lecture 2 : The Structural Basis of Kidney Function Flashcards Preview

LSS: Urinary system > lecture 2 : The Structural Basis of Kidney Function > Flashcards

Flashcards in lecture 2 : The Structural Basis of Kidney Function Deck (18)
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1
Q

what are the main function of the kidney?

what are the major actions of the kidney?

A

is the production of urine
Filtration of blood plasma –
- Glomerulus

  • Selective reabsorption of contents – Proximal
    convoluted tubule.
  • Retention of unwanted contents in urine – Loop of
    Henle
  • Concentration selection or urine – Distal convoluted
    tubule.
2
Q

which part of the kidney has the worst blood supply?

A

the pyramid

3
Q

what are the 4 overall stages of Urine Production

A
  1. filtration
  2. reabsorbtion
  3. creation of hyperosmotic extracellular fluid:
  4. Adjustment of ion content in urine:
4
Q

explain the filtration process

A
  1. Filtration:
    - The glomerulus filters the blood that passes through it
    - Filtrate ONLY contains molecules that weigh less than 50,000 Da.
    all larger structure are sieved out
    - the fluid that leaves is isotonic ( same concentration as the blood)
    - the capillary is fenestrated
    - there is high pressure to force the fluid out
5
Q

what are the components of the renal corpuscle?

A
Components
	- Bowman’s capsule
	- glomerulus consists of 
       capillaries
	- podocytes associated 
      with glomerulus
Filtration barrier consists of
	- fenestrae (“windows”) in 
       capillary endothelium
	- specialised basal lamina
        - filtration slits
6
Q

explain the reabsorption process?

A
  • Material to be retained is reabsorbed in proximal convoluted tubule

Includes ions, glucose, amino acids, small proteins, water, etc

7
Q

features of the PCT?

A
  • Cuboidal epithelium
  • Sealed with (fairly water-permeable) tight junctions
  • contains aquaporins
  • brush border
  • lots of vesicles
  • lots of mitochondria
8
Q

explain the creation of the hyper osmotic extracellular fluid?

A
  • Main function of loop of Henle and vasa recta (blood vessels)
  • Countercurrent mechanism
9
Q

what 3 parts of the loop of henle are involved in the countercurrent mechanism?

A
  • Descending thin tubule
  • Ascending thick limb
  • Vasa recta
10
Q

what happens in the Descending thin tubule

?

A

Passive osmotic equilibrium (aquaporins present)

Simple squamous epithelium

11
Q

what happens in the ascending thick limb?

A
  • Na+ and Cl- actively pumped out of tubular fluid
  • Very water-impermeable tight junctions
  • Membranes lack aquaporins - low permeability to water
  • Results in hypo-osmotic tubular fluid, hyper-osmotic extracellular fluid
  • Cuboidal epithelium, few microvilli
  • High energy requirement - prominent mitochondria
12
Q

what happens in the vasa recta?

A

Blood vessels also arranged in loop
Blood in rapid equilibrium with extracellular fluid
Loop structure stabilises hyper-osmotic [Na+]

13
Q

explain the adjustment of the ion content in the urine?

A
  • Principally a function of distal convoluted tubule

- Controls levels of Na+, K+, H+, NH4+

14
Q

what are the features of the distal convoluted tubule?

A
  • Site of osmotic re-equilibration (control by vasopressin)
  • Adjustment of Na+/K+/H+/NH4+ (control by aldosterone)
  • Cuboidal epithelium, few
    microvilli
  • Na+ pumps
  • Numerous large mitochondria
  • Specialisation at macula densa
15
Q

how does the control of concentration of urine work?

A
  • Occurs at collecting tubule
  • Movement of water down osmotic gradient into extracellular fluid
  • Controlled by vasopressin (=ADH, antidiuretic hormone)
16
Q

features of the collecting duct?

A
  • act of ADH is most important
  • Rate of water movement depends on aquaporin-2 in apical membrane
  • Basolateral membrane has aquaporin-3, not under control
  • simple cuboidal epithelium
  • Cell boundaries don’t interdigitate
  • Little active pumping so fewer mitochondria
17
Q

what is theJuxtaglomerular apparatus?

A
  • Endocrine specialisation
  • Secretes renin to control blood pressure via angiotensin
  • Senses stretch in arteriole wall and [Cl-] in tubule
18
Q

what are the cellular components of the Juxtaglomerular apparatus
?

A
  • macula densa of distal convoluted tubule

- juxtaglomerular cells of afferent arteriole