renal physiology Flashcards
function of kidney
maintain balance of salt and water
excrete waste
endocrine function
renal and urine flow
renal is 1L per min
urine is 1ml per min
renal blood supply
Left and right renal artery
what are podocytes
they help to filter out harmful substances
where does glomerular filtration happen
distal part of nephron
fenestration capillary enodthelium
first barrier
3 components of barrier
fenestration capillary endothelium
gbm
podocytes
what determines filtration barrier
Pressure Size of the molecule Charge of the molecule Rate of blood flow Binding to plasma proteins
what is nephroticsyndrome
damage to filtration barrier can lead to protein leak
caused by immune conditions genetic abnormalities
define gfr
is the filtration volume per unit time (minutes) from the glomerulus to the bowman’s space
autoregulation with regards increasing to pressure
Pressure within afferent arteriole rises stretches vessel wall triggers contraction of smooth muscle arteriolar constriction
role of macula densa cells
detect nacl arrival
release prostaglandins in response to nacl delivery
acts on granular cells triggering renin release activiating RAAS system
how to work out filtration fraction
Filtration fraction = GFR / renal plasma flow
what is renal clearance
The volume of plasma from which a substance is completely removed by the kidney per unit time (usually a minute)
what is gfr determined by
hydrostatic and oncotic pressure, surface area and permeability
what is needed for lower urinary tract function
urine storage
urine emptying
average plasma flow daily through nephrons
180L PERD DAY
histology of tubules
single epithelial layer
function of proximal tubule and location
in renal cortex
bulk reabsorption: na water and ions 90% bicarobinate glucose and amino acids
Has microvilli
how is glucose reabsorbed in PCT
sodium glucose transporter 2
sodium potassuim pump to make a conc grad
function of loop of henle
Ascending : na,k, and cl reabsorbed
Water impermeable
Thick
Descending : h20 reabsorption , water permeable
Thin
function of distal tubule
fine regulation of na k ca pi , seperation of na from H20
Has macula sense which detects na concentration
hc03- reabsorption process
bicarbonate reacts with h+ forming carbonic acid in lumen
carbonic acid is split by carbonic anhydrase to water and co2
Water and co3 dissociate into hco3- and h+ in cell
Hco3- enters the blood and h+ is recycled
function of collecting ducts
important for water reabsorption
principal cells- for salt and water absrob
and potassium removal
Intercalated cells for reabsorbing HCO3- and secreting H+
kidney function with regards to acid and base
regulate acid base balance in the body by regulating h
+ altering plasma
what do the kidneys do in response to acidosis
kindeys decrease excretion of HC03-
produce new hc03- which is added to plasma
Define an acid and base
Acid accept hydrogen ions
Base donates hydrogen ions
Bicarbonate buffer equation
Co2 + h20 ~> h2co3
H2co3~> h+ + hc03-
urinary phosphate buffer system
H+ from dihydrogen phosphate (h2po4-) ions are actively transported into lumen via hydrogen atp-ase
Excess luminal phosphate can bind to a large portion of hydrogen ions , buffering them as h2po4- before excretion
Excretion increases blood ph
urinary ammonia buffer system
Glutamine is converted to glutamate and ammonium in pct
Ammonium dissociates allowing it to pass through the lumen
Once in lumen it reforms ammonium
Excreted to increase blood ph
summary of respiratory acidosis
Low ph
Low hc03-
high pco2
summary of metabolic acidosis and alkalosis
acid- low ph, low hc03- low pc02
alka- opposite
EPO function
stimulates bone marrow which promotes RBC maturation
inhibits apoptosis
How to measure gfr
Use of a marker substance
Clinically we can use creatinine- free filtered , not metabolised , not secreted
Factors affecting gfr
Hydrostatic pressure out of capillary Hydrostatic pressure out of bc Oncotic pressure in capillary Surface area Capillary permeability
Equation to work out gfr
GFR= NFP x kf
How do the kidneys control water and blood pressure
Regulation of osmolality
RAAS system
ANP
Action of adh
Produced in hypothalamus Binds to avpr2 receptors Activates a G protein inside the cell ATP-> cAMP causes more aquaporin 2 to be released More aqp2 to embed into the cells More water into the blood
How does raas system affect BP
Juxtoglomerular cells detect drop in bp and release renin
Causes angiotensinogen to be converted to ANG1
Ang1->ang2 by ace in lungs
Importance of angiotensin 2
Increase release of adh causes more aquaporins to reabsorb more water
Adh acts on smooth muscle cells to constrict which increase the peripheral resistance
Which segment of the nephron does adh act on
Principal cells in the collecting duct
When is anp released
When the atrial wall stretch is too high
Actions of anp
Blocks sodium channels in collecting duct
Inhibits aldosterone release via renin inhibition
Vasodilation of afferent arteriolar
Function of parathyroid hormone
Regulates serum calcium concentrations
Function of aldosterone
Ion balance
Sodium in
K out
What hormones do the adrenal glands release
Aldosterone Cortisol Corticosterone DHEA Androstenedione
Precursor to all corticosteroids ?
Cholesterol
How is the cortex of adrenal gland separated
Zona glomerulosa
Zona fasiciculate
Zona reticularis
Will problems with pituitary gland and hypothalamus affect aldosterone
No
Role of Zona glomerulosa -mineral corticoids
Main one released is aldosterone
What does Zona fasciculata do
Important effects on glucose metabolism and secretes cortisol in response to stress
Normal functions of cortisol
Maintain normal bp Maintain blood glucose Inhibit inflammation Control cell damage Decrease capillary permeability
Basic stress function of cortisol
Increases organic metabolism and uses their energy to increase plasma cons
Where is epo produced
Peritubular cells of right cortical interstitium
where are m3 muscarinic and b3 receptors located
on detrusor muscle
where are nicotinic receptors located
external sphincter
where are alpha 1 receptors located
internal sphincter
too much or too little epo what can happen
too much- viscous blood
too little anaemia
