Page 115 - Physiology and Pathophysiology MNU 2024-2025 نظرى

Clinical pharmacy 2024/2025 Level 2 Pharm D Physiology and Pathophysiology (MD303)

Collecting Duct :under effect of ADH

▪ Medullary area impermeable to high [NaCI] that surrounds it :The ▪ Permeable to H2O depends upon the presence of ADH.

walls of the CD are permeable to H20. When ADH binds to its membrane receptors on CD, it acts via

▪ H2O is drawn out of the CD by osmosis :Rate of osmotic cAMP.

movement is determined by the # of aquaporins in the cell - Stimulates fusion of vesicles with plasma membrane ➔

membrane. Incorporates water channels into plasma membrane.

Secretion

K secreted from collecting duct (from Blood to urine) also from PCT Proximal Tubule

• Secretion of substances from the peritubular capillaries into interstitial Glucose and Amino Acid Reabsorption
• Filtered glucose and amino acids are normally reabsorbed by the
fluid.
nephrons.
 Then transported into lumen of tubule ➔into the urine.
In PCT occurs by secondary active transport with membrane carriers.
Allows the kidneys to rapidly eliminate certain potential toxins ▪ Carrier mediated transport displays:
- Saturation. & - Tm.
[Transported molecules] needed to saturate carriers and achieve
maximum transport rate.

Renal transport threshold:

Maximum plasma [substance] that results in excretion of that substance in the urine. Renal plasma threshold for glucose = 180-200 mg/dl.
Electrolyte Balance

+
+
+
-3
_
• Kidneys regulate Na , K , H , Ct, HC03 , and P04 .
+
• Control of plasma Na is important in regulation of blood volume and pressure.
+
• Control of plasma of K important in proper function of cardiac and skeletal muscles.
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