Kidneys Flashcards
1
Q
25-hydroxycholecalciferol is converted to 1, 25-dihydroxycholecalciferol. In which of the following tissues does this occur?
A
Kidneys
2
Q
What systemic mean arterial pressure range must renal blood flow, capillary pressure and GFR be maintained over
A
90-200 mmHg
3
Q
Main extra cellular solute in kidneys
A
Na+
4
Q
What can detect plasma volume
A
Baroreceptors
5
Q
What does low total body Na+ lead to
A
Low plasma volume
Lower BP
—> decrease GFR and increase Na+ reabsorption to decreaase losses
6
Q
Short term regulation of Na+
A
Changes in GFR
7
Q
Long term regulation of Na+
A
Renin angiotensin aldosterone system
8
Q
Effect of high total body Na+
A
Increased GFR
decreased Na+ reabsorption
9
Q
What percentage of Na+ is reabsorbed in the proximal tubule
A
60%
10
Q
What percentage of Na+ is reabsorbed in the loop of henle
A
25%
11
Q
What percentage of Na+ is reabsorbed in the distal tubule
A
10%
12
Q
What percentage of Na+ is reabsorbed in the collecting duct
A
4%
Regulated reabsorption - large effect due to high volumes of fluid filtered
13
Q
What has a direct effect on GFR
A
Arterial blood pressure
14
Q
GFR and reduced blood pressure
A
Reduced GFR
Blood osmolality and oncotic pressure also play a role in
15
Q
What has an indirect effect on GFR
A
Sympathetic nerves
16
Q
Sympathetic nervous system and GFR
A
Reflex of arterials in response to increased stretch of the vessels
Respond by constricting (mainly afferent arterioles) reducing blood entry into the glomerulus
17
Q
What increases GFR again after sympathetic stimulation
A
Neuroendocrine inputs (aldosterone)- reabsorption of Na+ go increase plasma volume
18
Q
Most abundant intracellular ion
A
K+
19
Q
Percentage of total body K+ in extracellular fluid
A
2%
20
Q
Function of extracellular K+
A
Excitable tissues (nerves and muscles)- affects the resting membrane potential
21
Q
Result of hyperkalaemia or hypokalaemia
A
Abnormal heart rhythms
Abnormalities of skeletal muscle contraction and neuronal action potential conduction
22
Q
How is K+ excreted
A
Urine- amount dependent on how much is ingested and losses in sweat/faeces
23
Q
What percentage of filtered K+ is reabsorbed in the proximal tubule
A
90%
24
Q
Where is K+ reabsorbed
A
Proximal tubule
25
How is K+ secretion related to Na+ in cortical collecting duct
During Na+ reabsorption, K+ is pumped into the cells by Na/K ATPase
K+ then diffuses out of collecting duct and Na+ is able to flow in
26
What cells can secrete K+
Cortical collecting duct cells
27
Factors affecting K+ secretion
A high K+ diet —>Increased plasma K+ concentration —> Basolateral uptake of K+ via the Na/K ATPase
Low K+ diet —> decreased plasma concentration —> reduced basolateral uptake and reduced secretion
Increased intake —> increased extracellular —> stimulates aldosterone production —> increases K+ secretion
28
What is aldosterone secreted by
Zona glomerulosa
29
What is the zona glomerulosa sensitive to
K+ concentration in ECF
30
What forms the juxtaglomerular apparatus
Afferent arterioles (granular cells) and distal convoluted tubule (macula densa cells)
31
Granular cells
Afferent arterioles endothelium expands to form mass of cells in juxtaglomerular apparatus
32
Macula densa cells
Cells of distal convoluted tubule at juxtaglomerular apparatus
Detect Na+ levels
33
What do macula densa cells secrete in response to low Na+
Prostaglandins
34
What do granular cells secrete
Renin
35
What stimulates granular cells
Prostaglandins
36
Role of macula densa cells if high Na+
Filtration is slow so more absorbed
Reduce afferent arterioles resistance and increase GFR
37
What are the 3 controlling steps of the RAAS
Macula densa cells detect less NaCl
Sympathetic stimulation
Little or no arteriolar stretch (from low blood volume)
38
Function of renin
Enters blood and cleaves larger plasma protein angiotensinogen into a smaller angiotensin I
39
Where is angiotensinogen produced
Liver
40
Fate of angiotensin I
Cleaved by angiotensin converting enzyme (ACE) into angiotensin II
41
Where is angiotensin converting enzyme (ACE) produced
Lungs
42
Aim of RAAS
Increase circulating blood volume and blood pressure
43
Effects of angiotensin II
Stimulates release of aldosterone, vasopressin and aldosterone
Stimulates thirst
Increases Na+ reabsorption in PCT
vasoconstriction of systemic arteries and renal arterioles (decreases GFR)
44
How is thirst stimulated
Increases osmo-sensitivity of system
45
How does vasoconstriction of renal arterioles decrease GFR
Effect is greater in efferent arterioles due to smaller basal diameter so increases pressure making it harder for blood to leave
46
Which cells secrete aldosterone
Zona glomerulosa cells in adrenal cortex of adrenal glands
47
Size of renin
40 kDa
48
What is renin
Proteolytic enzyme
49
Which transporter in macula densa cells takes up Na+
NKCC2
50
What are granular cells affected by
Local factors: stretch, prostaglandin secretion, nitric oxide (cell stress)
51
2 theories of signalling to granular cells
Nitric oxide
Adenosine secretion
52
Granular cells and nitric oxide
Acts through extraglomerular mesangial cells to signal secretion
53
Granular cells and adenosine secretion
By macula densa cells which bypass the mesangial cells and directly go to receptors on granular cells
54
Which cells secrete adenosine
Macula densa cells
55
What reduces the secretion of renin
Beta blockers - as block effects of adrenaline
56
What 3 things stimulate renin secretion
1. Reduced sodium delivery to the distal convoluted tubule detected by macular densa cells
2. Reduced perfusion pressure in the kidney detected by baroreceptors in the afferent arterioles
3. Sympathetic stimulation of the JGA via beta-1 adrenoreceptors
57
Sympathetic receptors of juxtaglomerular apparatus
Beta-1 adrenoreceptors
58
Which other hormone do kidneys produce
Erythropoietin- stimulates red blood cell production
59
Major complications of chronic renal failure
• Fluid retention, which could lead to swelling in your arms and legs, high blood pressure, or fluid in your lungs (pulmonary oedema)
• A sudden rise in potassium levels in your blood (hyperkalemia)
• Anaemia
• Heart disease
• Weak bones and an increased risk of bone fractures
• Decreased sex drive, erectile dysfunction or reduced fertility
• Damage to central nervous system, which can cause difficulty concentrating, personality changes or seizures
• Decreased immune response
• Pericarditis, an inflammation of the pericardium
• Pregnancy complications that carry risks for the mother and the developing foetus
• Irreversible damage to your kidneys (end-stage kidney disease), eventually requiring either dialysis or a kidney transplant for survival
60
Acute kidney injury
rapid decrease in glomerular filtration rate that results in abnormal fluid and electrolytes balance and azotaemia (high levels of nitrogen-containing compounds in blood)
61
Pre renal kidney disease
sudden and severe reduction in bp or interruption of blood flow to the kidneys from severe injury or illness
62
Causes of Pre renal kidney disease
• blood loss
• Dehydration
• Heart failure
• Sepsis (causes vasodilation- oedema)
• Vascular occlusion
• Hypotension
• Oedema
63
Intra-renal kidney disease
direct injury to the kidneys by inflammation, drugs, toxins, infection or reduced blood supply
64
Causes of intra-renal kidney disease
• acute tubular necrosis= drugs, toxins, prolonged hypotension
• Glomerulonephritis
• Acute interstitial nephritis
• Allergic reactions
• Small vessel vasculitis
• Eclampsia
• Chemotherapy
65
Postrenal kidney disease
sudden obstruction of urine flow due to enlargedprostate, kidney stones, bladder injury or tumour
66
Causes of Postrenal kidney disease
• benign prostatic hyperplasia
• Cervical cancer
• Retroperitoneal fibrosis
• Prostate cancer
• Urinary calculi
• Renal stone
• Prostate enlargement
• Lower urinary tract infection
67
Common causes of chronic kidney disease
• diabetes
• Hypertension
• High cholesterol
• Heart disease/ heart failure
• Obesity
• Over the age of 60
• Family history
• Personal history of acute kidney injury
• Smoking
• Glomerulonephritis
• Interstitial nephritis
• Polycystic kidney disease
• Prolonged obstruction of the urinary tract eg from an enlarged prostate, kidney stones or cancer
• Vesicoureteral reflux
• Recurrent kidney infection
68
Chronic kidney disease of unknown origin
A type of chronic kidney disease that mainly affects marginalized agricultural communities in specific areas of the world where a large number of people develop an unexplained, deadly form of kidney disease. In the clinical context, a patient is labelled as CKDu after excluding all the known causes of CKD. There are some common clinical characteristics that define CKDu and differentiate it from some of the known causes of CKD. Across locations reported globally, the disease is seen in young and middle-aged adults, mostly males who are engaged in strenuous work for their livelihood, like agriculture and manual labor. The patients have minimal or no proteinuria. CKDu patients typically are nondiabetic and have either normal blood pressure or are only mildly hypertensive. The disease is progressive leading to stage 5 CKD needing renal replacement therapy over a span of several months. Kidney biopsy, performed in few patients, has revealed varying degrees of tubular atrophy and interstitial fibrosis with inflammatory cells.
69
Environmental factors of chronic kidney disease of unknown origin
heat stress, heavy metal exposure via potable water sources, exposure to pesticides via agricultural farming practices, physically stressful working environments and low altitude.
70
Blood pressure is controlled in part by the renin-angiotensin-system.
How does renin convert angiotensinogen to angiotensin I
Renin cleaves the N-terminal of angiotensinogen
71
What cells are stimulated to release renin
Beta adrenergic receptors on the JGC
72
The ureter is a continuation of the renal pelvis.
Which type of cell lines the ureter?
Transitional epithelium
73
Filtration is a key process in the production of urine.
Which of the following is not found in the glomerular filtrate of a healthy individual?
Albumin
74
Blood pressure is controlled in part by the renin-angiotensin-system.
Angiotensin I is converted by renin from which of the following?
Angiotensinogen
75
A 63-year-old patient presents with an acute kidney injury.
Which of the following would not cause pre-renal acute kidney injury?
A.
Benign prostatic hypertrophy
B.
Cellulitis
C.
Decompensated heart failure
D.
Decompensated liver failure
E.
Diarrhoea and vomiting
Benign prostatic hypertrophy
76
Urine production is a key function of the kidney.
How does urine pass through the ureter
Urine passes through the ureter by peristalsis
77
The kidneys play a key role in fluid balance.
Which of the following best describes the anatomical location of the kidneys?
Retroperitoneal space
78
If the renal clearance of a substance X is 250ml/min.
Which best describes its method of clearance?
It must be secreted by the nephron
79
Renal clearance
the volume of plasma cleared of that molecule per minute
80
Clearance of molecule (mls/min) equation
Cx = (Ux X V)/Px
Ux = concentration of x in the urine
Px = concentration of x in the plasma
V = volume of urine formed per minute
81
Renal clearance of 125 mls/min
molecule that is filtered and passes unchanged into the urine e.g. inulin has a renal clearance of ~125 mls/min
82
Renal clearance of <125 mls/min
molecule that is filtered and reabsorbed will have a lower renal clearance e.g. urea ~ 80 mls/min
83
Renal clearance >125 mls/min
A molecule that is filtered and actively secreted will have a higher renal clearance e.g Para-amino hippuric acid (PAH) ~ 650-700 mls/min
84
Function of aldosterone
Acts on the distal collecting duct to cause an increase in the uptake of sodium.
• This increase in sodium causes an increase in the blood pressure
• Aldosterone has a diurnal pattern of release that mirrors that of cortisol
85
To function the kidney requires an adequate blood supply.
How much of the cardiac output passes through the kidneys?
20%
86
A 25-year-old patient awaiting a renal transplant is found to be anaemic.
Which of the following best describes the mechanism of anaemia in chronic renal failure?
Reduced production of erythropoietin
87
A 78-year-old women presents with shortness of breath. On examination you find she has signs of heart failure.
Which of the following is true concerning Atrial Naturetic Peptides (ANPs)
They act on the renal collecting tubules to promote Na+ excretion.
88
Release of ANP
released by the atrial myocytes in response to atrial stretch due to elevated atrial pressure and blood volume e.g cardiac failure
89
What does ANP cause
An increased glomerular filtration rate
Increased sodium excretion
Inhibition of release of vasoconstrictors e.g. angiotensin II, aldosterone and endothelin
A decrease in blood pressure
90
Regarding the anatomy of the kidney.
What name is given to the outermost layer of the kidney?
Capsule
91
Example of substance that is filtered only
Inulin
92
Example of substance that is filtered and secreted
Penicillin
Creatinine
93
Example of substance that is filtered and reabsorbed
Glucose
94
Example of substance that is filtered, reabsorbed and secreted
Potassium
95
What percentage of cardiac output is filtered through the kidneys
20%
