Renal System Physiology Quiz

Renal System Physiology

• The kidney is composed of a cortex and medulla surrounding the renal pelvis
• The nephron is the functional unit, consisting of vascular and tubular elements
• The vascular element includes the afferent arteriole, glomerulus, efferent arteriole, and peritubular capillaries
• The tubular element includes Bowman's capsule, proximal tubule, loop of Henle, distal tubule, and collecting duct
• Filtration, reabsorption, secretion, and excretion are the four processes in the kidney
• Filtration occurs between the glomerulus and Bowman's capsule, involving bulk flow of fluid and solutes from blood to Bowman's capsule
• Filtration pressure is determined by hydrostatic pressure, osmotic pressure, and capsular hydrostatic pressure(PH, Posm, and Pfluid)
• Glomerular filtration rate (GFR) averages 180 liters/day of plasma
• GFR regulation involves autoregulation (myogenic and tubuloglomerular), nervous system (sympathetic), and hormonal mechanisms
• Myogenic mechanism adjusts afferent arteriole blood flow to maintain GFR
• Tubuloglomerular mechanism responds to changes in fluid flow and Na+ concentration in the tubule
• Sympathetic nervous system reduces GFR during low blood pressure events, such as hemorrhage or dehydration
• Angiotensin II is a potent vasoconstrictor that reduces GFR
• Reabsorption is the movement of water and solutes from the filtrate into interstitial fluid
• Reabsorption involves four types of transport processes used to move solutes
• Saturation can occur in transport processes when the solute concentration increases
• Secretion involves the transfer of solutes from the interstitial fluid to the filtrate
• Examples of secreted solutes include Na+, K+, H+, and HCO3-
• Drugs can be secreted into the filtrate
• Excretion is the removal of solutes from the body in the urine
• Clearance is the volume of plasma cleared of a solute per unit time.
• Kidneys adjust urine concentration by altering water and NaCl reabsorption
• Calculation of glomerular filtration rate, urine excretion rates are used to determine if the solute is reabsorbed or secreted.
• Loop of Henle concentrates filtrate to 1200 mOsM in the descending limb and then dilutes it to 100 mOsM in the ascending limb, concentrating urine
• The high osmolarity of the medullary interstitial fluid is maintained through the vas recta
• Antidiuretic hormone (ADH) regulates water permeability in the distal tubules and collecting duct
• Water volume and ion concentration are regulated for proper body fluid balance
• Sodium (Na+) and potassium (K+) are crucial electrolytes; sodium is abundant in extracellular fluid, and potassium is found in intracellular fluid; maintaining proper levels is essential
• Renin-angiotensin-aldosterone system (RAAS) responds to low blood pressure or blood volume
• Stimuli for renin release include low blood pressure, decreased fluid flow past the macula densa, and increased sympathetic activity
• Angiotensin II is produced by angiotensin 1 from renin converted from angiotensinogen
• Aldosterone stimulates sodium reabsorption in the collecting ducts
• Atrial natriuretic peptide (ANP) increases sodium and water excretion, opposing the RAAS if blood pressure is too high
• Kidneys play a role in acid-base balance, with three mechanisms dealing with disturbances

Renin-Angiotensin-Aldosterone System (RAAS)

• RAAS is a hormone system that regulates blood pressure
• Low blood pressure, low blood volume, or low sodium delivery to the macula densa triggers the system
• Juxtaglomerular cells release renin, converting angiotensinogen to angiotensin I
• Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II
• Angiotensin II is a potent vasoconstrictor, increasing blood pressure
• Angiotensin II also stimulates the adrenal cortex to release aldosterone
• Aldosterone acts on the collecting ducts to increase sodium reabsorption, thus increasing blood volume