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SMP - Renal > Lectures 2 & 3 - Histology of the Renal System > Flashcards

Lectures 2 & 3 - Histology of the Renal System Flashcards

1
Q

Lining epithelium of ureters and bladder? What is it surrounded by? Purpose?

A

Transitional epithelium to accommodate different degrees of distention supported by a lamina propria of connective tissue, and which becomes gradually thicker as one goes down these passages toward the bladder

Surface cells are dome-shaped and binucleated.

Outside the lining mucosa are layers of smooth muscle that are surrounded by an adventitial membrane (except for the upper part of the bladder which is covered by the peritoneal serosa)

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2
Q

What makes up a kidney lobe?

A
  1. Medullary pyramid

2. Overlying cortical substance

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3
Q

How much does each kidney weight?

A

150 g

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4
Q

What enters/exits at the kidney hila?

A
  1. Renal artery
  2. Renal vein
  3. Renal pelvis
  4. Lymphatics
  5. Nerves
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5
Q

What are medullary rays? Are these considered part of the kidney cortex?

A

Small bands of medullary tissue that project into the cortical substance made of descending and ascending thick portions of loops of Henle and associated collecting ducts of superficial nephrons

YUP

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6
Q

How many kidneys lobes in each kidney?

A

8-18

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7
Q

Are kidney lobes visible on the outside surface of the kidney?

A

Yes in the fetus and pig but no in adults

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8
Q

Location of the minor calyces?

A

Wrap snugly around the cone-shaped papillae

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9
Q

Where in the kidney does urine exit to enter the renal pelvis?

A

Medullary papillae to enter minor calyces

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10
Q

Does a kidney lobe include the renal pyramids around it?

A

NOPE

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11
Q

What is the renal corpuscle?

A

Glomerulus + Bowman’s capsule

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12
Q

Do all structures of the nephron have the same embryological origin? Implication?

A

NOPE

Collecting ducts have a different embryological origin than the renal corpuscle and uriniferous tubules => often not considered to be part of the nephron

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13
Q

Purpose of blood exiting the glomerulus via arterioles and not venules?

A

It permits smooth muscle in the walls of the afferent and efferent arterioles to exert control over hydrostatic pressure within the glomerular capillary loops

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14
Q

Why are glomerular capillaries unique?

A

Lined by a glomerular endothelium perforated by numerous open fenestrations that do not have diaphragms

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15
Q

What are the endothelial loops of the glomerulus surrounded by?

A
  1. Thick basal lamina = glomerular basement membrane

2. Visceral layer of Bowman’s capsule = epithelium made of podocytes

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16
Q

What does each podocyte of the visceral layer of Bowman’s capsule consist of?

A
  1. Central nucleated region from which large branching major processes arise and wrap around underlying glomerular capillary loops
  2. Foot processes arising at nearly right angles from the major processes which interdigitate with foot processes from other podocytes
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17
Q

Difference between the major processes and the foot processes of the podocytes?

A

Foot processes are smaller and more uniformly shaped

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18
Q

What are foot processes from different podocytes separated by? Purpose?

A

By a space termed the filtration slit => morphological barrier to solute passing across the glomerular wall

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19
Q

Can the size of the filtration slits between foot processes change? Explain.

A

YUP!

Contractile proteins (i.e. actin throughout and myosin on lateral sides) within foot processes can cause these processes to change in shape and thereby regulate the size of intervening filtration slits and solute flow across the glomerular wall

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20
Q

What is the vascular pole of the renal corpuscle?

A

Region where the afferent and efferent arterioles enter and leave the glomerulus

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21
Q

What is the parietal epithelial layer of Bowman’s capsule?

A

Visceral epithelium podocytes reflecting back from the glomerular vessels and transforming into a layer of simple squamous cells at the vascular pole

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22
Q

What is the outermost layer of the renal corpuscle?

A

The parietal epithelial layer of Bowman’s capsule

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23
Q

What is the capsular space of Bowman?

A

Space between the parietal epithelial layer of Bowman’s capsule and the podocyte covered capillary tuft

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24
Q

What is the urinary pole of the renal corpuscle?

A

Opposite pole to the vascular pole, where the parietal epithelium forms an opening leading into the uriniferous tubules

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25
Q

What are the 3 cells types of the glomerulus?

A
  1. Podocytes
  2. Endothelial cells
  3. Mesangial cells => mesangium
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26
Q

Where are the mesangial cells of the glomerulus more prominent?

A

Vascular pole where they form tree-like ramifications that radiate out between the glomerular endothelium loops

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27
Q

Role of the mesangial cells of the glomerulus?

A
  1. Send cell processes (pseudopodia) between endothelial cells and can phagocytose material that may accumulate in the glomerular basement membrane during the filtration process
  2. Produce a significant amount of extracellular amorphous basement membrane-like material = mesangial matrix
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28
Q

What % of the blood that enters the kidney ends up as glomerular filtrate entering the proximal tubule?

A

20%

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29
Q

Volume of glomerular filtrate produced by both kidneys per min?

A

125 mL

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30
Q

What is the composition of the glomerular filtrate similar to?

A

Interstitial fluid, BUT contains very little plasma protein

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31
Q

Other name for capsular space of Bowman?

A

Urinary space

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32
Q

Consistency of the parietal epithelial layer of Bowman’s capsule?

A

Very rigid and tough

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33
Q

What is renal compensatory hypertrophy?

A

Hypertrophy of the kidney if you remove the other

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34
Q

Other name for the foot processes of the podocytes?

A

Pedicles

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35
Q

Do the mesangial cells extend outside of the renal corpuscle?

A

YUP = extraglomerular mesangial cells

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36
Q

Describe the glomerular wall that the glomerular filtrate needs to pass.

A
  1. Glomerular endothelial fenestrations without diaphragms
  2. Thick glomerular basement membrane
  3. Filtration slits between adjacent podocyte foot processes, which is spanned by a slit diaphragm
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37
Q

Diameter of the glomerular endothelial fenestrations? Do these restrict plasma proteins?

A

20-100 nm

NOPE

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38
Q

List the layers of the thick glomerular basement membrane from inner to outer.

A
  1. Lamina rara interna
  2. Lamina densa
  3. Lamina rara externa
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39
Q

How does the thick glomerular basement membrane act as a barrier for plasma proteins (e.g. albumin)?

A
  1. Mechanical barrier
  2. Electrostatic barrier: contains anionic sites (heparin sulfate) on the lamina rara interna and externa that repel negatively charged molecules
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40
Q

Describe the slit diaphragms of the glumerular filtration slits. Purpose?

A

Substructure consisting of rectangular-shaped pores that appear to be just small enough to prevent serum albumin from passing into the capsular space of Bowman

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41
Q

What is the role of the glycocalix on the glomerular podocytes and their filtration slits?

A

It is sialic acid rich and is negatively charged so causes repulsion of adjacent foot processes, thereby maintaining open filtration slits

42
Q

3 factors that determine whether or not a particular molecule would make it across the glomerular wall?

A
  1. Size: small/large
  2. Shape: slender/globular
  3. Charge: positive/negative
43
Q

What can increase the permeability of the glomerular wall to large molecules?

A

Disruption of blood flow through the glomerular capillaries

44
Q

What is a diagnostic feature of nephrotic syndrome?

A

Too much albumin is passing the glomerular wall so the foot processes come together to form a continuous layer but some of it escape through blow out sites => albuminurea

45
Q

Where is most of the glomerular filtrate reabsorbed into the peritubular capillary plexus?

A

Proximal convoluted tubule (65%)

46
Q

Other name for proximal convoluted tubule?

A

Pars convulata

47
Q

How do we call the portion of the proximal tubule that descends from the cortex into the outer stripe of the outer medulla? 5 names

A

Descending proximal tubule = pars recta = descending thick segment of the loop of Henle = straight segment of the proximal tubule = S3

48
Q

What portion of the uriniferous tubules are very sensitive to ischemia? Explain.

A

Proximal tubule => swell within seconds following an interruption of blood flow to the kidneys because they cannot pump out the solutes entering the cells so they become hypertonic so water follows => narrowing of tubule lumen + focal rupturing of the apical cell plasmalemma + extrusions of cytoplasmic debris into the tubule lumens

49
Q

How to prevent ischemia damage into the proximal tubule?

A

Vascular perfusion or dripping fixative on the living kidney

50
Q

Describe the cells making up the wall of the proximal convoluted tubule.

A

Highly metabolic cuboidal cells with:

  1. Elaborate basolateral folds
  2. Many mitochondria
  3. Extensive lysosomal system
  4. Microvillous brush border coated with rich glycocalyx
51
Q

What are the 3 segments of the proximal tubule? What are these separated based on? Describe each.

A

Based on differences in fine structure, histochemistry and function:

CONVOLUTED:

  1. First segment (S1): lined by taller cells, having more elaborate intercellular interdigitations, longer and more numerous mitochondria, less prominent lysosomes, and a taller microvillous brush border
  2. Second segment (S2): lined by shorter cells, having less elaborate intercellular interdigitations, shorter and less numerous mitochondria, more prominent lysosomes, and a shorter microvillous brush border

STRAIGHT:
3. Third segment (S3): relatively straight intercellular borders, smaller and fewer mitochondria, but still possess a prominent microvillous brush border

52
Q

What parts of the nephron are included in the inner zone of the medulla?

A
  1. Thin descending limb of loop of Henle of DEEP NEPHRONS
  2. Thin ascending limb of loop of Henle of DEEP NEPHRONS
  3. Collecting duct
53
Q

Which part of the proximal convoluted tubule is longer: S1 or S2?

A

S2

54
Q

4 morphological segments of the loop of Henle?

A
  1. Descending thick segment = S3
  2. Descending thin segment
  3. Ascending thin segment
  4. Ascending thick segment
55
Q

Cells of the thin ascending and descending segments of the loop of Henle?

A

Simple squamous cells

56
Q

2 other names for the ascending thick segment of the loop of Henle?

A

Ascending or straight distal tubule

57
Q

Cells of the thick ascending segment of the loop of Henle?

A

Cuboidal cells with elaborate basolateral folds and numerous mitochondria => as the ascending thick segment approaches the cortex, however, the lining cells transform into a lower simple cuboidal epithelium

58
Q

What marks the juncture between the inner medulla and the outer medulla?

A

The transition from the ascending thin segment to the ascending thick segment of deep nephrons

59
Q

How does the number of loops of Henle vary as one descends deeper into the inner medulla?

A

Fewer loops of Henle

60
Q

How does the number of collecting ducts vary as one descends deeper into the inner medulla? What does this mean?

A

Fewer because they merge with each other to form larger collecting ducts => larger lumens

61
Q

What does it mean for the deep inner medulla to have a reduction in kidney parenchyma? What is coincident with this? Explain the result.

A

Fewer loops of Henle and fewer collecting ducts + increase in interstitial tissue = reduction in tissue and characteristic tapered appearance of the kidney papillae

62
Q

When does the straight distal tubule become convoluted?

A

After the macula densa

63
Q

What % of the glomerular filtrate is reabsorbed in the descending limb of the loop of Henle? How come?

A

15%, mainly water because it passes through a very hypertonic portion of the kidney (NaCl rich)

64
Q

Is the ascending limb of the loop of Henle permeable to water?

A

NOPE

65
Q

What pump in the ascending loop of Henle helps make the inner medulla salty?

A

Cl- pump in the ascending loop of Henle

66
Q

What % of the glomerular filtrate is reabsorbed in the distal convoluted tubule? What ions are reabsorbed here?

A

10%

NaCl, with H2O following

67
Q

When is the collecting duct permeable to water? What % of the glomerular filtrate is reabsorbed then?

A

When stimulated by ADH, to reabsorb 9% of the glomerular filtrate

68
Q

What % of the glomerular filtrate is reabsorbed in the nephron?

A

99%

69
Q

Where do the thin segments of the descending loops of Henle of superficial and deep nephrons begin?

A

At the juncture of the inner and outer stripe of the outer zone of the medulla

70
Q

Are any thin segments of the loops of Henle present in the medullary rays?

A

NOPE

71
Q

Are any thick segments of the loops of Henle present in the inner zone of the medulla?

A

NOPE

72
Q

What parts of the nephron are included in the outer zone of the medulla?

A
  1. Thick descending limbs of loops of Henle of DEEP AND SUPERFICIAL NEPHRONS
  2. Thick ascending limbs of loops of Henle of DEEP AND SUPERFICIAL NEPHRONS
  3. Thin descending limb of loop of Henle of DEEP NEPHRONS
  4. Collecting duct
73
Q

Differences between cells in the proximal and distal convoluted tubules? Describe each.

A
  1. Cells in the proximal convoluted tubule are longer => cells in the distal convoluted tubule are not seen as frequently in histological cross-sections of the cortex
  2. Cells in the distal convoluted tubule do not have a microvillous brush border with a glycocalyx
  3. Cells in the distal convoluted tubule are not as broad => more nuclei seen in a cross section
  4. Cells in the distal convoluted tubule are not as sensitive to ischemic insults => do not exhibit the narrow lumens and luminal cytoplasmic debris which are characteristic of proximal convoluted tubules
74
Q

What is the connecting segment?

A

Short segment of tubule between the distal convoluted tubule and the collecting duct which appears to represent a gradual transition from cells that characterize the distal tubule to cells that characterize the collecting duct

75
Q

Does a cortical collecting duct only receive glomerular filtrate from one distal convoluted tubule?

A

NOPE - each receives many branches from the distal tubules as they pass through the medullary rays

76
Q

What 2 cell types characterize the cortical collecting ducts? Describe each.

A
  1. Principal cell type: relatively straight intercellular borders, scarcity of cytoplasmic organelles, very few apical surface microprojections, and 1 or 2 cilia projecting into the tubule lumen
  2. Second cell type: contains many more cytoplasmic organelles, a more electron-dense cytoplasm, and a free surface characterized by numerous free surface microprojections (either microvilli or microplicae), and the lack of rudimentary cilia
77
Q

Other names for the second cell type of the cortical collecting ducts? Why?

A
  1. Intercalated cell, because principal cell types usually surround the second cell type
  2. Dark cell, because it stains significantly darker than principal cells at both the light and electron microscopic level
78
Q

How does the collecting duct change as it descends deeper in the medulla? Implication?

A

Lined by taller and taller columnar cells with larger lumens => called papillary ducts of Bellini

79
Q

Are dark intercalated cells usually found in papillary collecting ducts?

A

NOPE

80
Q

What are the area cribosa?

A

18-24 small crevice-like openings of the papillary collecting ducts at the papilla tip of the medullary pyramid from which newly formed urine flows

81
Q

Do the descending segments of the loop of Henle have a microvillous brush border?

A

YUP - only thick portion!

82
Q

Do the ascending segments of the loop of Henle have a microvillous brush border?

A

NOPE

83
Q

How to distinguish the S3 of the proximal tubule?

A

Less mitochondria, but thick microvillous brush border

84
Q

Is a brush border found anywhere else than in the proximal tubule?

A

NOPE

85
Q

Other name for extraglomerular mesangial cells? Why?

A

Lacis cell has because they are surrounded by a considerable amount of extracellular matrix giving the appearance of a “lacis” or network

86
Q

Describe the macula densa cells.

A

Thinner, sometimes taller, and have dark staining nuclei

87
Q

Is there a lot of interstitial connective tissue in the renal cortex?

A

NOPE, very little and most of it is associated with the renal vessels

88
Q

Other than the glomerulus, what other parts of the nephron are surrounded by a thick basal lamina? What to note?

A
  1. The parietal epithelium of the renal corpuscle

2. All the uriniferous tubules, and it often fuses with the basal lamina of the peritubular capillaries

89
Q

Does the medulla contain more interstitium than the cortex? Which part contains the most?

A

YUP

Inner medulla contains a considerable amount of interstitium that becomes more abundant toward the tips of the medullary papillae

90
Q

What is found in the interstitium of the inner medulla?

A

Lipidladen interstitial cells that are transversely interposed between the longitudinally running tubules and vessels

91
Q

Do the kidneys receive more blood than any other organ in the body in proportion to their weight?

A

YUP

92
Q

Describe the lymph flow in the kidneys.

A

The cortical substance is supplied with subcapsular and deeper cortical lymphatic drainage primarily distributed along the interlobular and arcuate arteries

93
Q

Describe the innervation of the kidney. Role?

A

Abundantly supplied with nerves derived mainly from the celiac plexus and from the thoracic and lumbar splanchic nerves

Nerves establish neuroeffector junctions with renal vessels (to regulate the degree of constriction of afferent and efferent glomerular arterioles) and the proximal and distal tubules (role unclear)

94
Q

What substance can be used to protect proximal tubules from ischemia? How does it work? What else does this do?

A

Mannitol - acts as an impermeable osmotic agent to counteract the swelling

Also increases GFR

95
Q

What is particular about the rat kidney?

A

Unilobular

96
Q

What substance will impact the S2 segment of the proximal tubule specifically?

A

Mercury and other heavy metals

97
Q

Where are intercalated cells more prominent? Why?

A

Cortical collecting ducts (not as much in medulla) - something to do with acid base regulation

98
Q

Do the superficial nephron lacks vasa recta?

A

YUP

99
Q

Effect of contraction of mesangial cells?

A

Decreased surface area for filtration => decreased Kf

100
Q

What is nephrotic syndrome?

A

Kidney disorder that causes your body to excrete too much protein in your urine

101
Q

Are any renal corpuscles found in the medulla?

A

NOPE

SMP - Renal (20 decks)

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