study notes for lecture seven: fluid and ion balance

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8 Mar 2011
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LECTURE SEVEN: FLUID AND ION BALANCE
\Æmovement of sodium can indirectly affect water movement
::kidneys ::aldosterone ::vasopressin ::atrial natriuretic peptide
Æfiltration Æenhances Na+ reabsorption Æincreases H2O reabsorption Ædecreases Na+
Æcontrol urine concentration Æfavours water retention Ædirect effect on H2O, acting at kidney level Ædecreases H2O
Æsodium affects osmolarity
((why is maintaining fluid balance important for normal cell function?))
*Æfluid balance is indirectly talking about ion balance
Æfluid balance must be maintained in the extracellular compartment because the movement of water into and the exit of water out of the cell can
have a direct effect cell size
Æion balance regulates fluid balance, maintaining homeostatic conditions
Æbody = ~55% water
Æintracellular fluid = 2/3
Æextracellular fluid (interstitial fluid 75% + plasma 25%) = 1/3
balance of daily water intake and excretion
intake + *metabolic production = output
food, drink 0.3 L/day urine = 1.5 L/day
(2.2 L/day) sweat, breath = 0.9 L/day
feces = 0.1 L/day
*Æmany pathways produce water as by-products
urine flows from nephrons of the renal cortex and medulla into the renal pelvis
Æflow of blood to the kidney occurs via the renal artery
Æat the kidneys, it first filters through the renal cortex
Æthen blood moves inward to the medulla
Æfrom the medulla, waste is filtered as urine
Æwhatever is not filtered goes back to the body/renal system via the vein
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SPOTLIGHT ON: NEPHRON
Structure
Mechanism
Function
Other
Considerations
- composed on an initial
filtering component ± the
renal corpuscle, + tubule± the
renal tubule
::renal corpuscle
- filters out large solutes from
the blood
- delivers water and small
solute to the renal tubule for
modification
composition
- JORPHUXOXV%RZPDV
capsule, and the renal
corpuscle is the beginning of
the nephron
::renal tubule
- renal tubule is specialized for
reabsorption and secretion
compositon
- proximal tubule
- loop of Henle
(descending, ascending
{thick and thin} loops of
Henle)
- distal convoluted tubule
regulated by the endocrine system hormones (antidiuretic
hormone, aldosterone, PTH)
first site of filtration is at the glomerulus ± a capillary tuft that
receives blood from an afferent artierole of the renal circulation
glomerular blood pressure provides the driving force for water
and solutes to be filtered out of the blood and into the space made
by the BowmDQ¶VFDSVXOH
only 1/5 of all plasma that passes through the kidney is filtered
WKURXJKWKHJORPHUXODUZDOOLQWRWKH%RZPDVFDSVXOH
remainder of blood passes into the narrower efferent arteriole,
moves into the vasa recta ± collecting capillaries intertwined with
convoluted tubules through the interstitial space where reabsorbed
substances will enter
from the vasa recta, blood combines with efferent venules from
other nephrons into the renal vein to rejoin the main blood stream
%RZPDVFDSVXOHJOomerular capsule) a sac that
surrounds/encloses the golmerulus, is composed of a visceral
inner layer formed by podocytes and a parietal outer layer
composed for simple squamous epithelium
fluids from blood that came from the glomerulus are filtered
through the visceral layer of podocytes, and the resulting
glomerular filtrate is processes along the nephrons to form urine
fluid moves to the renal tubule ± first enters the proximal tubule,
moves through the loop of Henle, then through the distal
convoluted tubule
follows the cortical collecting duct to the bladder for excretion
o basic structural
and functional
unit of the
kidney
o regulates
concentration of
water and
soluble
substances like
sodium salts
o filters the blood,
reabsorbs
ZKDW¶VQHHGHG
excretes rest as
urine
o eliminates
wastes from the
body
o regulates blood
volume and
pressure
o controls levels
of electrolytes
and metabolites
o regulates blood
pH
¾ normal kidney
contains 800,000
± 1.5 million
nephrons
¾ the renal tubule is
the portion of the
nephrons
containing the
tubular fluid
filtered through
the glomerulus
¾ after passing
through the renal
tubule, the filtrate
continues to the
collecting duct
system ± not part
of the nephron
¾ distal tubule and
collecting duct
have receptors for
vasopressin and
aldosterone
hormones
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Document Summary

direct effect on h2o, acting at kidney level. \movement of sodium can indirectly affect water movement. control urine concentration ((why is maintaining fluid balance important for normal cell function?)) *fluid balance is indirectly talking about ion balance. fluid balance must be maintained in the extracellular compartment because the movement of water into and the exit of water out of the cell can have a direct effect cell size. ion balance regulates fluid balance, maintaining homeostatic conditions. extracellular fluid (interstitial fluid 75% + plasma 25%) = 1/3 balance of daily water intake and excretion intake food, drink (2. 2 l/day) *many pathways produce water as by-products urine flows from nephrons of the renal cortex and medulla into the renal pelvis. flow of blood to the kidney occurs via the renal artery. at the kidneys, it first filters through the renal cortex. from the medulla, waste is filtered as urine.

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