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Phase 2: Reproduction, Nephrology and Urology > PBL 3: Normal kidney function > Flashcards

PBL 3: Normal kidney function Flashcards

1
Q

Which spinal level is the kidneys located?

A

T11 to L3

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2
Q

___ kidney is lower than the ___ kidney. Why?

A

Right kidney is lower than the left kidney as the right kidney is displaced by the liver

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3
Q

What is located on the superior surface of the kidneys?

A

The adrenal glands

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4
Q

The kidneys are encased in 4 layers.

Name these layers

A
  • Renal capsule (inner layer)
  • Perirenal fat
  • Renal fascia
  • Pararenal fat (outer layer)
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5
Q

Fill in the blanks regarding the layers of the kidney

A
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6
Q

Renal parenchyma can be divided into two main regions.

Name these regions

A
  • Cortex (outer layer)
  • Medulla (inner layer)
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7
Q

The outer cortex extends into the medulla, dividing it into?

A

Renal pyramids

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8
Q

Name these parts of the kidneys

A
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9
Q

What structures are located in the cortex of the kidney

A

Filled with glomeruli, associated blood vessels and their attached tubules.

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10
Q

Describe the composition of the renal medulla

A
  • Highly salty as sodium chloride is pumped out of the ascending limp of the loop of Henle.
  • Medulla is primarily composed of different tubule types.
  • Medullary tissue is arranged in segments termed renal pyramids.
  • As it becomes collecting ducts, they descend through the pyramids, draining through the renal papilla.
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11
Q

Describe the pathway of the urine from the collecting ducts?

A

The fluid descend through the renal pyramids, draining through the renal papilla.

Renal papilla into the minor calyx into the major calyx. Finishes by draining into the renal pelvis via the renal calyx.

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12
Q

What is the functional unit of the kidney?

A

Nephron

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13
Q

What is the function of the nephrons?

A

Responsible for filtration, excretion and resorption

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14
Q

What structures make up the Renal corpuscle

A

Bowman’s capsule and glomerulus

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15
Q

What are the two types of nephrons?

A
  • Cortical nephrons
  • Juxtamedullary nephrons
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16
Q

Compare the two types of nephrons

A
  • Cortical nephrons
    • Short loop of Henle.
    • Renal corpuscles in the outer part of the cortex
    • 85% of all nephrons
  • Juxtamedullary nephrons
    • Long loops, extending into the medulla
    • Larger renal corpuscles in the inner third of the cortex
    • 15% of all nephrons
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17
Q

The cortical nephrons contain a ____ loop of Henle. The renal corpuscles is located in the ______. Cortical nephrons make up _____% of all nephrons.

A

A) Short

B) Outer part of the cortex

C) 85%

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18
Q

The juxtamedullary nephrons contain a ____ loop of Henle. The renal corpuscles is located in the ______. Cortical nephrons make up _____% of all nephrons.

A

A) Long

B) Inner third of the cortex

C) 15%

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19
Q

Name the parts of the nephron

A
  • Renal corpuscle (found in the renal cortex)
  • Proximal convoluted tubule (found in the renal cortex)
  • Loop of Henle (mostly in the medulla)
  • Distal convoluted tubule (found in the renal cortex)
  • Collecting tubule (in the medulla)
  • Collecting duct (in the medulla)
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20
Q

What structures make up the juxtaglomerular complex

A

The beginning of the distal convoluted tubule is found close to the renal corpuscle, in a structure known as the juxtaglomerular complex

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21
Q

Define the glomerulus

A

A compact mass of looped fenestrated capillaries

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22
Q

Define the bowman’s capsule

A
  • Blind ending of the nephron that encapsulates the glomerulus.
  • This blind ending is the proximal end of the renal tubule
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23
Q

The ____ arteriole enter the renal corpuscle. The ___ arteriole leaves the renal corpuscle

A

A) Afferent

B) Efferent (E-exit)

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24
Q

The capillary loops selectively filtrate the blood across glomerular filtration barrier.

Which molecules does it permit the passage and which does it block?

A

Permits the passage of small and some medium sized molecules e.g. water and electrolytes, while blocking the passage of larger molecules e.g. RBCs.

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25
Q

What pressures drive the filtration across the glomerular filtration barrier

A

hydrostatic and oncotic pressure

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26
Q

Name the 3 layers of the glomerular filtration barrier

A
  • Endothelium (inner layer)
  • Glomerular basement membrane (middle layer)
  • Podocytes (outermost layer)
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27
Q

Describe the endothelium of the glomerular filtration barrier

A
  • Single layer of fenestrated endothelium
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28
Q

Describe the formation of the glomerular basement membrane of the glomerular filtration barrier

A

Product of the fusion of the basement membrane produced by endothelial cells and podocytes.

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29
Q

Which type of collagen is the glomerular basement membrane composed of?

A

Collagen type 4

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30
Q

Describe podocytes

A
  • Epithelial cells
  • Contain numerous processes with each process having many smaller processes known as foot processes/pedicles.
  • The foot processes/pedicles are attached to the underlying glomerular basement membrane.
  • The foot processes are interlock with its neighbouring foot processes from adjacent podocytes.
  • The spaces between foot processes forms the filtration slits that act as a molecular sieve, providing an additional filtration barrier based mainly on size.
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31
Q

Name these parts of the glomerular filtration barrier

A
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32
Q

Name these parts of the glomerular filtration barrier

A
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33
Q

How many litres of filtrate move across the glomerulus into the tubular system per day?

A

180L per day

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34
Q

What substances are reabsorbed at the proximal covoluting tubule

A
  • Water (via osmosis)
  • Sodium chloride (65%)
  • Bicarbonate (90%)
  • Phosphate
  • Glucose and amino acids (100%)
  • Potassium (65%)
  • Urea (50%) the rest are secreted as urine
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35
Q

What substances are secreted at the proximal convoluting tubule

A
  • Ammonia
  • Drugs
36
Q

Describe the composition of the proximal covoluting tubule epithelium

A

Composed of simple cuboidal epithelium with microvilli that are joined by tight junctions.

37
Q

The _____ limb of Henle travels from the PT and forms a hairpin loop to become the _____ limb and the ____ limb before terminating into the distal convoluted tubule.

A

The thin descending limb of Henle travels from the PT and forms a hairpin loop to become the thin ascending limb and the thick ascending limb before terminating into the distal convoluted tubule.

38
Q

Describe the descending limb of the loop of Henle

A
  • Few mitochondria and little Na/K ATPase
  • Water reabsorption
  • Highly permeable to water and less permeable to solutes
  • Water leaves via osmosis due to the highly sodium chloride concentration in the interstitium.
  • Cells express abundant water channels (aquaporin I)
39
Q

Describe the ascending limb of the loop of henle

A
  • Known as the “diluting segment” as it effectively removing particles while remaining impermeable to water
  • Sodium and chloride reabsorption (25%)
  • Highly permeable to sodium but impermeable to water.
  • Thin: sodium chloride is passively absorbed.
  • Thick: activity pumping sodium chloride reabsorption
40
Q

Which limb of the loop of Henle reabsorbs water?

A

Descending limb

41
Q

Which limb of the loop of Henle reabsorbs sodium and chloride?

A

Ascending limb

42
Q

What is the main function of the distal convoluting tubules

A
  • Main function is the fine-tuning of ion concentrations and acid-base balance to maintain homeostasis.
43
Q

What is reabsorbed in the distal covoluting tubule

A
  • Calcium
  • Sodium
  • Chloride (pulled when sodium is absorbed)
  • Bicarbonate
  • Small amounts of water
44
Q

Calcium reabsorption in the distal convoluting tubules is under the influence of which hormone?

A

Parathyroid hormone

45
Q

Sodium reabsorption in the distal convoluting tubules is under the influence of which hormone?

A

Aldosterone

46
Q

What is secreted in the distal convoluting tubules

A
  • Hydrogen
  • Bicarbonate
  • Potassium
47
Q

Define the macula densa

A

The thickening where the distal convoluting tubule meets the glomerulus. Can detect sodium concentration of the fluid in the tubule.

48
Q

Juxtaglomerular apparatus is comprised of what?

A

Comprised of the macula densa and juxtaglomerular (JG) cells

49
Q

Where are the juxtaglomerular cells located?

A

Between the afferent arteriole region of the glomerular and the distal convoluted tubule.

50
Q

juxtaglomerular secrete what?

A

Renin

51
Q

What are the functions of the juxtaglomerular cells

A
  • JG cells have two main functions in response to stimuli:
    • Changes sodium and chloride concentration
    • Monitor blood pressure by measuring the afferent arteriole wall stretch (baroreceptors)
52
Q

Explain how the juxtaglomerular apparatus changes sodium and chloride concentrations

A

The macula densa cells sense sodium chloride concentration in the lumen of the distal convoluting tubule and stimulates the juxtaglomerular cells to synthesize and release renin into the bloodstream, activating the RAAS pathway.

Activated RAAS leads to aldosterone activation. Aldosterone acts of the distal convoluting tubule to increase sodium rebasorption

53
Q

Name these parts of the juxtaglomerular apparatus

A
54
Q

Renin is secreted in response to which stimuli

A
  1. When the baroreceptors located on the afferent arterioles detect a fall in arterial blood pressure they will trigger the release of renin by activating the juxtaglomerular cells
  2. When the macula densa detect a decrease in sodium chloride concentrations, prostaglandins are released from the macula densa cells which activate the juxtaglomerular cells.
  3. Sympathetic nervous system innervation releasing of renin via adrenaline and noradrenaline innervation of the beta1 adrenergic receptors located on the juxtaglomerular cells.
55
Q

What does renin do?

A

The release of renin in the bloodstream causes hydrolysis of angiotensinogen to form angiotensin I.

56
Q
  • Angiotensin I is converted by angiotensin-converting enzyme (ACE) to?
A

Angiotensin II.

57
Q

Angiotensin I is converted by ____ to angiotensin II.

A

Angiotensin-converting enzyme (ACE)

58
Q

What is the effect of angiotensin II?

A

Angiotensin II triggers the adrenal glands to produce and release aldosterone, which acts on distal convoluting tubules and collecting ducts to upregulate sodium and water reabsorption back into the blood.

59
Q

What are the two cell types of the collecting duct?

A

Intercalated cells

Principal cells

60
Q

What is the function of the intercalated cells

A
  • Fewer in number than the principal cells
  • Adjust bicarbonate or hydrogen ion reabsorption
  • Important for the regulation of blood pH
61
Q

What is the function of the principal cells

A
  • Predominant cell type
  • Contain Na+/K+ ATPase pump and aquaporin, which is an anti-diuretic hormone [ADH]-regulated water channel
62
Q

What is reabsorbed in the collecting duct

A
  • Sodium chloride
  • Urea
  • Water (under the influence of ADH)
63
Q

Na/K ATPase is situated on the ____ side of the renal tubule epithelial cells

A

Na/K ATPase is situated on the basolateral side of the renal tubule epithelial cells

64
Q

Describe them mechanism of sodium reabsorption in the nephrons

A
  • Na/K ATPase is situated on the basolateral side of the renal tubule epithelial cells. It exchanges 3x sodium ions for 2x potassium ions, as a result creates a low intracellular sodium concentration and a negative charge. Overall, creating an electrochemical force for sodium.
  • Transporters are located on the apical membrane, which allows sodium to flow from the tubule into the cell, down its electrochemical gradient.
65
Q

Name these vessels associated with the kidney

A

Peritubular capillaries also known as vasa recta

66
Q

Name the 8 functions of the kidney

A
  1. Excretion of small solutes
  2. Excretion of drugs
  3. Salt and water balance
  4. Blood pressure control
  5. Electrolyte balance
  6. Acid base balance
  7. Erythropoietin
  8. Vitamin D activation
67
Q

Define the term total glomerular filtration rate

A

Unit measure of kidney function.

68
Q

What is the equation for estimated glomerular filtration rate?

A

eGFR = (urine volume(ml) x [substance]urine) ÷ [substance]plasma

69
Q

What is the gold standard exogenous substances used to measure estimated glomerular filtration rate

A

Inulin

70
Q

Why is creatinine clearance a good estimate of GFR?

A

Because creatinine is produced at a constant rate, (almost) fully filtered at the glomerulus and neither re-absorbed or secreted (almost) in the tubule

71
Q

As eGFR of what means a reduced kidney function?

A

eGFR < 60ml/min/1.73m2

72
Q

What is the limitations of creatinine clearance as an estimate of GFR?

A
  • Slow recognition of loss of the first 70% of kidney function
  • Requires 24 hours collection
    • The measurement may be inaccurate if collections are incomplete.
    • Time-consuming
  • Overestimates the kidney function in the following groups:
    • Females
    • Elderly
    • Low muscle mass groups e.g. amputees.
  • Underestimates the kidney function in the following groups:
    • High muscle mass groups e.g. bodybuilders.
73
Q

What are limitations of urinary dipstick tests?

A
  • False negatives
  • Not very sensitive
  • Sensitivity is affected by some drugs
74
Q

What are the two tests used in urinalysis

A

Urine dipstick test

Urine microscopy

75
Q

What are the limiations of urine microscopy?

A
  • Certain medicines can alter the appearance of the urine under a microscope e.g. ampicillin.
  • Result may be affected by:
    • Stool in the sample
    • Menstrual blood
76
Q

Which type of kidney stone is the most common?

A

Calcium containing stone (80%)

Calcium oxalate stone (65%)

Calcium phosphate stone (15%)

77
Q

Describe the pathophysiology of kidney stone formation

A
  • Crystallised calculi can form in the tubule of the nephron by the accumulation of precipitance of some electrolytes.
    • Formed from the combination of excreted/secreted ions within the glomerular filtrate.
    • The cause that allows the precipitants to crystallised is not fully understood.
  • A solid concretion of crystal is now formed. If it is small enough, it will pass through the urinary tract.
  • If it is too big to pass through naturally, the crystal aggregates within the urinary space, growing as more precipitance aggregate.
  • As the calculi continues to grow, it can lead to an obstruction of the tubules. Results in an increase in pressure in the pre-calculi tubule leading to renal colic
78
Q

Define the term renal colic

A

Renal colic - is a type of pain you get when urinary stones block part of your urinary tract.

79
Q

Describe the signs and symptoms of kidney stones?

A
  • Acute severe flank pain that may radiate to the back and/or groin.
  • Associated fever (due to the inflammation)
  • Nausea/vomiting
  • Urinary frequency (polyurea)
  • Previous episodes of nephrolithiasis
  • Increase in urinary frequency/urgency
  • Haematuria (blood in the urine)
80
Q

What is the key symptoms/sign of kidney stone?

A

Acute severe flank pain that may radiate to the back and/or groin. ​

81
Q

renal calculi refers to

A

Kidney stones

Fancy way of saying it

82
Q

What imaging techniques are used to image renal calculi

A
  • Ultrasound- first line
  • X-ray- Can image the cells that are composed of calcium (80%)
  • CT

Always be warying using contrast in patients with kidney problems as they may have reduced excretion

83
Q

The glomerular capillaries drain into?

A

efferent arteriole

84
Q

How does the afferent and efferent arterioles of the nephron maintain a relatively high hydrostatic pressure

A

Contraction of this smooth muscle, maintains a relatively high hydrostatic pressure along the length of the capillaries.

85
Q

Which feature of the renal corpuscle enables blood to be filtered out

A

Fenestrations of the glomerular capillaries

Space between foot processes of the podocytes

Phase 2: Reproduction, Nephrology and Urology (25 decks)

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