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SA urinary > S1) Introduction to the Urinary System > Flashcards

S1) Introduction to the Urinary System Flashcards

1
Q

What is the mass of the kidneys?

A

Each weighs approx. 150g

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2
Q

Describe the location of the kidneys

A

Retroperitoneal:

  • Left: T11 - L2
  • Right: T12 - L3
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3
Q

Describe the relation of the ureter to the kidney

A
  • Each kidney has single ureter
  • Ureter is smooth muscle tube running from the renal pelvis to bladder
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4
Q

Identify and describe the 4 functions of the kidney

A
  • Regulation: control the [substances] in ECF
  • Excretion: waste products
  • Endocrine: renin, erythropoietin, prostaglandins
  • Metabolism: active form of Vitamin D, catabolism of insulin, PTH, calcitonin
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5
Q

Movement of water is driven by osmotic forces.

Define osmolarity and osmolality

A
  • Osmolality: number of osmoles of solute per kilogram
  • Osmolarity: number of osmoles of solute per litre
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6
Q

Define osmole

A

Osmole is a measure a solution’s ability to create osmotic pressure & thus affect movement of water

E.g. one mole of CaCl2 forms a 3 osmolar solution in 1L water

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7
Q

Relate osmolarity to osmosis in cells

A

Water moves from low osmolarity solutions to high:

  • If ECF Osmolarity is high – water moves out of cells
  • If ECF Osmolarity is low – water moves into cells
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8
Q

Intra- and extra cellular fluids have different electrolyte compositions. Differences are maintained by active transport.

Demonstrate this

A
  • Intracellular: high K+, low Na+, many large organic anions
  • Extracellular: low K+, high Na+, mainly Cl- and HCO3-
  • if you have a crash injury, lots of K will be released and damage the heart
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9
Q

Kidneys affect extracellular fluid concentrations directly.

What happens when this system fails?

A
  • Changes in BP
  • Changes in tissue fluid and cell function
  • Failure to control ECF osmolarity: cells shrink/swell
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10
Q

What is the functional unit of the kidney?

A

Nephron is a filter unit connected to a long tube for reabsorption

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11
Q

Describe the composition of a nephron

A
  • A glomerulus: tuft of capillaries between afferent and efferent arteriole
  • A tubule: Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
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12
Q

Which parts of the nephron are found in the cortex of the kidney?

A
  • Proximal convoluted tubule
  • Distal convoluted tubule
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13
Q

Which parts of the nephron are found in the medulla of the kidney?

A
  • Loop of Henle: dips into and out of medulla
  • Collecting duct: passes through medulla to pelvis
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14
Q

What is epithelium?

A

Epithelia are continuous sheet of cells covering exposed surfaces and lining internal cavities e.g. digestive, reproductive, urinary and respiratory

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15
Q

What is the role of epithelia in the kidney?

A
  • Excrete waste products from the body
  • Reabsorb needed materials from the filtrate
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16
Q

The kidney is one of the most active organs in the body.

Briefly, describe its metabolic demands.

A
  • Needs blood flow of 4 ml/g/min
  • 22% of cardiac output at rest
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17
Q

Describe the structure and function of the glomerulus

A
  • Structure: highly specialised filter
  • Function: water, electrolytes and small molecules are forced through it by constant filtration pressure in capillaries
18
Q

The proximal convoluted tubule is a major site for reabsorption.

Describe the processes occurring

A
  • PCT absorbs 100% of glucose and amino acids
  • Filtrate remains isotonic with plasma (water follows)
  • Reabsorbed materials leave by peritubular capillaries
19
Q

Describe the cellular mechanisms of reabsorption in the kidney

A
  • Tubules are lined with polarised epithelial cells
  • Different membrane properties on luminal and basolateral membranes
20
Q

Outline the role of sodium pumps in the kidney

A
  • Extrude Na+ across basolateral membrane
  • Na+ enters across luminal membrane down concentration gradient
  • Energy from sodium movement drives reabsorption of other substances e.g. glucose and H2O follows osmotically
21
Q

The Loop of Henle is a further site of reabsorption of salts in the kidney.

Describe its general functions

A
  • Create a gradient of increasing osmolarity in the medulla by counter-current multiplication
  • Forms concentrated urine if water has to be conserved
22
Q

Which processes occur in the distal convoluted tubule?

A
  • Variable reabsorption of electrolytes and H2O
  • Removes even more sodium and chloride and actively secretes H+ (fluid leaving loop of Henle is hypotonic)
23
Q

What happens to water in the distal convoluted tubule?

A

Water may or may not follow reabsorption of electrolytes:

  • Water is reabsorbed = concentrated urine (natriuresis)
  • Water is not reabsorbed = dilute urine (diuresis)
24
Q

Explain the role of the collecting duct in types of urine produced

A

The collecting duct passes through the high osmolarity environment of the medulla (created by the loop of Henle):

  • If water can cross the epithelium = concentrated urine
  • If water cannot cross = urine remains dilute
25
Q

Variable reabsorption occurs in the distal nephron.

Explain this in terms of sodium recovery

A

Sodium recovery controlled by RAAS which controls ECF volume

stimulated by sympathetic system

26
Q

Variable reabsorption occurs in the distal nephron.

Explain this in terms of water recovery

A

Water recovery controlled by ADH which controls:

  • Permeability of DCT and collecting duct to water
  • ECF osmolarity
27
Q

percentage of molecules recovered

A

<99% filtered sodium and chloride

<99% water (it follows sodium)

100% bicarbonate

100% glucose (so should be none in urine)

28
Q

what is renal blood flow

A
  • how much blood flows into the kidney (1L/min)
29
Q

what is renal plasma flow

A
  • volume of plasma that flows into the kidney (600ml/min)
  • RPF = RBF x (1-hamatocrit levels)
  • hematocrits levels → % of RBC that fill blood (normally 40-45%)
30
Q

Glomerular filtration rate

A

GFR = 125mil/min

amount of filtrate produced from blood flow

normally 80% of substances come back in circulation

31
Q

GFR/RPF

A

20%

32
Q

What does the glomerular filtrate contain

A
  • no blood or plasma
  • no proteins
  • composed of organic solutes
33
Q

in histology how can you determine the difference between proximal and distal convoluted

A
  • proximal has a cloudy lumen and contents
  • distal is empty - distal is also bunched up near the Bowmans capsule
34
Q

what is the role of podocytes

A
  • small gaps within the membrane to allow substances to pass through
  • negative charge to repel negative
35
Q

label the difference layers in the glomerular capillary membrane

A
36
Q

some reasons why GFR may drop?

A
  • decline in number of nephrons
  • decline in GRF within nephrons
37
Q

kidneys secrete renin, what does renin do?

A
  • tunica media in the thick part of the afferent arteriole wall secrets renin that changes in response to tubular fluid
  • acts on angiotensin which results in vasoconstriction
  • sympathetic response and results in a fall in plasma volume
38
Q

Kidneys secrete erythropoietin, what is the relevance of this?

A

produces red blood cells

39
Q

describe the reabsorption of glucose in the PCT

A
  1. normal conc → 2.5-5.5 mmol/L
  2. most reabsorption occurs In the PCT
  3. transported via active transport, uses the energy from Na/K pump
  4. travels via Na/Glucose carriers
40
Q

how is glycosuria causes

A
  • load of glucose is at excess and the transporters become saturated
  • Tm reduced (max reabsorbed)
41
Q

where are amino acids mainly reabsorbed?

A
  • Normal conc is 2.5-7.5 mmol/L
  • PCT
  • reabsorbed via secondary active transport

SA urinary (25 decks)

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