1. Kidney functions
Kidny not only eleminate wastes …* * homeostatic organ.
Water & electrolyte balance.
Acid-base balance.
Endocrine function(rennin for Bp & erythropitin for RBC).
Ca homeostasis (activat of vit D).

2. URINE FORMATION = Filt+Reab+Secretion
Net urinary exretion of subst = F-R+S
If more excreted than filtered……….net R or S….?
If less excreted than filtered……….net R or S…...?

3. Glomerular filtration rate (GFR)
GFR : is the amount of fluid that is filtered by all nephrons of both kidneys per minute (125 ml/min). It is one of the important renal function tests.
Clearance: Is the volume of blood cleared of a substance per unit time.
Clearance=UV/P
U= urine conc of subutance
V= urine volume
P= plasma conc of subutance
GFR can be measured by calculating the clearance of a substance which is:
Freely filtered.
Neither reabsorbed nor secreted by the tubules.
Not metabolized or stored in the kidney.
Not toxic and not affecting the GFR.

4. A substance known as Inulin fulfill the above criteria
A substance known as Inulin fulfill the above criteria. Therefore, inulin clearance can be used to measure GFR.  
However, measurement of endogenous creatinine clearance is more suitable because it does not need intravenous infusion as in inulin.

5. Glomerulotubular balance
To keep urinary excretion of a substance fixed in spite of GFR changes……….there will be proportional changes in tubular reabsorption
( ??Mechanism).
Thus when GFR is increased…….the tubular reabsorption will (increase or decrease?).

6. micturition

7. Micturition reflex A stretch reflex
150 ml…..start sense…300….marked sense…trigger reflex
↑ Intravesical P..…stretch B.neck……….
Potentiate(+) mict reflex
Inhibit(-) external sphincter
If inconv….voluntary control of ext sphincter………..(if stronger OK..otherwise…..).

8. Diuretics Types of diuretics
Diuretic is a substance that increases urine output by decreasing Na reabsorption from the tubules)natriuresis( and this in turn causes diuresis (increased water output or also called polyuria).
Because K, Cl, Mg, and Ca reabsorption also influenced secondarily by Na reabsorption, many diuretics cause urinary loss of these solutes as well.
Types of diuretics
Osmotic diuretic: Inhibit water reabsorption mainly in the proximal tubules (glucose,sucrose,manitol).
Carbonic anhydrase inhibitor inhibit H secretion which reduce Na reabsorption at proximal tubule (acetazolamide).
Loop diuretics (frusemide): inhibit Na-K-Cl co-transport at thick ascending loop of Henle.

9. Diuretics that inhibit Na-Cl co-transport in luminal membrane at early distal tubule (Thiazide ).
Sodium channel blockers in the luminal membrane of collecting tubules(triamterene , ameloride).
Aldosterone antagonist inhibit action of aldosterone so decrease Na reabsorption and decrease K secretion at collecting duct. They are called K sparing diuretics(spironolactone) .