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Medical Science > Renal System > Flashcards

Renal System Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

Main functions of the kidneys

A

Extract fluid from blood via filtration
Change composition of fluid by retaining substances and returning to blood or tissues
Excretion of waste or foreign substances

Regulate blood pH, erythrocyte production, hormone production and blood glucose levels

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2
Q

Three layers of the external kidney anatomy

A

Renal capsule
Adipose capsule
Renal fascia

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3
Q

Renal capsule

A

Connective tissue
Physical barrier to protect against trauma
Maintains kidney shape

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4
Q

Adipose capsule

A

Fatty connective tissue
Padding and physical protection
Maintains kidney position

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5
Q

Renal fascia

A

Connective tissue

Anchors kidneys to surrounding structures

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6
Q

Describe a lobe

A

Between 8 - 12 in humans

Contains a medullary pyramid, the overarching cortex and 2 halves of a renal column on either side

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7
Q

3 things you would find in the renal cortex

A

Cortical blood vessels
Part of nephrons
Lobule intersections

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8
Q

Interlobar

A

Between lobes

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9
Q

Interlobular

A

Between lobules

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10
Q

Peritubular capillaries of the cortex

A

Connect glomerulus to ascending and descending vasa recta

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11
Q

Ureter

A

Connects urinary bladder and renal pelvis

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12
Q

Papillary ducts

A

Found at bottom of medullary pyramid next to renal pelvis

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13
Q

Nephron

A

Starts in renal cortex, threads through medullary pyramid where collecting ducts of nephron feed into papillary ducts

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14
Q

Minor calyx

A

Connects bottom of renal columns to renal pelvis between medullary pyramids and papillary ducts

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15
Q

Major calyx

A

Large area of renal pelvis that connects minor calyces to blood supply

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16
Q

Peritubular capillaries of the medulla

A

Connect ascending and descending vasa recta

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17
Q

Ascending vasa recta

A

Run alongside descending loop of Henle
Venous, low oxygen levels
Connected to descending vasa recta by peritubular capillaries of the medulla

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18
Q

Descending vasa recta

A

Run alongside ascending loop of Henle
Arterial, high oxygen levels
Connected to ascending vasa recta by peritubular capillaries of the medulla

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19
Q

Glomerulus

A

Endothelium
Little ball of capillaries in the nephron
Accepts blood from afferent arterioles and pushes it into efferent arterioles and proximal convoluted tubule of nephron

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20
Q

Afferent renal arteriole

A

Accepts blood from interlobular artery and feeds it into glomerulus

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21
Q

Efferent renal arteriole

A

Accepts blood from glomerulus and transports it into descending vasa recta and peritubular capillaries of the cortex

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22
Q

Parenchyma

A

Functional portion of the kidney

Contains 1 million nephrons

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23
Q

Renal corpuscle

A

Glomerulus and Bowmans capsule

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24
Q

Summarise the basic structure of a nephron

A 
Glomerulus
Proximal convoluted tubule
Thick descending loop of Henle
Thin descending loop of Henle
Thin ascending loop of Henle
Thick ascending loop of Henle
Distal convoluted tubule
Collecting duct
Papillary duct
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25
Q

Bowmans capsule

A

Epithelium
Visceral podocytes
Parietal simple squamous epithelium forms the outer wall of the capsule

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26
Q

3 parts of the filtration membrane

A

Fenestrations
Basal lamina
Slit membrane

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27
Q

Fenestrations

A

Pores

Prevents filtration of blood cells but allows all components of blood plasma to pass

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28
Q

Basal lamina

A

Fusion of podocyte basement membrane and endothelium basement membrane
Prevents filtration of large proteins

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29
Q

Slit membrane

A

Between pedicels

Prevents filtration of medium sized proteins

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30
Q

Osmolarity

A

A measure of the effective gradient for water assuming all osmotic solute is completely impermeant
Number of dissolved particles

31
Q

Tonicity

A

Tendency of a solution to resist expansion of intracellular volume
Concentration of solute + permeability

32
Q

Isosmotic

A

Same number of dissolved particles per unit regardless of how much water would flow across a given membrane

33
Q

Isotonic

A

No water movement across a given membrane would occur regardless of how many particles are dissolved

34
Q

Describe the fluid in the body of a 70kg male

A

Water makes up 60% of males, about 42L
Intracellular fluid makes up 2/3 of the bodys fluids, about 28L
Extracellular fluid makes up the other 1/3, about 14L
20% of ECF is blood plasma, 80% interstitial fluid
2.8L plasma, 5L blood

35
Q

4 reasons to maintain osmolarity

A

Membrane potential
Electrical activity
Muscle contraction
Nutrient uptake

36
Q

Sources of water gain

A 
Metabolic water (8%)
Ingested foods (28%)
Ingested liquids (64%)
37
Q

Sources of water loss

A

GI tract (4%)
Lungs (12%)
Skin (24%)
Kidneys (60%)

38
Q

Ions with a higher concentration in the ECF than ICF

A

Sodium
Calcium
Chlorine

39
Q

Ions with a higher concentration in the ICF than ECF

A

Potassium

40
Q

3 processes of urine formation

A

Glomerulus filtration
Tubular reabsorption
Tubular secretion

41
Q

The filtration equation

A

Excretion of substance X = Filtered - reabsorbed + secreted

42
Q

Substances of little excretion

A

Water

Sodium ions

43
Q

Substance not excreted at all

A

Glucose

44
Q

Substance completely excreted

A

Creatinine

45
Q

Describe the equation NFP = GBHP - CHP - BCOP

A

Net filtration pressure = glomerular blood hydrostatic pressure - capsular hydrostatic pressure - blood colloid osmotic pressure
Glomerular blood hydrostatic pressure drives fluid out of the glomerulus, a force that is opposed by both capsular hydrostatic pressure and blood colloid osmotic pressure resulting in a net filtration pressure

46
Q

NFP

A

Net filtration pressure
Determines how much water and small dissolved solutes leave the blood
About 10 mmHg

47
Q

GBHP

A

Glomerular blood hydrostatic pressure
Mechanical pressure between afferent and efferent arterioles within glomerulus
Drives plasma filtrate from glomerular capillaries into capsular space
About 50 mmHg

48
Q

CHP

A

Capsular hydrostatic pressure
Pressure exerted on plasma filtrate by elastic recoil of glomerular capsule
About 15 mmHg

49
Q

BCOP

A

Blood colloid osmotic pressure
Osmotic force of proteins left in the plasma pulling the water from the plasma filtrate into the glomerulus
About 25 mmHg

50
Q

Describe how glomerular pressure is regulated

A

Vasoconstriction of afferent arterioles decreases glomerular pressure by restricting oncoming flow
Vasoconstriction of efferent arterioles increases glomerular pressure by restricting outgoing flow

51
Q

Glomerular filtration rate

A

About 125 mL per minute so about 180 L per day
Similar solute concentration to plasmin - lacks proteins, heavy compounds and blood cells
Kept relatively constant
Urine output directly proportional to renal pressure

52
Q

3 types of GFR regulation

A

Renal autoregulation
Neural regulation
Hormone regulation

53
Q

2 types of renal autoregulation

A

Myogenic mechanism

Tubuloglomerular feedback

54
Q

2 types of renal hormone regulation

A

Angiontensin II

Atrial natriuretic peptide

55
Q

Describe how the myogenic mechanism regulates GFR

A

Blood pressure increases causing stretching of smooth muscle fibres in afferent arteriole walls
Stretched smooth muscle fibres contract, narrowing afferent arteriole lumens and decreasing GFR

56
Q

Describe how tubuloglomerular feedback regulates GFR

A

High systemic blood pressure causes rapid delivery of sodium and chloride to macula densa cells
Juxtaglomerular apparatus decreases release of nitric oxide causing vasoconstriction of afferent arterioles and decreasing GFR

57
Q

Describe how neural mechanisms regulate GFR

A

Renal sympathetic nerve activity increases causing norepinephrine release
Renin released and alpha receptors activated causing constriction of afferent arterioles and decreasing GFR

58
Q

Describe how angiotensin II regulates GFR

A

Decreased blood volume or blood pressure increases angiotensin II production
ANG II causes afferent and efferent arteriole constriction and decreasing GFR

59
Q

Describe how atrial natriuretic peptide regulates GFR

A

Atrial stretching causes ANP release
ANP relaxes mesangial cells in glomerulus which increases capillary surface area available for filtration and increases GFR

60
Q

Reabsorption in the proximal convoluted tubule

A

Site of largest amount of solute and water reabsorption from filtered fluid
60% glomerular filtrate, NaCl, water
100% glucose
Also amino acids, organic nutrients and some HCO3 reabsorbed
Sodium movement by symporters and antiporters
Sodium actively pumped out, glucose uses already set up sodium gradient to be transported out via symporter
Brush border increases surface area

61
Q

Reabsorption in the descending loop of Henle

A

Mainly water reabsorbed by osmosis as interstitial fluid in renal medulla is 2 - 4 x more concentrated than glomerular filtrate
Low permeability to ions and urea
Very concentrated filtrate at the bottom of loop due to lots of water being removed but no other solutes

62
Q

Reabsorption in the ascending loop of Henle

A

Sodium, potassium and chlorine actively absorbed
Virtually impermeable to water so no more gets reabsorbed and tubular content becomes more dilute
Osmolarity about 100 mOmol/L

63
Q

Reabsorption in the late distal convoluted tubule and collecting duct

A

Additional reabsorption of NaCl

Water requires ADH in this section to be reabsorbed. In absence of ADH a very dilute urine is produced

64
Q

Location of dilute urine

A

Cortical nephrons

65
Q

Location of concentrated urine

A

Juxtamedullary nephrons

66
Q

Describe the negative feedback loop of GFR regulation

A

Increased GFR
Increased tubular flow rate
Increased tubular sodium, chlorine and water content sensed
Juxtaglomerular apparatus commences intracellular signalling
Afferent arteriole vasoconstriction
Decreased GFR

67
Q

Describe how ADH acts on urine concentration

A

Osmoreceptors in hypothalamus detect changes in osmolarity
ADH precursor synthesised in hypothalamus and stored in posterior pituitary
Osmolarity increases, ADH released from posterior pituitary into blood
ADH binds membrane receptor on the last part of the convoluted distal tubule and the collecting duct
cAMP is activated
ADH stimulates aquaporin-2 containing vesicles into apical membrane of collecting duct epithelium allowing water to move freely into the cell
Basolateral membrane always relatively permeable to water allowing water to be reabsorbed by osmosis into the blood

68
Q

Describe how osmoreceptors work

A

Cell shrinkage due to hypertonic solution opens stretch inhibited cation channels
Sodium enters and triggers a cell action potential
Plasma osmolarity increases causing ADH increase and thirst sensation is triggered by osmoreceptors

69
Q

3 ways angiotensin II affects renal physiology

A

Vasoconstriction of afferent arterioles causing decreased GFR
Small direct effect on reabsorption in proximal convoluted tubule
Stimulates release of aldosterone from adrenal cortex

70
Q

3 renin stimulators

A

Decreased NaCl in distal tubule
Decreased perfusion pressure by granular cells
Increased renal sympathetic nerve activity

71
Q

How macula densa cells respond to decreased NaCl

A

Increase prostaglandins

72
Q

Summary of the renin-angiotensin-aldosterone system

A

Angiontensinogen converts renin to angiotensin I
Angiotensin converting enzyme converts angiotensin I to angiotensin II
Angiotensin II acts on the adrenal cortex to increase aldosterone
Aldosterone increases transcription of sodium/potassium/ATPase pumps in the distal tubule and collecting ducts

73
Q

ACE inhibitors

A

Heart failure treatment
Kidneys normally try to increase renin and angiotensin II to increase blood volume. In heart failure, atria and ventricles hypertrophy causing increased blood volume and putting more strain on the heart
ACE inhibitors stop the conversion of ANG I to ANG II, decreasing blood volume and relieving some pressure on the heart

74
Q

Describe how increased salt intake results in decreased blood volume

A

Increased salt intake means increased plasma concentrations of Na+ and Cl- resulting in increased osmosis of water from ICF to interstitial fluid to plasma resulting in increased blood volume
Increased blood volume can increase atrial stretching resulting in atrial natriuretic peptide and decrease release of renin and therefore formation on ANG II and aldosterone
Decreased ANG II causes increased GFR and both decreased aldosterone and increased GFR causes reduced reabsorption of NaCl by kidneys
Reduced NaCl reabsorption causes increased loss of Na+ and Cl- in urine which also causes increased water loss in urine and therefore decreased blood volume

Medical Science (11 decks)

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