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MS1422017S2 > Renal System > Flashcards

Renal System Flashcards

1
Q

What is the main function of the kidneys?

A

To extract fluid from the blood by the process of filtration and collect the fluid and change its composition by returning or keeping substances to the bloodstream or tissue fluids

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2
Q

For the external anatomy of the kidney, name the structures starting from the inside:

A
  1. Renal capsule
  2. Adipose capsule
  3. Renal fascia
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3
Q

What is the following made up of and what is its function: renal capsule

A

Made of connective tissue. It is a physical barrier and protects against trauma whilst also helping to maintain the shape of the kidneys

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4
Q

What is the following made up of and what is its function: adipose capsule

A

Made of fat (CT). It acts as a padding - physical protection. It helps to maintain the position of the kidneys.

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5
Q

What is the following made up of and what is its function: renal fascia

A

Made of CT and it anchors the kidneys to surrounding structures

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6
Q

Describe the internal anatomy of a kidney:

A

The kidney is surrounded by a renal capsule that contains about 8-12 lobes. In each lobe there is a medullary pyramid contained in the overlying renal cortex and 1/2 of the adjacent renal columns. Between each medullary pyramid are the renal columns and between each lobe is the interlobar blood vessels. The subdivisions of the lobe are called the lobules. There are 1 million nephrons that converge into collecting ducts, then papillary ducts, then minor and major calyces. The filtrate then passes down the renal pelvis, down the ureter and into the urinary bladder

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7
Q

Describe the blood flow to the kidney:

A

The renal artery enters the kidney and divides into interlobar arteries which then arc up to form the arcuate arteries. These then form the interlobular arteries which enter into the afferent arteriole into the glomerulus. In the glomerulus there are glomerular capillaries which leave the glomerulus as the efferent arteriole. It then goes down the descending vasa recta along with the peritubular capillaries of the cortex. The blood is still oxygenated. It then goes up the ascending vasa recta where it is deoxygenated as it has passed through the peritubular capillaries of the medulla. It then joins the interlobular vein, then the renal vein, then the IVC then back to the right atrium.

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8
Q

Describe the structure of a nephron:

A

After the glomerulus is the proximal convoluted tubule which leads to the thick descending loop of henle, then the thin descending loop of henle. Then goes to thin ascending loop and then thick ascending loop of henle. Then comes the distal convolued tubule and the collecting ducts and finally the papillary ducts

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9
Q

What is the renal corpuscle?

A

A capsule on the outside of the glomerulus

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10
Q

What lines the afferent and efferent arterioles coming into the glomerulus?

A

Endothelium

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11
Q

What makes up the glomerular epithelium?

A
  1. Visceral - podocytes (modified epithelium)
  2. Capsular/urinary space
  3. Parietal - forms outer wall of capsule (simple squamous)
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12
Q

Describe the filtration membrane from the glomerular capillaries to the capsular space:

A

First there are fenestrations (pores) of glomerular endothelial cells which prevents filtration of the blood cells but allows all components of blood plasma to pass through. Then there is a basal lamina layer which prevents filtration of larger proteins. Finally there is a slit membrane between foot processes called pedicels that prevents filtration of medium proteins. Eventually only small proteins make it though to the capsular space

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13
Q

What are the symptoms of kidney failure?

A 
Swelling - retain water 
Increased blood pressure - hypertension
Shortness of breath - fluid in the lungs 
Fatigue
Nausea
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14
Q

Describe the process of osmosis:

A

The diffusion of water through a selectively permeable membrane from an area of lower solute conc (high water conc) to high solute conc (low water conc). Eventually so much water moves in that it creates a pressure which is called the osmotic pressure (the pressure needed to stop the movement)

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15
Q

Describe osmolarity:

A

Is a measure of the effective gradient for water assuming that all osmotic solute is completely impermeant. It is a count of the dissolved particles. A measure of the osmotic pressure exerted by a perfect semi permeable membrane compared to pure water. It is dependent on the number of particles in solution - not the nature of the particles.

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16
Q

Describe and give and example of: hyperosmotic

A

A solution with a higher osmolarity than another e.g 300mM/L NaCl vs 300mM/L Urea

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17
Q

Describe and give and example of: isosmotic

A

2 solutions with the same osmolarity e.g 150mM/L NaCl vs 300mM/L urea

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18
Q

Describe and give and example of: hyposmotic

A

A solution with a lower osmolarity than another e.g 150mM/L Urea vs 150mM/L NaCl

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19
Q

Describe tonicity:

A

A functional term that describes the tendency of a cell to resist expansion of the intracellular volume. It takes into account the concentration of solute and the ability of the particle to cross a semi-permeable membrane

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20
Q

Describe a hypertonic solution:

A

A solution with a higher osmolarity than another. Water will leave the cell causing cell shrinkage

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21
Q

Describe a isotonic solution

A

2 solutions with the same POsm. No net water movement

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22
Q

Describe a hypotonic solution

A

A solution with a lower Posm than another. Water will move into the cell causing swelling and maybe lysis

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23
Q

Why is it important to maintain osmolarity?

A

Setting the membrane potential
Generating the electrical activity in nerves and muscle
Initiation of muscle contraction
Providing energy for uptake of nutrients and expulsion of waste
Generation of intracellular signalling casacdes

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24
Q

What is the fluid compartments in the female body solid/fluid?

A

45% solid

55% fluid

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25
Q

What is the fluid compartments in the male body solid/fluid?

A

40% solid
60% fluid of which 2/3 intracellular fluid
1/3 extracellular fluid of which 80% interstitialfluid
20% plasma

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26
Q

What are the 3 major sources of water intake?

A
  1. Metabolic water (200mL)
  2. Ingested foods (700mL)
  3. Ingested liquids (1600mL)
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27
Q

What are the 4 major sources of water output?

A
  1. Gi tract (100mL)
  2. Lungs (300mL)
  3. Skin (600mL)
  4. Kidneys (1500mL)
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28
Q

Describe the concentrations of Na+, Cl- and Ca2+ on blood plasma, interstitial fluid and intracellular fluid:

A

They have a much higher concentration in the extracellular fluid than in intracellular fluid.

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29
Q

Describe the concentrations of K+ on blood plasma, interstitial fluid and intracellular fluid:

A

Much higher concentration in ICF than ECF

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30
Q

What are the 3 steps to forming urine?

A
  1. Filtration at the glomerulus
  2. Tubular reabsorption
  3. Tubular secretion
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31
Q

What is all excreted after filtration and none reabsorbed?

A

Creatinine

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32
Q

Describe glomerular filtrate:

A

About 180L/day
Similar solute concentration to plasma but lacks proteins and other high molecular weight compounds and is free from blood cells

33
Q

Is glomerular filtration rate constant or not?

A

Constant

34
Q

Urine output is directly proportional to….

A

Renal pressure

35
Q

Net filtration pressure = ?

A

NFP = glomerular blood hydrostatic pressure - capsular hydrostatic pressure - blood colloid osmotic pressure

36
Q

What is net filtration pressure?

A

The mechanical pressure between afferent and efferent arterioles. Because it has 2 arterioles, this allows for it tightly regulate pressure gradients to maintain constant glomerular filtration rate. Increases in arterial blood pressure can be buffered by vasoconstriction of the afferent arteriole (increasing resistance) and decreases can be buffered by vasoconstriction of efferent arteriole (incresing resistance).

37
Q

What is capsular hydrostatic pressure?

A

The pressure exerted on the plasma filtrate by elastic recoil of the glomerular capsule. (About 15mmHg)

38
Q

What is blood colloid osmotic pressure?

A

The osmotic force of proteins left in the plasma. They proteins exert an increasing osmotic pull on the water in the plasma filtrate. (About 25mmHg)

39
Q

What are the 3 ways that glomerular filtration is regulated?

A
  1. Autoregulation - myogenic or tuboglomerular feedback
  2. Neural - increased sympathtic nerve activity lead to constriction
  3. Hormonal - angiotensin II or atrial naturetic peptide
40
Q

Describe the autoregulation of glomerular filtration by myogenic mechanisms:

A

Increasing stretch of muscle fibres in afferent arterioles walls due to increased blood pressure, smooth muscles contract therefore lumens of afferent arterioles decrease and glomerular filtration decreases

41
Q

Describe the autoregulation of glomerular filtration by tuboglomerular feedback:

A

The juxtaglomerular apparatus sits between the afferent and efferent arterioles and contains macula densa cells, granular cells and mesangial cells. If there is an increase in glomerular filtration rate the there is an increase in tubular flow rate, so the macula densa cells sense an increase in tubular Na+ and Cl- and water content. Leads to afferent arteriole constricton

42
Q

What are juxtomedullary nephrons?

A

They sit in the medulla and are important in the production of concentrated urine

43
Q

What are cortical nephrons?

A

They dit in the cortex and they dilute urine

44
Q

What happens during the proximal convoluted tubule?

A

The largest amount of solute and water reabsorption from filtered fluid. Around 60% of glomerular filtrate, around 60% of NaCl and water and 100% of glucose is all reabsorbed here. Na+ movement occurs through symporters (Na+/glucose) and antiporters (Na+/H+). Water moves via osmosis. It has a brush border which increases surface area.

45
Q

What happens during the descending loop of henle?

A

It has a low permeability to ions and urea and highly permeable to water. Because the interstitial fluid is highly concentrated in the medulla of the kidney, water moves out of the tubule via osmosis, this leaves a highly concentrated filtrate at the bottom of the tube.

46
Q

What happens during the ascending loop of henle?

A

It is very impermeable to water. Na+, K+, Cl- are actively reabsorbed. By the time the filtrate gets back to the top, it is dilute again

47
Q

What is the purpose of the loop of henle countercurrent mechanism?

A

This is so the NaCl that comes out of the ascending loop, can then enter the blood stream (vasa recta) and help set up the gradient for the water to move out of the descending loop.

48
Q

What happens during the distal convoluted tubule?

A

Additional reabsorption of NaCl. In the absence of anti-diuretic hormone, it will become impermeable to water and result in the production of dilute urine. In the presence of ADH, water will be reabsorbed resulting in a concentrated urine

49
Q

How does alcohol affect urine production?

A

It inhibits ADH so it results in dilute urine and can lead to dehydration.

50
Q

Describe how osmoreceptors work:

A

Osmoreceptors in the hypothalamus detect changes in osmolarity. The osmoreceptors have stretch-inhibited cation channels. When cells shrink due to hypertonic stimulus, cation channels open. Na+ entering the cells triggers action potentials.

51
Q

Describe the release of ADH:

A

Osmoreceptors in the hypothalamus sense increase of osmolarity (increaseNa+). The precursor for ADH is produced in the hypothalamus and stored in vesicles in the posterior pituitary. When an action potential comes, ADH is released into the blood. ADH acts on the last part of the distal convoluted tubule and collecting duct. ADH stimulates the insertion of aquaporin-2 channels into the apical membrane of collecting duct epithelia. This is a water channel so water can no move out and can be reabsorbed back into the blood.

52
Q

What is another trigger for the release of ADH?

A

A decrease in blood pressure inhibits the baroreceptors that stimulates the release of ADH

53
Q

How do macula densa cells respond to a decrease in NaCl?

A

They increase prostaglandins

54
Q

What do the granular cells in the afferent arteriole do?

A

They release renin

55
Q

What triggers the release of renin?

A

Low blood pressure (low NaCl in distal tube)
Low blood volume
Increased sympathetic activity (via baroreflex)

56
Q

Describe the role of renin and how it affects Na+ concentrations:

A

It is an enzyme that is released by the juxtoglomerular cells in the kidney and acts on angiotensinogen to produce angiotensin I. Then angiotensin converting enzyme (ACE - lungs) converts it to angiotnesin II. This then causes vasoconstriction and aldosterone release(from the adrenal cortex) which transcribes more Na+/K+ ATPase pumps so Na+ and water are retained

57
Q

What would be the result of a angiotensin II converting enzyme being inhibited?

A

Heart failure, water retension, edema etc

58
Q

What does ANP do?

A

It is released in response to stretch atrial (an increase in blood volume). It acts to reduce renin, ADH and aldosterone release and increase glomerular filtration rate. Reduces Na+ and water reabsorbtion. It relaxes the mesangial cells so there is more SA available for filtration

59
Q

What is the order in which things are restored?

A
  1. Blood pressure
  2. Osmolarity
  3. Blood volume
  4. Blood cells
60
Q

What lines the proximal convoluted tubule?

A

Microvilli

61
Q

Where is ADH synthesised and stored?

A

The hypothalamus and stored in vesicles in the posterior pituitary gland

62
Q

What is the stimulus for the release of ADH?

A

Osmoreceptors with stretch inhibited cation channels in the hypothalamus can sense increases in osmolarity/Na conc

63
Q

What does ADH act on?

A

The collecting ducts and the last part of the distal convoluted tubule

64
Q

What is the effect of ADH on the kidney?

A

Stimulates the insertion of aquaporin-2 controlling vesicles into the apical membrane of the collecting duct as distal convoluted tubule epithelia. These are water channels so water can now be reabsorbed into the blood

65
Q

What is the final result of ADH?

A

Concentrated urine and decreased osmolarity

66
Q

How does ADH negative feedback work?

A

The decrease in osmolarity negatively feeds back to the osmoreceptors in the hypothalamus

67
Q

Where is angiotensionogen made?

A

The liver

68
Q

Where is renin released?

A

The juxtaglomeruler kidney cells

69
Q

When is renin released and what is it sensed by?

A

Low blood pressure - sensed by juxtaglomerular cells
Sympathetic nerves
Low NaCl sensed by macula densa cells that sends a message via prostaglandins.

70
Q

What does renin convert?

A

Angiotensinogen to angiotensin 1

71
Q

After angiotensin I is made what happens?

A

It travels via the blood stream to the lungs where it encounters ACE which converts it to angiotensin II

72
Q

What are the 4 things that angiotensin affects?

A
  1. Aldosterone release - increased Na+/H2O resorbtion and increased K+ excretion
  2. Increased blood volume - increased stroke volume and water retension
  3. Vasoconstriction in arterioles and increase in blood pressure
  4. Increased release of ADH
73
Q

What is the stimulus for the release of ANP?

A

Increased blood volume sensed by arterial stretching

74
Q

What does ANP do?

A

Reduces renin, ADH and aldosterone release
Decreases Na+ and H2O resorption
Increases GFR

75
Q

Where is aldosterone released from?

A

Adrenal cortex

76
Q

What causes aldosterone to be released?

A

Increase in angiotensin II

77
Q

What does aldosterone do?

A

Acts on the distal tubule and collecting ducts to increase Na+/K+ ATPase pumps. It increases Na+/H2O resorption and K+ excretion

78
Q

How does ANP increase GFR?

A

Acts on the mesangial cells within the kidney to cause increased capillary surface area for increased GFR .

MS1422017S2 (8 decks)

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