Lymphatic System

when I first learned about the immune system I remember being really confused I couldn't visualize where it was and what it did and how it related to other parts of the body so what I'm going to do in this video is we're going to take a look at a series of diagrams and reveal it piece by piece so that you understand by the end of this exactly what the lymphatic system does how it's organized and where it is in the body so let's uh jump to the Whiteboard and get started so let's start with the

three main functions of the lymphatic system the first thing is it's going to prevent swelling or edema by returning fluid to the bloodstream so there's going to be a buildup of fluid and tissues throughout our body the lymphatic system is going to take that fluid and return it to our blood circulation so they don't have swelling throughout our body the second thing is it's going to scan for pathogens and initiate an immune response if it finds them so it's going to take some of this fluid from the tissue in our body it's going to run

it through lymph nodes the lymph nodes will be full of B cells and t- cells all these immune system cells that are going to detect if there's a pathogen if there is it's going to fight that pathogen off and start this immune response so that we can get our body back to being healthy and that's why the lymphatic and the immune systems are often lumped together kind of as one system finally the third thing it's going to do is it's going to absorb fat from our digestive tract from the intestines and bring that fat into

blood circulation so it turns out that fats that we eat can't go from our intestines directly into our bloodstream it's got to take a detour through the lymphatic system in order to get to the bloodstream we'll talk about why that is later on so those are the three primary lymphatic system functions and throughout the video we're going to be looking at those and seeing how the fatic system is set up in order to accomplish those three functions first we're going to take a look at the fluid management part of this the part where I talked

about it reducing swelling or edema in the body so we're going to zoom in on some tissue in the body here here we've got an arterial which is going to be bringing blood into this tissue area and we've got a venule which is going to be bringing blood out of that tissue area and this arterial is bringing blood from the heart that's oxygen rich the venu is returning blood back to the heart that's oxygen poor in other words it's given off its oxygen it's returning back to the heart now let's draw some tissue cells in

here and so I've got a bunch of cells here it kind of looks like a skull that was unintentional there's a lot of epithelial cells and there's going to be spaces in between some of those epithelial cells the spaces between cells are going to be filled with fluid now to deliver the fluid and the oxygen and all the stuff that these cells need we're going to need capillaries so we have a capillary that's connecting in the arterial over to the venil in the diagram you see a color change from red to blue meaning that it's

going to be giving off oxygen I feel like I say this in every video I make but the blood never actually turns to Blue it's always red just a slightly different shade of red but in diagrams we use red and blue for oxygen poor and oxygen rich blood now it's not just one capillary we've got a whole bed of capillaries so we see this bed of capillaries with all these branches and that's so that it can give off the oxygen and fluid and everything to all the different cells here all right let's remove a few

cells so we have room to write some stuff here and like I said it's going to be giving off oxygen to these cells it's also going to be Distributing water or fluid these capillaries are leaky so the water the oxygen is going to be coming out of there it's also going to have other things coming out such as protein hormones nutrients all these different things that the cells need to survive all of that is leaking out of the capillary into the space between the cells the main two we're concerned about here are water and oxygen

though and of course there's other stuff that needs to go back into bloodstream circulation waste products that we don't need such as carbon dioxide that the cells produce during cellular respiration as well as a lot of that fluid that leaks out is going to be pulled back into to the capillaries so we have water coming out and we have water coming back in to return to circulation now there's various forces that are causing the fluid to move in and out we've got hydrostatic pressure which is kind of just the the fluid pressure of something moving

through a tube and that's going to be forcing a lot of this water out we also have osmotic pressure which is going to be pulling a lot of the water back in but also like I said there's proteins and other stuff that are leaking out so we've got proteins floating around in this interstitial space between the cells and that's going to be pulling on the water and keeping some of that water outside of the blood vessels because of osmotic pressure hydrostatic and osmotic pressure are a little bit confusing that's probably a topic for another video

but the main thing to know here is that water is coming out and water's coming back in but there's more water leaving the capillaries than there is water coming back into the capillaries and so that's going to lead to a buildup of fluid in this tissue over time leading to swelling so we need something else in this tissue that's going to remove that excess water and so that's where the lymphatic capillaries come in the lymphatic capillaries are these series of tubes that extend up into the capillary bed we always use green and diagrams to represent

the lymphatic system and they branch in and out here but they're not a continuous stream like the blood vessels are the cardiovascular system is a closed system meaning that the fluid could stay in the cardiovascular system and completing the circuit from the heart to the lungs back to the heart to the tissues of the rest of the body and then back to the heart and so on the lymphatic system is an open system it's not a continuous system that's going to go throughout the whole body and return back to its original location so it's going

to be absorbing some of this interstitial fluid and it's going to travel through here and that's eventually going to work its way back to the veins returning all that excess fluid that it picks up back back into Venus circulation but again the thing we're focused on right here is preventing swelling so like I said there's water leaving there's some water coming back in but not enough water coming back in so a lot of that buildup of fluid is going to enter into the lymphatic capillaries and travel down here so it can be returned back to

circulation now let's zoom in on the end of one of these little lymphatic capillaries so we've got our main capillary right here the end of the lymphatic capillary and we got all the tissue cells that are there now if you notice and look closely there's these spaces that are between the cells and the capillary that's where the fluid is going to be leaving as well as proteins and other things how they leave the capillary through those little spaces right there the lymphatic capillaries have spaces as well can't really tell in the diagram but those spaces

in the lymphatic capillaries are a little bit bigger and that's going to be important later on and of course we have red blood cells that are traveling through the capillary those are carrying oxygen in carbon dioxide out now we've got a lot of fluid in this diagram there's fluid here in the blood capillary there's fluid in the lymphatic capillary there's fluid between the cells and they all have different names so blood plasmas is what we call the fluid in the blood capillary we have lymphatic fluid or lymph which is the fluid that's in the lymphatic

capillary and then we have interstitial fluid which is the fluid between the cells and the tissue interstitial just means between things now most of this is all the same stuff it's mostly water there's other stuff dissolved in it and it's flowing in and out between all these areas we just give it different names depending on where it's located now let's break down all the movement happening in this diagram first of all we've got the blood that's coming in so that's going to be blood plasma or fluid and the red blood cell also white blood cells

coming through there that's coming from the heart and then we have fluid flowing out of this area traveling back to the heart of course those capillaries are leaky so we have fluid that's traveling out of the capillary which we see right here and a lot of that fluid that leaves is going to go back into the capillary which we see right here of course not as much fluid is traveling back into the capillary so we have a buildup of fluid in the tissue space or a buildup of interstitial fluid so a lot of that fluid

is going to travel into the lymphatic capillaries becoming lymph where it's then going to travel through the rest of the lymphatic system and then back to a vein the subclavian vein where it's back into circulation and again the fluid in here we call blood plasma once it leaves the capillary we call interstitial fluid and then once it moves from the interstitial fluid to the lymphatic capillary we call it lymph so this diagram is showing what's happening in the lymphatic system at the tissue level how these lymphatic capillaries are going to be pulling fluid this excess

fluid from the interstitial space and bringing it out of that tissue so that we don't have swelling or edema throughout the tissues in our body next we're going to zoom out and look kind of at the whole body level so I've got a diagram of a person here we're going to start here with the hands just because it's a distal end of the arm here and you can see all these little lymphatic capillaries that are extended out into all parts of the hand basically almost anywhere in your body where there's blood or blood capillaries there's

going to be lymphatic capillaries that are there to remove that fluid so those lymphatic capillaries are going to be picking up fluid which came from the bloodstream which then became interstitial fluid and now is in the lymph vessels so it's going to be bringing that lymph fluid up the arm closer to the middle part of the body and if you notice right here we've got some spots in the those lymph vessels and those are going to be lymph nodes and this is where we're getting into that second function of the lymphatic system where we're scanning

for pathogens and initiating an immune response the lymph nodes are where a lot of that is taking place so let's zoom in on one of those lymph nodes and take a look at the structure of the lymph node and how it does this all right so there's our cute little lymph node and we're going to have first some vessels that are bringing the lymph into the lymph node we call these afren vessels affrant just means toward and I have the a capitalized there because in a second we're going to see an ephant vessel so these

vessels like this one right here that's going to be an affrant vessel that's bringing lymph into the lymph node now notice on these vessels there are these little valves which are going to make sure that the lymph is only flowing in One Direction and if lymph tries to flow backward those are going to snap shut and prevent the lymph from back flowing since we don't have a lymphatic equivalent of a heart to push or pump the lymph fluid through the lymph vessels we've got these one-way valves so that that lymph fluid is only traveling in

the correct direction so lymph is coming in through multiple afferent vessels here and then the lymph is going to travel out of the lymph node through an errant vessel and there's only ever going to be one errant vessel leaving a lymph node all right now let's take a look at a couple regions of the lymph node here first we've got the medulla which is going to be kind of in the center of the lymph node right there where the lymph is passing through to get to the errant vessel and then we've got the cortex which

is going to be the outer part of the lymph node so all these sections right in here are part of the cortex now for this to scan for pathogens we have to have white blood cells present or lymphocytes present those lymphocytes are going to be B cells and t- cells and macrofagos and a few others but they've got to get there somehow now they're white blood cells they need to come through the bloodstream so we're going to have some blood vessels coming into each of the lymph nodes those blood vessels are going to enter in

right by the errant vessel right in here it's going to be bringing blood in including white blood cells and then of course you've got to have a vein which is going to be traveling out of that area and so we've got a little capillary bed and that's how the white blood cells are going to make it to the lymph node so we're going to have B cells all throughout this outer part of the cortex we're going to have t- cells kind of mainly clustered in the inner part of the cortex so any pathogens that get

into your bloodstream some of those are going to end up in the lymph fluid where they're going to pass through here and they're going to have to pass by these B cells and these t- cells which are going to be on the lookout for antigens on those pathogens that they recognize so they can start attacking them and initiate this immune response by the body so the lymph fluid is going to pass by there it's going to fill in this medulla and then come out through the eant vessel where it's going to continue on its path

and we're going to see where that path goes to next so again how does lymphatics system scan for pathogens and initiate the immune response well lymph is going to be traveling through these affrant vessels through the cortex where it passes by B cells and t- cells those are going to be trying to detect and see if there's a pathogen present and they'll start that immune Cascade if there is and if not that lymph fluid is just going to pass by out the eant vessel where it can continue on its path all right let's see where

all of this goes next but first I want to point out if you notice that the lymph nodes aren't just throughout every part of these lymph vessels they're kind of clustered in certain regions throughout this next part of our diagram here I'm going to be pointing out lymph node regions in green and this first section here that you'll see is the epitrochlear section of lymph nodes there's going to be located kind of on the medial side of the elbow right in there now all of this lymph fluid that's traveled up from the hand it's going

to be traveling up here through this axillary or armpit region and we're actually going to have a lot of lymph nodes in that axillary region so you got a lot of lymph nodes in your armpit kind of extending up here toward the neck region notice that almost all of those vessels are starting to converge into one bigger vessel right there this is where the lymph fluid is about to drain back into the veins so it can return to our blood circulation so here in our diagram we have the right subclavian vein and the left subclavian

vein the subclavian veins connect together to form the superior vnea and the superior vena is going to bring the blood back into the heart to the right atrium right ventricle it can pump it to the lungs but all of the lymph fluid that we gather is going to drain back into either the right subclavian vein or the left subclavian vein through two different ducts du s the first of those is the right lymphatic duct and then the second is going to be the thoracic duct the thoracic duct is going to extend down into your chest

and down toward the abdomen and the thoracic duct is going to get most of the lymph drainage and the right lymphatic duct is going to get just a smaller fraction of it we'll see more of this in a second but the right lymphatic duct is going to get lymph from the right arm the right side of the face and a little bit in this region right here whereas the thoracic duct is going to drain all of the lymph from the left arm the left side of the face as well as like the whole lower half

of the body so right lymphatic duct is getting just lymph from this region right here thoracic duct is getting lymph from this region down here and the whole lower half of the body the chest is also going to have a lot of lymphatics and so we see a lot of lymphatic vessels right here that are going to be collecting fluid and bringing up into that axillary region up next is the region where we actually have the most lymph nodes and that's going to be in the cervical region so there's going to be a lot of

lymph nodes in our neck there's going to be a lot kind of in the side of our face right in here and often times that's broken up not just into cervical but other names of regions as well but in this video video I'm just giving kind of an overview of the location of the lymph nodes so we've got all those lymph nodes in the cervical region in the left side of the face they're draining into the thoracic duct and then in the right side of the face all of those are going to be draining into

the right lymphatic duct so if you were to trace the path here from the hand the lymph is traveling up this way into the right lymphatic duct from the face is traveling down to the right lymphatic duct or from here it's traveling up the arm to the thoracic duct or from the face down to the thoracic duct now let's move on to the lower half of the body we're going to start down at the very bottom or inferior part we're going to have some lymph nose in the knees and those are going to be the

poal lymph nodes pole is just referring to the knee that lymph fluid is going to be draining upward it's going to head toward the inguinal lymph nodes the inguinal lymph nodes are found right in here and then from there lyph fluid is going to travel up into the abdominal lymph nodes right in through here so if you'll notice you don't have a lot of lymph nodes in the leg you don't really have any below the knee youve got a few in the knee you've got a lot in the inguinal area right here you've got a

lot in the abdominal area right here now almost all of the lymph fluid that's coming from the lower half of the body is going to be right in here where it's going to enter into something called the CNA kyai the CNA kyli is just this big collecting duct for lymphatic fluid it's going to connect all these lower lymphatic vessels up to the thoracic duct and all that lymphatic fluid is going to drain into the left subclavian vein via the thoracic duct a couple more branches here that I need to draw in the next one is

going to be the thoracic lymph node so there kind of a more lateral Branch that's going to come up here that's going to have some thoracic lymph nodes we're going to have those on the other side as well from what I can tell on most diagrams that I've seen there is a lymph connection from the CNA kyai right here up to the right lymphatic duct so I'd imagine there is a little bit of drainage from this lower part of the body up into the right lymphatic duct but the vast majority of lymphatic fluid from the

lower half of the body is going to travel up through the thoracic duct into the left subclavian vein so all of these lymphatic vessels that are in almost all parts of the body they're pulling fluid in to scan for pathogens and initiate an immune response so if there is an Invader in the body the lymph nodes are going to find it but don't forget about about our first function of the lymphatic system which is preventing swelling and so they're pulling this fluid from all these different body regions where that fluid may be building up more

than it should so they're pulling that fluid out all that fluid is going to travel toward those subclavian veins either via the right lymphatic duct or the thoracic duct to get all that excess fluid back into the bloodstream where it belongs so we don't have swelling throughout the body all right next let's talk about that third function the absorbing fat from intestines and delivering it to the bloodstream so let's draw in a little branch of the small intestine right here and we've got a lymphatic vessel that's going to be pulling fluid from that intestine and

connecting it to the cic kyi right in here we can drain it back into the thoracic duct I just have a small section of intestin drawn but that's so that my diagram doesn't get a little bit out of hand but really these lymphatic vessels are going to be connecting all throughout the small intestine to pull that fluid out so really this whole area right here would be full of these lymphatic vessels pulling fluid out of the intestines and into the cic kyli now when I first learned about all this stuff I learned that the fats

and sugars and proteins and all the nutrients that we eat are going to go from the digestive system straight to the bloodstream all those things get absorbed from the small intestine into the bloodstream but it turns out that's not quite the whole truth take a look at this diagram there's a lot going on here but let's break it down we've got a section of the small intestine inside that small intestine if we cut it open we'll see there's these Villi or these tiny little kind of squiggly looking surface membranes that are on the surface of

the small intestine all the food that we eat after it's been broken down is traveling through this tube of the small intestine now we got to get get those nutrients from the Lumin of the small intestine into the bloodstream so let's zoom in on one of these Villi or on a villis here are the absorptive cells or ocytes the nutrients that we've digested are going to pass through there and most of those are going to pass into the capillaries right here and they're going to be traveling through the capillary through the venule and then back

into circulation it goes directly into the bloodstream that's going to be true for proteins and sugars because they're soluble in water and they're pretty small they can pass through the membranes fats or lipids are a different story lipids are not water soluble so they can't just go directly into the water they've got to be packaged so in these absorptive cells they're going to be packaged into something called a kyom micron a kyom micron is a is a long fancy name for basically a little water soluble package that the lipids will get packaged into so they

can enter into the fluid so they get packaged into a kyom micron but unfortunately the kyom Micron it's a little bit bulky it's not going to fit into the capillaries to make it into the bloodstream there's just not enough space between the cells and the capillaries however the lymphatic capillaries actually have more space between the cells and the kyom microns can fit into there so with the lipids which are in the kyom microns what they're going to do is they're going to travel through the lymphatic vessel right here and they're going to travel out then

they're going to travel through here up through the cic kyi and the thoracic duct and then boom they're back into blood circulation but they never had to travel directly through a blood capillary they entered the lymphatic capillaries instead so that's the third function absorbing fats from the intestines delivering those to the bloodstream through the lymphatic system all right next let's go back to that pathogen and immune response thing again these other organs we're about to talk about are included in the lymphatic system because they help with this immune response the first one is going to

be the thymus the thymus is located sort of anterior to your heart it's actually bigger when you're a kid and then it shrinks over time by the time you're an adult it's like a tenth of its normal size usually but what the thymus does is it's going to produce T lymphocytes those T lymphocytes first grew in the bone marrow that's where your white blood cells and red blood cells are mainly produced they'll travel from there to the thymus and the thymus is going to have them develop and mature into te- cells why do we call

them te- cells well because they're made in the thymus which starts with T from the diagram I just realized it looks like the uh thoracic duct is going to be connected to the thymus it's not a thymus has blood vessels that are connected to it and that's how it's getting these te- cells and then sending these tea cells out and of course A lot of these t- cells are going to end up in the lymph nodes throughout the body so the thymus is considered a lymphatic organ because of that next we have bone marrow and

so the bone marrow is going to be in Bones throughout the body I just drew kind of the head of the femur down here to represent the bone marrow the bone marrow is going to be where all these white blood cells are created and specifically it's going to be where the B lymphocytes or B cells are developing and maturing why are they called B cells well because they're made in the bone marrow which starts with B of course a lot of those B lymphocytes are going to travel through the bloodstream and they're going to make

it to the lymph nodes throughout the body so they can hang out and look for pathogens in their lymph fluid the thymus and the bone mirror are considered primary lymphatic organs because they're actually producing the cells of the lymphatic system another organ to talk about here is the spleen which is considered a secondary lymphatic organ it does a couple things one thing it does is it kind of acts like a lymph node for your bloodstream there aren't lymphatic vessels going to it but there are blood vessels going to it and it's going to have a

lot of these B cells and t- cells that are going to kind of hang out and fight pathogens if there's any that come into the spleen through the blood vessels right there but another big thing that it does is it breaks down old red blood cells so red blood cells cells have a very limited lifespan and at the end of their lifespan they're going to get broken down by the spleen so that we can then get rid of them one more thing I don't have that diagram is our tonsils our tonsils kind of work like

the spleen does they contain lymphocytes to fight off pathogens but they're up in the face in some of the cavities up there all right that was a lot of information now I'm going to give you a chance to practice some of that information and see if you can recall it here's a blank graphic of the lymphatic system functions pause the video see if you can name the three functions of the lymphatic system and those functions are one it prevents swelling or by returning interstitial fluid to the bloodstream second it's going to scan for pathogens and

initiate an immune response if it finds pathogens and third it's going to absorb fats from intestines and deliver those to the bloodstream up next we have this diagram of the tissue capillaries and lymphatic capillaries take a minute pause the video see if you can describe everything that's in this diagram as well as describe what's happening in all the different parts of the diagram all right and here's a completed version of that diagram as a quick overview we've got blood coming in traveling through here it's going to be dropping off water and oxygen and proteins and

other nutrients to the tissue cells water and carbon dioxide is going to be traveling back into the tissue capillaries so that we can get rid of it however we've got a lot of water leaving and only about 90% of that water is coming back so we've got an extra 10% that we've got to get back into blood circulation that's where these lymphatic capillaries are going to come in so a lot of fluid is going to travel back into the lymphatic capillary and it's going to take it out of this tissue and get it back into

blood circulation we've got a zoomed in version of that which includes blood plasma interstitial fluid and then lymph or lymphatic fluid fluid from the blood plasma is going to travel out into the interstitial space about 90% is going to travel back into the blood capillary that other 10% we need to get it back into blood circulation so it's going to travel through the lymphatic vessel and then back into that subclavian vein later on another thing that we talked about is the lymph node so here's a blank diagram of the lymph node again pause the video

see if you can identify all the parts of the lymph node as well as the direction that fluid travels and what all it does all right here's that completed diagram now we've got lymphatic fluid that's coming in into the afren vessels we've got the lymphatic fluid coming out through the ephren vessel that fluid has to travel past B cells and t- cells which are scanning that fluid looking for any pathogens to fight off if it finds them it'll initiate the immune response if not that fluid will travel out through that errant vessel and we have

the medulla here and the cortex is the outer part where the B cells and t- cells are found and then finally here's our picture of the whole person pause the video see if you can name all of the lymph node regions as well as the other lymphatic organs and what all those lymphatic organs do and there's all those terms again the lymphatic fluid from the hand and the arm is going to travel up through this region past the epitrochlear lymph nodes through the axillary lymph nodes and then into the thoracic duct or on this side

up through the right lymphatic duct majority of our lymph nodes are here in the cervical region those are going to drain down into the thoracic and right lymphatic duct fluid from the lower leg is going to travel up through the poal lymph nodes up through the inguino lymph nodes abdominal lymph nodes into the cernic kyi which going to travel through the thoracic duct all of that lymph fluid is going to make it back into the left subclavian vein or the right subclavian vein we have lymph vessels that are taking fluid from the small intestine that's

where fats are going to get absorbed into the lymphatic system so they can return to Venus circulation and finally we have these other lymphatic organs the thymus where tea cells develop and IM mature the bone marrow where B cells develop and mature and we have the spleen which contains a lot of lymphocytes which will fight off pathogens as well as being a site where red blood cells are broken down all right so that was a lot of information it turns out the lymphatic system has a lot of parts there's a lot of complexity to it

I didn't get into how the B cells and T cells actually do the immune response if you're interested in that I've got a video on that so check that video out it should be linked right here special shout out to my patrons on patreon who helped make this video possible if you're looking for the diagrams from this video both the blank and completed diagrams those are available on my patreon so check that out there's a link below and good luck learning Anatomy hope to see you in the next video I'll see you then