Normal kidney function

list the roles of the kidney

Removing metabolic waste from the extracellular fluid (urea and acids)

Controlling the volume of extracellular fluid (close link to blood pressure)

Maintaining optimal concentrations of vital solutes in the extracellular fluid (Na, K, H, Ca, Mg, Cl, Phos)

what are the body fluid compartments

interstitial

intracellular

intravascular

what are the two main compartments of water in the body

intracellular and extracellular; interstitial and intravascular

what has more water per weight; fat or muscle

muscle

do men or women have a higher water weifht

women and also older people

what is the barrier of intravascular fluid

endothelium lining

what is the barrier of interstitial fluid

cell wall

what is the movement of water across the cell wall between intracellular and interstitial compartment determined by

osmotic forces

what is the osmolarity of either side of the cell membranes determined by

energy dependant sodium potassium exchanger

what does the sodium potassium exchanger also contribute to

maintenance of electroneutrality

what is the distribution of fluid between the intravascular and interstitial spaces determined by

hydrostatic and osmotic forces

what is the hydrostatic force determined by

higher pressure inside blood vessels compared with the interstitial space

do forces change across the length of the tissue capillaries

yes

what is extracellular fluid composition and volume dependant on

salt intake

water intake

salt and water losses

what is the role of the nephron

it will pump identified and removes waste products

waste will leave

any nutrients will go back to the body

list the 3 basic processes of the nephron

glomerular filtration

tubular secretion

tubular reabsorption

what is glomerular filtration

filtering of blood into tubule forming the primitive urine (glomerular filtrate)

what is tubular reabsorption

selective absorption of substances form tubule to blood

what is tubular secretion

secretion of substances from blood to tubular fluid

what is the glomerular filtration barrier made up of

capillary endothelium

glomerular basement membrane

podocytes

how to calculate GFR

Normal GFR approx 100ml/min = 144L per day

what is absorbed at different regions of the nephron

PCT - water and electrolytes (glucose and amino acids)

Descending loop - sodium

Ascending loop - water

DCT - water and electrolytes

what are the 4 main transporters of the kidney

Na pTub

ENaC

NaKCl

SGLT2

what is the Na pTub

reabsorption fo sodium in the exchange of 2 potassium for every 3 sodium

this will produce energy which will help with the reabsorption of other molecules

what are the types of specific membrane channels

energy dependant

down a concentration gradient

down am electrical gradient

down an osmotic gradient

give examples of systemic and local mediators which can control the presence and activity of membrane channels

Ang II

ADH

aldosterone

PTH

what is osmotic diuresis caused by

elevated plasma glucose may saturate the glucose reabsorption channels

where is ENaC found

collecting duct

what mediated ENaC

aldosterone

what is the role of ENaC

key transporter for potassium homeostasis and will help with potassium retention

role of aldosterone

sodium reabsorption and potassium secretion

where is Na pTub located

PCT

where is NaKCl located

thick ascending LoH

where us SGLT2 located

DCT

what % of sodium is reabsorbed in PCT

70%

what is almost fully reabsorbed in PCT

glucose and amino acids

where is potassium and hydrogen ions secreted to maintain homeostasis

cortical collecting duct

where are sodium and chloride reabsorbed

proximal tubule

what quantity of waste is excreted everyday

600mosm

what is the main component of kidney waste

urea

what would happen if there was no system for concentrating urine relative to plasma

no way of dealing with water deprivation

what happens if there is no way for diluting urine relative to plasma

no way of dealing with water excess

what state is the medulla in due to the countercurrent exchange multiplier

hypertonic

what is the counter current exchange multiplier

as filtrate goes into the descending loop, water will be secreted, this makes the filtrate inside the tubules more concentrated

after the bend there is a change in the gradient difference and electrolytes will be secreted which will cause the tubules to be diluted - this maintains homeostasis

what is the mosm at the medullary LoH

600mosm

what level of mosm goes in and what will come out

30mosm in and 100 mosm out

what hormone is responsible for urine concentration

ADH

what is the role of ADH

ADH will open aquaporins, when there is more aquaporins then there will be increase water absorbed to more concentrated urine

what region of nephron is impermeable to water

thick ascending limb

role of thick ascending limb

Thick ascending limb is impermeable to water, but actively transports sodium, potassium and chloride

what does the thick ascending limb provide

the concentration gradient to promote water reabsorption from the thin DLH

what is the thin descending limb permeable to

salt and water

what is RAAS pathway

changes in bp → renin is produced → angiotensin I → angiotensin II (can cause direct vasoconstriction) → adrenal cortex will produce aldosterone → moves sodium in and potassium out

what happens when there is pressure changes in kidney

baroreceptors in the common carotid and aortic arch will detec stretch, they will send signals to the brain (NTS)

what does sympathetic reponse do in pressure changes - juxta glomerular apparatus

juxtaglomerular apparatus:

maintains glomerular filtration rate in face of increases or decreases in blood flow to the kidney

what happens when there is an increased tubular flow

sensed by macular densa - produced adenosine which will cause afferent arteriole constriction

what happens when there is reduced tubular flow

sensed by macular densa which will have granular cells to produce renin

where does Ang II act on

PCT for water and electrolyte secretion

where does renin and aldosterone have an effect on

both affect Ang II but aldosterone also impact DCT

where does ADH act on

collecting duct

what does efferent glomerular arteriole constriction preserve

waste excretion

what does avid tubular sodium and water reabsorption preserve

extracellular fluid volume

what are contrary mediators in renal function

anti natiuretic peptide

what is the role of ANP

promote sodium loss

what may cause release of ANP

increased sensed volume oppose effects on Ang II on kidney

• Oliguria (<0.5ml/kg body weight per hour) - normal physiological response

• Concentrated urine (ie high osmoles/kg urine)

• Low urine sodium concentration (<20mmol/L)

• High urine potassium secretion

what would hyperkalaemia cause release of

aldosterone which will act to loose potassium

why do we not want excess acids in our body

Denature enzyme, cells die, this is what acids can do

Acids are not meant to be inside of our cell

cause release of potassium

what does acids buffer with

HCO3- to produce water and carbon dioxide

what is the role of kidney acid excretion

it will reabsorb filtered bicarbonate

filters non - volatile acids eg sulphuric acid

proximal tubule synthesises ammonium

what are calciotropic hormones

PTH, hydroxylated vit D

effector tissues of calcium

bone kidney and intestine

what is the calcium homeostasis pathwya

Low calcium -> PTH -> PTH release -> calcium out of bones and tells kidney to hold onto some calcium too -> inc vitamin D which will absorb calcium -> calcium homeostasis  as more calcium is retained

what is the vitamin D pathwya

skin → liver → kidney as 1.25 (OH) vitD → metabolically active form

what is the hypoxia pathway mediated by kidneys

Hypoxia -> released EPO by kidney -> make red cells -> this would not work if we don’t have the ingredients

where is EPO released from

interstitial cells of the kidney