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Human Physiology Y3 > Function of the Kidney > Flashcards

Function of the Kidney Flashcards

1
Q

What does the kidney excrete?

A

Metabolic waste products and foreign chemicals

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2
Q

What production does the kidney regulate?

A

Red blood cell production

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3
Q

What does the kidney keep in balance?

A

Regulates acid-base balance
Water & electrolyte balance

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4
Q

What pressure does the kidney regulate?

A

Arterial pressure

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5
Q

What part of body fluids does kidney regulate?

A

Body fluid osmolality
Electrolyte concentration

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6
Q

What hormone does the kidney synthesise?

A

Calcitriol

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7
Q

What are the 5 symptoms of kidney impairment?

A
  1. Body weakness
  2. Blood pressure is high
  3. Swollen legs
  4. Loss of appetite
  5. Vomiting
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8
Q

What abnormal levels of ions can affect the heart in kidney impairment?

A

High K+
Low Ca2+

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9
Q

What is a xenotransplant?

A

A transplant from a donor of a different species from the recipient

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10
Q

What does the ureter lead from and to?

A

From kidney to urinary bladder

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11
Q

What is the role of the urethra?

A

Urine stored in the bladder is emptied through the urethra

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12
Q

How many lobes does a kidney have and what are they composed of?

A

18 lobes composed of nephrons

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13
Q

What is the outer layer of the kidney called?

A

Renal cortex = granular apprearing

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14
Q

What is the inner layer of the kidney called?

A

Renal medulla = striated-appearing

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15
Q

What is the role of the renal pelvis?

A

Collects the urine as it is produced

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16
Q

What does the renal pelvis lie outside of?

A

Peritoneal cavity

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17
Q

What is the flow of urine through the calyxes?

A

Renal pyramid > Renal Papillae > Minor renal calyx > Major renal calyx > Renal pelvis

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18
Q

What happens to nephrons when damaged?

A

Nephrons cannot be regenerated
Treatment can only try to preserve what is remaining

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19
Q

What two layers separate the blood from the glomerular filtrate?

A

Capillary endothelium
Specialized epithelium of Bowman’s capsule

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20
Q

Describe the capillary endothelium

A

Endothelium is fenestrated = has small pores
Completely surrounded by glomerular basement membrane and podocytes
Podocytes create filtration slits

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21
Q

What are podocytes?

A

Bowman’s capsule cells that have foot processes
They interact with each other to forma mesh-like structure

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22
Q

Where are mesangial cells located?

A

Between endothelium and glomerular basement membrane (basal lamina)

Commonly found between two neighbouring capillaries

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23
Q

What do mesangial cells do?

A

Regulate blood flow in glomerulus

By regulating the surface area available for filtration by contracting or relaxing in response to various signals

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24
Q

What does the juxtaglomerular complex consist of?

A

Macula densa
Juxtaglomerular cells

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25
What and where are macula densa and their role?
Tubule cells in initial portion of the distal tubule They act as chemoreceptors, sensing changes in NaCl concentration in the tubular fluid
26
What are juxtaglomerular cells and their function?
Special cells of the blood vessel walls Blood vessels = afferent and efferent arterioles Produce and release the enzyme renin = primary function
27
What is the function of the juxtaglomerular complex?
Regulate blood pressure, Na reabsorption and glomerular filtration Synthesize renin
28
What are the two types of nephron?
Cortical nephron = 85% Juxtamedullary nephron = 15%
29
Describe the cortical nephron
Short loop of Henle Small network of vasa recta
30
Describe the juxtamedullary nephron
Long loop of Henle = reaches medulla Large network of vasa recta
31
What role does the juxtamedullary nephron play?
Concentrating and diluting urine
32
What is the vasa recta and their role?
Network of blood vessels that run parallel to the loops of Henle in the kidney medulla = arise from the efferent arterioles Supply oxygen and nutrients to the medullary tissue while also removing waste products Crucial role in maintaining the osmotic gradient in the medulla, which is essential for the kidney's ability to concentrate urine
33
What percentage is renal blood flow in relation to cardiac output?
22% of CO = 1,100 mL/min
34
What capillary beds does the renal circulation have?
Glomerular capillaries = starts and ends as arteriole Peritubular capillaries = starts as artery ends as venule
35
Location: glomerular vs peritubular capillaries
Glomerular = found within glomerulus Peritubular = surround the renal tubules in the kidney cortex and medulla
36
Function: glomerular vs peritubular capillaries
Glomerular = specialized for filtration Peritubular = involved in reabsorption and secretion
37
What is the GFR per day?
180L/day
38
What is the approximate urine volume?
1 - 1.5 L per day
39
What is excretion a sum of?
Excretion = glomerular filtration + tubular secretion - tubular reabsorption
40
What are the 4 methods of renal handling of substances?
1. Filtration only 2. Filtration and partial reabsorption 3. Filtration and complete reabsorption 4. Filtration and secretion
41
What substances are filtered only?
Inulin
42
What substances are filtered and partially reabsorbed?
Many electrolytes = Na, Cl
43
What substances are filtered and fully reabsorbed?
Amino acids and glucose
44
What substance are filtered then secreted?
Creatinine and certain drugs
45
What is tubular secretion?
Vital mechanism by which the kidneys selectively remove substances from the bloodstream and excrete them in the urine, contributing to the regulation of body fluid composition and overall homeostasis.
46
What is creatinine?
Waste product generated by the breakdown of creatine phosphate in muscles
47
What does tubular secretion regulate?
K+ and H+
48
What is the GFR per minute?
Volume of plasma ultrafiltrate formed each minute 125 mL/min Slightly lower in females
49
What is renal plasma flow?
Amount of plasma that is delivered to the kidneys for filtration and processing = crucial to assess kidney function and renal blood flow 625 mL/min
50
Filtration fraction equation
Glomerular Filtration Rate / Renal Plasma Flow = 125 / 625 = 0.2 20% of plasma flowing though kidneys = filtered through the glomerular capillaries
51
What factors determines the GFR?
Surface area of capillary bed Permeability of capillaries Hydrostatic and osmotic pressure gradient across capillary wall
52
Glomerular ultrafiltration coefficient (Kf)
Kf = glomerular capillary permeability x filtration surface area
53
How does capillary bed surface area affect GFR?
Angiotensin II = vasoconstrictor Contraction of mesangial cells = reduces area available for filtration Changes diameter of blood vessels
54
What is special about glomerular capillaries?
More permeable than other capillary beds
55
What is the rule about filtration based on permeability?
Molecules less than 4nm = freely filtered Intermediate size molecules filtered depending on CHARGE The basal lamina = negative So positive particles are readily filtered
56
What is capillary permeability for proteins?
Largely impermeable to protein
57
Example of a small plasma protein not being filtered
Albumin repelled because it is negatively charged so not filtered even though it is small
58
What happens in glomerulonephtitis?
Immune cells attack and damage glomerulus Glomerular negative charge lost Albumin can then enter urine
59
Define glomerular hydrostatic pressure
Pressure from blood in glomerular capillary wanting to enter nephron Favours filtration = +55mmHg
60
Define colloid osmotic pressure
Proteins attracting water out of nephron Opposes filtration = -30 mmHg
61
Define Bowman's hydrostatic pressure
Pressure from fluids in capillaries against Bowman's capsule Opposes filtration = -15mmHg
62
What is the net filtration pressure?
Favours filtration = +10 mmHg Difference between
63
What is the difference between gomerular capillaries and normal capillaries?
Glomerular capillaries = high pressure system Others = low pressure system
64
What factors cause a decrease in GFR?
Age, Renal disease, Diabetes mellitus, hypertension, decrease in Kf
65
Difference in diameter of arterioles?
Afferent arterioles = smaller than efferent Creates bottle-neck effect
66
What happens to GFR if there is in obstruction of the urinary tract?
Increase in Bowman's capsule hydrostatic pressure = decrease GFR
67
What happens to GFR when sympathetic activity increases?
Increase sympathetic activity = increase vasoconstrictor hormones Afferent arteriolar constriction Reduce renal blood flow Reduce glomerular hydrostatic pressure Reduce GFR
68
What does increased Angiotenin II do to GFR?
Efferent arteriolar constriction = INCREASE GFR Also causes mesangial contraction = reduction in GFR BUT, the strong effect on efferent arteriole usually leads to the effect of overall increase in GFR
69
What effect does artieral pressure have on GFR?
Minimal affect since renal blood flow is autoregulated
70
What effect does high salt and protein intake have on GFR?
Increases GFR
71
How is renal blood flow autoregulated?
Myogenic mechanism and tubuloglomerular feeback
72
How does the myogenic mechanism work?
Muscle reflex to adjust blood flow into the kidneys based on changes in blood pressure = adjusts to stretch
73
What is tubuloglomerular feedback?
Feedback mechanism that links changes in NaCl conc at macula densa to renal arteriolar resisance and autoregulation of GFR
74
What do macula densa monitor?
NaCl concentration = part of tubuloglomerular feedback
75
What happens to afferent arteriolar resistance when arterial presure decreases?
Glomerular hydrostatic presure decreases -> GFR decreases -> Decrease in macula densa NaCl -> Decrease afferent arteriolar resistance
76
What happens to efferent arteriolar resistance when arterial pressure decreases?
Senses decrease in NaCl -> Increases renin -> Increases Angiotensin II leading to increase in efferent arteriolar resistance [ THIS IS TO MAINTAIN GFR ]
77
What is renal plasma clearance?
Voume of plasma that is completely cleared of a substance by the kidneys per unit of time. It represents the efficiency with which the kidneys remove a particular substance from the bloodstream through filtration and/or secretion
78
Units of renal plasma clearance
mL per min
79
How to calculate clearance rate?
Conc of substance in urine / concentration of substance in blood
80
When does the clearance of the substance = GFR?
For substances that are only filtered (not reabsorbed or secreted)
81
How do you calculate urine flow rate?
Urine volume / time in minutes
82
How to calculate GFR?
(Conc of substance in urine / concentration of substance in blood ) x urine flow rate = GFR [urine flow rate = urine volume / time in minutes ]
83
What criteria are needed to choose a substance to measure to calculate GFR?
Substances that are only filtered, not toxic and not metabolized by the body = creatinine and inulin
84
What is inulin?
Polysaccharide
85
Difference between measuring GFR with inulin and creatinine?
Creatinine does NOT need to be administered = endogenous susbstance UNLIKE inulin
86
What happens if you cannot use collect creatinine in the urine to measure creatinine clearance?
Use plasma creatinine concentrations
87
What is the relationship between plasma creatinine conc and GFR?
INVERSELY PROPORTIONAL

Human Physiology Y3 (14 decks)

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