Flashcards in Lungs and Posterior Mediastinum Deck (75):
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?
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?
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?
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?
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
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?
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
6) respiratory bronchioles
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
Where does the horizontal fissure of the right lung run?
crosses the 4th rib in the mid-clavicular line and follows it to the sternum.
Does the left lung have a horizontal fissure?
Where do the oblique fissure of the right and left lungs run?
cross the 5th intercostal space in the mid-clavicular line and follow the 6th rib to the sternum.
What are the positions for listening to breath sounds of superior lobes?
above 4th rib
What are the positions for listening to breath sounds of the right middle lobe?
below 4th rib
What are the positions for listening to breath sounds of inferior lobes?
on the back below 6th rib.
[the inferior lobe has much more exposure on the posterior side of the body]
What are the lobes of the right lung?
superior, inferior, and middle
What are the lobes of the left lung?
superior and inferior
Where do the structures of the root of the lung leave the mediastinum and enter the substance of the lung?
Is the cardiac notch on the left or right lung?
left due to the position of the heart
Does the cardiac notch of the left lung sit superior or inferior to the lingula?
(the lingula is an inferior portion of the LEFT superior lobe)- only present in the left
What are the structures of the right hilum from anterior to posterior?
What are the structures of the left hilum from anterior to posterior?
NOTE: the inferior part of both hilum is called the pulmonary ligament- it may be a space for expansion of the hilum structures
How many bronchial arteries are there?
3- 2 left and 1 right
Where do the two left bronchial arteries arise?
arise from the anterior aspect of the thoracic aorta near the tracheal bifurcation
Where does the singular right bronchial artery arise?
usually arises from the first right posterior intercostal branch of the aorta
Where does the left bronchial vein empty?
into the accessory hemiazygos vein
Where does the right bronchial vein empty?
empties into the azygos vein near its junction with the SVC
What should sympathetic innervation to the pulmonary plexus cause?
vasoconstriction, bronchi dilation, and decreased bronchial mucous gland secretion
parasympathetic is opposite
What is the role of lymphatics in the lungs?
Capillaries secrete fluid ot nourish the lungs and lymphatics re-collect it and remove it to venous circulation
Where does the thoracic duct (the largest lymph vessel) empty?
just distal to the junction of the left internal jugular and subclavian veins
empties the 3/4 quadrant of the body
What happens if the lymphatic pump doesn't work properly?
results in edema, a build-up of fluid in the interstitium, the tissue spaces
All lymph above the diaphragm on the right side of the body drains into what?
the right lymphatic duct
includes the right side of the head, neck, right upper limb and right portion of the thoracic organs and wall
Where does the thoracic duct?
the cysterna chyli (which receives lymph from lumbar vessels and from intestinal vessels inferiorly. It lies inferior to the diaphragm)
How does the thoracic duct enter the thorax?
through the aortic hiatus
Describe the route of the thoracic duct from the aortic hiatus to where it empties.
TD courses superiorly from the aortic hiatus, posterior to the esophagus, anterior to azygos veins, intercostal arteries and vertebral column
It lies to the right side of the vertebral bodies until roughly the 5th thoracic vertebral level where it courses to the left side. It ascends posterior to aortic arch but then goes between the left subclavian artery and left brachiocephalic vein to empty into the junction between internal jugular and subclavian
Where do inferior tracheobronchial nodes lie?
just below the carina of the trachea
They are connected to paratracheal nodes whose efferents form the left and right bronchomediastinal lymph trunks that drain directly into directly into the internal jugular-subclavian vein junction or into the right lymphatic duct or into the thoracic duct
NOTE: although all three routes are possible, the most common drainage route of the lungs goes to the right lymphatic duct through the route described above
Does any lymph from the left lobe drain into the right bronchomedistinal trunk?
Yes, some from the lower lobe
Do any parts of the lungs drain through the abdomen?
Yes, some from the inferior portions of both lobes.
ClinCorr: cancer could spread from the lungs to the liver
What structures are posterior to the esophagus?
the thoracic duct**, posterior intercostal arteries and veins
What vertebral level does the esophagus enter the diaphragm?
What are the two active constrictors of the esophagus and what are their roles?
1) the upper esophageal sphincter. Located at the beginning of the esophagus. It opens during the swallowing reflex and closes to keep regurgitation to a minimum, at least under normal circumstances.
2) Another constrictor is inferiorly where the esophagus empties into the stomach, the lower esophageal sphincter. When working properly, this also keeps stomach contents from refluxing back up toward the pharynx and larynx
Where is a position for passive constriction of the esophagus and what it it (potentially) caused by?
as the esophagus passes posterior to the tracheal bifurcation, there is the potential for a constriction due to pressure from the left bronchus.
What do the right and left vagus nerves do after giving off the right/left recurrent laryngeal nerves?
They pass posterior to the root of the lung and they divide into a plexus, the esophageal plexus as they course along the esophagus.
They then re-group and change course slightly, due to rotation of the gut (which we will take up in abdomen), and become anterior and posterior vagal trunks on the surface of the esophagus just as it is penetrating the diaphragm
What blood source supplies the first 2 intercostal spaces?
the subclavian artery (9 pairs of posterior intercostal arteries supply the other spaces)
What vein drains the posterior mediastinum?
the azygos vein system
The azygos veins forms from the junction of what two veins?
the right ascending lumbar vein (posterior abdominal wall) and the right subcostal vein (this is inferior to the aortic hiatus)
Does the azygos vein travel on the left or right of the vertebrae through the thorax?
right. It travels anterior to the posterior intercostal arteries and receives inflow from the right posterior intercostal veins (up to space 5)
The azygos vein receives the posterior intercostal veins from the right superior intercostal vein from which intercostal spaces?
Where does this junction happen?
2-4 intercostal spaces (only on the right side)
the junction happens as the azygos vein rises over the root of the lung to enter the SVC (remember the azygos is going to arch anteriorly over the root of the lung form a posterior position to enter the SVC (which is anterior to the lung)
The hemiazygos vein arises from the junction of which two veins?
the left ascending lumbar and left subcostal veins
Describe the route of the hemiazygos vein
The hemiazygos vein ascends along the left side of the vertebral column as high as the 9th thoracic vertebra and then turns to the right across anterior face of the vertebral column (and posterior to the aorta, esophagus and thoracic duct) to empty into the azygos vein
The accessory hemiazygos vein receives posterior intercostal veins from which spaces?
4 through 8. It is connected to the azygous vein near the 8th intercostal space where it passes posterior to the esophagus, the thoracic duct, and the aorta
It is also frequently connected to the left superior intercostal vein that drains the superior 3-4 spaces into the left brachiocephalic vein
Describe the position of the IVC hiatus of the diaphragm?
slightly to the right of the midline and goes through the central tendon. This is located at approximately the level of TV8. The IVC enters the right atrium immediately superior to the hiatus.
Describe the position of the hiatus of the esophagus of the diaphragm?
very slightly to the left of midline at the level of TV10. It is formed by muscular loops contributed to by the crura of the diaphragm (to be described with the abdomen).