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AUBF > 2 - RENAL FUNCTION - LEC > Flashcards

2 - RENAL FUNCTION - LEC Flashcards

1
Q

Each kidney contains approximately 1 to 1.5 million functional units called

A

nephrons

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2
Q

the human kidney contains two types of nephrons namely:

A

Cortical nephrons
Juxtamedullary nephrons

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3
Q

Make up approximately 85% of nephrons, are situated primarily in the cortex of the kidney. They are responsible primarily for removal of waste products and reabsorption of nutrients.

[type of nephron]

A

Cortical nephrons

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4
Q

Have longer loops of Henle that extend deep into the medulla of the kidney. Their primary function is concentration of the urine.

[type of nephron]

A

Juxtamedullary nephrons

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5
Q

The ability of the kidneys to clear waste products selectively from the blood and simultaneously to maintain the body’s essential water and electrolyte balances is controlled in the nephron by the following renal functions

A
  • Renal blood flow
  • Glomerular filtration
  • Tubular reabsorption
  • Tubular secretion
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6
Q

The human kidneys receive approximately [percent of blood] of the blood pumped through the heart at all times.

A

25%

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7
Q

Blood enters the capillaries of the nephron through the ______________ It then flows through the ______________ and into the ____________

A

afferent arteriole

glomerulus

efferent arteriole

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8
Q

help create the hydrostatic pressure differential that is important for glomerular filtration and to maintain consistency of glomerular capillary pressure and renal blood flow within the glomerulus

A

varying sizes of the arterioles found in the kidney

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9
Q

Which of the two arterioles are smaller in size

A

efferent arteriole

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10
Q

After leaving the efferent arteriole, which structures does blood enter before returning to the renal vein?

A

The peritubular capillaries and the vasa recta.

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11
Q

What is the total renal blood flow in an average adult with a body surface area of 1.73 m²?

A

Approximately 1200 mL/min

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12
Q

What is the normal range for total renal plasma flow in an average adult?

A

600 to 700 mL/min

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13
Q

Why must corrections be made when measuring renal function in individuals with body sizes significantly different from the average of 1.73 m²?

A

To determine whether the observed measurements represent normal function.

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14
Q

What should be considered when evaluating renal function studies in different age groups?

A

Variations in normal values for renal blood flow and renal function tests.

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15
Q

What is the standard body surface area used in renal calculations?

A

1.73 m²

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16
Q

Which test is related to this correction for body size in renal studies?

A

GFR (Glomerular Filtration Rate)

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17
Q

What should be considered when evaluating renal function in different age groups?

A

Variations in normal values.

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18
Q

What does the glomerulus consist of?

A

A coil of approximately eight capillary lobes.

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19
Q

Where is the glomerulus located?

A

Bowman capsule

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20
Q

What is the molecular weight cutoff for substances filtered by the glomerulus

A

Less than 70,000

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21
Q

Is the glomerulus a selective or nonselective filter?

A

Nonselective filter.

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22
Q

What are the factors influencing glomerular filtration?

A

Capillary and Bowman capsule structure
Hydrostatic pressure
Oncotic pressure
RAAS feedback mechanisms

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23
Q

What does RAAS stand for?

A

Renin–Angiotensin–Aldosterone System.

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24
Q

The walls of the glomerulus are referred to as the

A

glomerular filtration barrier

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25
Q

It is the beginning of the renal tubule

A

Bowman capsule

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26
Q

How many layers must plasma filtrate pass through in the glomerular filtration barrier?

A

Three layers.

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27
Q

What are the three layers of the glomerular filtration barrier?

A

Capillary wall membrane
Basement membrane (basal lamina)
Visceral epithelium of the Bowman capsule

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28
Q

What is the unique feature of the capillary wall in the glomerulus?

A

It contains pores, making it a fenestrated endothelium.

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29
Q

What is the function of the pores in the capillary wall of the glomerulus?

A

They increase permeability but do not allow large molecules or blood cells to pass.

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30
Q

Where does further restriction of large molecules occur after passing the capillary wall?

A

The basement membrane and filtration slits formed by podocytes

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31
Q

What forms the filtration slits in the glomerular filtration barrier?

A

The intertwining foot processes of podocytes.

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32
Q

A barrier that repels negatively charged molecules, even if they are small enough to pass.

A

shield of negativity

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33
Q

Which protein that is primarily associated with renal disease does the shield of negativity specifically repel

A

Albumin

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34
Q

Where are podocytes found

A

Inner layer of the bowman capsule

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35
Q

What happens if there were no shield of negativity

A

Positive readings for protein and albumin

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36
Q

What enhances filtration in the glomerulus?

A

Hydrostatic pressure.

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37
Q

What causes hydrostatic pressure in the glomerulus?

A

Smaller efferent arteriole and glomerular capillaries.

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38
Q

What pressures oppose hydrostatic pressure in the glomerulus?

A

Bowman capsule fluid and oncotic pressure.

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39
Q

What maintains constant glomerular blood pressure?

A

Autoregulatory mechanism.

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40
Q

What structure is responsible for this autoregulation?

A

Juxtaglomerular apparatus.

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41
Q

What happens to the afferent and efferent arterioles when blood pressure drops?

A

Afferent dilates, efferent constricts

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42
Q

Why do arterioles adjust during low blood pressure?

A

To maintain kidney blood flow and prevent toxic waste buildup.

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43
Q

What happens to the afferent arteriole when blood pressure rises?

A

Afferent constricts

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44
Q

Why does the afferent arteriole constrict during high blood pressure?

A

To prevent over-filtration and glomerular damage.

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45
Q

What regulates blood flow to the glomerulus?

A

The RAAS (Renin-Angiotensin-Aldosterone System).

46
Q

What does the juxtaglomerular apparatus consist of?

A

Juxtaglomerular cells (afferent arteriole) and macula densa (distal convoluted tubule).

47
Q

What happens when plasma sodium decreases?

A

Decreased water retention, reduced blood volume, and lower blood pressure

48
Q

What enzyme do juxtaglomerular cells secrete?

A

Renin.

49
Q

What does renin react with to form angiotensin I?

A

Angiotensinogen.

50
Q

Where is angiotensin I converted to angiotensin II?

A

In the lungs by angiotensin-converting enzyme (ACE).

51
Q

Name one function of angiotensin II.

A

Vasodilation of afferent arterioles and constriction of efferent arterioles.

52
Q

What hormones does angiotensin II stimulate the release of?

A

Aldosterone (adrenal cortex) and antidiuretic hormone (hypothalamus).

53
Q

How much water is filtered by glomeruli each minute?

A

Approximately 120 mL

54
Q

What substances are absent in glomerular filtrate compared to plasma?

A

Plasma proteins, protein-bound substances, and cells.

55
Q

What is the specific gravity of the filtrate leaving the glomerulus?

A

1.010.

56
Q

Angiotensin II corrects renal blood flow in the following ways:

A
  • Causing vasodilation of the afferent arterioles and constriction of the efferent arterioles
  • Stimulating reabsorption of sodium and water in the proximal convoluted tubules
  • Triggering the release of the sodium-retaining hormone aldosterone by the adrenal cortex and antidiuretic hormone by the hypothalamus
57
Q

Why can’t the body lose 120 mL of water every minute?

A

It contains essential substances that need to be reabsorbed.

58
Q

Where does reabsorption begin?

A

In the proximal convoluted tubule.

59
Q

What are the two types of reabsorption mechanisms?

A

Active transport and passive transport.

60
Q

What is required for active transport?

A

A substance must combine with a carrier protein in the renal tubular epithelial cells.

61
Q

What powers active transport?

A

Electrochemical energy from the interaction between the substance and the carrier protein.

62
Q

What substances are actively reabsorbed in the proximal convoluted tubule?

A

Glucose, amino acids, and salts.

63
Q

What is actively reabsorbed in the ascending loop of Henle?

A

Chloride.

64
Q

What is actively reabsorbed in the distal convoluted tubule?

A

Sodium

65
Q

What drives passive transport?

A

Differences in concentration or electrical potential (gradients).

66
Q

Where does passive reabsorption of water NOT occur in the nephron?

A

Ascending loop of Henle.

67
Q

Where is urea passively reabsorbed?

A

In the proximal convoluted tubule and ascending loop of Henle.

68
Q

What accompanies the active transport of chloride in the ascending loop?

A

Passive reabsorption of sodium.

69
Q

How can active transport be influenced?

A

By the concentration of the substance being transported.

70
Q

What happens when the plasma concentration of a substance exceeds the tubular reabsorptive capacity (Tm)?

A

The substance appears in the urine.

71
Q

What is the plasma concentration at which active transport stops called?

A

Renal threshold.

72
Q

What is the renal threshold for glucose?

A

160 to 180 mg/dL.

73
Q

What indicates that glucose will appear in the urine?

A

When plasma glucose concentration reaches the renal threshold.

74
Q

How can renal threshold and plasma concentration help in diagnosis?

A

They can distinguish between excess solute filtration and renal tubular damage.

75
Q

What accompanies the active transport of more than two-thirds of filtered sodium in the proximal convoluted tubule?

A

Passive reabsorption of an equal amount of water.

76
Q

How does the fluid leaving the proximal convoluted tubule compare to the ultrafiltrate?

A

It maintains the same concentration

77
Q

What does glucose appearing in the urine with a normal blood glucose level indicate?

A

Tubular damage, not diabetes mellitus.

78
Q

What would happen to the plasma glucose of a non-fasting patient with high glucose intake?

A

Plasma glucose would reach the renal threshold and appear in the urine.

79
Q

Where does renal concentration begin?

A

In the descending and ascending loops of Henle.

80
Q

What happens in the descending loop of Henle?

A

Water is removed by osmosis.

81
Q

What is reabsorbed in the ascending loop of Henle?

A

Sodium and chloride.

82
Q

How does the ascending loop of Henle prevent excessive water reabsorption?

A

Its walls are impermeable to water.

83
Q

What is the selective reabsorption process called?

A

Countercurrent mechanism.

84
Q

What does the countercurrent mechanism maintain?

A

The osmotic gradient of the medulla.

85
Q

How do sodium and chloride in the ascending loop affect the medullary interstitium?

A

They prevent its dilution by water reabsorbed from the descending loop.

86
Q

Why is maintaining the osmotic gradient essential?

A

For the final concentration of the filtrate in the collecting duct.

87
Q

Where does the final concentration of filtrate occur after reabsorption?

A

In the late distal convoluted tubule and the collecting duct.

88
Q

What regulates water reabsorption in the collecting duct?

A

The osmotic gradient in the medulla and vasopressin (ADH).

89
Q

When is vasopressin (ADH) released?

A

When the amount of water in the body decreases.

90
Q

What effect does ADH have on the walls of the distal convoluted tubule and collecting duct?

A

It makes them permeable or impermeable to water.

91
Q

What happens when ADH levels are high?

A

The walls become more permeable to water, increasing reabsorption and resulting in low-volume concentrated urine.

92
Q

What happens in the absence of ADH?

A

The walls are impermeable to water, resulting in a large volume of dilute urine.

93
Q

What determines the production of ADH?

A

The state of body hydration.

94
Q

What is the final determinant of urine volume and concentration?

A

The chemical balance in the body.

95
Q

What part of the nephron does ADH affect?

A

Walls of the distal convoluted tubule and collecting duct.

96
Q

Where is vasopressin (ADH) released from?

A

The posterior pituitary gland.

97
Q

What is the major site for the removal of nonfiltered substances through tubular secretion?

A

Proximal convoluted tubule.

98
Q

How do protein-bound substances enter the tubular filtrate?

A

They dissociate from their carrier proteins in the peritubular capillaries, develop a stronger affinity for tubular cells, and are transported into the filtrate

99
Q

Why can some foreign substances, like medications, not be filtered by the glomerulus?

A

They are bound to plasma proteins.

100
Q

What are the two major functions of tubular secretion?

A

Eliminating waste products not filtered by the glomerulus and regulating acid–base balance by secreting hydrogen ions.

101
Q

What distinguishes tubular secretion from tubular reabsorption?

A

Tubular secretion involves substances moving from the blood in the peritubular capillaries to the tubular filtrate, while reabsorption involves substances being removed from the filtrate and returned to the blood.

102
Q

What is required to maintain the normal blood pH of 7.4?

A

Buffering and elimination of excess acid from dietary intake and body metabolism.

103
Q

What ions are crucial for the blood’s buffering capacity?

A

Bicarbonate (HCO₃⁻) ions.

104
Q

How are bicarbonate ions handled by the kidneys to maintain pH?

A

Bicarbonate is filtered by the glomerulus and reabsorbed into the blood, preventing its excretion in urine.

105
Q

Where does the reabsorption of filtered bicarbonate primarily occur?

A

proximal convoluted tubule.

106
Q

What process helps maintain pH balance by managing hydrogen ions (H+)?

A

Secretion of H+ into the filtrate, which helps return bicarbonate ions to the plasma.

107
Q

How are excess hydrogen ions excreted from the body?

A

They are converted into ammonium ions (NH₄⁺) which are then excreted in the urine.

108
Q

Where else, besides the proximal convoluted tubule, can ammonium ions be produced?

A

In the distal convoluted tubule and the collecting duct.

109
Q

What health conditions can arise from disruptions in the secretion and reabsorption processes related to acid–base balance

A

Metabolic acidosis or renal tubular acidosis, which is characterized by the inability to produce acid urine.

110
Q

Renal Blood Flow

A
  1. Renal artery
  2. Afferent arteriole
  3. Glomerulus
  4. Efferent arteriole
  5. Peritubular capillaries
  6. Vasa recta
  7. Renal vein
111
Q

Urinary Filtrate Flow

A
  1. Bowman capsule
  2. Proximal convoluted tubule
  3. Descending loop of Henle
  4. Ascending loop of Henle
  5. Distal convoluted tubule
  6. Collecting duct
  7. Renal calyces
  8. Ureter
  9. Bladder
  10. Urethra

AUBF (22 decks)

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