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BLOCK D - RENAL > Histology of the Kidney and Urinary System > Flashcards

Histology of the Kidney and Urinary System Flashcards

1
Q

Name the 4 components of the urinary system

A

kidneys, ureters, urinary bladder and urethra

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2
Q

The urinary system functions (4)

A
  • the excretion of waste products of metabolism
  • water regulation
  • electrolyte balance regulation
  • secretion or renin and erythropoietin
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3
Q

Kidney shape

A

Bean-shaped with concave border (hilum)

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4
Q

What is the outer layer of the kidney

A

Capsule

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5
Q

What is the layer of the kidney directly below the capsule?

A

Cortex (grainy)

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6
Q

What is the layer of the kidney directly below the cortex?

A

Medulla (striated)

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7
Q

What separates the cortex and medulla

A

Cortico-medullary junction

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8
Q

Medullary pyramids contain… (2)

A

loops of Henle and collecting ducts

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9
Q

What is found in between medullary pyramids (in the medulla)

A

columns of Bertin (interlobar cortical tissue and collecting tubules)

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10
Q

The human kidney is divided in … and …

A

lobes and lobules

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11
Q

What is the area cribrosa?

A

~25 orifices at the apex of medullary pyramids (renal papilla)

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12
Q

What is the name for the apex of the medullary pyramids?

A

renal papilla

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13
Q

What are medullary rays?

A

Collections of tubules extending from the renal medulla to the cortex.

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14
Q

Each renal papilla opens into a…

A

minor calyx

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15
Q

Two to three adjacent minor calyces fuse to form…

A

major calyces

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16
Q

Major calyces open into…

A

the renal pelvis

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17
Q

Each kidney is composed of … nephrons.

A

1-4 million nephrons

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18
Q

What is another name for glomerular capillaries?

A

Glomerular tuft

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19
Q

Another name for glomerulus?

A

renal corpuscle

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20
Q

The PCT is highly
a) acidophilic
b) basophilic

A

a) acidophilic

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21
Q

What are the 3 portions of the loop of Henle?

A

Thick straight descending limb
Thin limb
Thick straight ascending limb

Unlike the proximal and distal tubules, the loop of Henle is NOT a convoluted nor a cortical structure.

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22
Q

Describe the 2 parts of the renal tubule.

A

A) Nephron:
* glomerulus
* proximal convoluted tubule
* loop of Henle
* distal convoluted tubule

B) Collecting tubules/duct

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23
Q

Once the collecting tubules pierce the cortico-medullary junction, they are called…

A

collecting duct

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24
Q

The collecting duct opens into…

A

the area cribrosa

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25
Q

Nephrons originate from….

A

metanephric blastema (metanephric mesenchyme)

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26
Q

The collecting tubules and collecting duct originate from…

A

ureteric bud

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27
Q

The renal corpuscle (glomerulus) is surrounded by…

A

the Bowman’s capsule

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28
Q

The parietal layer of the Bowman’s capsule is formed by…

A

squamous cells, BM and reticular fibres

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29
Q

The visceral layer of the Bowman’s capsule is formed by…

A

podocytes (specialized epithelial cells)

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30
Q

The visceral and parietal layers of the Bowman’s capsule are continuous at…

A

the vascular pole

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31
Q

Characteristic feature of podocytes

A

foot processes

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32
Q

Capsular space is enclosed by…

A

the visceral and parietal layer of the Bowman’s capsule

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33
Q

Vascular pole vs urinary pole

A

Two distinct regions of the glomerulus.
Vascular: This is the point where the afferent arteriole enters the glomerulus and the efferent arteriole exits.
Urinary: This is the opposite end of the glomerulus where the Bowman’s capsule transitions into the proximal convoluted tubule.

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34
Q

What marks the beginnning of the proximal convoluted tubule?

A

urinary pole

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35
Q

Function of juxtaglomerular cells

A

renin secretion

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36
Q

Location of juxtaglomerular cells

A

afferent arteriole

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37
Q

Function of macula densa cells

A

Specialized cells in the DCT.
Detect NaCl levels and signal to the afferent arteriole to either increase or decrease the GFR.

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38
Q

Location of macula densa cells

A

distal convoluted tubule

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39
Q

What is the name of secondary processes of podocytes

A

pedicels (branch off the primary process)

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40
Q

The endothelium in the kidney is…

A

fenestrated

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41
Q

Mesangial cell

A

Specialized cells in the glomerulus. Maintain structure and function of glomerulus.

42
Q

What are the 2 types of mesangial cells?
What are their distinct roles

A

intra-glomerular: support structure of glomerulus
extra-glomerular: at the vascular pole, mediate signal transmission between macula densa cells and juxtaglomerular cells

43
Q

2 functions of mesangial cells (as seen in lecture)

A
  1. Phagocytosis of particles, germs, BM & structural support of capillaries
  2. Production of cytokines (Interleukin 6)
44
Q

Pedicels form… around glomerular capillaries

A

Filtration slits (25nm).
Note the presence of diaphragms

45
Q

What cannot pass across the filtration slits formed by pedicels?

A

negatively charged proteins
proteins greater than albumin

46
Q

Location of medullary rays

A

Cortex

47
Q

Proximal tubules have … cells
a) cuboidal
b) columnar
c) squamous

A

b) columnar

cuboidal to columnar epthelium

48
Q

Characteristic feature of proximal tubule cells

A

Brush border (microvilli)

49
Q

What is found in the infoldings of the cells in the proximal tubule?

A

Mitochondria

50
Q

The cells of the thin limb of the loop of Henle are…
a) cuboidal
b) columnar
c) squamous

A

c) squamous

51
Q

Which portion of the loop of Henle is permeable to water (free diffusion of water)? Which is not permeable to water?

A

Descending limb: permeable to water
Ascending limb: impermeable to water

52
Q

Which cells are more acidophilic (proximal or distal)? How does this translate under the microscope?

A

Proximal tubule cells are more acidophilic, so they appear more eosinophilic (pink)

53
Q

What is the difference between the nuclei in proximal and distal tubular cells?

A

Proximal: in the middle of the cell
Distal: “kissing” the lumen of the tubule

54
Q

Aldosterone is secreted by…

A

adrenal glands

55
Q

What is the site of action of aldosterone? What are its effects?

A

Acts on the DCT and stimulates the reabsorption of NaCl.

56
Q

Describe the epithelium of the thick descending limb?

A

similar to proximal convoluted tubule

57
Q

Describe the epithelium of the thick ascending limb?

A

similar to distal convoluted tubule

58
Q

The thick descending limb of the loop of Henle is located in…

A

medullary rays (cortex) and upper medulla

59
Q

The thin limb of the loop of Henle is located in…

A

medulla

60
Q

The thick ascending limb of the loop of Henle is located in…

A

medulla and medullary rays (cortex)

61
Q

Diameter of collecting tubules

A

40-50 um

62
Q

Where can we find collecting tubules?

A

in cortex and medullary rays

63
Q

How can we distinguish the collecting tubules from the collecting duct? (3)

A

Collecting duct is 200nm in diameter (much larger than 40-50um CTs).
Found in medulla
Nuclei are less centered

64
Q

What is the site of action for ADH? What are its effects?

A

Collecting duct.
ADH makes the CD permeable to water (promotes water reabsorption).

65
Q

What is the juxtaglomerular apparatus?

A

It comprises 3 groups of cells:
* macula densa of the DCT
* juxtaglomerular cells of the afferent arteriole
* extraglomerular mesangial cells

66
Q

Define juxtaglomerular cells. They are rich in…

A

Modified smooth muscle cells of afferent arterioles. They are rich in granules containing renin.

67
Q

What is important about the junction between juxtaglomerular cells and macula densa cells?

A

The basal lamina (BM) is absent.

68
Q

When is renin released by juxtaglomerular cells? (3)

A
  • low blood pressure
  • low Na in DCT
  • sympathetic nervous system activation
69
Q

What are the effects of renin secretion?

A

Renin converts angiotensinogen to angiotensin I.
Angiotensin I is converted to angiotensin II by angiotensin-converting enzyme (ACE).

70
Q

What are the effects of angiotensin II? (3)

A
  • Vasoconstriction to increase BP
  • Aldosterone secretion to promote sodium and water reabsorption
  • Antiduretic hormone (ADH) secretion to promote water reabsorption
71
Q

Explain the function of the macula densa.

A

The macula densa is made of specialized epithelial cells in the DCT that detect the sodium concentration of the filtrate.
If sodium levels are high, the MD signals to reduce the GFR via vasoconstriction of the afferent arteriole.
If sodium levels are low, the MD signals to increase the GFR via vasodilation of the afferent arteriole.

72
Q

How does the macula densa trigger vasoconstriction and vasodilation?

A

Vasoconstriction: MD signals to the juxtaglomerular cells to release vasoconstrictors like adenosine
Vasodilation: MD signals to the juxtaglomerular cells to release vasodilators like nitric oxide (NO).

73
Q

Under the microscope, most of what we see in the medulla are…

A

collecting ducts

74
Q

In the medulla, smaller openings in between the collecting ducts are…

A

thin limb of the loop of Henle

75
Q

At the level of the medullary pyramids, the renal arteries branch into…

A

interlobar arteries

76
Q

The interlobar artery forms an elbow called…

A

arcuate artery

77
Q

The arcuate artery is located at the level of the…

A

cortico-medullary junction

78
Q

The arcuate artery branches into…

A

lobular arteries

79
Q

Lobular arteries are located in…

A

the cortex

80
Q

How do the lobular arteries branch?

A

Lobular arteries travel all the way to the capsule and form a capillary network underneath the capsule.

81
Q

What gives rise to the afferent arteriole?

A

Lobular artery

82
Q

The afferent arteriole branches into a capillary network in the glomerulus before converging into the efferent arteriole.
The efferent arteriole branches into…

A

peritubular capillaries, which surround the PCT and DCT.

83
Q

Blood from the peritubular capillaries is collected by…

A

post-capillary venules, that drain into the lobular vein

84
Q

Blood from the capillary network beneath the capsule will be collected by…

A

stellate veins, that drain into the lobular vein

85
Q

Which capillaries are involved in the secretion of erythropoietin?

A

Peritubular capillaries

86
Q

What is erythropoietin?

A

Glycoprotein that promotes proliferation and differentiation of erythrocyte precursors.

87
Q

What is the major site of erythropoietin production?

A

Kidney
(liver is the major extra-renal site of production)

88
Q

Define juxtamedullary renal corpuscles.

A

Renal corpuscles located near the junction of the cortex and medulla.

89
Q

What are the vasa recta?

A

Capillaries that emerge from efferent arterioles of juxtamedullary renal corpuscles and drain into the arcuate veins.

90
Q

What is the location of the vasa recta?

A

Medulla

91
Q

The vasa recta are a type of…

A

peritubular capillary

92
Q

What is the role of the vasa recta?

A

Return the water reabsorbed in the medulla to the circulation

93
Q

How are the vasa recta oriented in terms of the loop of Henle?

A

they are parallel to the loop of Henle

94
Q

There is a high concentration of…? in the medulla.

A

Na+ (sodium)

95
Q

Normally, the collecting ducts are…
a) impermeable to water
b) permeable to water

A

a) impermeable to water

96
Q

How does vasopressin (ADH) affect the permeability of the collecting ducts?

A

it makes the CD permeable to water

97
Q

Name 2 conditions in which the glomerular filtration is altered?

A
  • diabetes mellitus
  • glomerulonephritis
98
Q

How does diabetes mellitus and glomerulonephritis impact glomerular filtration?

A

Becomes much more permeable to proteins with subsequent release of protein into the urine (proteinuria)

99
Q

How can a significant hemorrhage impact kidney function, and how will the kidney respond.

A

Decreased blood pressure will result in increased renin secretion.
This will cause the production of angiotensin II.
Angiotensin II will increase blood pressure by constricting arterioles and stimulating the secretion of aldosterone.
Aldosterone increases the absorption of Na by the DCT.

100
Q

What is Addison’s disease (chronic adrenal insufficiency)? What does it result in?

A

Chronic endocrine disorder.
Adrenal glands do not produce sufficient steroid hormones, including aldosterone.
Results in excess loss of Na in the urine.

101
Q

What is the consequence of excessive Na loss in the urine?

A

Very low blood pressure and coma.

BLOCK D - RENAL (18 decks)

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