okay let's talk about the mediastinum we'll answer the questions what is the mediastinum and what regional anatomy does the medium contain hello everyone my name is Dr Morton and I am the noted anatomist uh the medium means Midway in Latin and so what does that mean Midway well here's a cross-section or an axial section through the chest and there are the lungs that fill the lateral spaces of the thoracic cavity and Midway in between the lungs is a is this area known as the mediastinum basically midway between the lungs if we go side to side and front to back it's between midway between the sternum and the vertebrae and then top to bottom the medius dyum uh has the following regions the superior mediastinum between the first rib and that transverse thoracic plane and then the inferior media stum which is between the transverse thoracic plane in the diaphragm and the infir medum has three different sub regions because we're anatomist we have to name the Daylights out of everything so the intermedius stum is the region in front of the heart and it's filled with the thymus then there's the middle mediastinum which is filled with the paracardial sac and the which contains the heart and then the posterior medium which is everything behind the heart and those are the structures the dates that we'll talk about in a minute well what's the take-home message from this well the take-home message is the following intermedia stum I'm not really going to cover because it's the thymus and that's about it and then the middle medum we've covered in a previous lecture so I'm not going to cover that and so basically the superior medium and the posterior medum are the two areas we're going to focus on let's first do the posterior media stum so the posterior media stum is like the area behind our living room TV so let's take a look at our living room shall we I'm just kidding that's not my living room there's our TV okay so there's our TV in our living room if we were to look behind the TV this is what it looks like you see that tell wait there's our TV right there and then you see U behind the TV things like the following there is this red wire that goes all the way up somewhere in her ceiling and I'm not sure where it goes and then here's this green wire that goes all the way up and that goes somewhere into the ceiling that goes into uh speakers for surround sound and then there is this gray cable that comes from like a beta vcr and goes somewhere else and so basically behind our TV is a bunch of different wires shoved in behind the television well the posterior media stum is like the area behind our living room TV where our heart is our living room TV and the posterior medum is everything posterior to the heart all those different wires but unlike my living room they're extremely organized and so the posterior media stum the stuff the wires the material behind the TV or behind the heart are the following dates which is an acronym for desending aorta aaga system of veins thoracic duct esophagus and or sympath pathetics so let's start with our descending aorta the descending aort comes from the aortic Arch and at every segmental level it gives rise to these posterior intercostal arteries and I'm not drawing all of them but at every level and then the descending aort goes and pierces the diaphragm through the um aorta catus at the T12 vertebral level and so if we now look at a lateral view in red there's the descending aorta we see the arch that at every segmental level we're going to see all of these posterior intercostal arteries that segmentally go and provide and enter the intercostal space and then you'll notice that an asmosis with the anterior intercostal arteries laterally next is our aigus system of veins and so here we have an anterior View and let's goost way through so now there's our aigus system of veins where there's the azus vein the accessory hemus vein and the hemus vein let's talk about them in more detail where you see all those posterior intercostal veins drain into this system and so the azika system of veins drains Venus blood from the posterior wall of the abdominal and thoracic cavities let's take a look at that accessory hemus fan it drains those posterior intercostals from the upper left thoracic region then our hem Asus vein drains posterior noals from the lower left thoracic and abdominal region and then there's our aigus vein which drains all the posterior intercostals from the right side of the abdominal and thoracic cavities and then the azus system of veins ultimately drains into the superior venas so there's our azus vein and then goes into the back side of the superior vena where it drains into that SVC let's do this again from a lateral view where there's our aigus vein as it courses all the way up and then this aigus vein is going to collect all these posterior intercostal veins and that are going to be seen segmentally entering into the aigus vein and so what happens then is this azus vein courses over that right primary broncus and that that transverse thoracic plane dumps into this superior vena there all right now let's talk about the thoracic lymphatic duct and turn that green because it's the largest lymphatic vessel in the body it arises from the cestal kyly and then it's going to coarse in from the abdominal into the thoracic into the neck region and the thoracic lymphatic duct transports about four liters of lymph uh per day and so as closer view and there's this thoracic lymphatic dect it's very deep right along those vertebral body it courses up and at this transverse thoracic plane courses over to the opposite side and ascends up and ultimately drains into the uh Circ systemic circulation let's look at the esophagus now so the esophagus is this structure here in brown and it transports food from the ferx all the way down into the stomach but first it's got to pierce the diaphragm at the esophageal Hiatus which is located at the T10 vertebral level and the vagus nerve so the vus nerve is going to innervate the esophagus the left vagus nerve comes down after innervating the heart and the lungs it then sends a branch to the front of the esophagus and then once the esophagus hits the diaphragm that vagus nerve horses along right along the esophagus and then enters into the abdominal cavity on route to the stomach whereas the right vegus nerve courses and when he hits the esophagus it more goes posterior deep to the esophagus and then both of these right and left Vegas nerves are going to go to the Celiac ganglia now they do not synapse in these ganglia but they course along with the sympathetics to the for gut and mid gut now there's the esophagus and so the right and left Vagas nerves form an esophageal plexus of nerves all around the esophagus now let's talk about sympathetics shall we and so the sympathetics such as the sympathetic trunk all along the par vertebral region and so think Pearl for sympathetic gangle and a pearl necklace so Pearl is sympathetic ganglia and the Pearl Necklace is a sympathetic chain and the sympathetic ganglia are those cell bodies of post ganglionic sympathetic neuronal cell bodies and their informations destined for sweat glands um in the skin as well as structures in the head neck as well as the heart and lungs there we've got one sympathetic ganglia there and there's another sympathetic ganglia there and there's an internodal fiber that go in between so there we've got sympathetic ganglia the internodal fibers but the whole thing is a sympathetic chain what about the sympathetic inovation to abdominal pelvic organs these splank Niks greater lesser and least splank niic nerves let's talk about those so the greater splank niic nerve um comes from T5 to T9 sympathetic ganglia levels and so let's look at this where there there's T5 T6 t7 T8 and T9 sympathetic ganglia and so if we now find this splenic nerve from the T5 sympathetic gangle and then from the T6 and then from the t7 and then from the T8 and then the splank niic nerve from the T9 sympathetic ganglion they form a really big splank niic nerve we call it the great or the greater splank niic nerve that gives contributions from T5 to T9 it then courses through to synapse with a preotic ganglion specifically a Celiac or Superior mesenteric ganglia let's look at the Lesser splenic nerve that comes off of T5 and t11 and then it courses down from both of these sympathetic ganglia and it synapses with a preotic ganglion as well and then the least blank niic nerve it looks like it's coming from the diaphragm I just don't have drawn it's deep to that is the T12 12 sympathetic gangion and then it synapses with a preor gangling as well specifically aoral renal gangling there we got that's posterior medum let's go into Superior medum and the superior medum between the first rib and that transverse thoracic plane there there are three different planes from front to back Venus arterial and visceral let's talk about each of them let's start with the Venus plane first and so the in the we've got there is a right internal jugular vein that drains blood from the right side of the brain and head and it joins with the right subclavian vein that's draining blood from the right Upper Limb so they collectively come together to become a vein that drains the arm and the head brachial for arm calic for head so the right brachial calic vein which if you have a right then there's also a left brachos falic vein and both of these brachio falic veins come together to make the superior vena that then drains down into the right atrium of the heart so there we have our Venus plane whoops pardon me there we've got I didn't mean to do that there is our Venus plane with all the different veins labeled okay now let's take a look at the the finish of the story of the thoracic duct um because when we look at this thoracic duct coming from the cernal kyi we keep talking about it being in the back of the poster medyum but what happens in the superior measum is that this thoracic duct there drains in at that point drains into the junction of the left internal jugular vein which is there and the left subclavian vein which is there that's where that thoracic duct drains and so review of the lymphatic drainage it's best to figure out before I talk about what the thoracic duct drains is what the right lymphatic duct drains it drains limp from the right side of the head and neck as well as the uh right chest and arm region and the thoracic duct drains everything else drains limp from the rest of the body okay okay so now let's take a look at the arterial plane and there is our aortic Arch and the aortic Arch courses around at the very top of the aortic Arch it gives rise to three primary branches the brachio falic artery or trunk that gives rise to a branch that goes to the arm the right subclavian artery and sephy the head the right common cored artery that goes to the right side of the brain and the right side of the face then we have our left common cred artery that courses up the left side of the head and brain and then our left subclavian artery that's going to give arterial supply to the left Upper Limb there we've got our arterial limb with everything labeled there next is our visceral plane where we see our trachea or the wind pipe and behind the trachea is the esophagus or our food pipe and there we've got our visceral plane and so my friends there is our medius dyum in a nutshell the mediastinum if we take a look at that transverse thoracic plane above it is a superior medium which has a Venus arterial and visceral plane and then the posterior Medi in which the structures are the dates and my friends that's the medius Dynam in a [Music] nutshell [Music] d