Renal System Flashcards
Functions of Kidney
Remove waste
Regulate blood pH
Regulate blood pressure
Assists in formation of RBC
Steps in Urine Formation (3)
- Glomerular FILTRATION
- Tubular REABSORPTION
- Tubular SECRETION
….Water conservation (returns it to blood, minus the waste)
How much filtered per day?
48 Gallons!
What causes filtration in Glomerulus?
High glomerular blood pressure forces filtrate through capillary wall.
What stays in blood during filtration?
RBC & proteins
What are the filters in the renal corpuscle?
Podocytes
Large network of capillaries with large surface area?
Glomerulus
Incoming and outgoing arterioles -
Afferent arteriole
INCOMING, Large
Efferent arteriole
OUTGOING, small
Net filtration pressure
10mm Hg
Glomerular blood pressure moving into glomerulus (hint: it’s higher here)
60 mmHg
Blood osmotic pressure & glomerulus
- 32 mmHg
Capsular Hydrostatic pressure at glomerulus
-18mm Hg
Equation showing net pressure:
blood pressure moving fluid in = 60mmHg
Blood osmotic - 32mmHg
Capsular hydrostatic -18mmHg
Net =
60 - 32 - 18 = 10mmHg
Factors that impact filtration pressure
Kidney Disease
Blood Pressure Drops
Stress
Kidney Stones
Impact of kidney disease on filtration pressure
glomerulus highly permeable. Plasma proteins can get out
Impact of blood pressure drops on filtration pressure
hemorrhaging
Drop in filtration pressure
very low - anuria
Impact of stress on filtration pressure
Increased sympathetic stimulation
Increased constriction of afferent arteriole
Drop in filtrate + urine volume
Impact of kidney stones on filtration pressure
Ureter blocked ->
pressure backs in in nephron, capsule
Filtration drops. Can damage
Causes of kidney stones
Dehydration
pH imbalances
Frequent UTI
Enlarged prostate
Glomerular Filtration Rate too high….
Filtrate flows too rapidly for reabsorption
Therefore:
Dehydration and electrolyte depletion
GFR too low
Everything is reabsorbed, including waste
How is GFR controlled?
By adjusting glomerular blood pressure moment to moment
Mechanisms for GFR control
Intrinsic:
Renal autoregulation
Extrinsic:
Sympathetic control
Juxtaglomerular apparatus
How does intrinsic renal autoregulation work
Nephrons self-adjust to maintain stable GFR
GFR
Glomerular Filtration Rate
Myogenic mechanism (within intrinsic renal autoregulation) What happens when blood pressure rises?
the afferent arteriole and it constricts to prevent increased blood flow
Myogenic mechanism for intrinsic renal autoregulation- what happens when blood pressure falls?
Afferent arteriole relaxes to allow more blood in
Tubuloglomerular feedback in Macula dense cells
Monitor changes in flow of filtrate through nephron (via NaCl concentration)
Tubuloglomerular feedback when GFR is high/low
GFR is high - MACULA DENSE releases chemicals to cause vasoconstriction of afferent arteriole to slow GFR
GFR is low - vasoconstriors are inhibited
Limits of autoregulation
has narrow upper and lower bands - arterial pressure of 90-180 mmHg
What happens below 70 mmHg?
glomerular filtration and urine output cease
Extrinsic - Sympathetic Nervous System Acivation
Strenuous exercise or circulatory shock
Extrinsic- Sympathetic activation impact
Overrides autoregulatory mechanisms
Afferent arterioles constrict
Reduces GFR and urine output
Redirects blood to heart, brain, skeletal muscles
Extrinsic - Juxtaglomerular Apparatus
Afferent arteriole - sensitive to changes in blood pressure - secretes renin
Macula densa - monitors GFR through NaCl levels - stimulates RELEASE OF RENIN
Juxtaglomerular apparatus - response to LOW BLOOD PRESSURE AND LOW GFR
Release Renin - triggers increase in Blood pressure and GFR
Renin-Angiotensin Pathway
Renin ->
Angiotensinogen (plasma protein) - + Renin ->
Angiotensin I
Angiotensin I + An… Converting enzyme (ACE) ->
Angiotensin II
ACE
Angiotensin-Converting Enzyme (in lungs and kidneys)
Active hormone in pathways
Angiotensin II
Impacts of Angiotensin II
- Vasoconstriction
- Aldosterone secretion
- Antidiuretic Hormone secretion
- Increased thirst
…. Overall = INCREASED BLOOD PRESSURE
How many gallons filtered to excreted?
48 gallons filtered : 1/2 gallon excreted (99% filtrate reabsorbed)
Methods for reabsorption
Active transport, facilitated diffusion, diffusion, osmosis, solvent drag
What substances are reabsorbed?
Water Salts Urea Glucose Amino Acids Vitamins
Na+ reabsorption
ACTIVELY TRANSPORTED from proximal convoluted tubule, distal tuble, ascending limb
Water reabsorption
80% Osmosis, mostly in proximal tubule
Cl- reabsorption
Follows along electrical gradient
Urea reabsorption
Concentration rises as water leaves - solvent drag
50% returned by blood
Amino Acid reabsorption
Active transport from proximal tubules
Vitamins reabsorption
Active transport
Glucose reabsorption
Normally - active transport
(up to 220 mg/dL)
EXCESS excreted in urine
Glucose reabsorption limit?
Yes. 220 mg/dL
H20 reabsorption
Water will move towards SALT - Therefore tissues around nephron must be MORE SALTY
Salt Gradient created by
Vasa recta, loop of henle
Vasa Recta description, function (re: salt gradient)
Region of peritubular capillaries.
Recycles salt
Loop of Henle function (re: salt gradient)
Pumps salt out of nephron
Salt gradient in Cortex of kidne
300 mOsm
Salt gradient in Inner medulla of kidney
1200 mOsm
Salt concentration in limbs of loop of henle
Descending (Na+Cl = low) absorbs FROM tissues
Ascending (Na+Cl = high)
returns Solutes TO TISSUES
Hypertonic Urine
Concentrated Urine
Permeability to H20 in loop of Henle
Descending - freely permeable to H20
Ascending - NOT permeable (therefore Na+Cl- actively transported out)
Collecting tubule - freely permeable
Where is Na+Cl- most concentrated in kidney?
Inner Medulla 1200
Function of loop of henle
Water drawn out of collecting tubule and tissue is salty
Therefore allows water to be absorbed even though urine volume is low. Conserves water
What regulates the amount of water reabsorbed from the collecting tubule?
ADH - antidiuretic hormone
What secretes ADH (antidiuretic hormone)?
Posterior pituitary
Impact of ADH - when present….
Distal tubule AND collecting tubule become permeable to water MORE WATER REABSORBED Causing: hypertonic (concentrated) urine AND increase blood pressure
Impact when ADH is absent
Distal tubule & collecting become impermeable to water
LESS ABSORPTION
Urine is hypotonic (dilute)
Blood pressure decreases
What stimulates ADH?
Dehydration, reduced blood volume, pain
What inhibits ADH?
Alcohol, caffeine, ingestion of water
What does Aldosterone regulate?
Na+ excretion
Where is Aldosterone produced?
Adrenal cortex
What does Aldosterone stimulate?
Na+ reabsorption
Goal of aldosterone and reabsorption
Regulates blood pressure
Atrial Natriuretic Peptide (ANP) - source
comes from heart in response to high blood pressure
ANP - 4 actions
Dilates afferent, constricts efferent (GFR UP)
Inhibits Renin and aldosterone
Inhibits secretion of ADH
Inhibits NaCl reabsoprtion
Results of ANP
Excretion of more salt and water in urine
REDUCED BLOOD PRESSURE AND VOLUME