Renal Flashcards
1
Q
what surrounds the kidneys
A
- layers after the kidney are:
- renal capsule
- perirenal fat
- renal fascia
- pararenal fat
2
Q
the left kidney is slightly lower down than the right
T/F
A
False
the right is lower down due to being pushed by the kidney
3
Q
what vertebral levels are the kidneys found at
A
T12 - L3
they are ~ 3 vertebrae in length
4
Q
describe adrenal gland vasculature
A
- arteries x3
- superior artery = branch of the inferior phrenic artery
- middle artery = branch of the abdominal aorta
- inferior artery = branch of the renal artery
- one vein drains the gland = the adrenal vein
- the right adrenal vein drains directly into the IVC as its is in close proximity
- the left adrenal vein drains into the left renal vein first
5
Q
describe the anatomy of the adrenal glands
A
- capsule
- cortex
- zona Glomerulosa
- mineraolcorticoids synthesis
- Zona Fascicularis
- Glucocorticoids synthesis
- Zona Reticularis
- androgens synthesis
- zona Glomerulosa
- medulla
- catecholamine synthesis
6
Q
what doe the renal hilum contain
A
- renal vein
- renal artery
- lymphatics
- nerves
- ureters
7
Q
describe the renal vasculature
A
- right and left renal arteries from the abdominal aorta
- right and left renal veins that drain directly into the IVC
- the right vein is shorter than the left
8
Q
where do the right and left gonadal veins drain into
A
right drains directly into IVC
left drains into left renal vein first
9
Q
Describe the anatomy of the internal kidney
A
- cortex around the outside
- medulla in the middle
- arranged into pyramids
- calyces
- minor calyces → major calyces → renal pelvis → ureter
10
Q
what is a nephron
A
a functional unit of the kidney
11
Q
how is the nephron arranged within the kidney - where do the separate structure lie
A
- the glomerulus, Bowman’s capsule, proximal and distal tubules and part of the collecting duct are in the cortex
- the loop of henle and the rest of the collecting duct are in the renal pyramids
12
Q
what is the renal papilla and what is its function
A
the apex of the medulla
it is the opening into a minor calyx for outflow of urine
13
Q
explain the pathway of the ureter
A
it passes from the kidney to the bladder and travels behind the numerous arteries including the uterine and ovarian arteries.
“water under the bridge”
14
Q
urine is transported in the ureters by peristalsis
T/F
A
True
they have muscular walls
15
Q
describe the passage of blood in the kidneys starting from the abdominal aorta
A
Abdominal aorta → renal artery → segmental arteries → interlobular arteries → arcuate arteries → afferent arteriole → Glomerulus → efferent arteriole → peritubular capillaries → interlobular veins → Arcuate vein → interlobular vein → renal vein → IVC
16
Q
What are the functions of the kidney
A
A WET BED
- Acid/base balance
- Water removal
- Erythropoietin
- Toxins
- Blood Pressure
- Electrolyte
- D - vitamin D activation
17
Q
how much of the cardiac output goes to the kidneys
A
20%
18
Q
what is glomerular filtration rate
A
The volume of fluid filtered through the from the glomerulus to the bowman’s space
Glomerulus = the collection of capillaries carrying blood to filtered
bowman’s capsule = the space into which filtrate is captured
19
Q
what makes up the filtration barrier
A
- fenestrated endothelium
- basement membrane
- podocytes
20
Q
GFR value
A
125ml/min in an average 70kg person
21
Q
equation for GFR calculation
A
GFR = KF (PGC-PBS-πGC)
- KF – filtration coeffiecnt
- PGC – hydrostatic pressure of glomerular capillaries
- PBS – Hydrostatic pressure of bowman’s space
- πGC – Oncotic pressure of glomerular capillaries
22
Q
why is there no oncotic pressure of the Bowmas capsule
A
there are no proteins in bowmans space
23
Q
why is creatinine used as a marker substance
A
- it’s freely filtered
- not secreted or reabsorbed
- not metabolised
24
Q
what factors affect GFR
A
- Pressure
- Size of the molecule
- Charge of the molecule
- Blood flow
- Binding to plasma proteins
25
describe the physiology of glomerular filtration and urine production
1. the glomerular capillaries are fenestrated, meaning they have gaps to allow molecules in the blood to be filtered out, everything except RBCs.
* the endothelial cells have glycocaelyx - proteins - which are -vely charged to repel the passage of proteins [also -vely charged] through.
2. the afferent arteriole dilates while the efferent one constricts which raises the hydrostatic pressure exerted on the blood in the glomerulus → ultrafiltration.
3. the filtrate passes into Bowman’s capsule and is basically protein free plasma.
4. as the filtrate moves through the tubules, certain substances are **reabsorbed** either by diffusion or by mediated transport[ATP]
5. whats left enters the collecting duct into the calyces to form the urine
26
how is GFR controlled
* To increase GFR;
* Constrict the efferent arteriole (build up pressure before)•Dilate the afferent arteriole (builds up pressure after)
* To decrease GFR;
* Constrict the afferent arteriole (reduce blow flow)•Dilate the efferent arteriole (allows blood to escape easier)
27
what is the glomerular filter layers made of
1. fenestrated endothelial cells
2. basement membrane
* made from fusion of capillary and podocyte basement membrane.
3. podocytes
28
what is the glomerular filter layers made of
1. fenestrated endothelial cells
2. basement membrane
* made from fusion of capillary and podocyte basement membrane.
3. podocytes
29
what is autoregulation in the kidneys and why is it important
**Pressure within afferent arteriole rises → stretches vessel wall → triggers contraction of smooth muscle → arteriolar constriction**
* important because it prevents a rise in systemic arterial pressure reaching the capillaries in the nephron THUS it prevents damage and maintains constant level of filtration
* revers happens in low pressure to maintain a constant rate of filtration
30
what are the mechanisms of autoregulation within the glomerulus
* **Myogenic**; smooth muscle contraction in response to external stretching force, occurs in capillary walls, passive mechanism
* **Tubuloglomerular feedback**;
* constriction of afferent arteriole to increased sodium chloride concentration.
* Dilation in response to decreased concentration.
* Fast response via GFR and slow via RAAS
31
explain tubuloglomerular feedback
1. GFR of individual nephron regulated by the rate at which filtered fluid reaches the distal tubule
2. Cells of **macula densa** (distal tubule) detect NaCl arrival
3. Macular densa cells release **prostaglandins** in response to reduced NaCl delivery.
4. This acts on **granular** cells, triggering **renin** release, activating the **renin-angiotensin system**
32
protein is never found in the urine
T/F
False
* The only protein that is normally found in urine is Tamm– Horsfall protein (uromodulin) which is produced by the thick ascending limb
* otherwise other proteins shouldnt be present in the urine and indicate leaky nephrons
33
what is the filtration fraction
* **Filtration Fraction = GFR / Renal Plasma Flow**
* i.e. the proportion that gets filtered.
34
what is renal clearance
renal clearance is the volume of plasma completely cleared of a substance by the kidneys per unit time.
35
main function of the proximal tubule
* **bulk reabsorption of essentials:**
* Na+
* Cl-
* water
* glucose
* bicarbonate
* amino acids
* phosphate
* lactate
* **⅔ of all filtrate reabsorbed here**
36
how is sodium transported in the PCT
1. the Na/K ATPase transporter transports 3Na+ into the blood and 2K+ into the PCT cell.
2. this lowers sodium the conc. within the cell and encourages Na movement from the PCT to the cell via
* exchange for H+ or cotransport with glucose
* The Na/K ATPase is energy dependent; the cell uses a lot of energy and needs a good vascular supply
37
HOW IS WATER REABSORBED IN THE PCT
* via Aquaporin 1 channels on the apical and basolateral membranes
* movement of water down the osmotic gradient
* tight junctions are leaky to water so ~ 2-% moves paracellularly
38
how is glucose reabsorbed in the PCT
* via SGLT1 and SGLT2 transporters
* these a co transporters that carry Na+ and glucose into the cell
* SGLT1= 2Na+ and 1glucose
* SGLT2=1Na+ and 1glucose
* glucose reenters the blood passively via GLUT channels
39
how is Cl- transported in the PCT
•Moves paracellularly•
Exchanged for a base on the apical membrane
40
main function of the loop of Henle
* Descending limb = H20 reabsorption
* ascending limb = Na, Cl and K reabsorption
41
function of the distal convoluted tubule
* “fine tuning” of sodium reabsorption, potassium and acid-base balance
* impermeable to water
* Macula densa located in juxtaglomerular apparatus which is in the DCT-
* detects [Na+] and can activate RAAS.
42
function os the collecting duct
* Collecting duct mediates water reabsorption and maintains acid base homeostasis
* Principal cells - Na and water reabsorption and K excretion
* site of ADH action
* Intercalated cells (alfa and beta) – secrete H or HCO3
* •Essential for acid base homeostasis
43
what is the normal pH range for blood
* 7.35-7.45
* Acidosis: pH\<7.35
* Alkalosis: pH\>7.45
44
where is the juxtaglomerular apparatus located
and what is it composed of
located in the distal convoluted tubule next to the glomerulus
* macula densa cells
* granular cells
* afferent arteriole
* distal convoluted tubule
45
what are urinary buffers
types of urinary buffers
1. phosphate urinary buffer
2. ammonium urinary buffer
* bicarbonate buffering is incorporated into these 2
46
describe phosphate buffering
* H20 +CO2 → H2CO3 → H+ +HCO3- [in the tubular epithelial cells]
* H+ generated from the dissociation of H2CO3 from within the tubular epithelial cells, combines with HPO42- in the tubule, to form H2PO4- which is then excreted in urine.
* H2CO3 is reabsoorbed into the plama → alkaline blood
47
describe ammonium buffering
1. Cells take up glutamine from both the glomerular filtrate & peritubular plasma and metabolise it to form NH3 (ammonia) & HCO3- (bicarbonate)
2. The NH3 then reacts with the H+ in the cell to form NH4+ (ammonium ion)
3. The NH4+ is then actively secreted via Na+/NH4+ counter transport into the lumen and excreted, while the HCO3- moves into blood plasma and thereby increases HCO3- levels and alkalinity
48
where are juxtaglomerular cells located
in the walls of the afferent arteriole
49
what is RAAS
The Renin-Angiotensin-Aldosterone System (RAAS) is a hormone system within the body that is essential for the regulation of blood pressure and fluid balance
50
what stimulates the RAAS
* decreased blood pressure
* detected by little or no arteriolar stretch (from low blood volume due to low Na+ and thus H2O).
* decreased NaCl detected in the macula densa cells
* sympathetic innervation
when any of these happens, then renin is released by the juxtaglomerular cells in the afferent arterioles
51
what is renin and what does it do
an enzyme
cleaves angiotensinogen → angiotensin1
52
where is angiotensinogen produced
the liver
53
where is ACE produced
in the pulmonary and renal endothelium
54
what are the effects of angiotensin 2
1. **stimulates the adrenal gland → aldosterone secretion**
* increases reabsotption of salt and water
* increases K+ excretion
2. **stimulates the posterior pituitary gland → ADH secretion →** more conc. urine
3. **stimulates vasoconstriction of systemic arteries and arterioles**
4. **stimulates thirst in the hypothalamus**
5. **increases total peripheral resistance thus raises BP**
6. **stimulates sympathetic nervous system** to increase release of noradrenaline
* Increase in cardiac output.
* Vasoconstriction of arterioles.
* Release of renin.
55
where is ADH produced
hypothalamus
56
which cells does ADH take effect in
principal cells of the collecting duct
57
what effect does ADH have
1. it binds to the V2R receptors of the principal cells →
2. upregulation of aquaporin channels in the collecting tubule walls →
3. increased H2O reabsorption and less urine produced
58
where is erythropoietin produced
what is its function
in the kidneys
increases production of RBCs in the bone marrow
59
what hormones are produced in the adrenal glands
1. Aldosterone
2. cortisol
3. corticosterone
4. DHEA
5. androstenedione
1= glomerulosa
2+3=fasciculata
4+5 = reticularis
60
what is the role of the adrenal medulla
* part of the autonomic nervous system
* production of catecholamines
* adrenaline 80% and noradrenaline20%
* main site for adrenaline synthesis
* production of catecholamines is dependent on cortisol levels [permissive effect]
61
what is the effect of catecholamine release
1. lipolysis in adipocytes
2. gluconeogenesis in liver and muscles
3. tachycardia and increased cardiac contractility
4. redistribution of circulatory volume
62
where are corticosteroids produced
in the adrenal cortex
63
how do corticosteroids work
* they are lipid soluble so can pass through the lipid membrane and:
* act on intracellular receptors
* alter gene transcription directly or indirectly
64
what are steroids and steroid hormones made from
cholesterol
65
role of ACTH
ACTH stimulates the synthesis of corticosteroids and cortisol acutely
66
where are glucocorticoids produced
in the zona fasciculata and reticularis
(more-so in fascicularis)
67
glucocorticoids are essential to life
T/F
true
* glucocorticoids are essential to life
68
what stimulates the production of glucocorticoids
* hypothalamus releasing CRH - corticotropin releasing hormone
* CRH→ APG causing release of ACTH
* ACTH acts on the zona fasciculata in the adrenal cortex to produce cortisol
69
what are the effects of cortisol and glucocorticoids
* Increase glucose mobilisation
* Augment gluconeogenesis
* Amino acid generation
* Increased lipolysis Important during “stress”
* Maintenance of circulation
* Vascular tone
* Salt and water balance
* Immunomodulation
* Dampen immune response
70
how are glucocorticoids transported
* In the circulation glucocorticoids are mostly bound to proteins –
* 90% bound to Corticosteroid-Binding Globulin (CBG)
* 5% bound to albumin
* 5% “free”
71
what fraction of glucocorticoids in blood are bioavailable
the free glucocorticoids are bioavailable thus ~5%
when stressed level of binding reduces so there is more free cortisol as CBG is cleaved
72
how is cortisol production regulated
via negative feedback
73
cortisol has a diurnal rhythm - what does this mean
the the secretion follows a daily cycle
cortisol secretion is higher in the morning and early afternoon
74
what factors stimulate cortisol secretion
stress
diurnal / circadian rhythm
cytokines
75
what is calssified as stress
* “The sum of the bodies responses to adverse stimuli”
* Infection
* Trauma
* Haemorrhage
* Medical illness
* Psychological
* Exercise/exhaustion
76
how does the HPA axis change in acute illness
1. there is less negative feedback so more cortisol is produced
2. less CBG synthesised and more broken down → more free cortisol
77
what are mineralocorticoid -give example
where are they produced
aldosterone
produced in the zona glomerulosa
78
function of aldosterone
* critical for salt and water balance in the:
* kidneys
* pancreas
* colon
* salivary glands
* sweat glands
79
what triggers aldosterone secretion
renin from the juxtaglomerular cells
80
effects of aldosterone secretion
* salt balance in th kidneys, colon, pancreas, salivary glands and sweat glands.
* in the kidneys it acts on the distal convoluted tubule and collecting duct
* increases epithelial Na+ channels and Na/K ATPase expression
81
where are adrenal androgens produced
in the zona reticularis
82
what androgens are produced in the adrenal glands
* DHEA
* androstenadione
83
what is the most abundant adrenal steroid
DHEA
84
which androgen has 1/10th adrongenic activty as testosterone
androstenedione
85
what is a major source of androgens in women
androstenedione and DHEA
86
what stimulates production of DHEA anandrostenedione
ACTH [not ghrh]
87
effect of atrial natriuretic peptide
* acts on several tubular portions to increase sodium excretion and decrease blood volume
* acts as a renal vasodilator esp. on the afferent arteriole→ dilation of the afferent arteriole → increased GFR → more Na+ loss → more water loss and lower blood volume and BP
*
88
where is ANP produced
what stimulates its release
* produced in the atria, specifically the right atrium as it pumps the systemic venous return.
* secreted in response to a level of atrial stretch indicating high blood volume
