Counter current mechanism multiplier and exchanger

hello all this ppt consists of the main part of renal physiology which is an essay. the counter current mechanism
i have explained the counter current exchanger and multiplier where solutes and water get reabsorbed and also i have explained the osmosis and osmolarity. Thank you

1. Counter current mechanism Dhayanithi.C

2. contents Osmolarity and diffusion Osmosis & osmotic pressure Structure of nephron Counter current mechanism Counter current multiplier and exchanger Functions of ADH

3. Osmosis & OSMOTIC PRESSURE the movement of water(solvent) from a region of high water concentration through a semipermeable membrane to a region of low concentration of water It is a passive transport. OSMOTIC PRESSURE Osmotic pressure is the minimum amount of pressure needed to prevent a pure solvent from flowing into a solution across a semipermeable membrane.

4. OSMOLARITY & DIFFUSION The number of osmoles per litre is osmolarity. The osmolarity increases from 300 mOsmolL-1 in the cortex to 1200 mOsmolL-1 in the inner medulla by counter current mechanism. DIFFUSION the movement of a molecule down a concentration gradient, from an area of its high concentration to an area of its low concentration. 

5. STRUCTURE OF NEPHRON

6. PCT (   PCT) is  a segment of the renal tubule responsible for the reabsorption and secretion of various solutes and water It reabsorbs Water and solutes

7. LOOP OF HENELE long U-shaped portion of the tubule that conducts urine within each nephron of the kidney It reabsorbs water in thin descending limb . It reabsorbs solutes in thin ascending limb.

8. DCT & CD DCT a short nephron segment, interposed between the macula densa  and collecting duct CD   reabsorb  sodium and chloride  across the apical membrane

9. COUNTER CURRENT MECHANISM? The countercurrent mechanism is a mechanism in which the exchange of two fluids can take place from one direction to another with their concentrations. Osmolality gradient is created by LOH --  CC multiplier This is maintained by vasa recta - -> counter current exchanger. CD acts as osmotic equilibrating device.

10. Counter current multiplier descending limb of LOH – permeable to water.(Becomes Hypertonic) Thin ascending limb of LOH – impermeable to water Thick ascending limb of LOH- Na+ Cl- actively transported by Na+K ATPase

11. ROLE OF CD It is permeable to water and urea.(it becomes Hypertonic). Urea transporters helps in movement of Urea in CD. UT-A1 (influenced by ADH). UT-A2 (acts on PCT) Inner medullary part of CD is permeable to urea

12. Counter current exchanger(Vasa recta) Osmolal gradient is mainted by VASA RECTA. Descending limb of Vasa recta solute diffusion takes place. Na+Cl - is permeable in descending limb of vasa recta. Impermeable to ascending limb. Helps in maintain ECF volume

13. NET- EFFECT In LOH water comes out of descending limb into interstitium & solutes come out of ascending limb. (vice- versa happens in vasa recta) The longer LOH accumulates more solutes across its length from outer layers into Deeper layers of medulla,Thus osmolality increases along the length of LOH Higher osmolality in the medullary interstitium further enhanced by diffusion of urea from the CD. Water moves out passively from CD but it is removed by vasa recta from interstitium . Deeper portion of medulla- osmolality 1200-1400 mOsm /kg of H2O is maintained

14. THANK YOU…