance for diffusion (impaired O2 diffusion)
How does fibrosis smoking affect lung function?
causes fibroblasts to increase the amount of connective tissue in the respiratory membrane, which can increase the barrier width (i.e. impaired oxygen diffusion)
How can infection smoking affect lung function?
it can cause the accumulation of bacteria or the large amounts of capsular materials that bacteria secrete.
Or, the bacteria can produce toxins that cause abscesses in which tissue is destroyed (and lung tissue does not regenerate).
How do pulmonary embolisms affect lung function?
It increases the resistance to blood flow and, thus, increases the pressure on the right side of the heart (making inspiration difficult)
How many bronchial lobes are there in each lung?
right-3
left-2 (left lung is slightly smaller)
What are the divisions of the bronchi in order from the bifurcation from the trachea?
1) 1 bronchi
2) 2 bronchi (lobar bronchi)
3) segmental bronchi
4) subsegmental bronchi
5) bronchioles
6) respiratory bronchioles
7) alveoli
How many segmental bronchi are there in each lung?
10 in both (even though there are 3 lobar bronchi in the right and only 2 in the left)
What are the components of a bronchopulmonary segment?
1) A segmental bronchus and associated lung tissue
2) associated pulmonary artery (carrying deoxygenated blood)
3) bronchial artery (carrying oxygenated blood)
4) pulmonary vein (carrying oxygenated blood
NOTE: there are also bronchial veins, but they have minimal role in blood flow
Are pulmonary arteries high pressure systems?
No. because they come from the low pressure right heart
What is the job of the pulmonary arteries? Where do they come from?
come from the right ventricle and deliver de-oxygenated blood to alveolar capillaries for gas exchange.
What is the job of the bronchial arteries?
Are they high pressure systems?
Where do they come from?
nourishing tissues of the lung
Yes, they are high pressure (because they originate from the thoracic aorta/left heart)
What part of the lung do the bronchial arteries end in/on?
at the beginning of the respiratory bronchioles. They are not needed distal to this point