Renal Histology Flashcards

1
Q

Functions of the urinary system

-Elimination?

A

Eliminates urine and toxic metabolites from the blood

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2
Q

Functions of the urinary system

-Conservation?

A

Conserves salts, glucose, proteins, and water

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3
Q

Functions of the urinary system

-Regulation?

A

Regulates blood pressure, hemodynamics, and acid-base balance

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4
Q

Functions of the urinary system

-Endocrine?

A

Produces vitamin D, renin, erythropoietin, and prostaglandins (hormonal control of other tissues/organs)

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5
Q

Kidney blood supply

A
  • As a blood filtering organ, the kidney’s blood supply is critical to its function
  • Supplied by renal arteries which branch directly from the aorta
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6
Q

Blood supply of the kidney

-Renal artery splits off into?

A

-Renal a–>segmental (lobar) a–>interlobar a–>arcuate a–>interlobular a (cortical radial a)–>afferent arteriole–>glomerulus capillary–>efferent a–>peritubular capillary/vasa recta–>interlobular v–>arcuate vein–>interlobar vein–>renal vein

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7
Q

What is significant about segmental arteries?

A

Segmental arteries are end arteries

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8
Q

The nephron

A

Functional unit of the kidney

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9
Q

The nephron-functional unit of the kidney

  • Parts are modified for specific physiological functions
    - Renal corpuscle function?
    - Tubular portion function?
A
  • Renal corpuscle filters fluid from blood

- Tubular portion modifies filtrate into urine

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10
Q

Afferent arteriole leads into?

A

Glomerulus-a capillary bed which leads to the efferent arteriole

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11
Q

Types of nephrons?

-The type depends on?

A
  • Two types of nephrons-cortical (short) and juxtamedullary (long)
  • Depends on location of their Henle loop
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12
Q

Types of nephrons

-Cortical (short)-Two types?

A
  • superficial

- midcortical

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13
Q

Whole renal pathway summary on slides 12 and 13

A

look at them

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14
Q

Renal corpuscle

-Glomerulus?

A

Tuft of fenestrated capillaries

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15
Q

Renal corpuscle

-Glomerulus is surrounded by?

A

-The glomerulus is surrounded by urinary (Bowman’s) capsule

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16
Q

Renal corpuscle

A
  • Capillaries invaginate into Bowman’s capsule
  • Capillaries are in contact with the visceral layer (podocytes)
  • Parietal layer is simple squamous epithelium
  • Separate by the urinary space
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17
Q

Mesangial cells

-What are they?

A
  • Supporting cells

- Modified smooth muscle

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18
Q

Mesangial cells

-Functions?

A
  • Contractile
  • Supportive
  • Phagocytic
  • Secretory
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19
Q

Mesangial cells

-Functions-contractile?

A

-Reduce/increase blood flow through capillaries

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20
Q

Mesangial cells

-Functions-supportive?

A

Supportive in area where the visceral layer of the renal corpuscle is absent

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21
Q

Mesangial cells

-Functions-Phagocytic?

A

Resorption and maintenance of the basal lamina

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22
Q

Mesangial cells

-Functions-secretory?

A

Secrete prostaglandins and endothelins (induce constriction of afferent and efferent arterioles)

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23
Q

Glomerular filtration barrier

A
  • Fluid from capillaries leaks into the urinary space through a complex filtration barrier
  • Fenestrated capillary endothelium
  • Basal lamina (basement membrane)
  • Podocytes of the visceral layer of Bowman’s capsule
  • High polyanionic charge on some components of both basal lamina and surface of podocyte processes
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24
Q

Glomerular capillaries

-Characteristics?

A
  • Fenestrated
  • Large pores not covered by a diaphragm
  • Permeable to water, urea, glucose, and small proteins
  • Barrier only to formed elements in blood and large maccromolecules
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25
Q

Basal lamina

-Lamina rarae contains:

A
  • Type 4 collagen
  • Laminin
  • Fibronectin
  • Negatively charged proteoglycans
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26
Q

Pedicels and filtration slits

  • Pedicels?
  • Filtration slits?
  • Covered by?
A
  • Each pedicel has a glycocalyx of negatively charged podocalyxin
  • Separated by clefts-filtration slits
  • Covered by a porous slit diaphragm
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27
Q

Filtration slit diaphragm

-contains what protein? what does this protein do?

A
  • Diaphragm contains the protein nephrin

- Nephrin seems to halt passage of molecules through the fenestrations and basal lamina

28
Q

Mutations in gene for nephrin are associated with what disease?

A

Congenital nephrotic syndrome

29
Q

Filtration process

A
  • Blood enters glomerulus via afferent arteriole
  • Arteriole pressure forces fluid through fenestrae of capillary endothelium
  • Large molecules are trapped by the basal lamina
  • Negatively charged molecules are stopped by the basal lamina and podocytes
  • Fluid passes through pores in slit diaphragm to enter the urinary space
30
Q

Proximal convoluted tubule

A
  • Site of “bulk operations”, it begins at urinary pole
  • Lined by cuboidal/low columnar epithelium
  • Microvilli and well-defined brush border
31
Q

Proximal tubule

-Bulk operations?

A
  • Extensive reabsorption of glomerular filtrate
  • Na (active transport), Cl (passive diffusion), water (aquaporin-1) (small transmembrane channel)
  • Reduction in fluid volume
  • Proteins and small peptides are endocytosed in PCT
32
Q

Loop of henle concentration

A

Concentration of the interstitium

33
Q

Loop of Henle function?

A

To assist in forming hypertonic urine by establishing an osmotic gradient in the interstitial fluid of the medulla

34
Q

Loop of Henle structure?

A
  • U-shaped epithelial tube

- Consists of a thick (PCT) and thin descending limb and a thick and thin descending limb

35
Q

Loop of Henle structure

-Difference between thick and thin portions in both the ascending and descending limbs?

A

Epithelial change

  • Thick-cuboidal
  • Thin-squamous
36
Q

Thin ascending is really only found in what type of nephron?

A

Juxtamedullary nephrons

37
Q

Loop of Henle: descending portion

A
  • Permeable to both water and salt
  • As filtrate (isotonic) in the lumen passes deeper into the medulla, it loses water to the interstitium
  • Filtrate becomes more hypertonic
  • Filtrate volume also decreases with loss of water
38
Q

Loop of Henle: Ascending portion

A
  • Plays a more active role in setting up the osmotic gradient required to make the interstitium hypertonic
  • Contains an Na/K/Cl pump-symporter
  • Constantly pumps these ions from the filtrate into the interstitium
39
Q

Loop of Henle: Ascending portion cont.

A
  • Impermeable to water (water cannot follow salt into the interstitium)
  • Loss of salt, but not water, causes the filtrate in Loop of Henle to become isotonic or even hypotonic
  • Filtrate ascends toward the DCT in the cortex
40
Q

Distal convoluted tubule

  • Lined by?
  • Compared to proximal convolute tubule?
A
  • Lined by low cuboidal epithelium

- Fewer microvilli in comparison to PCT (lumen looks larger)

41
Q

Distal convoluted tubule

-2 cell types?

A
  • Principal cells

- Intercalated cells

42
Q

Distal convoluted tubule

-Principal cells-function?

A

Resorb Na and secrete K

43
Q

Distal convoluted tubule

-Intercalated cells-function?

A

Secrete H+ or HCO3-

44
Q

Macula Densa

A
  • Modified segment at transition between the thick ascending loop of Henle and the DCT wall
  • Sensitive to Cl- ion or NaCl content of tubular fluid
  • Produces molecular signals promoting constriction of afferent arteriole
  • Regulate the rate of glomerular filtration (GFR)
45
Q

Juxtaglomerular apparatus

A
  • Involved in maintaining blood pressure and volume through production of renin
  • Juxtaglomerular cells of afferent arteriole (produce renin)
  • Extraglomerular mesangial cells (lacis, polkissen)
  • Macula densa of Loop of Henle/DCT transition
46
Q

Juxtaglomerular apparatus

-Macula densa function?

A

-Macula densa acts as a sensor, regulating juxtaglomerular function by monitoring Na+ and Cl- levels in the DCT

47
Q

Juxtaglomerular apparatus

-Decrease in blood volume/pressure elicits what reaction by JG cells?

A

JG cells secrete renin–>angiotensinogen–>active angiotensin–>aldosterone

48
Q

Aldosterone is secreted by?

A

Suprarenal glands

49
Q

Angiotensinogen–>?

A
  • Angiotensinogen converted to angiotensin I by renin
  • Angiotensin I converted to ang II by ACE
  • Ang II stimulates aldosterone production by suprarenal glands
  • Reabsorption of Na and water by DCT, CT, and CD
50
Q

Treatment of chronic hypertension?

A

ACE inhibitor

51
Q

DCT and aldosterone

A
  • Crucial to acid-base balance and urine concentration
  • Aldosterone (adrenal cortex) cause DCT cells to resorb remaining Na
  • Pump H+ and K+ ions into lumen
  • Control body’s extracellular K+ level and urine acidity
52
Q
  • Atrial Natriuretic factor

- secreted by?

A

Atrial myocytes

53
Q

Atrial Natriuretic factor

-Function?

A
  • Increases Na (natriuresis) and water (diuresis) EXCRETION

- Opposes action of aldosterone, inhibits the release of ADH

54
Q

Urodilatin

-Secreted by?

A

DCT and CD cells

55
Q

Urodilatin

-Function?

A

-Inhibits NaCl and water reabsorption by the medullary part of the collecting ducts

56
Q

Collecting tubules

-Function?

A

Receive isotonic urine from DCT

57
Q

Collecting ducts

-Function?

A
  • Receive isotonic urine from collecting tubules

- Play important role in final concentration of urine (interstitium and vasa recta)

58
Q

Collecting ducts

-pathway?

A
  • Leave cortex in medullary rays and enter medulla

- Collecting ducts open at papilla into minor calyx

59
Q

Collecting ducts

-Epithelium responsive to?

A

ADH

60
Q

ADH is released by?

A

Neurohypophysis

61
Q

Collecting ducts

-How are they affected by presence of ADH?

A

Water is lost from collecting ducts–>hypertonic urine

62
Q

Collecting ducts

-How are they affected by absence of ADH?

A

Ducts remain impermeable to water–>iso-/hypotonic urine

63
Q

Pathway of urine in kidney?

A

Minor calyces–>major calyces–>renal pelvis–>ureter

64
Q

Urothelium

-Histology?

A
  • Stratified
  • Surface layer of umbrella cells linked by desmosomes and tight junctions
  • Possibly impermeable to water and salt
  • Forms osmotic barrier
65
Q

Functions of the urinary system?

A
  • Elimination
  • Conservation
  • Regulation
  • Endocrine