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HUBS 192 Renal/Urinary > L33 - The Nephron > Flashcards

L33 - The Nephron Flashcards

1
Q

What is a Nephron

A

Microscopic functional unit of the kidney
Approx 1 million per kidney
Responsible for urine format

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2
Q

Types of Nephron

A

Cortical Nephron

  • 85% of all nephrons
  • lie mainly in the cortex
  • short nephron loop
  • Glomerulus further from junction

Juxtamedullary nephron

  • Extend deep into the medulla
  • Important for the formation of concentrated urine
  • long nephron loop
  • Glomerulus closer to junction
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3
Q

Functions of the Nephron

A

Selectively filter blood
Return to blood anything we want to keep
Carry waste for storage and removal

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4
Q

Components of the nephron

A

Bowmans capsule
Renal Tubules
Collecting duct

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5
Q

Each nephron is associated with

A

Glomerulus

Peritubular capillaries

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6
Q

Glomerular Capillaries

A

Specialised for filtration
Thin walled single layer of fenstrated endothelial cells
Fed and drained by arterioles
high pressure and tightly regulated

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7
Q

Peritubular Capillaries

A

Specialised for absorption
Adjacent to renal tubes
Arise from efferent arteriole draining glomeruli
After filtration the blood is viscous and protein/cell rich
Low Pressure

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8
Q

Vasta Recta

A

Long Straight Vessels

associated with loop of hence in juxtamedullary nephrons

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9
Q

Renla Corpuscle

A
  • Glomerulus is enclosed by bowman’s capsule
  • Site of filtration - blood/urine barrier
  • Where blood and nephron meet
  • Site of filtration barrier
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10
Q

Bowman’s Capsule

A

2 Layers

1) Outer parietal layer of simple squamous epithelium
2) Inner visceral layer of podocytes
- Between two layers is Bowman’s space (aka capsular space/urinary Space)

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11
Q

Podocytes

A
  • Surround glomerular capillaries
  • Very branched, specialised epithelium
  • Branches form intertwining foot process called pedicels
  • Filtration slits form between pedicels
  • Filtered blood goes through these slits and passes into Bowman’s space
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12
Q

Filtration Barrier

A
  • Lies between blood and Bowman’s space
  • Allows free passage of water and small molecules
  • Restricts passage of most proteins
  • RBC’s are not filtered into nephron
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13
Q

3 layers of filtration barrier

A
  1. Fenestrated endothelium of glomerular capillary
  2. Fused basement membrane
  3. Filtration slits between the pedicels of podocytes
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14
Q

After Filtration

A
  • Urine is waste fluid and solutes filtered from blood
  • Not everything is excreted
  • Some is reabsorbed
  • And some of what wasn’t filtered is secreted in
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15
Q

Proximal Convoluted tubule

A

Bulk Reabsorption

Surrounded by peritubular capillaries

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16
Q

Structure of proximal convoluted tubes

A
  • Cuboidal epithelial cells!
  • Dense microvilli (brush border) on luminal membrane
  • Highly folded basolateral membrane
  • Many mitochondria for active transport
  • Leaky epithelium
17
Q

Loop of Henle

A
  • Part of it is in the medulla
  • Length is important in production of highly concentrated or very dilute urine
  • Surrounded by vasa recta
  • Only tubule to penetrate the medulla
18
Q

Descending limb of loop of henle

A
  • Reabsorption of water from filtrate
  • Structure:
    ○ Thick - similar to PCT
    ○ Thin - simple squamous epithelium
19
Q

Ascending limb

A
  • Reabsorption of water from filtrate
  • Structure:
    ○ Thick - similar to PCT
    ○ Thin - simple squamous epithelium
20
Q

Distal Convoluted tube

A
  • Fine tuning
  • Cuboidal epithelium, but thinner than PCT
  • Few microvilli = no brush border
  • Fewer mitochondria
  • Reabsorption influenced by Aldosterone
21
Q

Collecting Duct

A
  • Fine tuning
  • Filtrate from several DCTs drains into one collecting duct, which empty at papilla
  • Wall of simple cuboidal epithelium
    ○ Principal cells - Reabsorption!
    ○ Intercalated cells - Acid/Base balance!
  • Reabsorption influenced by ADH, through use of aquaporins
22
Q

Juxtaglomerular apparatus JGA

A
  • Specialised zone in every nephron
  • Located where DCT lies against afferent arteriole
  • Controls glomerular filtration rate, ensuring system working at full capacity
    Stabilises blood pressure!
23
Q

Afferent arteriole:

A
  • Juxtaglomerular cells!
  • Mechanoreceptors!
  • Release renin in response to BP!
    Renin stimulates angiotensin II formation!
24
Q

DCT:

A
  • Macula densa cells
  • Chemoreceptors
    Detect Na+ conc in filtrate

HUBS 192 Renal/Urinary (2 decks)

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