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HUBS192 > Renal System > Flashcards

Renal System Flashcards

1
Q

What is the role of the renal system?

A

To maintain balance by filtering the blood, and expelling excess water, salts, toxins and drugs.

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2
Q

How much blood flows through the kidneys, and how much urine does the typical person produce?

A

1200mL per minute

800-2000mL per day

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3
Q

What is the pH of urine?

A

~4.6 to 8

It is not tightly regulated, and is influenced by what is secreted.

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4
Q

Name the main gross structures of the renal system.

A

2 kidneys
2 ureters
Urinary bladder
Urethra

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5
Q

Describe the location of the kidneys.

A

Between T12 and L3 vertebrae.
Retroperitoneal
Right kidney is slightly lower because the liver pushes it down.
Convex side faces laterally.

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6
Q

How are the kidneys protected?

A

By 11th and 12th ribs
Adipose surrounds and protects them
Fibrous capsule encloses them

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7
Q

Where is the hilum of the kidneys, and what travels through it?

A

In the concave medial surface.

Renal blood vessels, lymphatics, nerves, and ureter.

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8
Q

Name the three regions of the kidney.

A

Cortex
Medulla
Pelvis

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9
Q

Describe the structure of the renal medulla.

A

Divided into medullary pyramids. Each pyramid ends in a renal papilla that points into the renal pelvis.

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10
Q

Describe the structure of the renal cortex.

A

Continuous layer that surround the medullary pyramids and comes in between them to form renal columns.

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11
Q

Define a kidney lobe.

A

A functional lobe (number varies between people) that contains a medullary pyramid and the renal cortex surrounding it- including renal columns.

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12
Q

What type of unit makes up the bulk of a kidney lobe?

A

Nephrons- tiny tubes that filter blood and create urine

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13
Q

Where does urine go after it drains from each renal papilla?

A

Collects in minor calyx, then major calyx, then the renal pelvis, and finally exits through the hilum via the ureter.

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14
Q

What is a pyelogram?

A

A type of X-ray in which the patient drinks a dye to show the renal system.

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15
Q

In which region of the kidney does filtration occur?

A

Renal cortex

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16
Q

Describe the blood supply to the glomerulus.

A
  • renal artery branches off the abdominal aorta and enters hilum
  • branching arteries getting smaller until they reach the cortex
  • afferent arteriole from artery to glomerular capillary
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17
Q

Describe the blood drainage from the glomerulus.

A
  • efferent arteriole from glomerular capillary to peritubular capillary
  • peritubular to series of veins
  • renal vein from smaller veins to inferior vena cava
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18
Q

How is the kidney innervated?

A

Renal plexus- a network of autonomic nerves and ganglia

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19
Q

How do sympathetic nerves regulate blood flow through the kidneys?

A

They act to adjust the diameter of renal arterioles.

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20
Q

Name four key components of a nephron.

A

Renal corpuscle- contains glomerular capsule
Proximal convoluted tubule- closer to corpuscle
Nephron loop
Distal convoluted tubule

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21
Q

Where does urine from multiple nephrons meet?

A

In the collecting duct.

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22
Q

Define the two types of nephrons.

A

Cortical nephrons- mainly in cortex

Juxtamedullary nephrons- nephron loop extends deep into medulla, important for the formation of concentrated urine

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23
Q

What is the function of the nephron?

A

To selectively filter blood, return to blood and carry away what is needed.

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24
Q

Describe glomerular capillary structure.

A

Thin walled single layer of fenestrated endothelial cells.

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25
Q

Where are peritubular capillaries located?

A

Wrapped around renal tubules. Vasa recta are straight peritubular capillaries that follow nephron loops of juxtamedullary nephrons deep into the medulla.

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26
Q

What do peritubular capillaries receive?

A

Filtered blood from the glomerulus via efferent arterioles.

Reabsorbed filtrate from nephron.

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27
Q

Describe the renal corpuscle.

A

Where the glomerulus and nephron meet. Site of the filtration barrier.

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28
Q

Describe the glomerular capsule.

A

Two layers: parietal simple squamous, visceral podocytes

Capsular space in between

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29
Q

Define podocytes, pedicels, and filtration slits.

A

Podocytes are very branched epithelial cells surrounding the glomerular capillaries. The branches form foot processes called pedicels. Filtration slits between pedicels allows filtrate to pass into the capsular space.

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30
Q

What can get through the filtration barrier?

A

Water and small molecules, not most proteins and RBCs.

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31
Q

What are the three layers of the filtration barrier?

A

Fenestrated endothelium of glomerular capillary
Fused basement membrane
Filtration slits between pedicels

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32
Q

Urine = filtrate - _________ + __________

A

What is reabsorbed + what is secreted into the nephron.

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33
Q

Describe the epithelium of the proximal convoluted tubule. What is its function?

A

Cuboidal epithelium with dense microvilli brush border on apical membrane, and highly folded basolateral membrane. Contain many mitochondria for active transport. Tight junctions are not very tight.

Bulk reabsorption into peritubular capillaries.

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34
Q

Describe the epithelium of the four limbs of the nephron loop.

A

Thick descending limb- cuboidal (like PCT)
Thin descending limb- simple squamous
Thin ascending limb- simple squamous
Thick ascending limb- cuboidal (like DCT)

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35
Q

Describe the epithelium of the distal convoluted tubule. What is its function?

A

Thin layer of cuboidal epithelium with few microvilli, and fewer mitochondria.

Fine tuning (regulated reabsorption).

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36
Q

Describe the epithelium of the collecting duct. What is its function?

A

Simple cuboidal epithelium:

  • principal cells for reabsorption
  • intercalated cells for acid/ base balance

Fine tuning (regulated reabsorption).

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37
Q

Describe the juxtaglomerular apparatus, and the two types of specialised cells that can be found here.

A

A specialised zone in the nephron where the DCT lies against the afferent arteriole, that controls glomerular filtration rate.

Macula densa in DCT: chemoreceptors that detect sodium levels
Juxtaglomerular cells in afferent arteriole: mechanoreceptors that detect blood pressure

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38
Q

Describe transitional epithelium.

A

Epithelium present in the ureters, bladder, and part of the urethra. Made up of stratified, rounded cells that flatten out when stretched. These protect the tissue underneath from urine waste leaking through.

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39
Q

Where do the ureters run from and to?

A

Arise from the renal pelvis at each hilum, run vertically and retroperitoneally through the abdomen, then enter the bladder at its posterolateral corners at an oblique angle.

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40
Q

How does urine move through the ureters?

A

Peristalsis

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41
Q

Describe the three layers of the ureter wall.

A 
Transitional epithelium (innermost)
Muscularis with inner longitudinal and outer circular
Adventitia (FCT)
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42
Q

What does the transitional epithelium secrete into the surface of the ureter lumen?

A

Protective protein plaques

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43
Q

Why does the muscularis of the ureter have inner longitudinal and outer circular layers?

A

When the circular layer contracts, it pushes on the inner longitudinal fibres which block the passageway, preventing backflow of urine.

44
Q

What is the advantage of positioning the entrance of ureters into the bladder at its posterolateral corners?

A

When the bladder expands, the pressure increases and compressed the ureters- making them act as sphincters/ valves.

45
Q

What is the trigone?

A

Triangular region between two openings of the ureters into the bladder and the opening of the urethra out of the bladder. Flat area where urine can pool and not be expelled- causing UTI.

46
Q

How does bladder shape change as its size increases?

A

Empty: pyramidal, lies within the pelvis.
Full: spherical, expands superiorly into abdominal cavity.

47
Q

How does bladder location differ between males and females?

A

Male: anterior to rectum, superior to prostate gland.
Female: anterior to rectum, uterus, and vagina.

48
Q

Describe the three layers of the urinary bladder wall.

A

Mucosa: transitional epithelium + lamina propria
Submucosa
Detrusor muscle: longitudinal, circular, and oblique layers

49
Q

What function are the detrusor muscles arranged for?

A

Collapse of the bladder (not motility).

50
Q

Describe how the epithelium changes through the urethra.

A

Transitional near bladder
Columnar in the middle- for goblet cells to produce mucous for protection and lubrication
Stratified squamous near external opening- protection against abrasion

51
Q

How do female and male urethras differ?

A

Female: 5cm, separate from reproductive system
Male: 25cm, part of reproductive system, prostatic, membranous, and spongy/ penile sections

52
Q

Describe the urethral sphincters.

A

Internal urethral sphincter: at junction of bladder and urethra, made of detrusor muscle (involuntary)
External urethral sphincter: where urethra passes through urogenital diaphragm (voluntary)

53
Q

Briefly describe how urination occurs.

A

As the bladder expands, stretch receptors send APs to the brain- the more frequent APs, the more urgency. First, the internal sphincter relaxes, then we consciously relax the external sphincter.

54
Q

What does healthy urine contain?

A 
Water (~1.5L)
Creatinine
Urea, uric acid
H+, NH3
Na+, K+
Drugs
Toxins
55
Q

What can pathologic urine contain, and which diseases do these signal?

A 
Glucose- glucosuria, diabetes
Protein- proteinuria
Blood- haematuria
Hb- haemoglobinuria
Leukocytes, bacteria- infection
56
Q

How does healthy urine look, taste and smell?

A

Clear, light or dark amber
Tastes acidic, not sweet
Doesn’t smell like much

57
Q

How can pathologic urine look, taste and smell?

A

Golden, red, brown, or blue
Tastes sweet (excess glucose)
Smells like fruits, or rotten

58
Q

Name 9 functions of the kidney.

A 
Filters blood
Water homeostasis
Salt/ ion homeostasis
Re-absorption of nutrients
Excretion of drugs, endogenous metabolites, and toxins
Hormone production
Metabolism
Gluconeogenesis
pH regulation
59
Q

Which hormone does the kidney release when it detects low oxygen levels? What does it do? Which related disease can chronic renal failure cause?

A

Erythropoietin
Stimulates bone marrow to produce more RBCs
Anaemia

60
Q

Why is salt/ ion homeostasis an an important function of the kidney? Which related disease can kidney failure cause?

A

K+ concentration is vital- determines RMP of all cells, and electrical activity in neurons and cardiomyocytes
Too much K+ can kill you- hyperkalemia

61
Q

What is the difference between the excretion of lipophilic and hydrophilic drugs and toxins?

A 
Lipophilic drugs (e.g. lidocaine) need to be metabolised in the liver before being excreted by the kidneys.
Hydrophilic drugs (e.g. aspirin) are excreted directly by the kidneys.
62
Q

When does the kidney carry out gluconeogenesis?

A

In periods of fast or starvation.

63
Q

Name one molecule the kidney metabolises.

A

Amino acids

64
Q

Define alkalosis and acidosis.

A 
Alkalosis= blood pH > 7.4
Acidosis= blood pH < 7.4
65
Q

What is a non-volatile acid?

A

An acid that isn’t excreted as CO2 via the lungs (has to be excreted by the kidney).

66
Q

Which compound neutralises non-volatile acids in the blood to keep a pH of 7.4?

A

Bicarbonate HCO3-

67
Q

How do the lungs and kidney control bicarbonate concentration (and therefore pH) in the blood?

A

Lungs- exhalation of CO2

Kidney- reabsorption of bicarbonate, or secretion of H+ ions

68
Q

What is p-aminohippurate PAH used for by clinicians?

A

To measure blood flow to the kidney- some is filtered, but most is actively secreted into the urine.

69
Q

Is glucose filtered, reabsorbed, and/or secreted?

A

Filtered (small molecule), and completely reabsorbed for energy.

70
Q

Is K+ filtered, reabsorbed, and/or secreted? Where?

A

Filtered (small ion), reabsorbed in the PCT or secreted in the DCT, depending on diet.

71
Q

Is water filtered, reabsorbed, and/or secreted? Where?

A

Filtered, reabsorbed in most parts of tubule.

72
Q

Are drugs and toxins filtered, reabsorbed, and/or secreted?

A

Not often filtered (too big), actively secreted.

73
Q

What three things determine renal filtration?

A

Renal blood flow
Filtration barrier structure
Driving forces

74
Q

How much cardiac output do the kidneys receive, and why?

A

20-25%, for filtration. (1-1.2L per min)

75
Q

Define the four pressures determining net filtration pressure.

A

->Glomerular hydrostatic pressure GHP (blood pressure)

Capsular colloid osmotic pressure CsCOP

76
Q

Why is capsular colloid osmotic pressure CsCOP always zero?

A

No proteins pass through the filtration barrier into the capsular space, so the only substances determining osmotic pressure are Na+ and Cl-. NaCl concentration is the same inside the glomerulus and the capsular space, so there is no force on water.

77
Q

How do we define renal filtration?

A

Renal clearance- rate at which a substance is cleared by kidneys

78
Q

Name the calculation for renal clearance.

A

Cs = Us x V/Ps
Clearance of solute = urine concentration of solute x volume of urine produced per unit time / plasma concentration of solute

79
Q

Define glomerular filtration rate.

A

GFR is the amount of fluid (plasma) filtered per unit time.

80
Q

Why does GFR decline over time?

A

Nephrons die as we age- less filtration.

81
Q

Name two substances that can be measured, and describe why.

A

Inulin and creatinine. They are filtered out by the glomerulus, but not reabsorbed, secreted, or metabolised.

82
Q

How do we measure GFR?

A

Use renal clearance equation for creatinine.

83
Q

Why are some drugs dangerous if plasma creatinine is high (GFR is below 25)?

A

Abnormal kidney function- drugs won’t get filtered out of the blood.

84
Q

Define the filtration fraction.

A

GFR/RPF = 125/625
Glomerular filtration rate/ renal plasma flow (half of renal blood flow)

Proportion of plasma flowing through glomerulus that gets filtered (20%).

85
Q

Define filtered load.

A

Amount of a particular substance filtered per minute.

= GFR x solute plasma concentration

86
Q

How is body water distributed?

A

2/3 ICF
1/3 ECF
- 4/5 ISF
- 1/5 plasma

87
Q

Define osmolarity.

A

Concentration of osmotically active (pulling water) ions/ solutes of a solution.

88
Q

What is the concentration of NaCl in the ECF?

A

145mM

89
Q

What is the osmolarity of ECF and ICF?

A

290 mosmol/L (275-295)

90
Q

Define hypo- and hyperosmotic.

A 
Hyposmotic= solution has lower osmolarity (more water)
Hyperosmotic= solution has higher osmolarity (more solute)
91
Q

Define tonicity.

A

The effect of a certain solution on a cell.

92
Q

Define hypo- and hypertonic.

A 
Hypotonic= solution causes cell to take up water from ECF
Hypertonic= solution causes cell to lose water to ECF
93
Q

Give concentrations for Na+ and K+ in the ECF and ICF

A

Na+: ECF=145mM, ICF=15mM

K+: ECF=4-5mM, ICF=150mM

94
Q

Describe how much of sodium’s filtered load is reabsorbed throughout the nephron.

A

PCT- 67%
Thick AL- 25%
DCT- 5%
CD- 3%

95
Q

How much of sodium’s filtered load is excreted?

A

0.5-1%

96
Q

Describe how much of water’s filtered load is reabsorbed throughout the nephron.

A

PCT- 67%
Thin DL- 25%
CD- 2-8%

97
Q

How much of water’s filtered load is excreted?

A

0.5-8%

98
Q

Describe the mechanism of glucose reabsorption in the PCT.

A
  • Co-transported with sodium across apical membrane (SGLT sodium-glucose cotransporter)
  • Glucose carrier across basolateral membrane
  • Na+/K+ ATPase keeps intracellular Na+ low
99
Q

How do water reabsorption and glucose reabsorption link in the PCT?

A

Transport of glucose and sodium into the blood create an osmotic gradient, driving the reabsorption of water via aquaporins, and paracellular pathway.

100
Q

Define the High Osmotic Medullary Gradient HOMG.

A

tDL has a very leaky epithelium, facilitating water reabsorption via aquaporins, but is impermeable to solutes, so solute concentration of urine increases.

TAL is impermeable to water, and Na+ and Cl- are pumped out to decrease solute concentration of urine.

101
Q

Define obligatory and facultative water reabsorption.

A

Obligatory- 92% of total, not regulated, transcellular and paracellular (PCT, tDL)
Facultative- 2-8% of total, regulated by ADH, only transcellular- tight epithelia (DCT, CD)

102
Q

Why are RBCs dependent on an isotonic environment?

A

Otherwise they will shrivel up/ expand too far, impairing their function.

103
Q

What detects changes in plasma osmolarity? What is stimulated in response?

A

Osmoreceptors in the hypothalamus (detect increased Na+ levels is ECF)
Pituitary gland to release more/less ADH

104
Q

How does ADH affect the kidney? What is this called?

A

Increase in ADH increases permeability collecting duct to water reabsorption, via intracellular signalling cascades to increase number of aquaporins of apical membrane.

Anti-diuresis

105
Q

What occurs if macula densa cells sense low sodium in the DCT? What could be two causes of this?

A

Juxtaglomerular cells release renin.
Low salt diet
Blood loss

106
Q

Describe the RAAS system.

A

Renin Angiotensin Aldosterone System
Renin triggers the synthesis of angiotensin II.
Angiotensin II causes vasoconstriction, and activates aldosterone.
Aldosterone increases sodium reabsorption, and water reabsorption (hand in hand) in collecting duct.

107
Q

What is ANP, what does it respond to, and what does it stimulate?

A

Atrial natriuretic peptides.
Isotonic drink or high salt diet sensed by baroreceptors in the heart, causing release of ANP.
Effects hypothalamus, kidneys, and blood vessels for decreased reabsorption of sodium and water (nephron).

HUBS192 (6 decks)

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