L2: Glomerular structure and function Flashcards
hilum of the kidney=
where blood vessels come in and ureter comes out
2 main parts of the kidney
cortex and medulla
what is in the medulla
renal pyramids
how many renal pyramids
8-18
where do the renal pyramids drain into
major calyxes
where are the renal pyramids found
border between medulla and cortex
what arteries supply the kidneys
renal arteries
renal arteries branch into
inter-lobar arteries
inter-lobar arteries branch into
arcuate arteries
arcuate arteries branch into
interlobular arteries
what do interlobular arteries form
afferent arterioles
what do afferent arterioles branch into
glomerular capillaries
what do glomerular capillaries form
efferent arterioles
what blood supply does each nephron receive
one afferent arteriole
what do the efferent arteries in the cortex form
peritubular capillaries
what arteries may extend down from the efferent arteries
vasa recta
what do vasa recta supply
tubular portions of the nephron in the renal medulla
which part of the kidney has the best blood supply
the cortex
what does a nephron consist of
renal corpuscle and tubules
what does the renal corpuscle consist of
glomerulus surrounded by bowman’s capsule
what is the glomerulus
a tuft of capillaries
6 parts of the kidney tubule
- proximal kidney tubule
- thin descending loop
- thin ascending loop
- thick ascending loop
- distal convoluted tubule
- collecting tubule
histology of the proximal kidney tubule=
- cuboidal cells and microvilli + lots of mitochondria
- basolateral membrane has tight junctions
where is urine formed
renal pelvis
2 types of nephrons
- cortical/ superficial nephron
2. juxta-medullary nephron
where are cortical/ superficial nephrons found
mainly in the cortex (very short loop of henle)
percentage of juxta-medullary nephrons
15%
what do cortical nephrons receive a blood supply from
peritubular capillaries
what do juxtamedullar nephrons receive a blood supply from
vasa recta
histology of thin descending and ascending loops
simple squamous
histology of thick ascending loop
simple cuboidal to low columnar
histology of DCT
- simply cuboidal
- and later on get principal and intercalated cells
what do principal cells have receptors for
ADH and aldosterone
what do intercalated cells do
homeostasis of blood pH
what is the first step in the urine production
glomerular filtration
what happens in glomerular filtration
water and most solutes in blood plasma move across from the capillaries into the glomerular capsule and into the renal tubule
what are glomerular capillaries impermeable to
proteins
what type of capillaries are the glomerular ones
fenestrated
3 things the capillaries are made up off
endothelium
basement membrane
podocytes
what is the charge of the basement membrane
negative charge
what is the juxtaglomerular apparatus comprised of (3)
- granular cells
- Macula densa
- extraglomerular mesangial cells
where are the granular cells in the JGA
in afferent arterioles walls
what are the granular cells
- modified smooth muscle cells that contain renin
- innervated by sympathetic NS
where are the macula densa found in the JGA
where the DCT comes into contact with afferent and efferent arterioles
what is the role of the JGA
to synthesise and store renin
3 things glomerular filtration is based on
surface area
membrane permeability
net filtration pressure
what is the glomerular capillary pressure
pressure of blood entering the afferent arteriole drives fluid across filtration barrier
what opposes the glomerular capillary pressure
fluid in Bowman’s space (hydrostatic pressure)
what other pressure is caused by the Bowman’s space
weak osmotic pressure
what does Bowman’s space weak osmotic pressure cause
forces fluid out from blood
what exerts the plasma oncotic pressure
plasma proteins
how much urine production a day in normal
1-2 litres
Kf=
ultrafiltration coefficient
Puf=
net filtration pressure
what is Kf a product of
permeability of membrane and surface area
the filtration of a solute depends on 3 things
- molecular size
- electrical charge
- shape of the molecule
how come albumin cannot cross
negatively charged so basement membrane repels it
renal blood flow= (equation)
renal artery pressure - renal vein pressure
/ total renal vascular resistance
which arteries offer maximum resistance
efferent arterioles
why do efferent arterioles offer maximum resistance
they are much smaller in comparison to afferent
what is different about capillaries in the kidney vs rest of the body
main high pressure all the way through the capillary
what is autoregulation between
80-180mmHg
afferent arteriolar dilation affect on GFR=
increases GFR
efferent arteriolar dilation effect on GFR=
decreases GFR
afferent arteriolar constriction affect on GFR=
fall in GFR (and hydrostatic pressure)
efferent arteriolar constriction on GFR=
increase GFR
what is the effect on the afferent arterioles with Ang 2, Noradrenaline, Endothelin and ADH
vasoconstriction–> decrease in GFR
2 mechanisms involved in autoregulation
myogenic mechanism
tubuloglomerular feedback
myogenic mechanism for high BP =
- increase Bp
- stretch of afferent arterioles
- increased GFR and NFP (net filtration pressure)
- triggers smooth muscle arteriolar vasoconstriction
- decrease glomerular Bp
- decrease NFP
- decreased filtration
in shock/ haemorrhage what happens with myogenic mechanism
sympathetic vasoconstriction of afferent arterioles decrease GFR
tubuloglomerular feedback uses which cells
macular densa in JGA
what is tubuloglomerular feedback when GFR is increased
- increased GFR
- increases tubular fluid flow
- increases NaCL reabsorbed in macula densa
- causes vasoconstriction substance (possibly adenosine) released onto JGA
- vasoconstriction of afferent arteriole
what do macula densa act as a sensor of
sodium
where is renin released from
JGA
when is renin released from JGA
decreased blood pressure
what cells release renin
granular cells
what does renin do
converts angiotensinogen into angiotensin 1
what happens to angiotensin 1
is converted to angiotensin 2 in the lungs by ACE
what is angiotensin 2 affect on systemic arteries
vasoconstriction increasing Blood pressure
what is Ang 2 affect on adrenal cortex
releases aldosterone
what affect does aldosterone have on the kidneys
-increases reabsorption of sodium and water by the kidneys (more concentrated urine)
what does aldosterone stimulate the release off from the pituitary gland
ADH
what does ADH do
stimulates pituitary gland to secrete ADH
affect of increased sympathetic activity on GFR=
decrease GFR
affect of angiotensin 2 on GFR
decrease GFR
affect of atrial natriuretic peptide on GFR
increase
name 2 invasive techniques for measuring GFR
- inulin or isothalamate clearance
2. chromium labelled EDTA
4 problems with using serum creatinine for GFR
- actively secreted by tubules
- insensitive as marker for early kidney disease
- affected by muscle mass
- affected by certain drugs
MDRD=
modification of diet in renal disease
what does MDRD use to estimate eGFR
serum creatinine, age, sex, ethnicity