p.4
Thick Ascending Limb Functions
What is the primary function of the thick ascending limb of the Loop of Henle?
Reabsorption of sodium, potassium, and chloride.
p.1
Mechanisms of Transport in the Loop of Henle
What is the primary function of the Loop of Henle?
To concentrate urine and reabsorb water and salts.
p.1
Late Distal Tubule and Cortical Collecting Duct Functions
What is the function of the collecting duct in the kidney?
To regulate water and electrolyte balance.
p.14
Principal Cells and Sodium Reabsorption
What are principal cells?
Cells located in the late distal tubules and cortical collecting ducts of the nephron.
p.13
Aldosterone and Potassium-Sparing Diuretics
What type of drugs are spironolactone and eplerenone?
Mineralocorticoid receptor antagonists.
p.13
Aldosterone and Potassium-Sparing Diuretics
How do spironolactone and eplerenone affect aldosterone?
They compete with aldosterone for receptor sites in the principal cells, inhibiting its effects.
p.14
Principal Cells and Sodium Reabsorption
How do principal cells contribute to potassium balance?
By secreting potassium into the tubular fluid.
p.13
Principal Cells and Sodium Reabsorption
What is the consequence of decreased sodium transport due to amiloride and triamterene?
Decreased transport of potassium into the cells and reduced potassium secretion into the tubular fluid.
p.2
Thin Descending Limb Characteristics
What is the metabolic activity level in the thin segments of the Loop of Henle?
Minimal level of metabolic activity.
p.7
Reabsorption in Distal Convoluted Tubules
What is the function of the macula densa?
Regulation of GFR (glomerular filtration rate) and blood flow.
p.14
Principal Cells and Sodium Reabsorption
What is the primary function of principal cells?
To reabsorb sodium and secrete potassium.
p.2
Reabsorption in the Loop of Henle
What are the main segments of the Loop of Henle?
1. Thin Descending limb 2. Hair pin loop/turn 3. Thin Ascending limb 4. Thick ascending limb.
p.10
Late Distal Tubule and Cortical Collecting Duct Functions
What is the functional characteristic of the second half of the distal tubule and cortical collecting duct?
They have similar functional characteristics.
p.1
Reabsorption in Distal Convoluted Tubules
What role do distal tubules play in substance transport?
They are involved in the reabsorption of sodium and water.
p.2
Thin Descending Limb Characteristics
What characterizes the epithelium of the thin segments in the Loop of Henle?
It has thin epithelium with no brush border, few mitochondria, and minimal metabolic activity.
p.7
Reabsorption in Distal Convoluted Tubules
What segment empties into the Distal Convoluted Tubules (DCT)?
The thick ascending segment of the Loop of Henle (LOH).
p.7
Reabsorption in Distal Convoluted Tubules
How does the DCT compare to the thick ascending limb of the Loop of Henle?
It has similar characteristics but is highly convoluted.
p.10
Late Distal Tubule and Cortical Collecting Duct Functions
What are the two distinct cell types found in the late distal tubules and cortical collecting ducts?
Principal Cells and Intercalated Cells.
p.9
Reabsorption in Distal Convoluted Tubules
How does the early distal tubule contribute to urine concentration?
By reabsorbing solutes without significant water reabsorption, it dilutes the tubular fluid.
p.8
Early Distal Tubule Mechanisms
How does chloride exit the cell in the early distal tubules?
Chloride diffuses out into the renal interstitial fluid through chloride channels in the basolateral membrane.
p.8
Early Distal Tubule Mechanisms
What conditions are thiazide diuretics commonly used to treat?
Hypertension and heart failure.
p.11
Principal Cells and Sodium Reabsorption
What do Principal Cells reabsorb and secrete?
Reabsorb sodium and secrete potassium.
p.12
Principal Cells and Sodium Reabsorption
What are the principal cells primarily responsible for?
They are the primary sites of action of potassium-sparing diuretics.
p.8
Early Distal Tubule Mechanisms
What does the sodium-chloride co-transporter do in the early distal tubules?
It moves sodium and chloride from the tubular lumen into the cell.
p.6
Secretion Mechanisms in the Loop of Henle
What is the role of potassium ions in the loop of Henle?
There is a slight back leak of potassium ions into the lumen, creating a positive charge.
p.5
Reabsorption in the Loop of Henle
What channels are involved in potassium transport in the thick ascending limb?
ROMK and other K+ channels.
p.4
Thick Ascending Limb Functions
What characteristic is notable about the thick ascending limb of the Loop of Henle?
It has high metabolic activity.
p.3
Thin Descending Limb Characteristics
What solutes is the thin descending limb moderately permeable to?
Urea and sodium (via passive diffusion).
p.8
Early Distal Tubule Mechanisms
How is sodium transported out of the cell in the early distal tubules?
Through the sodium-potassium ATPase pump across the basolateral membrane.
p.7
Reabsorption in Distal Convoluted Tubules
What structure is formed by the first part of the DCT?
Macula densa, part of the juxtaglomerular apparatus.
p.1
Mechanisms of Transport in the Loop of Henle
What are the main structures involved in the transport mechanisms of various substances?
Loop of Henle, distal tubules, and collecting duct.
p.9
Reabsorption in Distal Convoluted Tubules
What type of transport mechanism is primarily used for sodium reabsorption in the early distal tubule?
Active transport via sodium-potassium ATPase.
p.11
Principal Cells and Sodium Reabsorption
How does low intracellular sodium concentration affect sodium diffusion in Principal Cells?
It favors sodium diffusion into the cell through special channels.
p.13
Principal Cells and Sodium Reabsorption
What is the mechanism of action of amiloride and triamterene?
They are sodium channel blockers that inhibit sodium entry into luminal membranes.
p.13
Principal Cells and Sodium Reabsorption
What effect do amiloride and triamterene have on sodium transport?
They reduce the amount of sodium transported across the basolateral membranes by the sodium-potassium ATPase pump.
p.5
Reabsorption in the Loop of Henle
What types of channels are present in the basolateral membrane of the thick ascending limb?
Special chloride channels.
p.9
Reabsorption in Distal Convoluted Tubules
What is the primary function of the early distal tubule?
Reabsorption of sodium and chloride ions.
p.11
Principal Cells and Sodium Reabsorption
What is the role of the sodium-potassium ATPase pump in Principal Cells?
It is located on the basolateral membrane and helps maintain sodium and potassium concentrations.
p.9
Reabsorption in Distal Convoluted Tubules
What is the role of chloride ions in the early distal tubule?
Chloride ions are reabsorbed along with sodium ions to maintain electrochemical balance.
p.14
Principal Cells and Sodium Reabsorption
What role do principal cells play in water reabsorption?
They are involved in water reabsorption through aquaporins, influenced by antidiuretic hormone (ADH).
p.5
Reabsorption in the Loop of Henle
What is the role of the sodium-potassium ATPase pump in the basolateral membrane?
It helps maintain sodium and potassium gradients.
p.7
Reabsorption in Distal Convoluted Tubules
What ions are avidly reabsorbed in the DCT?
Sodium, potassium, and chloride.
p.12
Aldosterone and Potassium-Sparing Diuretics
Which potassium-sparing diuretics are sodium channel blockers?
Amiloride and Triamterene.
p.7
Reabsorption in Distal Convoluted Tubules
Why is the DCT considered a diluting segment?
Because it dilutes the tubular fluid.
p.11
Principal Cells and Sodium Reabsorption
What are the two steps involved in potassium secretion by Principal Cells?
1. Sodium-potassium ATPase pump maintains high intracellular potassium concentration. 2. Potassium diffuses down its concentration gradient into the tubular fluid.
p.3
Thick Ascending Limb Functions
Why is the impermeability of the ascending limb important?
It is important for the concentration of urine.
p.8
Early Distal Tubule Mechanisms
What is the effect of thiazide diuretics on the sodium-chloride co-transporter?
Thiazide diuretics inhibit the sodium-chloride co-transporter.
p.6
Secretion Mechanisms in the Loop of Henle
What effect does the positive charge in the tubular lumen have on cations?
It forces cations like Mg++ and Ca++ to diffuse from the tubular lumen into the interstitial fluid.
