Urinary System 2 - Sructural basis of kidney function Flashcards Preview

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Flashcards in Urinary System 2 - Sructural basis of kidney function Deck (16)
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1
Q

List the functions of the kidneys

A
  • Filtration of blood plasma
  • Selective reabsorption of contents to be retained
  • Tubular secretion of some components
  • Concentration of urine as necessary
  • Sensitive to body needs via hormones, nerves
  • Endocrine function - signals to rest of body (hormones include renin, erythropoietin, 1,25-OH vitamin D
2
Q

List the stages of urine production

A
  • Filtration
  • Reabsorption
  • Creation of hyper-osmotic extracellular fluid
  • Adjustment of ion content of urine
  • Concentration of urine
3
Q

List the components of the renal corpuscle

A
  • Bowman’s capsule
  • Glomerulus consists of capillaries
  • Podocytes associated with glomerulus
4
Q

Describe the blood supply of the renal corpuscle

A
  • At vascular pole of corpuscle
  • From afferent arteriole, exit to efferent arteriole
  • Glomerular capillaries at high pressure
5
Q

List the functions of the proximal convoluted tubule

A
  • Reabsorption of 70% of glomerular filtrate
  • Na+ uptake by basolateral Na+ pump
  • Water and anions follow Na+
  • Glucose uptake by Na+/glucose co-transporter
  • Amino acids by Na+/amino acid co-transporter
  • Protein uptake by endocytosis
6
Q

List the structural features of the proximal convoluted tubule

A
  • Cuboidal epithelium
    Sealed with (fairly water-permeable) tight junctions
  • Membrane area increased to maximise rate of resorption brush border at apical surface interdigitations of lateral membrane
  • Contains aquaporins - membrane protein mediating transcellular
    water diffusion
  • Prominent mitochondria reflect high energy requirement
7
Q

What happens in the descending loop of henle?

A
  • Passive osmotic equilibrium

- Simple squamous epithelium

8
Q

What happens in the ascending limb of the loop of henle?

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
9
Q

Where is the vasa recta and what is its structure?

A
  • Straight capillaries in the medulla parallel to the loop of henle
  • Blood is in equilibrium with extracellular fluid
  • Loop structure stabilises hyper-osmotic
10
Q

What is the function of the distal convoluted tubule?

A
  • Osmotic re-equilibration (controlled by vasopressin)

- Adjustmant of ions (control by aldosterone)

11
Q

Describe the structure of the distal convoluted tubule

A
  • Cuboidal epithelium, few microvilli
  • Lateral membrane interdigitations with Na+ pumps
  • Numerous mitochondria
  • Specialisation at macula densa (part of the juxtaglomerular apparatus)
12
Q

What process happens in the collecting duct of the kidney?

A
  • Passes through medulla with its hyper-osmotic extracellular fluid
  • Water moves down osmotic gradient to concentrate urine
  • Rate of water movement depends on aquaporin-2 in apical membrane (content varied by exo-/endocytosis mechanism)
  • Under control from the pituitary hormone vasopressin
13
Q

Describe the structure of the medulla collecting duct

A
  • Basolateral membrane has aquaporin 3
  • Duct has simple cuboidal epithelium
  • Cell boundaries dont interdigitate
  • Little active pumping so fewer mitochindria
14
Q

Describe the pathway of urine from the collecting duct

A
  • Drains into minor calyx at the papilla of medullary pyramid
  • Drains into major calyces
  • Drains into the ureter
15
Q

Describe the function of the juxtaglomerular apparatus

A
  • Secretes renin to control blood pressure via angiotensin, causing vasoconstriction (due to SNS, low Na+, low BP, low fluid volume)
  • Senses stretch in the arteriole wall and Cl- in the tubule
16
Q

List the cellular components of the juxtaglomerular apparatus

A
  • Macula densa

- Juxtaglomerular cells of afferent arteriole