Page 119 - Physiology and Pathophysiology MNU 2024-2025 نظرى

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

Region in each nephron where the afferent arteriole comes in contact with the thick ascending limb LH.

• Granular cells within afferent arteriole secrete renin:

▪ Converts angiotensinogen to angiotensin I.
▪ Initiates the renin-angiotensin-aldosterone system.

▪ Negative feedback.

• Macula densa:

▪ Region where ascending limb is in contact with afferent
arteriole.

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▪ Inhibits renin secretion when blood [Na ] in blood increases

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Atrial Natriuretic Peptide ANP
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• Produced by atria due to stretching of walls ➔ Antagonist to • Increases Na and H20 excretion (Acts as an endogenous diuretic)
aldosterone.

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Na , K , and H Relationship Renal Acid-Base Regulation
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• Na reabsorption in collecting ducts (CD) creates electrical • Kidneys help regulate blood pH by

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gradient for K secretion.  excreting H and reabsorbing HC03~.
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• Plasma [K ] indirectly affects [H ]. ✓ Most of the H secretion occurs across the walls of the PCT in
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• When extracellular [H ] increases, H moves into the cell, causing K exchange for Na )Antiport mechanism) =Moves Na and H in
to diffuse into the ECF. opposite directions.

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• In severe acidosis, H is secreted at the expense of K . • Normal urine normally is slightly acidic ➔ kidneys reabsorb almost all
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HCO3 and excrete H . [Returns blood pH back to normal range].
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