Histology: Urinary Flashcards

1
Q

Kidney Structure

A

Renal Cortex

Renal Medulla

  • Contains pyramids
  • Extensions of cortex are renal columns

8-18 Lobes

  • Renal pyramid, minor calyx and surrounding column
    • Minor calyces combine to form major calyces and finally renal pelvis
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2
Q

Nephron Organization

A

Nephron is functional unit

  • Renal Corpuscle
    • Glomerulus (tuft of capillaries)
    • Glomerular Capsule
  • Proximal Convoluted Tubule
  • Nephron Loop (loop of Henle)
  • Distal Convoluted Tubule
  • Collecting Ducts
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3
Q

Renal Cortex

A
  • Renal Corpuscles
  • Convoluted Tubules
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4
Q

Renal Medulla

A
  • Straight Tubules
  • Nephron Loops
  • Collecting Ducts
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5
Q

Types of Nephrons

A

Cortical Nephrons

  • Short loop nephrons
    • Loop of Henle into _outer_ medulla

Juxtamedullary Nephrons

  • Long loop nephrons
    • Loop of Henle into _inner_ medulla
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6
Q

Blood Circulation in Kidney

A

Receive 25% cardiac output

  • Renal artery –> Segmental Arteries –> Interlobar arteries –> Arcuate arteries (arching over top of pyramids) –> Interlobular/Cortical Radial arteries –> Afferent arteriole –> Glomerulus –> Efferent arterioles –>
    • Peritubular capillaries (surrounding convoluted tubules)
    • OR vasa recta (follow loop of henle)
  • Interlobular veins –> Arcuate veins –> Interlobar veins –> Renal veins
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7
Q

Arterioles

A
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8
Q

Renal Capillaries

A

Which pathway?

  • Peritubular Capillaries
    • Arise from cortical glomeruli
    • Reabsorb water/solutes in tubules
  • Vasa Recta
    • Arise from juxtamedullary glomeruli
    • Along lopp of henle
    • Countercurrent exchange of water/solutes
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9
Q

Renal Corpuscle

A

Glomerulus

  • Fenestrated capillaries

Glomerular Capsule

  • Visceral layer made of podocytes
  • Parietal layer (simple squamous epithelium)
  • Capsular/urinary space in b/w

Vascular Pole

  • Where arterioles enter/exit

Tubular/Urinary Pole

  • opens into PCT
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10
Q

Glomerular Filtration

A
  • Water and solutes leave vascular space, enter capsular space (called filtrate)
    • Glomerular Filtrate
      • Similar to blood plasma, LITTLE protein
    • Glomerular Filtration Rate
      • 125 mL/min –> 180 L/day
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11
Q

Glomerular Filtration Barrier

A
  • Endothelium of glomerular capillaries (fenestrated)
    • Prevents filtration of blood/platelets
  • Glomerular basement membrane (basal lamina of endothelium and podocytes)
    • Prevents filtration of proteins/anions
  • Pedicels of Podocytes
    • Form filtration slits
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12
Q

Podocytes

A
  • Processes surround glomerular capillaries
  • Pedicels form filtration slits
    • Joined by modified tight junctions
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13
Q

Mesangium

A
  • Enclosed within glomerular basement membrane
  • contains mesangial cells and ECM
    • Resemble vasulr pericytes
      • Provide structural support
      • Phagocytosis
      • Immune defense and injury repair

(MM) is mesangial matrix on image

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14
Q

Proximal Convoluted Tubule

A
  • Simple cuboidal epithelium
  • Star-shaped lumen
    • Appears occluded due to microvilli
    • Indisctinct cell boundaries
  • Primary site of reabsorption (2/3 of filtrate)
    • Glucose, amino acids, small polypeptides
    • Microvilli with glycocalyx
    • Tight junctions/zonula adherens
    • Basal striations with mitochondria (power Na+/K+ pumps to establish Na+ gradient to absorb water)
      • Also, aquaporin-1 channels in lateral PM
  • Secretes anions/cations
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15
Q

Nephron Loop

A

Proximal Straight Tubule (thick descending limb)

  • Recovers remaining Glucose
  • Resembles PCT (simple cuboidal epithelium, brush border, star-shaped)

Thin Segment (simple squamous epithelium)

  • Thin Descending Limb
    • Permeable to water, concentrates fluid
  • Thin Ascending Limb
    • Permeable to ions (not water)
    • fluid becomes dilute

Distal Straight Tubule

  • Reabsorbs NaCl
  • Resembles DCT (simple cuboidal epithelium, smaller lumen than PCT, round, few microvilli)
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16
Q

Distal Convoluted tubule

A
  • In renal cortex
  • Simple cuboidal epithelium
    • No brush border
    • Round
    • Smaller than PCT
  • Reabsorbs Na+, Cl-, Ca2+
  • Acidies urine:
    • Absorb bicarbonate
    • Secretes H+/ammonium
  • Basal striations with mitochondria (Na+/K+ pumps)
  • Impermeable to water
17
Q

Juxtoglomerular Apparatus

A
  • Adjacent to vascular pole (afferent/efferent arterioles)
  • Distal Straight Tubule/DCT contacts vascular pole
  • Regulates blood pressure via renin-angiotensin-aldosterone system

Juxtaglomerular Cells

  • Smooth muscle cells in afferent arteriole
  • Secrete renin

Extraglomerular Mesangial Cells

  • Lacis cells
  • Produce erythropoietin (more RBCs)

Macula Densa

  • Cells in wall of distal straight tubule
  • Monitors Na+ levels in tubular fluid
    • Low Na+ (low blood pressure)
      • Dilate afferent arteriole –> increase glomerular filtration rate
      • Stimulates JG cells to secrete renin –> increases blood pressure
    • High Na+ (high blood pressure)
      • Contrict afferent arteriole –> decrease GFR
      • Decrease renin –> decrease blood pressure
18
Q

Collecting Duct

A
  • Cortical and medullary portions
    • Cells become increasingly columnar (compared to cuboidal in cortex)
  • Reabsorbs water
  • Visible cell boundaries

Principal (Light) Cells

  • Single primary cilium
  • Aquaporin-2 channels (regulated by ADH)
    • Increased with ADH, more concetrated urine
  • Aldosterone stimulates Na+ uptake, increases blood volume

Intercalated (dark) Cells

  • many mitochondria
  • Regulate urine pH
  • Apical microplicae
19
Q

Renal Papilla

A
  • Collecting ducts open at tip of renal papilla
    • Papillary ducts of Bellini
    • Above minor calyx
20
Q

Transitional Epithelium

A
  • Stratified epithelium
  • Accommodates distension

Superficial Layer:

  • Umbrella Cells

Intermediate Layer

  • # of layers vary with state of distention

Basal Layer

  • Stem cells
21
Q

Ureter

A

Star-shaped lumen

Mucosa

  • Transitional Epithelium
  • Lamina propria

Muscularis

  • Inner longitudinal
  • Middle Circular (thickest)
  • Outer longitudinal (closer to bladder)

Adventitia

  • Adipose, nerves, blood vessels

Serosa:

  • Anterior surface
22
Q

Bladder

A

Mucosa

  • Transitional Epithelium

Submucosa

  • Dense CT
  • Blood vessels, nerves, smooth muscle

Muscularis

  • Detrusor muscle
23
Q

Urethra

A

Male

  • Prostatic Urethra
    • Transitional Epithelium
  • Membranous Urethra
    • Stratified or Pseudostratified columnar epithelium
  • Spongy Urethra
    • Pseudostratified by columnar epithelium
    • Becomes stratified squamous distally

Female:

  • Transitional epithelium
  • Becomes stratified squamous distally
24
Q
A