Renal (SUGER) Flashcards
what is the kidney derived from
mesoderm
where is the kidney located
between t12 & l3
why is the right kidney lower than left
pushed down by liver
what does a renal corpuscle consists of
glomerulus
bowman’s capsule
PCT
DCT
does the medulla have renal corpuscles
no
are there glomeruli in the medulla
no
what is the renal pelvis
space that urine drains into
- continuous w collecting ducts proximally n ureteres distally
where do the tips of the medullary pyramids project into
renal pelvis
where does the renal artery come off the abdominal aorta
L1
what is the path from the abdominal aorta to afferent arterioles?
abdominal aorta –> renal artery –> segmental arteries –> arcuate arteries –> interloper arteries –> interlobular arteries –> afferent arterioles
what does a lobe consist of
a medullary pyramid and the overlying cortex
what is the diff btwn cortex and medulla
cortex: PCT/DCT & renal corpuscles
medulla: loop of Henle & collecting ducts
what is the function of the renal corpuscle
filter
what is the role of the PCT
for reabsorbing solutes (bulk reabsorption)
what is the role of the loop of henle
for concentrating urine (urinary dilution)
what is the role of the DCT
for rebabsorbing water and solutes (selective reabsorption)
what is the role of the collecting duct
for reabsorbing water and controlling acid, base and ion balance (like DCT)
what are the granular cells
endothelium of afferent arteriole is expanded to form a mass of granular cells; detect BP and secrete renin
what are macula densa cells
expansion of cells at juxtaglomerular apparatus: detects SODIUM levels
what does the juxtaglomerular apparatus consist of
afferent arteriole
DCT
what do the cells of the PCT have lots of and why
mitochondria; actively transport ions from glomerular filtrate (inc 2/3 of Na/K)
what is the loop of henle supplied by
rich vasa recta (straight capillaries)
where does the loop of henle travel
each loop dips down into medulla then returns to form the DCT and returns to same nephron it left
why is the loop of hell prone to ischaemia (temp loss of blood supply)
bc vasa recta are quite far from glomerulus so before blood has reached, it has already lost some oxygen
is the descending limb of the loop of henle permeable to water
yes
is the ascending limb of the loop of henle permeable to water
no
what is the ascending loop of henle permeable to
salt
what is the DCT involved in
regulating acid base balance
how does DCT acidify urine
by secreting H+ ions
what are the 2 cell types of the collecting duct
- principal cells
- intercalated cells
what do principal cells do
responds to aldosterone (exchanging Na+ for K+) n ADH (increases water reabsorption by insertion of aqua porin 2)
what can a mutation in aquaporin 2 gene cause
diabetes insipidus
what are intercalated cells responsible for
exchanging acid for base
what do alpha and beta intercalated sells secrete
alpha - acid
beta - bicarbonate
what kind of epithelium is the renal pelvis
urothelium (transitional epithelium)
what drains into the renal pelvis
collecting duct
what does the surface layer of urothelium consist of
umbrella cells that have tight junctions to prevent urine from getting btwn cells
what is the inner and outer layer of muscle in the ureters (n how is this diff to GI)
inner: longitudinal
outer: circular
opposite in GI
how is urine propelled along ureter
peristalsis
what are the 3 main functions of the kidneys
- endocrine function (hormone secretion)
- maintain balance of salt, water & pH
- excretion of waste products
what % of blood supply does each kidney receive
20%
what is the total renal blood flow
1L/min
what is total urine flow
1ml/min
each nephron has 2 capillary beds; where?
1 at the glomerulus
1 at the peritubular area
what are the 2 sets of capillaries in the kidneys and what are they connected by
glomerular capillaries
peritubular capillaries
connected by an efferent arteriole
what wraps around capillaries in kidney
podocytes
what is bowman’s space
fluid-filled space within bowman’s capsule (protein free fluid filters from glomerulus into here)
what is the filtration barrier in the bowman’s capsule
- single celled capillary endothelium
- basement membrane aka basal lamina
- single celled epithelial lining of bowman’s capsule
what are peritubular capillaries at the loop of Henle aka
vasa recta
what is the glomerulus
a cluster of capillaries (basic filtration unit)
what are the 2 types of nephrons (and respective %)?
15% - juxtamedullary
85% - cortical
briefly describe juxtamedullary nephrons
- LOH of nephrons plunge deep into medulla
- responsible for generating an osmotic gradient
briefly describe cortical nephrons
- renal corpuscles lie in outer cortex and LOH do not penetrate deep into medulla
- do not contribute to hypertonic medullary interstitium
what is the juxtaglomerular apparatus (JGA)
combinationn of macula densa & juxtaglomerular cells
what is the flow of the glomerular filtrate
glomerular capsule –> pct –> nephron loop –> dct –> collecting duct –> papillary duct –> minor calyx –> major calyx –> renal pelvis –> ureter –> urinary bladder –> urethra
from tubular lumen –> peritubular capillary
tubular reabsorption
peritubular capillary plasma –> tubular lumen
tubular secretion
what is measured GFR
conc of M in urine x urine flow rate/conc of M in plasma - creatinin
what is renal clearance
vol of plasma from which a substance is completely removed by the kidney
does the bowman’s capsule have oncotic pressure
no bc no proteins
what factors affect filtration rate
- size of molecule
- charge of the molecule (basement membrane is neg)
- rate of blood flow
- binding to plasma proteins
what impact does constricting afferent arterioles have on hydrostatic pressure in glomerular capillaries
decreases thus decreases GFR
how do you increase GFR
constrist efferent arterioles which increases hydrostatic pressure in glomerular capillaries
how can GFR be measured
by marking the excretion of a marker substance (M)
what must a marker substance be
- freely filtered
- not secreted/absorbed in tubules
- not metabolised
is the GFR a good measure of kidney function
if a disease = less nephrons, GFR will fall so good measure of kidney function but only 1 aspect. can still have other problems eg w secretion so no
what is often used to estimate GFR (used as M)
creatinine
if macula densa cells detect a reduction in NaCl, what do they release (tubuloglomerular feedback)
prostaglandins –> act on granular cells –> triggers renin release –> activation of RAAS
what is PCT responsible for
bulk reabsorption - leaky
what is DCT responsible for
fine tuning - impermeable
what is autoregulation?
incr blood flow in afferent arteriole –> wall stretch –> smooth muscle contracts –> arteriolar constriction
systemic circulation BP change doesn’t affect renal circulation
what can easily cross filtration barrier
small and positively charged molecules
what charge does the glomerular basement membrane have
negative
what is the diff btwn osmolarity and osmolality
conc of solute in LITRES vs KG
what are the 3 main things that happen in PCT
- basolateral Na/K pump establishes conditions for mass reabsorption
- glucose and phosphate absorbed with sodium - symporter
- sodium reabsorbed as H+ excreted - antiporter
what are the 4 steps of bicarb reabsorption in PCT
- H+ combines w/ bicarb –> carbonic acid (h2co3)
- converted to carbon dioxide/water by carbonic anhydrase
- carbon dioxide diffuses into cell –> carbonic acid reformed
- bicarb pumped into capillary through basolateral membrane
how many Na+ are actively transported out in exchange for how many K+ ions
3Na+ OUT for 2K+ IN
why is Na+ exchanged for K+
keeps intracellular conc of Na+ low compared to lumen so Na+ moved downhill out of lumen into tubular epithelial cells –> other substances eg glucose/phosphate also follow (Cotransported)
as Na+ moved into proximal tubule cells, what moves outing the lumen?
H+
what does Na+ reabsorption promote?
H+ secretion
what else are there cotransporters in PCT for
reabsorption of diff amino acids
what is the transport maximum
many oft he mediated-transport-reabsorptive systems have limit to amounts of material they can transfer per unit time bc binding sites become saturated when conc of transported substance incr to a certain level
does a greater GFT result in a higher or lower osmotic pressure and thus reabsorption?
increased both
what is the diff btwn descending and ascending limb of LOH
descending - water absorption
ascending - solute absorption
how does LOH generate a hyper osmotic interstitium
via countercurrent multiplication
where is there higher osmolarity (which limb)
down descending limb
what is the diff in osmolarity btwn top and bottom of LOH
top = low osmolarity bottom = high osmolarity
why is there a diff in osmolarity btwn LOH
creates conditions for selective reabsorption in collecting duct
what is countercurrent multiplication
opposing flows in 2 limbs
what is the NKCC2 pump
transports 1Na+, 1K+ + 2Cl- into ascending limb
are cotransporters present in lower ascending limb
no, reabsorption there occurs via simple diffusion
why don’t medullary capillaries cancel out the countercurrent system
vasa recta form hairpin loops that run parallel to LOH: minimise excessive loss
what does DCT do
continues urine dilution - reabsorption of Na, impermeable to water
what cotransporter does DCT have
NCC (Na Cl cotransporter) - helps reabsorption of both
what does the collecting duct do
similar to DCT, also acid secretion and regulation of water reabsorption (conc urine)
what is collecting duct surrounded by
hypertonic medullary intersititum set up by LOH
what do principle cells contain
ENaC (epithelial Na channel)
what does aldosterone mean in collecting duct
more ENaC channels –> incr Na reabsorption/K excretion
what does ADH do in collecting duct
V2 receptors –> aquaporins in apical membrane –> increased water permeability –> incr water reabsorption –> more concentratedurine
what do intercalated cells do
secrete acid
- ATPase pumps out H+ –> byproduct of bicarb production in renal cell
- ammonia diffuses into tubular fluid –> combines with H to form NH3
what is water distribution in ICF/ECF
ICF: 2/3
ECF: 1/3
what is water distribution in ECF?
75%: interstitial fluid
25%: plasma
what is the major cation in ECF
Na
what is the major cation in ICF
K
what is intracellular pH
7.0
what is extracellular pH
7.4
is pH lower in inside or outside of cells
inside
how do u calculate plasma osmolality
2(Na+K) + glucose + urea
how is fluid movement regulated
by controlling Na movement
how is tonicity (osmotic pressure gradient) regulated
by controlling water movement
where is ADH synthesised
hypothalamus (supraoptic nuclei)
where is ADH secreted from
posterior pituitary
what is the release of ADH controlled by
hypothalamic osmoreceptors
name 2 locations where baroreceptors are located
aortic arch
carotid sinus
what impact does an increased cardiovascular pressure have in ADH secretion
decreased ADH secretion
what is thirst stimulated by
increase in plasma osmolarity and by a decrease in ECF volume –> ADH secretion –> increased water reabsorption
where is Na reabsorbed in specific parts of the kidney and what %
60%: PCT
25%: LOH
10%: DCT
4%: collecting duc
does urinary excretion increase or decrease with an excess of Na in the body
increases
is Na actively reabsorbed or secreted
actively reabsorbed
if Na+ is low, what impact does this have in net glomerular filtration pressure (and why)
decreases
- bc of decreased arterial pressure
- reflexes acting on renal arterioles (vasoconstriction)
for long-term regulation of Na+ excretion: is control of Na+ reabsorption more important or control of GFR
control of Na+ reabsorption
which hormone has a major impact on determining rate of Na+ reabsorption
aldosterone
what releases renin
juxtaglomerular cells of kidney
where is angiotensinogen produced
liver
where is ACE produced
lungs
what does ACE do
converts angiotensin I to angiotensin II
what does renin do
cleaves angiotensinogen –> angiotensin I
what does angiotensin II do
stimulates cells of zona glomerulosa (adrenal cortex or adrenal glands) to secrete aldosterone
what is aldosterone
a vasoconstrictor (esp at efferent arteriole) which incr pressure –> increases GFR –> increases Na+ reabsorption in PCT –> stimulates ADH release
which cells does aldosterone act on
principal cells of collecting ducts
if u reabsorb more Na+, what will leak out more of
K+
which cells synthesis and secrete ANP
cells in the cardiac atria
what does ANP stand for
atrial natriuretic peptide
what does ANP do to glomerular arterioles
dilates –> increases GFR –> increases Na+ excretion
how does ANP inhibit Na+ reabsorption
blockis ENaC’s in collecting ducts
how does ANP impact ADH secretion
directly inhibits –> increases Na+ excretion
how does ANP secretion increase when there is excess Na+ in body
bc excess Na+ = excess water in vessels = increased blood volume = stretched atria = ANP secreted
what ion concentration is the resting membrane potentials of excitable tissues eg nerves/muscles directly related to
K+
does ANP stimulate or inhibit renin secretion
inhibits
what are the 2 main hormones that affect the renal system
PTH
ANP
how does PTH impact reabsorption of phosphate/Ca
- blocks phosphate reabsorption in PCT
- increases calcium reabsorption everywhere else
what does PTH stimulate
active form of vit d (calcitriol)
what does 25-hydroxyvitamin D hydrolysed to in the kidneys
1,25dihydroxyvitamin D (active)
where is 90% of filtered K+ reabsorbed
pct
what is the main cause of changes in K+ excretion
cortical collecting ducts can secrete K+
how does a high K+ diet result in enhanced K+ secretion?
plasma K+ conc increases –> enhanced basolateral uptake K+ via NaKATPase pump –> enhanced secretion
how does aldosterone affect K+ secretion
enhances
what is base excess
quantity of acid required to return plasma pH to normal
what is standard base excess
quantity of acid required to return ECF back to normal
what is the anion gap
diff btwn measured anions and cations ([Na+] + [K+] - [Cl-] + [HCO3-])
name 2 urinary buffers
urinary phosphate buffer
ammonia buffer
what is the purpose of hydrogen ion secretion
- to reabsorb bicarb
- to excrete daily acid load
what is the minimum urine pH
4.5
what Is the commonest urinary buffer
alkaline phosphate
what is the urinary ammonia buffer purpose
it’s an adaptive response to acid load
describe the phosphate buffer briefly
- most common
- impermeable to apical membrane
describe the ammonia buffer briefly
- adaptive response to acid load –> synthesised from glutamine
- ammonia diffuses into tubular fluid –> ammonium ions impermeable to apical membrane
- PCT –> reabsorbed in LOH –> intercalated disc in collecting duct
what can cause resp acidosis
hypoventilation
- -> hypercapnia (can’t get rid of CO2)
- -> eqm shifts right
- more H+
what is renal compensation for resp acidosis
- increased H+ secretion
- increased bicarb production
- increased ammonia secretion
what can cause resp alkalosis
hypoventilation
- -> hypocapnia
- -> elm shifts left
- less H+
what is renal compensation for resp alkalosis
- decreased H+ secretion
- increased bicarb secretion
what is metabolic acidosis caused by
excess acid production
or decreased bicarb concentration
what is resp compensation for metabolic acidosis
- low pH stimulates chemoreceptors
- increased ventilation –> decreased pCO2
what can cause metabolic alkalosis
vomiting = acid loss
what is resp compensation for metabolic alkalosis
- high pH stimulates chemoreceptors
- decreased ventilation –> increased pCO2
what is the diff in shape of R vs L adrenal gland
R = pyramidal L = semilunar
what 3 regions is the adrenal cortex divided into
zona Glomerulosa
zona Fasiculata
zona Reticularis
what is the adrenal gland divided into
adrenal cortex (–> 3) and adrenal medulla
what does the adrenal cortex secrete
zG - mineralocorticoids eg aldosterone
zF - glucocorticoids eg cortisol
zR - androgens eg testosterone
what does the adrenal medulla secrete
catecholamines eg adrenaline
what are the steroid hormones prod in adrenal glands derived from
cholesterol
what receptors do mineralocorticoids act on
only on mineralocorticoid receptors
what receptors do glucocorticoids act on
mineralocorticoid and glucocorticoid receptors
what receptors do androgens act on
only androgen receptors
what does zona glomerulosa secrete
mineralocorticoids
what does zona fasciculata secrete
glucocorticoids
what does zona reticularis secrete
sex hormones and small amounts of cortisol
what is an example of a mineralocorticoid
aldosterone
what is an example of a glucocorticoid
cortisol
what is an example of an androgen
testosterone
what is an example of a catecholamine
adrenaline
what is cortisol released in response to (2)
- stress
- low blood glucose levels
what does cortisol do
increases gluconeogenesis
increases fat/protein metabolism
what type of hormones are catecholamines released from adrenal medulla
peptide hormones
what is the function of adrenaline (3)
- gluconeogenesis
- lipolysis
- increased heart rate
what do alpha receptors in smooth muscle involve
vasoconstriction/dilation
what do the 3 beta receptors do
beta 1 - amylase secretion
beta 2 - bronchodilation
beta 3 - lipolysis in adipocytes
where do the superior, middle and inferior adrenal arteries come from
superior - inferior phrenic
middle - abdominal aorta
inferior - renal artery
where do the left L and R renal vein drain into
right - IVC
left - left renal vein
what is the nerve supply of adrenal glands
splanchnic nerves
all 3 zones of adrenal cortex produce steroids classed under the band of what
corticosteroids
which type of feedback is important for glucocorticoids and mineralocorticoids
neg
what is the precursor for all corticosteroids
cholesterol
list 3 features of corticosteroids
- lipid soluble (pass through bio membranes easily)
- bind to specific intracellular receptors
- alter gene expression
what is the role of mineralocorticoids
regulate body electrolytes
what is aldosterone important for (2)
maintaining salt balance and BP
will problems with hypothalamus or pituitary impact aldosterone secretion
no bc triggered by release of renin by juxtaglomerular cells of afferent arterioles of kidney
why is cortisol called a glucocorticoid
has important impact on metabolism of glucose
how is cortisol release stimulated
- stress is detected and transmitted neurally to hypothalamus
- stimulates secretion of CRH (corticotropin releasing hormone) from hypothalamus
- carried to anterior pituitary –> ACTH released
- ACTH circulates in blood and travels to adrenal cortex –> cortisol released
why is cortisol important in foetal and neonatal life
responsible for diff of numerous tissue and glands
what hormone is essential for surfactant production
cortisol!
what is the most abundant (yet weak) adrenal steroid
DHEA (dehydroepiadrosterone)
which NS is adrenal medulla part of
autonomic
what do alpha receptors have a high affinity for (adrenaline or noradrenaline)
noradrenaline
what do beta receptors have a high affinity for (adrenaline or noradrenaline)
adrenaline
is resp compensation for acidosis/alkalosis slow or fast
fast
is renal compensation for acidosis/alkalosis slow or fast
slow
what are the 3 layers of kidney tissue (outer to inner)
- renal fascia
- perirenal fat capsule
- fibrous capsule
