Urine Concentration and Volume: Regulation (Nursing)

00:01 So one of the main functions of the kidneys is to make adjustments that are needed to maintain our bodies osmotic concentration.

00:11 The normal osmotic concentration of our bodily fluids should be 300 milliosmoles.

00:19 This is measured by osmolality, which is the number of solute particles per 1 kilogram of water.

00:27 1 osmole is equal to 1 mole of particle per kilogram of water.

00:34 Because our body fluids have smaller amounts of solutes.

00:38 We normally express the osmolality as milliosmoles.

00:45 The kidneys are going to produce only a very small amount of urine if the body is dehydrated, but will produce a very dilute urine if the body is over hydrated.

00:58 This is accomplished by mechanism known as the counter current mechanism in which fluid is going to flow in opposite directions and adjacent segments of the same tube with a hairpin term such as what we see in the Nephron loop where you have a descending limb and in ascending limb.

01:20 There are two types of counter-current mechanisms.

01:24 We have the counter-current multiplier, which is going to involve an interaction of filtrate flow in the ascending and descending limbs of the Nephron Loops of the juxtamedullary nephrons.

01:37 We also have counter-current exchanger.

01:40 This is going to help us maintain the concentrations are the medullary gradient by controlling the blood flow and the ascending and descending limbs of the vasa recta that it's going to surround the nephron loop.

01:57 These two counter-current mechanisms again are going to work together to establish a medullary osmotic gradient.

02:06 This is going to move from the renal cortex through the medulla.

02:10 The gradient is going to run from about 300 milliosmoles, which is osmotic with our blood our blood osmolality and then as it gets closer to the medulla, it's going to become more concentrated at about 1200 milliosmoles.

02:28 The counter-current multiplier and the ascending and descending limbs of the nephron loop are what create this gradient and the counter-current exchanger is going to be responsible for maintaining the gradient created by the nephron loop.

02:45 From there, the collecting ducts can use this gradient in order to vary the urine concentration.

02:53 So taking a closer look at the counter-current exchange.

02:57 We find that the long nephron loops of the juxta medullary nephrons are going to create the medullary gradient.

03:05 The loops act as the counter current multipliers.

03:10 The blood vessels surrounding the loop also known as the vasa recta are going to preserve the gradient.

03:16 They serve as the counter-current exchanger.

03:21 Finally the collecting ducts of all nephrons can use the gradient that exist in the medulla in order to adjust the urine osmolality.