hello all this is dr fox let's begin our discussion of the lungs and ventilation pathway
by talking about the pleurae in this video i'll describe the pleura including the recesses and
potential spaces created by the pleural sac and the margins of these recesses at the mid
clavicular mid axillary in paravertebral lines i'll also discuss how this anatomy relates to
various clinical conditions and procedures so to begin pleurae is the plural of pleura
the pleura is a serous membrane which is lining a pulmonary cavity the serous membrane has two
distinct layers there is the visceral pleura the visceral pleura is adhered to the surface
of the lung itself in this case this is an example of atelectasis or a collapsed lung
so that we can see an exaggeration of the pleural cavity which is surrounding
the visceral pleura adhered to the lung and then there's also the parietal layer or the
parietal pleura which is adhered to the cavity walls on all sides on the right hand side here
that would be audience right not donor right we can see how the various layers of the
parietal pleura can be further classified so for instance adhering inferiorly to the diaphragm in
green here we have the diaphragmatic pleura adhere to the ribs in intercostal spaces and meeting that
diaphragmatic pleura we have the costal also known as the costovertebral pleura
lining the shared boundary between the pulmonary cavity and the mediastinum
we have the mediastinopleura which also meets the diaphragmatic pleura inferiorly
then finally above the level of the first rib we have what's known as the
cervical pleura the cervical pleura is sometimes referred to as its own segment of the pleura
and sometimes referred to as where the mediastinal meets the costal pleura
you may conceptualize it any way that you'd like just keep in mind that between the
visceral and parietal pleura there is a potential space called the pleural cavity
and we say that it's a potential space because these layers of visceral and parietal pleura
are very adjacent to one another they're very close and as the walls and floor of the thoracic
cavity change with contracting musculature so will the lung expand and contract as you'll see
so the various portions of the uh the pluri are innervated uh variously so for instance um there
are three uh major sources of innervation for the pleurae there are intercostal nerves
so those would be ventral primary rami of thoracic nerves one through 11. so
and these are going to provide innervation to the costal pleura
and the peripheral portions of the diaphragmatic pleura so
all of this region inclusive of a portion of that cervical pleura will be innervated by
intercostal nerves
the phrenic nerves remember c345 keeps the diaphragm alive which are descending
down on either side of the mediastinum are going to innervate the mediastinal pleura
and the central portion of the diaphragmatic pleura and the medial portion of that cervical
pleura as well so this portion of the parietal pleura will report via the
phrenic nerves and then finally the visceral pleura that which is adhered to the lung directly
is going to be innervated via the pulmonary plexuses
these are the autonomic plexuses which serve the lungs and the visceral afferent fibers recall
that visceral afferent fibers are neither sympathetic nor parasympathetic are going
to travel with the sympathetic fibers back to the central nervous system so that visceral pleura is
ANS so visceral afferents following sympathetics
now because the pleural cavity is a potential space it can be entered by various materials
a very common material to enter into this space is air this is a condition known as a pneumothorax if
the quantity of air is sufficient enough this can lead to atelectasis or a collapsed lung
as a result because that pressure is going to be greater than the pressure within
the lung various fluids can also enter into that that space as well
uh so there can be an over abundance of serous fluid and that's known as a hydro so water
thorax red blood cells may enter this space or just blood and that's known as a hemothorax
lymph can enter this space and that's known as a chylothorax where possibilities can enter this
space and that's known as a pyothorax or empyema usually that's the result of a bacterial
infection or a pneumonia the the treatment for this or part of the diagnostic pathway may either
be diagnostic or therapeutic is a procedure known as thoracentesis and with thoracentesis
a needle is placed through the intercostal space to withdraw the collected fluid
and that withdrawal of the fluid can be therapeutic because it reduces the pressure on the
lungs and it can also be part of the diagnostic procedure because that fluid may then be analyzed
inferior to the entirety of the thorax but certainly inferior to the pulmonary cavities
and lined by the diaphragmatic pleura we have the diaphragm
the diaphragm is a bimodal dome-shaped structure and what i mean by that
is if we follow that the classical lines of the diaphragm we can see one
dome a flattened area that's where the pericardium will be attached and then another
more gentle dome or cupula
each side of the diaphragm is innervated by its own phrenic nerve and so sometimes we
refer to each side as the hemi diaphragm uh the diaphragm is oftentimes referred to as a muscle
and that is absolutely true but unlike most muscles most of its tendon is in
the middle of the muscle and that's known as the central tendon that central tendon is about at the
eighth thoracic vertebrae level and as we can see the the two cupula may rise above that level hence
the the bimodality of that dome so a lot of people rather simplistically think that the diaphragm
kind of looks like a an arch dome like that and it actually is a little
more like that right go blue
the attachment sites of the diaphragm include the the costal margin so there we have
the xiphoid process there is part of that coming down and around the uh the lateral margins of
the 11th and 12th ribs and then posteriorly down from the first to the third lumbar
vertebra so if we think about this here we are at t8 and then the the posterior portion of
the uh that diaphragm can go down to lumbar one there lumbar two even as far down as lumbar
three so that should give you the sense that posteriorly that diaphragm really dives down deep
at the posterior margin of the thorax which we'll see
now the the complex attachment of the diaphragm is going to create a recessed space
another potential space called the costo diaphragmatic recess costo
ribs diaphragmatic diaphragm so this is just the space here that i've outlined in blue
between the diaphragm and the ribs and so there's going to be diaphragmatic pleura on the diaphragm
costal pleura on the ribs and intercostal spaces and then above there's going to be visceral pleura
adhered to the lungs so those are going to be the boundaries of that costo diaphragmatic recess
the costal pleura the diaphragmatic pleura and the visceral pleura and lung this is the space
that into which the lungs will largely fill during forced inspiration so that's a very deep breath
and the space from which the lungs will retreat during expiration now there are variable margins
to this space when we consider the well loosely front side and back to it so we have specialized
names for these regions and so the first would be the mid clavicular the midclavicular we just
take the clavicle which is the bone that would be approximately there and we run down
approximately midline on that clavicle i've highlighted it there in green and the uh
the midclavicular margins of this costo diaphragmatic recess are going between
the sixth to the eighths ribs so between ribs six and eight um as we move mid axillary so
from the axilla down those margins are going to drop to eight to ten so look at this six to eight
occupies two ribs worth eight to ten occupies two ribs worth and then if we were to flip the donor
around we would see pair of vertebrally again align next to the vertebral column going down
off a little there apologies it would be between the 10th to 12th ribs so 2 2 2 we know there are
12 sets of ribs we know that the the diaphragm is going to skirt that margin of the twelfth rib
so that's going to be the floor of the costa diaphragmatic recess ultimately in the back
we can then reason that the posterior portion of the costodiaphragmatic recess
is going to be deeper than the lateral or the anterior portion now we care about uh these
things for a variety of reasons so knowledge of the cost of diaphragmatic recess um is important
to consider for imaging so for a uh an anterior or thoracic uh chest x-ray um you can diagnose a
pleural effusion so the the presence of a fluid in the uh in the plural space by a a couple of
um phenomena the first will be the filling and blunting of the costophrenic angle so costophrenic
phrenic reference is the diaphragm and i'll show you a really good example of a costophrenic angle
right there now as we look on the right side that costophrenic angle should be
there but what we're seeing is that that angle is filled and blunted
there is also a filling in brunting blunting of the cardiophrenic angle so between the in
this case the right border of the heart which would normally go down to the diaphragm like so
we can see that that is filled and between these two there is a meniscus that forms
and so in radiology when you're learning about diagnosing a pleural effusion with blunting of
these costophrenic and cardiophrenic angles and the presence of a meniscus
it's important to consider that complex shape of that casto diaphragmatic recess
now knowledge of the margins here are going to be of primary importance for that
thoracentesis procedure because when inserting a needle between the lung and the remainder of
the pleural space you want to be able to access whatever fluid accumulates
in there without perforating the lung in creating a pneumothorax and so
it's probably best performed a pair of vertebrally or mid axillary but anywhere where there is
good access certainly you'll be able to draw more fluid away pair vertebrally because it's
deeper in the posterior so knowing these margins here six to eight midclavicular eight to ten
midaxillary and ten to twelve are going to guide your ability to accurately perform a thoracentesis
now there is another potential space called the costomedia steinle recess so costa
diaphragmatic is between the ribs and the diaphragm steinle is between the
costal pleura and the mediastinal pleura so costal pleura more anterior mediastinal pleura
more medial and deep and then the final margin will be the lungs themselves so if we can imagine
just drawing that down this way and
that way uh for where um where the lungs can be a boundary for this space so i've i've outlined what
we can see of the costomediastinal recess here in blue as the lungs fill during inspiration they
will invade into this space and during expiration they will retreat out of it probably the lion's
share of this space as being well documentable will be in this region so here we can see so the
cardiac notch of the left lung and that's where the costo media style recess is its greatest
so we've discussed the pluri and their parietal
and visceral layers we've discussed the pleural cavity and the various clinical conditions of
substances within the pleural cavity we've also discussed the costo diaphragmatic recess its
variable margins and clinical relevances as well as the costo mediastinal recess its boundaries
and how the lungs may move in and out of it this is your summary slide i thank you for your time