B3.2 Transport in Animals [IB Biology SL/HL]

in this video we'll be looking at transport in animals which is the standard level part of b3.2 now first let's talk a little bit about how animal transport systems are organized in humans we have our heart and our heart is going to pump blood away from the heart and to other regions of the body through these structures called arteries okay so arteries are going to carry blood away from the heart a for artery a for away and veins are going to return blood back to the heart now both of those are very important for moving

blood but neither one is the spot where materials actually diffuse in or out of the blood or in or out of tissues that's going to happen in these very teeny tiny blood vessels called capillaries okay so these capillaries are actually the site of exchange between the blood and the environment and they are right here so the way that these capillaries work is that this Blood leaving the heart and going through the arteries is going to Branch off into smaller and smaller blood vessels first little arterials and then into these capillaries and this is where materials

are going to diffuse out of the blood and into tissues okay so some of this these like new nutrients are going to diffuse out of the blood and I'll get rid of this so that this isn't confusing anymore some of this is going to diffuse out of the capillaries and into the blood and then that blood is going to pick up waste products from tissues that waste is going to diffuse back into the capillaries and then through the venules into the veins and then back to the heart now tissues that require a lot of oxygen

or other nutrients are going to have a high capillary density right so when we think about like muscles in particular they're going to need lots of oxygen lots of glucose they're going to need lots of capillaries here okay so if we want to be thinking diffusion we want to be thinking a large surface area and having a lot of it okay so that we can get that diffusion process going as efficiently as possible so let's add a little detail to this so blood is going to be flowing through these arteries and then through these little

arterials and when it reaches these capillaries that's when we're going to get this fluid that comes out and this fluid is going to have lots of great things in it things like oxygen water glucose all this good stuff that the tissues need okay that tissue fluid is then going to flow between tissues and things are going to diffuse into the cells and tissues um as they need it to they're also going to be producing waste those tissues are going to be producing waste that needs to diffuse back into the capillaries so this waste is going

to go back into the capillaries and it's going to become part of the blood that is in that capillary Network and then that is going to flow through these venules through these veins and back to the heart okay so that blood by that time has made a complete circuit okay so here I just want to like note the difference between how this fluid works okay and how this waste works so what is it that's great about the capillaries for getting this to happen Well what we'll notice here if we were to zoom in on these

capillaries is that they would have pores and these pores are going to help make this Exchange of materials much more efficient so again theme B all about Form and Function if the function is to get things to diffuse in and out we need that form to be amenable to that now because they have different functions the features or the structural components of arteries and veins are going to be a little bit different we need to not only be able to describe these in words but also Point them out in pictures so let's talk about these

artery first they are responsible for getting that blood away from the heart they are going to have a very thick muscular wall so we can kind of see that here and they are going to have a relatively narrow Lumen so the Lumen is a term for this like space inside of something this hollow space we'll see that in a lot of other structures as well they are generally circular in shape okay and they maintain their shape relatively well on the inside this picture doesn't have it but on the inside you may notice that they are

a little bit bumpy or have some ridges and that's called inner surface corrugation okay and it has to do with that muscle layer that's on the inside and we are also going to find that in a microscope image we will be able to see wall fibers so in the arterial walls we'll see lots of muscle tissue and we're going to see collagen and all the things that are helpful in terms of getting that artery to be able to force blood away from the heart and towards the outer parts of the body veins on the other

hand have a much different structure because they have a much different function they are going to have a thin wall now that thin wall is because it's they don't have the ability to contract and push blood like the arteries do the arteries can do that on their own these veins rely on muscles like skeletal muscles that surround the veins to squeeze and contract and push that blood back towards the heart so in order for the veins to be able to be squeezed by that surrounding skeletal muscle they need to have thin walls now they are

also going to have a much wider Lumen so you can see that here that this space is much wider than in the arteries that's in order to maintain low pressure so that that blood can be squeezed back towards the heart they can sometimes be circular but a lot of the times they're going to look like a flattened shape okay like they've been squished again that's the muscles squeezing them we won't notice any inner surface corrugation because there's not much of a muscular wall here and we won't be able to see any of those collagen or

muscular fibers in the wall so let's let see if we can find them in this micrograph this is a skill that we need to be able to have I'm going to look first for an artery so I want to find something that has a thick wall and it's circular in shape and it's got this inner surface coration and that's right here okay so what I'm going to do is I'm going to kind of try to highlight this artery it's this whole structure right here that's the artery okay so again what am I looking at here

this is a very thick wall so this entire feature here is the wall you can see it's got these ridges on the inside that's that corrugation it's got a circular Lumen that's relatively narrow and in general it keeps its circular shape veins on the other hand are going to look very different so I'm going to highlight the vein in the picture I'm going to circle the vein in the picture and that's this structure right here okay okay so this vein has a very thin wall so you can see that's much thinner than the wall of

the artery and it's kind of been flattened so it's probably a circle in shape but it's being flattened by the surrounding muscular tissue and it's got a very wide Lumen okay that's that space in the middle and I can't see any corrugation or fibers now if we want to think about the features of arteries that make them very good at transporting blood away from the heart we first need to think about what that might require so this needs to be something that can carry blood at high pressure right so away from the heart all the

way to the extremities of your body it needs to be able to contract on its own okay to force that blood and then it also needs to be able to recoil right to expand back in between those heartbeats it also needs to be elastic and strong okay so it needs needs to have all of these features in order to get that blood away from the heart well what are the structural components that are going to be helpful there well this narrow Lumen okay this area right in here in the middle is going to be very

good at helping to maintain that high pressure again it's going through a relatively small area this thick muscular wall that we're seeing on the outside here is going to allow that artery to both contract and recoil right so when the heart is you know beating when that when your ventricles of your heart are forcing blood through your arteries there's lots of pressure that blood is moving on its own but when that heart is relaxed we need the arteries themselves to contract to keep forcing that blood through those blood vessels so that muscle wall is going

to be very very important and then we also need it to be elastic and strong to be able to withstand all that pressure and so that's when all of these collagen and elastic fibers that are in this wall here um are going to be very helpful okay so they're going to help maintain that arterial structure so that it doesn't burst under that high pressure so that it can recoil again all of these functions um require specially adapted features so here's another way of organizing that that narrow lumen helps to maintain that high pressure those thick

fibrous walls can expand and contract without bursting and those elastic fibers in there are really interesting because when they expand and then the pressure drops it also recoils so that's going to mean that I need less energy for a full contraction and again those muscles are going to help push that blood through so again Form and Function very important here in transport now because those arteries are expanding and Contracting we can actually um feel them and that's called our pulse there are several areas on the body where you can take your pulse one is right

here okay on your neck and then you can also take it on your wrist I recommend trying to practice finding your pulses you can also um use what we're seeing here in this picture this is a digital um pulse reader and I'm looking at the pulse right here now pulse and heartbeat aren't the same thing your heartbeat is like your heart muscle Contracting when we say pulse what we're feeling are again those arteries expanding and Contracting so they're not the same thing but they do happen at the same time so we can use those numbers

interchangeably so if I say my pulse rate it will be the same as my heart rate now let's think about this absurdly drawn human here this human has a heart right about here okay now we have this network of blood vessels that includes veins that extends to all reaches of our body let's say that there is blood um in this person's leg and this blood has to make its way back up to the heart well it's going to do that through veins but one of the interesting problems here that veins tend to have is that

a lot of them are pushing blood against the force of gravity so in order to bring blood back to the heart that's going to require some special adaptations especially because they're bringing that blood at relatively low pressure so here I kind of have a cross-section of a vein right okay and so this blood is going to be going this way back towards the heart so what we're going to find here is a very thin wall and that wall needs to be thin because on either side of the vein and I'll try to maybe draw it

here and like here like this on either side of that vein we're going to be relying on skeletal muscle to kind of contract and squeeze that vein and squeeze the blood through the vein so you can think of it like squeezing toothpaste through a tube now what happens when those muscles relax well then that blood is going to want to come back down this wrong way and so one of the things that veins have in order to prevent that is they have these valves okay and so these valves can close um and that is going

to help prevent that backf flow okay so these valves right here can close when the skeletal muscle relaxes to prevent blood from flowing the wrong way and here's maybe a better view of these valves here right so as the skeletal muscle is squeezing and we should maybe draw that in here here's my skeletal muscle on either side of my veins when they're squeezing that's forcing the blood back through the heart when they're relaxed blood will want to go backwards but these valves can close to prevent that back flow of blood so those really important features

here again a WI Lumen is going to make it easier for the muscles to squeeze them um and that's because a wider Lumen will cause that blood to be at a much lower pressure than in those arteries okay um again that thin muscular wall it's very thin so the muscles don't meet a lot of resistance when squeezing there and those valves are there to prevent back flow of blood so in general arteries carry blood away from the heart so here's the heart and here's this really awesome artery right here called the aorta so blood is

going to leave the heart travel through the aorta and then all across the regions of your body branching off of the aorta are these special blood vessels called coronary arteries and I'll kind of try to use green here these coronary arteries carry this blood from the aorta directly to the heart tissue itself and they carry lots of oxygenated blood full of glucose that heart muscle is working really hard so we need this like constant oxygen rich blood supply now some bad things can happen if those get uded uded is just a fancy way to say

blocked okay so if those coronary arteries and that's just blown up here in green so if I look at one of these in Greater detail it looks like this if if you have a blockage here that prevents blood from getting to this heart tissue that can be very bad and that's called CHD coronary heart disease so there's um a few different things that can block them but it could um start with a narrowing really and that narrowing can be caused by a buildup of what we call plaque so this plaque is kind of like a

collection of like cholesterol and maybe some other lipids and when it Narrows that coronary artery it can cause a blockage and then we get something called a myocardial infarction also known as a heart attack and so basically what's happening is that if this is blocked you are preventing this heart muscle here from getting the oxygen and nutrients that it needs and it starts to die so there are some risk factors here with CHD um smoking obesity not having enough exercise certain genetic um traits can lead to increased risk of myocardial inunction high blood pressure which

is also known as hypertension poor diet and age all of these can be risk factors for um causing blockages of these coronary arteries and again if we're understanding Form and Function the function is for them to bring oxygenated blood to the heart we really need them to be able to do that so that's why we need them to remain open um and not blocked and if we have any of these risk factors it's really important that we keep an eye on our heart health