renal physiology Flashcards by Maryam Mahmood

function of kidney

maintain balance of salt and water
excrete waste
endocrine function

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renal and urine flow

renal is 1L per min

urine is 1ml per min

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renal blood supply

Left and right renal artery

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what are podocytes

they help to filter out harmful substances

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where does glomerular filtration happen

distal part of nephron

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fenestration capillary enodthelium

first barrier

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3 components of barrier

fenestration capillary endothelium
gbm
podocytes

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what determines filtration barrier

Pressure
Size of the molecule
Charge of the molecule
Rate of blood flow
Binding to plasma proteins

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what is nephroticsyndrome

damage to filtration barrier can lead to protein leak

caused by immune conditions genetic abnormalities

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define gfr

is the filtration volume per unit time (minutes) from the glomerulus to the bowman’s space

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autoregulation with regards increasing to pressure

Pressure within afferent arteriole rises  stretches vessel wall  triggers contraction of smooth muscle  arteriolar constriction

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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

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how to work out filtration fraction

Filtration fraction = GFR / renal plasma flow

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what is renal clearance

The volume of plasma from which a substance is completely removed by the kidney per unit time (usually a minute)

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what is gfr determined by

hydrostatic and oncotic pressure, surface area and permeability

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what is needed for lower urinary tract function

urine storage

urine emptying

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average plasma flow daily through nephrons

180L PERD DAY

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histology of tubules

single epithelial layer

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function of proximal tubule and location

in renal cortex
bulk reabsorption: na water and ions 90% bicarobinate glucose and amino acids
Has microvilli

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how is glucose reabsorbed in PCT

sodium glucose transporter 2

sodium potassuim pump to make a conc grad

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function of loop of henle

Ascending : na,k, and cl reabsorbed
Water impermeable
Thick

Descending : h20 reabsorption , water permeable
Thin

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function of distal tubule

fine regulation of na k ca pi , seperation of na from H20

Has macula sense which detects na concentration

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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

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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

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