pathology5 - vascular and fluid balance Flashcards
the average animal has how much TBW?
60%
the more lean you are the more TBW % you have.
what are the roles of water in the body? (TBW)
TBW - stands for total body water.
- transport of metabolites
- background matrix
- basis for bp and volume
- electrolyte balance
- excretion
- maintain ICP.
what factors affect TBW %?
weight (body fat) - lean = more body water
higest at newborn
declines after birth
depends on nutrirional state, age, sex, breed
what is the ratio of ECF to ICF? what are the 3 parts to ECF?
icf - 40% ecf - 20% consists of - interstotial -5% plasma - 5% transcellular - variable as disease state may change it - CSF, BILE, JOINT FLUID, URINE, GI TRACT, PERICARDIAL, PLEURAL, PERITONEAL.
how is TBW regulated? give examples of both the inputs and the outputs?
input = output. renal control of salt is a big part of this and must be kept constant too.
inputs: drink, food, metabolic, HCO3 (acid-base)
outputs: urine, faeces, skin sweat lungs, lactation
the main factors controlled for fluid balance directly are?
drinking and urination
there are 5 ways to control water balance?
- control GFR
- renin-angiotensin
- ADH
- ANP
- thirst
How is urine normally formed?
glomerulus - afferent arteriole comes in and efferent out. PCT, LOH, DCT, collecting duct. water is reabsorbed in the PCT, LOH and collecting duct. secretion from the DCT AND collecting duct. filtration occurs in the glomerulus.
Controlling GFR? what effect does BP have?
if BP drops below a minimum level then it doesnt work. lowered ECF = lowered ECV. means lowered CO and BP and GFR, less NA and water will be excreted therefore brings BP back up and holds onto fluid so ECF is restored. ALSO, vascular resistance plays a part.
explain the renin angiotensin system? RAAS - renin angiotensin aldosterone system.
maintains blood volume. renin produced by juxta glomerular cells in the kidney afferent arteriole. lowered perfusion causes this. (macula densa senses amount of NA being absorbed and changes GFR depending. by constricting efferent etc)
renin converts angiotensinogen - angiotensin 1 then enzymes - angiotensin 2 which acts on the adrenal cortex which promotes ALDOSTERONE RELEASE from cortex and this enhances NA absorbtion therefore water reabsorbtion!!.
what is the role of ADH in controlling total body water?
it control primarily plasma osmolarity (solutes)
made in the hypothalamus. released when osmoreceptors are stimulated. - triggered when osmolarity is high - water low.
controls permeability in the DCT and collecting ducts. ADH released and allows NA back into the bloos stream and water follows by osmosis. (less urine volume)
another stimulus is decreased blood volume/pressure - ADH……….BARORECEPTORS in the left atrium detect BP. fire when its high. when it is low they dont fire and so ADH released. retain water to increase blood volume.
ANP stands for? what is its role?
atrial neuretic peptide. produced by the heart and released when the heart is stretched (high BP) they cause loss of NA in the collecting ducts. therefore loss of water. they also cause vasodilation.
thrist also plays a big role to increase water colume.
uptake driven by low ECV. and hig osmolarity. left atrial receptors.
electrolytes must also be balanced……main electrolytes? cell balance?
ECF - NA, CL, HCO3
ICF - K, MG, phosphate
inside cell = high K and low NA
outside cell = low K and high NA
what might cause abnormal plasma concentrations of electrolytes?
- low or high intake
- shifts to and from ICF
- high renal retention
- high loss eg. urine/sweat.
