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Hello! Let's continue with the process of excretion. Today we're going to learn

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how urine is formed and also other organs involved in the process of excretion.

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We start with 2.3 functions of the excretory system.

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At this point you should go to the aula virtual and check for a drawing that you have to do

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about of a nephron a nephron that in spanish we call it nephrona is a basic unit of the

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kidney so each kidney has a lot of these nephrons that compound it and they are going to be

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responsible for the formation of urine what is the purpose of them so we had if you check in

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your drawing of the anatomy of the urinary system the renal artery artery that is going to take

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blood which carries waste it's going to get into the kidney and there is going to to go into

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capillaries in the nephrons in the nephrons occurs a process that we have learned now and after this

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process the left renal vein is going to get out of the kidney with clean blood so it's in with

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the artery the blood that is dirty and gets out with the vein the blood that is clean if you're

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taking your drawing you would see that the artery is red and the vein is blue so with that another

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remember the differences between arteries and veins and we say that it's not because the artery

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is clean and the vein is um is not clean no it's not that we always say that arteries goes from the

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heart to the organs and veins go from organs to heart remember that difference

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with your beautiful drawing of the nephron all color and beautiful and nice

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you're going to follow the explanation okay the stages of urine formation uh it's not that

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things get out of the nephron and we form the urine no it's not that the process is more complex

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first of all there is a filtration and second step is absorption. Where does filtration

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take place? It takes place in the glomerulus. In the glomerulus what happens

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is that a lot of substances get out of the blood and gets inside the nephron, inside these tubes

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this tube that surrounds the glomerulus. Actually, there are a lot of substances

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that get out and they form a liquid which is called primary urine. This

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primary urine is a compound of water, is a compound of mineral salts, is a

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compound of toxic substances, those substances that we want to get rid of

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them and also useful substances. These useful substances could be, for example,

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glucose, could be some amino acids that are okay, that we want to keep. So we

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need to get from all this primary urine what is good for us and we need to get

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them back to the blood circulation. How does it happen? With absorption. So from

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this what do we need we need the useful substances we want also mineral salts

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and we want water because if we lose too much water we can dehydrate it okay it's

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good if we drink too much water to get rid of it so depending on the amount of

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water that we have in our body will keep more water inside out or we take more

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water out that's why sometimes our urine is very yellowish because it's more

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concentrated and sometimes it's more like water depending on the amount of water that you have

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drink during the day so useful substance mineral salt and water they are going to be reabsorbed

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reabsorbed they are going to be reabsorbed and going back to the blood circulation

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and finally we get the urine okay so we take this out and finally the toxic substances the urea

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forms the urine and what is the function of the urine you can write it here

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underneath okay because I don't have more space here okay we have we have two

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main function of the urea urine purifying meaning that we take all these

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substances that we don't need out of our body and also regulating as i said we have too much water

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inside out we're going to take it out by urine if we have too much imagine that we have eating

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food that is very very salty we need to get rid of those salts because if not we have a problem

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of salt concentration in the blood so we get rid of it by urine so also regulating is a very

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important function of urine not only the kidneys and the urinary system is responsible for the

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excretion in the body there are other organs that we already know and also they are involved in this

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process 2.4 other organs involved in expression there are three organs that we are going to study

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involved in this process of excretion first of all the liver we have already studied the liver we

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talk about the liver when we said that the liver neutralize toxins there are a lot of

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toxins that come in our body we talk about the preservative that we use in the food

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we talk about pesticides and we talk about drugs for example alcohol is one of them if a person

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drinks alcohol all the alcohol is going to end up in his or her liver the problem with people

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that drink a lot is that the liver cannot get rid of all of it so they can end up in an illness

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okay and the liver won't work correctly so it's very important to take care of the liver

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so but apart from neutralizing toxics the liver is also responsible for decomposing red blood cells

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When we studied the red blood cells or erythrocytes, we said that they were cells without a nucleus.

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They have a membrane, they have cytoplasm, but they do not have nucleus.

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So they have a short lifetime. They move around our body from about 60 to 80 days.

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After that time, they need to be decomposed and that happens in our liver.

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they go to the liver and in other organs of our body start forming new red blood cells.

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So it's very important that the liver has this function correctly.

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Other organs that we have studied already are the lungs.

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The lungs reside in the respiratory system and we said that they,

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first of all, they take oxygen of course, but we are talking about excretion.

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excretion the lungs eliminate carbon dioxide which is not good for our body and the lungs

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get ready to eliminate it what about the sweat glands all the sweat glands that we have on our

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skin actually when we sweat this sweat is a has the same composition as urine but diluted so sweat

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is similar sweat is similar to the urine it has also urea that we have already seen that was one

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of the waste products and we eliminate some portion of the urea through our sweat a very

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little proportion okay we still need to go to it but sweat glands also has this function

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And this is all about the discretion and the different organs involved in this process.