counter current system -1. regulation of extracellular fluid osmolarity and sodium concentration for...
TRANSCRIPT
![Page 1: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/1.jpg)
Counter Current System -1
![Page 2: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/2.jpg)
Regulation of Extracellular Fluid Osmolarity and Sodium Concentration
• For the cells of the body to function properly
they must be bathed in extracellular fluid with
a relatively constant concentration of
electrolytes and other solutes
![Page 3: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/3.jpg)
Total Concentration Of Solutes
• Osmolarity is determined by the amount of
solute divided by the volume of the extracellular
fluid.
• The extracellular fluid sodium concentration and
osmolarity are regulated by the amount of
extracellular water
![Page 4: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/4.jpg)
Function of Kidneys
• The normal kidney has tremendous capability
to vary the relative proportions of solutes and
water in the urine in various states
![Page 5: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/5.jpg)
• Kidney can excrete a large volume of dilute
urine or small volume of concentrated urine
without major changes in rates of excretion of
solutes such as sodium and potassium
![Page 6: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/6.jpg)
• This ability to regulate water excretion
independently of solute excretion is necessary
for survival especially when fluid intake is
limited
![Page 7: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/7.jpg)
Formation of Dilute and Concentration Urine
• Osmolarity of glomerular filtrate is same as
that of plasma i.e 300 mOsm/L
• Urine can be concentrated till its osmolarity is
four times more than that of plasma i.e. 1200
mOsm/L
![Page 8: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/8.jpg)
The formation of a dilute or concentrated
urine depends upon two factors:
• Medullary gradient.
• Antidiuretic hormone.
![Page 9: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/9.jpg)
Anti-Diuretic Hormone
Rate of ADH secretion to a large extent
determines, whether dilute or conc. urine
is going to be excreted
![Page 10: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/10.jpg)
Osmolarity Of The Body Fluids:
• Conc. body fluids due to increase solutes
• Secretion of ADH by Posterior pituitary
• Increase permeability of water from distal tubules and collecting ducts
• Absorption of large amounts of water
![Page 11: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/11.jpg)
• Decreased urine volume ( without altering rate
of renal excretion of the solutes)
![Page 12: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/12.jpg)
![Page 13: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/13.jpg)
![Page 14: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/14.jpg)
• Osmolarity Of The Body Fluids:
• Excess water in the body fluids
• Decrease ADH secretion
• Reduce permeability of water from distal tubule and collecting ducts
• Excretion of large amount of dilute urine
![Page 15: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/15.jpg)
![Page 16: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/16.jpg)
Medullary Hyperosmolarity
• Osmolarity of the interstitial fluid in the renal
medulla near the cortex is 300 mOsm/L
• Towards the inner part of medulla, it increases
gradually and reaches the maximum at the
inner most part of medulla near renal sinus i.e
1200 mOsm/L
![Page 17: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/17.jpg)
![Page 18: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/18.jpg)
Medullary Gradient
• This type of gradual increase in the osmolarity
of the medullary interstitial fluid is called the
medullary gradient
• The vertical osmotic gradient remains constant
regardless of the fluid balance of the body
![Page 19: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/19.jpg)
![Page 20: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/20.jpg)
Development and Maintenance of Medullary Gradient
• Kidney has some unique anatomical
arrangements, which are responsible for the
development of medullary gradient and for the
hyperosmolarity of interstitial fluid in the inner
medulla. These arrangements are together
called Counter current system
![Page 21: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/21.jpg)
Counter Current System
• In kidney the structures which form the
counter current system are the Loop of Henle
and the Vasa recta
• It is a system of “U” shaped tubules in which
the flow of fluid is in opposite direction in
different limbs of the “U” shaped tubules
![Page 22: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/22.jpg)
![Page 23: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/23.jpg)
• In both the direction of flow of fluid in the
descending limb is just opposite to that in the
ascending limb
• Loop of Henle forms the Counter Current
Multiplier
• Vasa recta form the Counter Current
Exchanger
![Page 24: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/24.jpg)
![Page 25: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/25.jpg)
MOA Of The Counter Current
System
![Page 26: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/26.jpg)
• Long loops of Henle establish the vertical
osmotic gradient
• Vasa recta prevent the dissolution of this
gradient while providing blood to the renal
medulla
![Page 27: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/27.jpg)
• Collectively this entire functional organization
is known as the Medullary Counter Current
System
• Collecting tubules in conjunction with the
vasopressin use the gradient to produce urine
of varying concentrations
![Page 28: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/28.jpg)
![Page 29: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/29.jpg)
At The Level Of The Proximal Tubule
• Immediately after the filtrate is formed,
uncontrolled osmotic reabsorption of filtered
water occurs in the proximal tubule secondary
to active Na+ reabsorption.
![Page 30: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/30.jpg)
![Page 31: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/31.jpg)
• By the end of the proximal tubule, about 65%
of the filtrate has been reabsorbed
• 35% remaining in the tubular lumen still has
the same osmolarity as the body fluids
• Therefore, the fluid entering the loop of Henle
is still isotonic
![Page 32: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/32.jpg)
![Page 33: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/33.jpg)
![Page 34: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/34.jpg)
At The Level Of loop of Henle
• An additional 15% of the filtered H2O is
obligatorily reabsorbed from the loop of Henle
during the establishment and maintenance of
the vertical osmotic gradient, with the
osmolarity of the tubular fluid being altered in
the process
![Page 35: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/35.jpg)
![Page 36: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/36.jpg)
Descending Limb Of Loop Of Henle
It carries fluid from the proximal tubule down
into the depths of the medulla.
• Is highly permeable to water
• Does not actively extrude Sodium ions
![Page 37: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/37.jpg)
![Page 38: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/38.jpg)
Ascending Limb Of Loop Of Henle
![Page 39: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/39.jpg)
Carries fluid up and out of the medulla into the
distal tubule
•Actively transports NaCl out of the tubular
lumen into the surrounding interstitial fluid
•Impermeable to water so salt leaves the tubular
fluid without water osmotically following along
![Page 40: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/40.jpg)
![Page 41: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/41.jpg)
Ability of kidney to form a urine that
is more concentrated than plasma is
essential for survival
![Page 42: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/42.jpg)
• Water is continuously lost from the body
through various routes:
• Lungs
• Gastrointestinal tract
• Skin
• kidneys
![Page 43: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/43.jpg)
• Fluid intake is required to match this loss,
ability of the kidney to form a small volume of
concentrated urine minimizes the intake of
fluid required to maintain homeostasis, this
function is especially important when water is
in short supply
![Page 44: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/44.jpg)
Obligatory Urine Volume
![Page 45: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/45.jpg)
• A normal 70-kg human must excrete about
600 milliosmoles of solute each day
• Maximal urine concentrating ability is 1200
mOsm/L
• Minimal volume of urine excreted is called
Obligatory urine volume
![Page 46: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/46.jpg)
Obligatory Urine Volume
• It is calculated by:
![Page 47: Counter Current System -1. Regulation of Extracellular Fluid Osmolarity and Sodium Concentration For the cells of the body to function properly they must](https://reader035.vdocument.in/reader035/viewer/2022062714/56649d0b5503460f949ddf42/html5/thumbnails/47.jpg)
• End Of Todays Lecture!!!