Renal Function

Front 1

How is blood supplied to the kidneys?

Back 1

Via the renal arteries which are branches of the abdominal aorta.

Front 2

How is blood drained from the kidneys?

Back 2

Via renal veins, which are branches of the inferior vena cava.

Front 3

Nephron

Back 3

Functional unit of the kidney.

Front 4

Cortical nephrons

Back 4

85%. Loop remains within the cortex of the nephron. Removal of waste products and reabsorption of nutrients.

Front 5

Juxtamedullary nephrons

Back 5

Longer loops of henle. Extend deep into the nephron medulla. Urine concentration.

Front 6

Renal functions

Back 6

Renal blood flow, glomerular filtration, tubular reabsorption, and tubular secretion.

Front 7

How many nephrons does each kidney contain?

Back 7

1 to 1.5 million.

Front 8

The kidneys receive approximately 25% of:

Back 8

Blood pumped through the heart at all times.

Front 9

Blood enters the capillaries of the nephron through the:

Back 9

Afferent arteriole. Supplies blood to kidneys.

Front 10

Where does the blood flow to after it enteres through the afferent arteriole?

Back 10

Glomerulus, then efferent arteriole.

Front 11

What does the varying sizes of arteriole do help create?

Back 11

Hydrostatic pressure. Important for glomerular filtration and to maintain consistency of glomerular capillary pressure and renal blood flow within glomerulus.

Front 12

Where does blood flow to after it leaves the efferent arteriole?

Back 12

Peritubular capillaries and the vasa recta. Flows slowly through the cortex and medulla of the kidney close to the tubules.

Front 13

What do the peritubular capillaries surround?

Back 13

Surround the proximal and distal convoluted tubules, providing important reabsorption of essential substances from the fluid in the proximal convoluted tubule and final adjustment of urinary composition in the distal convoluted tubule.

Front 14

Where are the vasa recta located? What occurs here? What does it maintain?

Back 14

Adjacent to the ascending and descending loops of Henle in juxtamedullary nephrons. Major exchanges of water and salts take place between the blood and medullary interstitium. Maintains osmotic gradient in medulla, which is necessary for renal concentration.

Front 15

Average body size

Back 15

1.73 m^2.

Front 16

Average renal blood flow

Back 16

1200 ml/min.

Front 17

Average renal plasma flow

Back 17

600-700 mL/min.

Front 18

The glomerulus consists of:

Back 18

A tuft of 8 capillary lobes, the walls of which are referred to as he glomerular filtration barrier.

Front 19

Where is the glomerulus located?

Back 19

Within the Bowman's capsule, which forms the beginning of the renal tubule.

Front 20

Function of the glomerulus

Back 20

Nonselective filter of plasma.

Front 21

Filtration factors

Back 21

Cellular structure, hydrostatic and oncotic pressure, and renin-angiotensin-aldosterone system.

Front 22

What 3 glomerular filtration barrier cellular layers must plasma pass through?

Back 22

Capillary wall membrane, basement membrane, and the Bowman's capsule inner layer.

Front 23

Endothelial cells of the capillary wall

Back 23

Differ by containing pores and are referred to as gene started. Increase capillary permeability, but don't allow the passage of large molecules and blood cells.

Front 24

Bowman's capsule inner layer

Back 24

The thin membranes covering the filtration slits formed by the intertwining foot processes of the podocytes.

Front 25

Basement membrane

Back 25

Further restriction of large molecules.

Front 26

Shield of negativity

Back 26

Repels molecule with a positive charge. Molecules small enough to pass through the three layers of the barrier.

Front 27

Why is the shield of negativity important?

Back 27

Albumin, the primary protein associated with renal disease, has a positive charge and would easily pass the barrier.

Front 28

What % of plasma proteins are albumin?

Back 28

60.

Front 29

Juxtaglomerular apparatus

Back 29

Regulation of arteriole size. Maintains glomerular blood pressure at a relatively constant rate regardless of fluctuations in the systemic blood pressure.

Front 30

Low systemic blood pressure

Back 30

Larger afferent and smaller efferent. Prevents decreased glomerular blood flow.

Front 31

High systemic blood pressure

Back 31

Smaller afferent arteriole. Prevents overfiltration and glomerular damage.

Front 32

Renin-Angiotensin-Aldosterone System (RAAS)

Back 32

Regulates blood flow to and within the glomerulus. Responds to blood pressure and plasma sodium changes that are monitored by juxtaglomerular cells in the afferent arteriole and the macula densa of the distal convoluted tubules.

Front 33

What does the macula densa initiate?

Back 33

Initiates RAAS in response to blood pressure changes.

Front 34

Renin

Back 34

An enzyme produced by the juxtaglomerular cells and is secreted and reacts with the blood borne substrate angiotensin to produce the inert hormone antgiotensin 1. Responds to low sodium levels.

Front 35

What happens as angiotensin 1 passes through the alveoli of the lungs?

Back 35

ACE (angiotensin converting enzyme) changes it to the active form angiotensin 2.

Front 36

How does angiotensin 2 correct renal blood flow?

Back 36

Causes vasodilation of afferent arterioles and constriction of the efferent arterioles, stimulating reabsorption of sodium and water in the proximal convoluted tubules, and triggering release of aldosterone by the adrenal cortex and antidiuretic hormone by the hypothalamus.

Front 37

Aldosterone

Back 37

Retains sodium in the distal convoluted tubules.

Front 38

What does the actions of angiotensin 2 produce?

Back 38

Constant pressure in the nephrons.

Front 39

Normal glomerular filtration rate

Back 39

120 mL/min of filtrate.

Front 40

Specific gravity of ultrafiltrate as it leaves the glomerulus

Back 40

1.010

Front 41

When does reabsorption start?

Back 41

When the plasma ultrafiltrate enters the proximal convoluted tubules.

Front 42

Active transport

Back 42

Carrier proteins and cellular energy needed for transport back to blood.

Front 43

Where is glucose, amino acids, and salts reabsorbed in active transport?

Back 43

Proximal convoluted tubules.

Front 44

Where is chloride reabsorbed? (Active transport)

Back 44

Ascending loop of Henle.

Front 45

Where is sodium reabsorbed? (Active transport)

Back 45

Proximal and distal convoluted tubules.

Front 46

Passive transport

Back 46

Controlled by the differences in the substance concentration gradients in both sides of the membrane.

Front 47

Where does water reabsorption occur? (Passive transport)

Back 47

Through the nephron. Exception is ascending loop of Henle. Accompanies high amount of sodium reabsorption in the PCT. PCT, descending loop of Henle, and collecting duct.

Front 48

Where is Urea reabsorbed in passive transport?

Back 48

PCT and ascending loop of Henle.

Front 49

Where is sodium reabsorbed in passive transport?

Back 49

Ascending loop of Henle.

Front 50

Maximal reabsorptive capacity

Back 50

Plasma concentration of a substance that is normally completely reabsorbed reaches an abnormally high level and substances found in urine.

Front 51

Renal threshold

Back 51

Plasma concentration of a substance at which active transport stops and increased amounts are excreted in the urine.

Front 52

Glucose threshold

Back 52

160-180 mg/dL.

Front 53

What does threshold distinguish?

Back 53

Excess filtration from tubular damage.

Front 54

Tubular concentration: descending loop of Henle

Back 54

Passive absorption of water into high osmotic gradient of the renal medulla.

Front 55

Tubular concentration: ascending loop of Henle

Back 55

Chloride actively reabsorbed, sodium passively reabsorbed, and walls are impermeable to water.

Front 56

Concurrent mechanism

Back 56

Maintains concentration in the medulla. Medulla is diluted by the water from the descending loop. Reconcentrated by sodium and chloride from the filtrate in the ascending loop.

Front 57

DCT: tubular concentration

Back 57

Aldosterone controlled sodium reabsorption if needed by the body.

Front 58

What does reabsorption depend on?

Back 58

Osmotic gradient in the medulla and the hormone vasopressin.

Front 59

Final filtrate concentration

Back 59

Water reabsorption controlled by ADH in response to body hydration.

Front 60

ADH

Back 60

Controls permeability of DCT and CT walls to water. Amount of ADH produced by the hypothalamus determines permeability.

Front 61

What is the final determinant of urine volume and concentration?

Back 61

Chemical balance in body because ADH is determined by state of hydration.

Front 62

What is the final determinant of urine volume and concentration?

Back 62

Chemical balance in body because ADH is determined by state of hydration.

Front 63

ADH regulation

Back 63

Increased body hydration = low ADH = increased urine.

Decreased body hydration = increased ADH = decreased urine volume.

Front 64

Tubular secretion

Back 64

Involves passage of substances from the blood in peritubular capillaries to the tubular filtrate.

Front 65

Reabsorption

Back 65

Filtrate to peritubular capillaries.

Front 66

Function of tubular secretion

Back 66

Eliminating waste products not filtered by the glomerulus and regulating the acid base balance in the body through the secretion of hydrogen ions.

Front 67

Major site for removal of non filtered substances

Back 67

PCT.

Front 68

Normal blood ph

Back 68

7.35-7.45

Front 69

How is ph of blood maintained?

Back 69

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

Front 70

What does the buffering capacity of blood depend on?

Back 70

Bicarbonate returned to blood: secretion of hydrogen ions into filtrate, 100% of bicarbonate reabsorption, and occurs in PCT.

Front 71

Actual exertion of excess hydrogen ions depends on:

Back 71

Tubular secretion.

Front 72

In PCT, ammonia is produced from:

Back 72

Breakdown of amino acid glutamine. Reacts with the hydrogen ion to form ammonium ion.

Front 73

Disruption of acid base balance causes

Back 73

Metabolic acidosis (diabetics) and renal tubular acidosis (incorrect function of tubules).

Front 74

Renal function test evaluate:

Back 74

Glomerular filtration, tubular reabsorption, tubular secretion , and renal blood flow.

Front 75

Test that measures glomerular filtration

Back 75

Clearance test.

Front 76

Clearance tests

Back 76

Measure rate at which the kidneys can remove a filterable substance from the blood. Substance analyzed can't be reabsorbed or secreted by tubules. Stability of substance during a long urine collection period. Consistency of plasma level. Availability of the body. Availability of tests to measure the substance.

Front 77

Substances measuring GFR

Back 77

Creatinine, beta 2 micro globulin, cystatin c, radioisotopes, exogenous procedure (infused into you), and endogenous procedure (in body already).

Front 78

Creatinine clearance test

Back 78

Creatinine is current routine substance.

Front 79

Advantages of creatinine clearance

Back 79

Waste product of muscle metabolism found at relatively constant plasma level. Automated chemical tests, calculate an eGFR utilizing serum creatinine and do not require urine testing.

Front 80

Disadvantages of creatinine clearance

Back 80

1. Tubular secretion increases with high blood creatinine levels.

2. Gentamicin, cephalosporins, and cimetidine (acid blocks) inhibit tubular secretion.

3. Bacteria breakdown creatinine if urine is stored at room temp.

4. Diet heavy in meat during timed collection increases urine creatinine.

5. Not reliable with muscle wasting diseases.

6. Accurate results depend on accurate collection of 24 hour urine specimen.

7. It must be corrected for smaller/larger body surface area.

Front 81

Greatest error of creatinine clearance

Back 81

Improperly timed urine specimen.

Front 82

Principle of creatinine clearance test

Back 82

To determine amount of creatinine (mL) completely cleared from the plasma during 1 minute. Report in mL/min. Referred to as glomerular filtration rate. (GFR)

Front 83

Required measurements of creatinine clearance

Back 83

Urine volume in mL/min (v)

Urine creatinine in mg/dL (u)

Plasma creatinine in mg/dL (p)

Calculation of urine volume

Front 84

Creatinine production

Back 84

Produced as a result of muscle metabolism. Therefore, normal values are based on body size; the larger the person, the more creatinine produced.

Front 85

Normal values of creatinine

Back 85

Men: 107-139 mL/min

Women: 87-107 mL/min

Values lower in older people

Plasma creatinine 0.5-1.5

Front 86

Reason for increased clearance. Causes of low creatinine clearance.

Back 86

Pregnancy. Concerned about low values.

Causes: COPD, CHF, dehydration, glomerulonephritis, and nephrotic syndrome.

Front 87

eGFR modification of diet in renal disease formula

Back 87

Doesn't require weight. Used different variables including BUN, albumin, and ethnicity. Advantage: without weight all calculations are available from lab computer.

Front 88

Methods not requiring urine collection

Back 88

Cystatin C: small protein produced by all nucleated cells. Filtered by glomerulus.

Front 89

What is cystatin c absorbed by?

Back 89

Renal tubules and broken down, none is secreted.

Front 90

Cystatin C

Back 90

Doesn't require urine collection. small protein produced by all nucleated cells. Filtered by glomerulus.

Front 91

What does cystatin c monitor?

Back 91

Pediatric patients, diabetics, elderly, and critically ill patients.

Front 92

Beta 2 microglobulin

Back 92

Doesn't require urine collection. Small protein that dissociates from human leukocyte antigens at a constant rate.

Front 93

What is beta 2 microglobulin removed by?

Back 93

Rapidly removed from the plasma by kidneys.

Front 94

What is beta 2 microglobulin a sensitive indicator of?

Back 94

Decrease in GFR.

Front 95

What is beta 2 microglobulin unreliable in?

Back 95

Patients with immunological disorders and malignancies.

Front 96

Exogenous method

Back 96

Radioisotopes: measures disappearance of an injected isotope. Iothalamate. Provides simultaneous visualization of the kidneys.

Front 97

Tubular reabsorption tests

Back 97

Good indicator of early renal disease. Measures renal concentrating ability (salts and water). Often termed concentration tests.

Front 98

Baseline for determining concentration

Back 98

1.010 SG of original ultrafiltrate.

Front 99

Control of what is necessary for accurate results of tubular reabsorption tests?

Back 99

Control of fluid.

Front 100

Clinical significance of renal function tests

Back 100

Results are based on functioning nephrons. Monitor extent of known renal disease. Determine feasibility of administering medications that may build up to toxic blood levels.

Front 101

Osmolality

Back 101

Has replaced SG as the test to assess renal concentration.

Front 102

SG includes:

Back 102

Number and size of molecules.

Front 103

Osmolality includes:

Back 103

Number of small molecules; Na and Cl are both equal to a large urea molecule.

Front 104

Clinical unit of measure for osmolarity

Back 104

Milliosmole.

Front 105

Colligative properties

Back 105

Solution properties related to number of molecules in the solvent, lower freezing point, higher boiling point, increased osmotic pressure, lower vapor pressure, and urine/plasma values compared with those of pure water.

Front 106

Osmometry method of choice

Back 106

Freezing point is method of choice.

Front 107

Renal concentration osmolarity

Back 107

Overnight deprivation of fluid for 12 hours.

Front 108

Urine: depends on fluid intake or exercise for renal concentration osmolality. Values of urine osmolality.

Back 108

Greater than or equal to 800 milliosmoles.

Front 109

Ratio of urine to serum more accurate: controlled intake ratio

Back 109

3:1

Front 110

What is needed if tests are abnormal? (Renal concentration osmolality)

Back 110

Further studies. ADH. If not enough, more urine is produced.

Front 111

Actual measure of vapor pressure osmometers

Back 111

Dew point: temp at which water vapor condenses to a liquid.

Front 112

Vapor pressure osmometers

Back 112

Microsamples on small filter paper disks in sealed chamber; a appearing sample forms vapor. Temp lowered, vapor condenses, thermocoupler measures heat of condensation that raised temp to dew point.

Front 113

What sample is used for vapor pressure osmometers?

Back 113

Serum. Used to test sweat also (chloride). Cystic fibrosis.

Front 114

Interfering factors for tubular reabsorption tests

Back 114

Lipemic serum: affects both instruments, insoluble lipids displace serum water.

Lactic acid: elevates readings in both instruments, separate or refrigerate within 20 mins.

Volitile/Ethanol: Elecate results for freezing point osmometers l, no effect on vapor pressure instruments.

Front 115

Clinical significance of osmolarity tests

Back 115

Evaluating renal concentrating ability, monitoring course of renal disease, monitoring fluid and electrolyte therapy, differential diagnosis of hypoatremia and hyperatremia, and evaluating secretion of and response to ADH.

Front 116

Free water clearance

Back 116

If enough water is secreted. Expands serum:urine ratio. Osmolar clearance performed first using water deprivation, timed urine, and serum.

Front 117

Explanation of free water clearance

Back 117

Ultrafiltrate has same osmolarity as plasma. Indicates if enough water is excreted to remove wastes and the kidney's response to body hydration.

Front 118

Secretion is dependent on:

Back 118

Renal blood flow.

Front 119

P-Aminohippuric Acid (PAH)

Back 119

Test for renal blood flow.

Front 120

What is PAH secreted in? What is it bound to?

Back 120

PCH, not by glomerular filtration. Plasma proteins.

Front 121

When is PAH removed from blood?

Back 121

Removed completely each time it comes in contact with functional renal tissue.

Front 122

PAH test values

Back 122

Normal values based on normal hct. Only in plasma, so normal would be 600-700 mL/min effective renal plasma flow. About 8% doesn't come in contact with functional renal tissue.

Front 123

Normal acid levels

Back 123

70 mEq/day of acid in form of H+, H2PO4-, and NH4+.

Front 124

Normal acid levels

Back 124

70 mEq/day of acid in form of H+, H2PO4-, and NH4+.

Front 125

Alkaline tide

Back 125

First morning, postprandial 2 to 8 pm. Lowest pH at night.

Front 126

Renal tubular acidosis

Back 126

Inability to produce an acid in urine = metabolic acidosis.

Front 127

PCT = ___________

DCT = ___________ (titeatable acidity/urine ammonia)

Back 127

PCT = secretion of H+

DCT = secretion of NH3

Front 128

Titratable acidity/ urine ammonia test procedure

Back 128

Measurement of pH, titratable acidity, and ammonia. Prime patients with load of ammonia chloride. 2 hour urine specimen. Titratable free H + and total acidity. Total acidity - titratable acidity = ammonia.