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Renal & GIT Physiology > Formation of Urine (Basic Renal Process) > Flashcards

Formation of Urine (Basic Renal Process) Flashcards

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1
Q

What are the three main processes involved in urine formation?

A

Glomerular filtration, tubular reabsorption, and tubular secretion.

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2
Q

What is glomerular filtration?

A

The process by which the kidneys filter blood, removing excess wastes and fluids.

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3
Q

Where does glomerular filtration occur?

A

In the glomerulus of the nephron.

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4
Q

What drives the glomerular filtration process?

A

Blood pressure forces plasma and small solutes through the glomerular capillary walls.

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5
Q

What is the composition of the filtrate produced in the glomerulus?

A

Filtrate contains water, ions, glucose, amino acids, and small proteins, but no blood cells or large proteins.

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6
Q

How is the glomerular filtration rate (GFR) regulated?

A

Through intrinsic (autoregulation) and extrinsic (hormonal and neural) mechanisms.

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7
Q

What is the role of the afferent and efferent arterioles in GFR regulation?

A

Afferent arteriole dilation increases GFR, while efferent arteriole constriction also increases GFR.

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8
Q

What is tubular reabsorption?

A

The process of moving substances from the filtrate back into the blood.

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9
Q

Where does the majority of tubular reabsorption take place?

A

In the proximal convoluted tubule.

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10
Q

What substances are primarily reabsorbed in the proximal convoluted tubule?

A

Sodium, water, glucose, amino acids, and bicarbonate.

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11
Q

How is sodium reabsorbed in the proximal convoluted tubule?

A

Via active transport mechanisms involving sodium-potassium ATPase pumps.

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12
Q

What is the role of the loop of Henle in urine concentration?

A

To create a concentration gradient that allows for the reabsorption of water.

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13
Q

How does the countercurrent multiplier mechanism function in the loop of Henle?

A

It multiplies the osmotic gradient through active transport of sodium and chloride in the ascending limb.

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14
Q

What is tubular secretion?

A

The transfer of substances from the blood into the tubular fluid.

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15
Q

Where does tubular secretion primarily occur?

A

In the distal convoluted tubule and collecting ducts.

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16
Q

What are the main substances secreted in the distal convoluted tubule?

A

Potassium, hydrogen ions, and certain drugs.

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17
Q

How does the collecting duct contribute to urine concentration?

A

By adjusting the reabsorption of water, influenced by hormones like ADH.

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18
Q

What is the role of antidiuretic hormone (ADH) in the collecting duct?

A

ADH increases the permeability of the collecting ducts to water, enhancing reabsorption.

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19
Q

How does aldosterone affect the distal convoluted tubule and collecting duct?

A

Aldosterone increases sodium reabsorption and potassium secretion.

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20
Q

What is the significance of the juxtaglomerular apparatus in renal function?

A

It regulates blood pressure and GFR through the release of renin.

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21
Q

How does the macula densa contribute to the regulation of GFR?

A

By sensing sodium chloride concentration in the distal tubule and adjusting renin release.

22
Q

What is the function of renin released by the juxtaglomerular cells?

A

Renin activates the RAAS, increasing blood pressure and sodium retention.

23
Q

How does angiotensin II affect kidney function?

A

Angiotensin II constricts blood vessels and stimulates aldosterone release, increasing blood pressure.

24
Q

What is the importance of maintaining a stable GFR?

A

To ensure efficient filtration and reabsorption of essential substances.

25
Q

How is glucose reabsorbed in the kidneys?

A

Via secondary active transport linked to sodium reabsorption.

26
Q

What is the renal threshold for glucose?

A

The plasma concentration at which glucose begins to appear in the urine (~180 mg/dL).

27
Q

How are amino acids reabsorbed in the kidneys?

A

Through co-transport with sodium in the proximal convoluted tubule.

28
Q

What is the role of the peritubular capillaries in renal function?

A

They surround the renal tubules, allowing for the exchange of substances between blood and tubular fluid.

29
Q

How does the renal medulla contribute to the concentration gradient necessary for urine concentration?

A

It helps create a hyperosmotic environment necessary for water reabsorption.

30
Q

What is the significance of urea recycling in the kidneys?

A

Urea helps maintain the osmotic gradient in the renal medulla, facilitating water reabsorption.

31
Q

How is water reabsorbed in the proximal convoluted tubule?

A

Passively along the osmotic gradient created by sodium reabsorption.

32
Q

How does the thin descending limb of the loop of Henle differ in function from the thick ascending limb?

A

The thin descending limb is permeable to water, while the thick ascending limb actively transports sodium and is impermeable to water.

33
Q

What is the role of the distal convoluted tubule in acid-base balance?

A

It secretes hydrogen ions and reabsorbs bicarbonate, contributing to pH regulation.

34
Q

How do the kidneys regulate potassium levels?

A

By secreting or reabsorbing potassium in the distal tubule and collecting duct.

35
Q

What is the role of atrial natriuretic peptide (ANP) in the kidneys?

A

ANP inhibits sodium reabsorption, reducing blood volume and pressure.

36
Q

How does the sympathetic nervous system influence renal function?

A

By constricting arterioles and reducing renal blood flow, decreasing GFR.

37
Q

What is renal clearance and how is it measured?

A

Renal clearance measures the volume of plasma cleared of a substance per unit time.

38
Q

How does inulin clearance provide a measure of GFR?

A

Inulin clearance is used because it is freely filtered and neither reabsorbed nor secreted.

39
Q

What is the role of the vasa recta in the kidney?

A

The vasa recta maintains the osmotic gradient in the medulla by countercurrent exchange.

40
Q

How does the kidney handle bicarbonate to maintain acid-base balance?

A

By reabsorbing bicarbonate and secreting hydrogen ions.

41
Q

What is the significance of creatinine clearance in assessing renal function?

A

It provides an estimate of GFR as creatinine is filtered but not reabsorbed significantly.

42
Q

How does the renal handling of calcium differ from that of phosphate?

A

Calcium is actively reabsorbed in the distal tubule, while phosphate reabsorption is regulated by PTH.

43
Q

How do diuretics affect kidney function?

A

They increase urine output by inhibiting reabsorption of sodium and water.

44
Q

What is the effect of loop diuretics on the nephron?

A

Loop diuretics inhibit sodium, potassium, and chloride reabsorption in the ascending loop of Henle.

45
Q

How do thiazide diuretics affect the distal convoluted tubule?

A

Thiazides inhibit sodium reabsorption in the distal convoluted tubule.

46
Q

What is the role of aquaporins in the kidney?

A

Aquaporins are water channels that facilitate water reabsorption in the collecting ducts.

47
Q

How do changes in blood pressure affect renal function?

A

Increased blood pressure increases GFR, while decreased blood pressure reduces GFR.

48
Q

What is the role of prostaglandins in renal physiology?

A

Prostaglandins increase renal blood flow and counteract the effects of vasoconstrictors.

49
Q

How does chronic kidney disease affect urine formation?

A

It impairs the kidney’s ability to filter blood, reabsorb essential substances, and excrete wastes.

50
Q

What are the primary differences between cortical and juxtamedullary nephrons?

A

Cortical nephrons are primarily involved in filtration, while juxtamedullary nephrons play a key role in concentrating urine.

Renal & GIT Physiology (15 decks)

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