2 - RENAL FUNCTION - LEC

Question 1

Each kidney contains approximately 1 to 1.5 million functional units called

Answer 1

nephrons

Question 2

the human kidney contains two types of nephrons namely:

Answer 2

Cortical nephrons
Juxtamedullary nephrons

Question 3

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]

Answer 3

Cortical nephrons

Question 4

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]

Answer 4

Juxtamedullary nephrons

Question 5

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

Answer 5

• Renal blood flow
• Glomerular filtration
• Tubular reabsorption
• Tubular secretion

Question 6

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

Answer 6

25%

Question 7

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

Answer 7

afferent arteriole

glomerulus

efferent arteriole

Question 8

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

Answer 8

varying sizes of the arterioles found in the kidney

Question 9

Which of the two arterioles are smaller in size

Answer 9

efferent arteriole

Question 10

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

Answer 10

The peritubular capillaries and the vasa recta.

Question 11

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

Answer 11

Approximately 1200 mL/min

Question 12

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

Answer 12

600 to 700 mL/min

Question 13

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

Answer 13

To determine whether the observed measurements represent normal function.

Question 14

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

Answer 14

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

Question 15

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

Answer 15

1.73 m²

Question 16

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

Answer 16

GFR (Glomerular Filtration Rate)

Question 17

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

Answer 17

Variations in normal values.

Question 18

What does the glomerulus consist of?

Answer 18

A coil of approximately eight capillary lobes.

Question 19

Where is the glomerulus located?

Answer 19

Bowman capsule

Question 20

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

Answer 20

Less than 70,000

Question 21

Is the glomerulus a selective or nonselective filter?

Answer 21

Nonselective filter.

Question 22

What are the factors influencing glomerular filtration?

Answer 22

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

Question 23

What does RAAS stand for?

Answer 23

Renin–Angiotensin–Aldosterone System.

Question 24

The walls of the glomerulus are referred to as the

Answer 24

glomerular filtration barrier

Question 25

It is the beginning of the renal tubule

Answer 25

Bowman capsule

Question 26

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

Answer 26

Three layers.

Question 27

What are the three layers of the glomerular filtration barrier?

Answer 27

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

Question 28

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

Answer 28

It contains pores, making it a fenestrated endothelium.

Question 29

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

Answer 29

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

Question 30

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

Answer 30

The basement membrane and filtration slits formed by podocytes

Question 31

What forms the filtration slits in the glomerular filtration barrier?

Answer 31

The intertwining foot processes of podocytes.

Question 32

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

Answer 32

shield of negativity

Question 33

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

Answer 33

Albumin

Question 34

Where are podocytes found

Answer 34

Inner layer of the bowman capsule

Question 35

What happens if there were no shield of negativity

Answer 35

Positive readings for protein and albumin

Question 36

What enhances filtration in the glomerulus?

Answer 36

Hydrostatic pressure.

Question 37

What causes hydrostatic pressure in the glomerulus?

Answer 37

Smaller efferent arteriole and glomerular capillaries.

Question 38

What pressures oppose hydrostatic pressure in the glomerulus?

Answer 38

Bowman capsule fluid and oncotic pressure.

Question 39

What maintains constant glomerular blood pressure?

Answer 39

Autoregulatory mechanism.

Question 40

What structure is responsible for this autoregulation?

Answer 40

Juxtaglomerular apparatus.

Question 41

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

Answer 41

Afferent dilates, efferent constricts

Question 42

Why do arterioles adjust during low blood pressure?

Answer 42

To maintain kidney blood flow and prevent toxic waste buildup.

Question 43

What happens to the afferent arteriole when blood pressure rises?

Answer 43

Afferent constricts

Question 44

Why does the afferent arteriole constrict during high blood pressure?

Answer 44

To prevent over-filtration and glomerular damage.

Question 45

What regulates blood flow to the glomerulus?

Answer 45

The RAAS (Renin-Angiotensin-Aldosterone System).

Question 46

What does the juxtaglomerular apparatus consist of?

Answer 46

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

Question 47

What happens when plasma sodium decreases?

Answer 47

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

Question 48

What enzyme do juxtaglomerular cells secrete?

Answer 48

Renin.

Question 49

What does renin react with to form angiotensin I?

Answer 49

Angiotensinogen.

Question 50

Where is angiotensin I converted to angiotensin II?

Answer 50

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

Question 51

Name one function of angiotensin II.

Answer 51

Vasodilation of afferent arterioles and constriction of efferent arterioles.

Question 52

What hormones does angiotensin II stimulate the release of?

Answer 52

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

Question 53

How much water is filtered by glomeruli each minute?

Answer 53

Approximately 120 mL

Question 54

What substances are absent in glomerular filtrate compared to plasma?

Answer 54

Plasma proteins, protein-bound substances, and cells.

Question 55

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

Answer 55

1.010.

Question 56

Angiotensin II corrects renal blood flow in the following ways:

Answer 56

* 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

Question 57

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

Answer 57

It contains essential substances that need to be reabsorbed.

Question 58

Where does reabsorption begin?

Answer 58

In the proximal convoluted tubule.

Question 59

What are the two types of reabsorption mechanisms?

Answer 59

Active transport and passive transport.

Question 60

What is required for active transport?

Answer 60

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

Question 61

What powers active transport?

Answer 61

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

Question 62

What substances are actively reabsorbed in the proximal convoluted tubule?

Answer 62

Glucose, amino acids, and salts.

Question 63

What is actively reabsorbed in the ascending loop of Henle?

Answer 63

Chloride.

Question 64

What is actively reabsorbed in the distal convoluted tubule?

Answer 64

Sodium

Question 65

What drives passive transport?

Answer 65

Differences in concentration or electrical potential (gradients).

Question 66

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

Answer 66

Ascending loop of Henle.

Question 67

Where is urea passively reabsorbed?

Answer 67

In the proximal convoluted tubule and ascending loop of Henle.

Question 68

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

Answer 68

Passive reabsorption of sodium.

Question 69

How can active transport be influenced?

Answer 69

By the concentration of the substance being transported.

Question 70

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

Answer 70

The substance appears in the urine.

Question 71

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

Answer 71

Renal threshold.

Question 72

What is the renal threshold for glucose?

Answer 72

160 to 180 mg/dL.

Question 73

What indicates that glucose will appear in the urine?

Answer 73

When plasma glucose concentration reaches the renal threshold.

Question 74

How can renal threshold and plasma concentration help in diagnosis?

Answer 74

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

Question 75

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

Answer 75

Passive reabsorption of an equal amount of water.

Question 76

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

Answer 76

It maintains the same concentration

Question 77

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

Answer 77

Tubular damage, not diabetes mellitus.

Question 78

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

Answer 78

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

Question 79

Where does renal concentration begin?

Answer 79

In the descending and ascending loops of Henle.

Question 80

What happens in the descending loop of Henle?

Answer 80

Water is removed by osmosis.

Question 81

What is reabsorbed in the ascending loop of Henle?

Answer 81

Sodium and chloride.

Question 82

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

Answer 82

Its walls are impermeable to water.

Question 83

What is the selective reabsorption process called?

Answer 83

Countercurrent mechanism.

Question 84

What does the countercurrent mechanism maintain?

Answer 84

The osmotic gradient of the medulla.

Question 85

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

Answer 85

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

Question 86

Why is maintaining the osmotic gradient essential?

Answer 86

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

Question 87

Where does the final concentration of filtrate occur after reabsorption?

Answer 87

In the late distal convoluted tubule and the collecting duct.

Question 88

What regulates water reabsorption in the collecting duct?

Answer 88

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

Question 89

When is vasopressin (ADH) released?

Answer 89

When the amount of water in the body decreases.

Question 90

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

Answer 90

It makes them permeable or impermeable to water.

Question 91

What happens when ADH levels are high?

Answer 91

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

Question 92

What happens in the absence of ADH?

Answer 92

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

Question 93

What determines the production of ADH?

Answer 93

The state of body hydration.

Question 94

What is the final determinant of urine volume and concentration?

Answer 94

The chemical balance in the body.

Question 95

What part of the nephron does ADH affect?

Answer 95

Walls of the distal convoluted tubule and collecting duct.

Question 96

Where is vasopressin (ADH) released from?

Answer 96

The posterior pituitary gland.

Question 97

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

Answer 97

Proximal convoluted tubule.

Question 98

How do protein-bound substances enter the tubular filtrate?

Answer 98

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

Question 99

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

Answer 99

They are bound to plasma proteins.

Question 100

What are the two major functions of tubular secretion?

Answer 100

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

Question 101

What distinguishes tubular secretion from tubular reabsorption?

Answer 101

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.

Question 102

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

Answer 102

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

Question 103

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

Answer 103

Bicarbonate (HCO₃⁻) ions.

Question 104

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

Answer 104

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

Question 105

Where does the reabsorption of filtered bicarbonate primarily occur?

Answer 105

proximal convoluted tubule.

Question 106

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

Answer 106

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

Question 107

How are excess hydrogen ions excreted from the body?

Answer 107

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

Question 108

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

Answer 108

In the distal convoluted tubule and the collecting duct.

Question 109

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

Answer 109

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

Question 110

Renal Blood Flow

Answer 110

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

Question 111

Urinary Filtrate Flow

Answer 111

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