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CPR Week 7 > 3.7.3. Histology of the Urinary System > Flashcards

3.7.3. Histology of the Urinary System Flashcards

1
Q

Describe the general structures found in the kidney.

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2
Q

How does blood flow work in the kidneys?

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3
Q

Diagram the cortical glomerulus system (blood vessels).

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4
Q

Diagram the juxtamedullary glomerulus system (blood vessels).

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5
Q

What is the renal corpuscle?

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6
Q

What is this structure?

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The renal corpuscle (possible urinary pole at bottome left of image, vascular pole at top right)

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7
Q

Where is the urinary space in the renal corpuscle?

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8
Q

Name two cell layer types we see in the urinary space of the renal corpuscle

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9
Q

Be able to ID the urinary space, podocytes, and parietal layer of bowman’s capsule on histology

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10
Q

Describe the physical filtration system of the glomeruli (podocytes, pedicels, etc.)

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11
Q

What are the three lamina found in the glomerulus?

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12
Q

Glomerular basement membrane is composed of:

A
  1. Composed of:
    1. fenestrated capillary endothelium (size barrier)
    2. fused basement membrane with heparan sulfate (negatively charged barrier)
    3. epithelial layer consisting of podocyte foot processes
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13
Q

What happens to the heparan sulfate barrier in nephrotic syndrome?

A

The charge barrier of heparan sulfate is LOST in nephrotic syndrome, which results in albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia

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14
Q

How are the lamina of the glomerulus structured between the endothelial cells and the podocytes? What does each lamina contain?

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15
Q

What are mesangial cells?

A

Mesangial cells - Little vacuum cleaner cells on the basement membrane

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16
Q

What are the two types of mesangial cells?

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  1. Types
    1. Intraglomerular = phagocytes - Enclosed in the BM and keep it free of debris. They also provide structural support in BM gaps and secrete IL1, PDGF which are important in injury response
    2. Extraglomerular are part of the juxtaglomerular apparatus
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17
Q

Where are the mesangial cells of the glomeruli? (inside/outside of basement membrane? associate with capillaries or podocytes?)

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18
Q

How the mesangial cells appear on histology?

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19
Q

How might the medulla appear on histology? What can we expect to see?

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20
Q

What are the four major functions of a nephron (with regards to solute movement)?

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21
Q

What is autoregulation?

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22
Q

If pressure changes, then ____ must change accordingly to maintain flow.

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23
Q

Purpose of autoregulation of renal blood flow?

A

Assure the appropriate delivery of blood to the renal tubules

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24
Q

How can resistances change to maintain renal bloodflow in the efferent and afferent arterioles?

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25
Q

What is GFR?

A

GFR = quantification of the process of filtration of blood water and solutes into Bowman’s space.

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26
Q

What is normal GFR?

A

Normal GFR is 125mL/min or 180L/day, and this represents a fractional filtration rate (FF) of 0.2 of the renal plasma flow.

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27
Q

How can we relate fractional filtration, GFR, and renal plasma flow?

A

FF = GFR / RPF

GFR and FF are dependent on the flow rate in the capillary (RPF)

GFR is responsible for plasma filtration according to SIZE and NET CHARGE of things to be filtered.

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28
Q

How does GFR relate to RPF (renal plasma flow)

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29
Q

How does fractional filtration relate to RPF?

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30
Q

What are some factors that can affect GFR with respect to the things being filtered?

A
  1. Physical barrier that defines what substances can cross the filtration barrier
    1. Molecular size < 5500Da
    2. Electrical charge - negatively charged molecules are restricted
    3. Shape - Deformable molecules cross easier than rigid
31
Q

What do we need to estimate GFR? What molecule do we use for this purpose?

A

An endogenous substance that is only filtered and excreted in the urine and has a stable plasma concentration would be preferable, but none exist. Creatinine comes close.

32
Q

What is Creatinine?

A
  1. Metabolite of phosphocreatine/creatine
  2. Concentrations are related to a person’s muscle mass
  3. 1-2%/day creatine is converted to creatinine and excreted
    1. Therefore, plasma levels of creatinine reflect the efficiency of glomerular filtration
    2. 0.5 - 1.0 for women, 0.7 - 1.2 for men
      1. Women have lower mass typically = lower creatinine synthesis
  4. In healthy or only early renal disease when GFR is only moderately affected, plasma creatinine levels may not correlate well with true GFR
33
Q

How do we calculate resorption and secretion rates?

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34
Q

How do changes in glomerular dynamics alter RPF, GFR, and FF?

(think afferent arteriole constriction, changes in plasma protein conc., constriction of ureter, etc.)

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35
Q

What are some pharmacological alterations of afferent and efferent arteriolar tone?

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36
Q

What are the two components of Renal autoregulation?

A

Myogenic - based on intrinsic vascular smooth muscle receptors

Tubuloglomerular feedback: Based on ion sensing. Changes in ion content of the forming urine is related to blood flow/pressure in the afferent arteriole

37
Q

What is the difference in effect on GFR if the afferent arteriole constricts versus the efferent arteriole?

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38
Q

What is the effect of tubuloglomerular feedback (at the level of the nephron still, specifically the glomerulus)?

A
  1. Leads to paracrine secretions from the tubular cells - ATP, adenosine, thromboxane - that stimulate contraction of SM to maintain GFR and renal solute/solvent delivery
  2. Renin also secreted to do this, and those cells are located here
39
Q

What are the macula densa cells, what do they do?

A
  1. Macula densa cells, found in the distal convoluted tubule, are the critical link between renal salt and water excretion and glomerular hemodynamics. Macula densa cells are unique renal biosensor cells that detect changes in luminal NaCl concentration and transmit signals to the mesangial cell/afferent arteriolar complex.
    1. Patch clamp studies of macula densa cells identified an NaCl luminal concentration-sensitive ATP-permeable channel
    2. ATP is released at the basolateral membrane of macula densa cells in a manner dependent on NaCl luminal concentration
40
Q

What is the calcium paradox?

A

“Calcium paradox” - Increasing calcium inhibits renin release and cAMP is the positive signal. It’s a paradox because Ca is always a stimulator

41
Q

How do the mesangial cells communicate with the mesangial cells and others?

A
42
Q

What response will be generated by the nephron to a decrease in arterial pressure?

A
  1. Decreased arterial pressure is going to cause a decreased glomerular hydrostatic pressure, leading to a decreased GFR. This leads to a decrease in macula densa NaCl activity.
    1. Macula densa activity also decreased by any kind of increase in proximal NaCl reabsorption, which can also be stimulated by a decrease in GFR
  2. Decrease in this activity leads to two things: Decrease in afferent arteriolar resistance directly and an increase in Renin. Renin increase leads to Angiotensin II increase which increases efferent arteriolar resistance
  3. These events will lead to a slow increasing of glomerular hydrostatic pressure so that it goes back to normal
43
Q

What is Effective Renal Plasma Flow?

A

An estimate of blood flow to the kidney (also called “Effective Renal Plasma Flow” - ERPF)

44
Q

What is PAH and what do we use it for?

A

Clearance of PAH (Para-aminohippuric acid) is used to measure renal plasma flow. Because PAH is both filtered and vigorously secreted into the proximal tubule, it is nearly completely cleared from the plasma flowing through the kidneys

45
Q

What are some important calculations to know regarding effective renal plasma flow and renal blood flow?

A
  1. FA summary of equations (pg 525):
    1. ERPF = UPAH * (V / PPAH)= CPAH
    2. RBF = RPF / (1 - hematocrit)

NOTE: ERPF underestimates the true renal plasma flow (RPF) by about 10%

46
Q

How much fluid is filtered by the kidneys each day? How much do we reabsorb and excrete?

A

The glomerular capillaries filter approximately 180L of fluid per day into the renal tubules

Peritubular capillaries re-absorb approximately 178.5 liters of this fluid per day

About 1.5 liters of urine are produced daily

Urine is modified in the tubules

47
Q

Describe the proximal convoluted tubules.

A
48
Q

What occurs at the PCT (proximal convoluted tubule)?

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49
Q

What does the PCT look like histologically?

A
50
Q

What does the PCT look in EM?

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51
Q

What is one limitation of the PCT? (with regards to filtration)

A

Tubules have limits to the amount of each substance they can absorb or secrete due to the capacity of the transporter for each substance. This concentration is known as the transporter maximum

52
Q

What comes after the PCT?

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53
Q

What does the Loop of Henle look like in EM?

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54
Q

What occurs throughout the loop of henle?

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55
Q

What are the two types of nephrons in the kidney?

A
56
Q

What comes after the Loop of Henle?

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57
Q

What occurs at the distal tubules?

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58
Q

What does the DCT (distal convoluted tubule) look like on histology?

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59
Q

What special cell type is contained within one part of the DCT?

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60
Q

What doe the macula densa cells do?

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61
Q

At what structures do other nephrons start to merge together?

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62
Q

What does the flow rate look like through each piece of the nephron?

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63
Q

What percent of the glomerular filtrate makes it to the distal parts of the nephron (and ureter)?

A
  1. Glomerular filtrate reabsorbed in Proximal tubules, loop of henle, and distal tubules (65%, 15% and then 10% respectively), leaving 9.4% in the collecting tubules and usually about 0.7% by the time you get to the ureter.
64
Q

What are the sodium channels in the tubule collecting system?

A
  1. Proximal tubule
    1. NHE-3 = sodium hydrogen exchanger
    2. NaPi-2 = Sodium, phosphate
  2. Thick ascending limb
    1. NHE-3
    2. NKCC-2 = Sodium, potassium, chloride
  3. Distal convoluted Tubule
    1. NCC = Sodium, chloride (thiazide sensitive)
  4. Collecting Duct
    1. ENaC = Epithelial sodium chloride
65
Q

What does the ureter look like on histology?

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66
Q

What epithelia do we see at the ureter?

A

Stratified and transitional epithelium (now called uroepithelium, which becomes more specific as we get to the bladder)

67
Q

How does the bladder look on histology? What muscle is present, what epithelium?

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68
Q

What does transitional epithelium look like in a relaxed bladder?

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69
Q

What do we call the “bumps” on top of the transitional epithelium?

A

Dome cells

70
Q

What does the urethra look like on histology? What are its characteristics (muscle, epithelium, etc.)?

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71
Q

How do we micturate? What effects do parasympathetic and sympathetic stimulation have?

A
  1. Micturition
    1. Stretch causes reflex contraction, which is overridden by conscious contraction of external sphincter
    2. Parasympathetic stimulates wall contraction, but relaxes sphincter
    3. Sympathetics constrict internal sphincter when nervous

CPR Week 7 (12 decks)

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