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Renal Functional Anatomy

by Carlo Raj, MD
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    00:00 So renal functioning, what’s happening further? Well, here you have more pictures.

    00:04 And this particular picture, the kidney that you see here on your left taking that little area, and I have blown it up in this amplification here, well, let me set this up for you.

    00:16 I need you to go from top to bottom, top to bottom. The top will be the superficial, so therefore, that will be the cortex. And then the bottom that you're seeing here, what is that? That’s the medulla.

    00:28 Now, this is an entire pyramid that has been amplified, right? A pyramid. Be careful.

    00:35 A lot of words here begin with the letter P. They're all clinically relevant. Well, with the pyramid down in the medulla, you have something called the papilla. Now, around the medulla and the papilla, what are you seeing there? What's at the very bottom at that point? You call that what? The collecting duct. And then you have the minor calyx, major calyx, and you have the pelvis.

    01:00 In other words, you’re forming the ureter, aren’t you? What’s my point? Well here, let’s say that you have a patient who’s a female. She’s pregnant. Well, that’s a lot of pressure on the urinary bladder. Tell me about the urethra. To begin with, tell me about the anatomy of a female urethra, itty-bitty tiny. To begin with, it’s tiny. On top of that, she’s pregnant.

    01:23 The urethra is facing the external world like that. What is she susceptible to? In addition, let’s say that there is increased glucose in the urine, you’re making that urine mighty tasty for whom? Welcome to E. coli. Oh boy! So, what is that E. coli doing? It comes into urethra, a pregnant lady, passed the urethra, very, very quickly. So now you have a urinary tract infection.

    01:48 What is she saying? I have to go to the bathroom a lot, burning sensation perhaps, not a good thing. What about this organism, E. Coli? It’s mountain climbing up the urethra.

    02:00 Do you see that? Here comes the E. coli coming up the urethra. That's always a pleasant picture.

    02:03 Coming into urinary bladder, uh-oh. I have cystitis. Are we done? No, no, no.

    02:08 We’re going to keep climbing. Climbing where? Up the ureter, you’re going to climb up the ureter.

    02:13 What kind of infection is this now? Ascending. Are you seeing the difference between the names? Urethritis, cystitis, we’re going to move up the ureter. Keep going. Keep going. What did I hit? Now, your female patient is saying, “Ouch! I have pain in my back.” Flank is what it’s called.

    02:33 In addition, she might have a little bit of a fever and she has to go to the bathroom a lot, lots of urination. This is pyelonephritis. So, what’s my point? Well, where am I? I just ascended up my ureter. Where are you in this pyramid? Good, the medulla. I just called that what? The papillary or the papilla, so therefore, E. coli is coming up, coming up, coming up and comes up the papilla into the ureter through the calyx. Where are you? It’s called papilla necrosis, not a good thing. So, the scarring of pyelonephritis, pyramidal. What does that mean? That entire section, then you have an ascending E. coli. I just gave you the patient.

    03:13 Who is your patient? Maybe perhaps a pregnant woman putting a lot of pressure on the urinary bladder making the urethra even more welcoming to the E. coli.

    03:21 Here comes ascending infection. Up it comes, where is it going to then cause damage, up in the papilla.

    03:28 You highlight in your head ducts of the papillary surface. Let’s move on. You have a necrosis taking place. And this necrosis, up where? The papilla. What is this junction exactly? It’s called the pelvico–calyceal system. What does that mean? It means that the pelvis is then combining with your calyceal system. Where's my calyx? Major, minor calyx right there.

    03:54 So therefore, it can behave like a stone especially when there's necrosis. So some of that mass that you're going to form with the papilla, renal papillary necrosis may then behave like a renal stone.

    04:05 Have you known a patient as such? You will if you haven't already. How often is urinary tract infection? Quite often, quite often. So, you want to keep those things in mind. All we’re doing here is taking anatomy that you've seen before, a little bit of physiology, mix it up with a little bit of microbiology and you come up with pathology. So what is pathology? It’s a huge cooking class. You’re taking all these different ingredients. You’re putting it in.

    04:31 You come up with your dish. In this case, urinary tract infection. Yummy. Move on. Loss of papillae.

    04:40 What else may happen? Sickle cell disease. So, if it’s sickle cell disease, what's my issue? It’s homozygous. Tell me more. More likely in what kind of population? African, good.

    04:52 What else do you want to know? Sixth position, what happens? Glutamic acid replaced by valine.

    04:57 Good, keep going. What's sickle cell disease? Homozygous. SS, is what you have, homozygous, S and S.

    05:06 Wow! What happened? RBCs, now we're going to get sickle especially when there’s a little bit of stress.

    05:13 Then what happens? I told you earlier that if there is such a ischemia taking place, that what part of the pyramid and the nephron is susceptible to ischemia? It is your medulla.

    05:27 So here, not urinary tract infection, sickle cell disease, therefore loss of papilla.

    05:34 Also, you might find issues. Everything that we just talked about is going to come into play because when you hear the term isosthenuria, that is not a good thing. What happened? Close your eyes. Come to the glomerulus. Where are you? At Bowman's space. Tell me about osmolarity.

    05:53 300, approximately, keep it simple. What’s 300 mean to you? It’s equivalent to plasma osmolarity.

    06:01 Approximately, isotonic. Where am I? Bowman's space, continue. You're going through the PCT.

    06:08 You’re going through descending limb. What should happen normally? You’re reabsorbing what, two-thirds of your water. What's left behind in the nephron? Solute. What happens by the time you get down to the medulla, the loop of Henle? What happens there? You remove the water.

    06:28 It should become what kind of urine? Hypertonic, hypertonic, hypertonic, meaning what? Greater than 300, the urine osmolarity, maybe 600, maybe 800, maybe 900, it could potentially get them to 1200, right? What’s normal? Isotonic, 300. What if you have sickle cell disease and you lost the function of your medulla? Are you able to properly concentrate your urine? Read this. Nope. So therefore, if you're not able to properly concentrate because the medulla isn’t working properly, my urine might actually be isotonic. And down in the medulla, that is not a good thing. This is a pathology. So the fact that you have isosthenuria means that you've lost ability in the medulla to properly concentrate that urine. Does that stanza make sense to you now? How significant is isosthenuria? Quite. We’ll talk more about that later.

    07:29 The kidney is no longer able to concentrate or dilute the urine. It’s lost its function. Where? Medulla.

    07:35 Let’s move on.


    About the Lecture

    The lecture Renal Functional Anatomy by Carlo Raj, MD is from the course Renal Diagnostics.


    Included Quiz Questions

    1. Urine at the same osmolality as plasma.
    2. Urine that is hypertonic relative to plasma
    3. Inability to urinate
    4. Plasma that is isotonic to blood
    5. Urine that is hypotonic relative to plasma
    1. Urethra, bladder, ureters, calyces, papilla
    2. Ureter, urethra, bladder, calyces, papilla
    3. Urethra, bladder, ureters, papilla, calyces
    4. Ureter, bladder, calyces, ureters, papilla,
    5. Urethra, ureters, bladder, papilla, calyces,
    1. Descending limb
    2. Thick Ascending limb
    3. Distal convoluted tubule
    4. Collecting duct
    5. Thin ascending limb
    1. E. coli
    2. P. mirabilis
    3. K. pneumoniae
    4. Enterococcus
    5. P. aeruginosa

    Author of lecture Renal Functional Anatomy

     Carlo Raj, MD

    Carlo Raj, MD


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