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HUBS192 > Lecture 29- The nephron > Flashcards

Lecture 29- The nephron Flashcards

1
Q

How big are nephrons and approximately how many are there per kidney?

A
  • Microscopic (roughly 3 cm long)

- Approx. 1 million per kidney

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2
Q

What is the basic function of a nephron?

A

Urine formation via…

  • Selectively filter blood
  • Return to blood anything to be kept
  • Carry waste away for storage & expulsion
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3
Q

What are the two types of nephrons and how do they differ?

A

Basic structure is the same between the two types, difference is in location:

  • Cortical nephrons lie mainly in the cortex. Also more numerous (85% of nephrons)
  • Juxtamedullary nephrons have the nephron loop extending deep into medulla. They are Important for the formation of concentrated urine
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4
Q

What is each nephron composed of (the basic parts)?

A 
Made of...
-A Glomerular capsule
-Renal tubules (proximal and distal)
-A collecting duct
Associated with...
-A glomerulus
-Peritubular capillaries
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5
Q

What are glomerular capillaries specialized for and what does this require of their structure?

A
  • Specialized for filtration

- Thin walled single layer of fenestrated endothelial cells

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6
Q

What are glomerular capillaries fed and drained by and why?

A
  • Fed and drained by arterioles

- Because blood pressure here needs to be tightly regulated

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7
Q

A ball of glomerular capillaries=

A

The glomerulus

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8
Q

What are peritubular capillaries specialized for and what does this require of their structure/placement?

A

-Specialised for absorption
-Wrap around renal tubules
-Receives filtered blood from glomerulus via efferent
arterioles
-Receives reabsorbed filtrate from nephron
-Some non-filtered solutes that need to be excreted can pass from here into nephron

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9
Q

What are vasa recta?

A
  • Straight blood vessel extensions of the peritubular capillaries that follow nephron loops deep into the medulla
  • Only found with juxtamedullary nephrons
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10
Q

What is the structure of the renal corpuscle? What occurs there?

A
  • The glomerulus enclosed by the Glomerular capsule is collectively called the renal corpuscle
  • Where capillary and nephron meet
  • Site of filtration barrier
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11
Q

What is the first part of the nephron?

A

Glomerular capsule

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12
Q

What are the two layers of the glomerular capsule?

A
  • Outer parietal layer of simple squamous cells
  • Inner visceral layer of podocytes
  • Between the two layers is the capsular space which receives filtrate
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13
Q

What are podocytes? What does their structure allow?

A

-Surround the glomerular capillaries
-Very branched, very specialized epithelium
-Branches form intertwining foot processes called
pedicels
-Filtration slits form between pedicels
-Filtered blood (filtrate) goes through these slits and passes into capsular space

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14
Q

What is the filtration barrier?

A
  • Also called the blood-urine barrier

- Lies between blood and capsular space

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15
Q

What can freely past through the filtration barrier and what cannot?

A
  • Allows free passage of water and small molecules

- Restricts passage of most proteins and RBCs. These are not filtered into the nephron as they are too big.

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16
Q

What are the three layers of the filtration barrier?

A
  • Fenestrated endothelium of glomerular capillary
  • Fused basement membrane
  • Filtration slits between the pedicels of the podocytes
17
Q 
Which of the following is not a component of the
blood-urine barrier:
A. Fused basement membrane
B. Filtration slits
C. Podocytes
D. Pedicels
E. Sinusoidal endothelium
A

E. Sinusoidal endothelium

Its fenestrated not sinusoidal (this is found in the liver)

18
Q

Is everything that is filtered into the nephron excreted as urine?

A
  • No, some filtrate is reabsorbed (2/3 water, 100% glucose)
  • And some of what wasn’t filtered is secreted into the nephron
  • Urine = Filtered – Reabsorbed + Secreted
19
Q

What is the structure of the proximal convoluted tubule (PCT) like and how does this relate to its function?

A
  • Bulk reabsorption
  • Surrounded by peritubular capillaries

Structure:

  • Cuboidal epithelial cells
  • Dense microvilli (brush border) on luminal membrane to increase surface area
  • Highly folded basolateral membrane
  • Many mitochondria for active transport (provides energy)
  • Leaky epithelium as allows things to pass through via the paracellular pathway (between cells)
20
Q

What is the structure of the nephron loop like and how does this relate to its function?

A
  • Loops down into the medulla
  • Length is important in production of dilute/concentrated urine
  • Surrounded by vasa recta (juxtamedullary nephrons only)

Structure:

  • Thick descending limb which is similar to PCT structure
  • Thin descending limb made of Simple squamous epithelium
  • Thin ascending limb made of Simple squamous epithelium
  • Thick ascending limb similar to DCT structure
  • Different permeabilities to water and sodium
21
Q

What is the structure of the distal convoluted tubule(DCT) like and how does this relate to its function?

A

-Fine tuning

Structure:

  • Cuboidal epithelium, but thinner than PCT
  • Few microvilli = no brush border (not as vital to have large surface area as not being used for bulk transport)
  • Fewer mitochondria (not as much energy required)
  • Reabsorption influenced mainly by the hormone Aldosterone
22
Q

What is the structure of the collecting duct like and how does this relate to its function?

A
  • Fine tuning
  • Filtrate from several DCTs drains into one collecting duct, which empty at papilla

Structure:

  • Wall of simple cuboidal epithelium
  • Principal cells specialized for reabsorption
  • Intercalated cells keep an Acid/Base balance
  • Reabsorption influenced by ADH (antidiuretic hormone) and Aldosterone
23
Q

What is the Juxtaglomerular apparatus (JGA)? What is its function?

A
  • Specialised zone in every nephron
  • Located where DCT lies against afferent arteriole

Both vessels have specialized
cells:
-DCT: Macula densa cells. Chemoreceptors. Detect sodium levels
-Afferent arteriole: juxtaglomerular cells. Mechanoreceptors. Detect blood pressure
-Controls glomerular filtration rate, ensuring system working at full capacity
-Stabilizes blood pressure

HUBS192 (38 decks)

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