Renal A&P Flashcards
What are the different functions of the kidney?
-Excreting metabolic wastes
-Maintaining extracellular fluid
-Maintain electrolytes
-Maintain acid-base balance
-Hormonal functions
What is the anatomy of the kidney?
-Cortex and Medulla
-25% of CO
-Medial margins are concave/indented
-Retroperitoneal with right kidney lower than left (due to liver)
-Hilus (L1): where structures enter and leave
-Renal vessels lie anterior to kidney (Some branches may be posterior)
What is the innervation to the kidney?
-PNS: Vagus Nerve
-SNS: T8-L1 preganglionic
Ureters: S2-S4
What is the innervation to the bladder?
-PNS: S2-S4 (stretch, motor)
-SNS: T11-L2 (pain, touch, temp)
What is the functional unit of the kidney?
The Nephron.
Where does Acetazolamide function?
In the PCT.
-Carbonic Anhydrase Inhibitor
Where does Mannitol function?
Descending Loop of Henle
Where do Loop Diuretics function?
Ascending Loop of Henle
Where does Spironolactone function?
Collecting Ducts.
-K+ sparing
How do things enter the glomerulus?
Via the AFFERENT Arteriole.
-Production of urine begins with water and solute filtration from plasma flowing into the glomerulus via the AFFERENT arteriole
What are the major determinants of GFR?
-Glomerular capillary pressure (arterial pressure)
-Glomerular oncotic pressure (renal blood flow)
What is the Efferent Arteriole?
How flow exits Bowman’s capsule.
-Not exiting fast enough = pressure buildup in the capsule
What causes pressure changes in the Afferent Arteriole?
-Increases with intense SNS activity. Filtration and GFR decrease
-Dilation with nitric oxide and prostaglandins. Increases blood flow and GFR.
What causes pressure changes in the Efferent Arteriole?
-Increase with mild SNS or angiotensin activity. Increases filtration pressure and GFR.
Why does the renal system autoregulate blood flow?
-Renal autoregulation of blood flow and filtration modulated by the glomerular arterial tone
-Protects glomeruli from excessive perfusion pressures
-Maintain over a wide range
What is the Myogenic Reflex?
Due to arteriolar wall stretching and constricting.
-Increase in arterial pressure causes afferent arteriolar wall to stretch and then constrict by reflex (constriction decreases capsular pressure due to dec flow, protective mechanism)
-Decrease in arterial pressure cause reflex afferent arteriolar dilatation (increases flow)
What is Tubuloglomerular Feedback?
-Composition of distal tubular fluid influences glomerular function involving juxtaglomerular apparatus
-When RBF falls, GFR decreases resulting in less chloride delivery to apparatus
-Causes afferent arteriole to dilate
-When GFR falls, JGA triggers release of renin which causes formation of angiotensin II
-Efferent arteriolar constriction increases glomerular pressure and GFR
What is Renal Autoregulation?
The body’s mechanism of maintaining constant flow.
-GFR relatively constant with changes in MAP from 80-200 mmHg.
-Below 80, will see changes in flow and can be dramatic based on what MAP is.
-Between 80-200, body maintains constant RBF and filtration rate.
Describe the filtration/reabsorption of sodium
-Actively reabsorbed almost immediately as the glomerular filtrate enters proximal tubule
-Proximal tubule reabsorbs 2/3 of filtered sodium
-No active Na transport in loop of Henle until medullary thick ascending limb
Describe the filtration/reabsorption of H2O.
-Passively reabsorbed that is osmotically driven
-Depends on peritubular capillary pressure
-High capillary pressure opposes H2O reabsorption and increases urine output
-Proximal tubule reabsorbs about 65% of filtered water
Describe the role of ADH and the kidney.
-Secreted by pituitary gland
-Released in response to increase extracellular Na concentration or osmolality
-Increases water permeability of collecting ducts and allows passive diffusion of sodium and water back into circulation
Describe the role of Baroreceptors and kidney function.
Arterial baroreceptors are activated when hypovolemia leads to a decrease in blood pressure.
-atrial receptors are stimulated by a decline in atrial filling pressure
What can stimulate the release of Renin?
-Hypotension
-Decreased tubular chloride concentrations
-Severe SNS stimulation
All lead to the release of Renin from the J-G Apparatus
What does Angiotensin 2 cause?
-Renal Efferent Arteriole vasoconstriction (inc pressure in the glomerulus, things are reabsorbed, increasing volume in circulation)
-ADH release (inc Na/Water permeability in the CD)
-Aldosterone release (inc Na reabsorption, water following passively in the distal CT/beginning of CD)
When is ANP released and what does it do?
-Released by atrium in response to increased stretch
-Inc GFR, systemic vasodilation, inhibit renin release, opposes production and action of angiotensin II, decreases aldosterone secretion
Nagelhout:
-Inc urine flow and Na excretion
-Inc RBF and GFR
-Decreases renin, aldosterone, and ADH
What does N2O do to the renal system?
-Produced in kidney
-Opposes renal vasoconstrictor effects of AngII and the adrenergic nervous system
-End up with decreased circulating volume
What are Prostaglandins?
-Produced in the kidney in response to stress, renal ischemia, and hypotension
-Cause dilation of renal arterioles
-Distal tubular effects result in an increase in sodium and water excretion
What are the S/Sx of Hyponatremia?
-Symptoms rarely unless < 125mEq/L
-S&S - anorexia, nausea, and lethargy to convulsions, dysrhythmias, coma, and even death due to osmotic brain swelling
-If acute, risk of neurological complications higher
-Treat to prevent cerebral edema and seizures
What are the S/Sx of Hypernatremia?
-Serum level > 145mEq/L
-Generally due to sodium gain or water loss (usually the latter)
-Can cause dehydration of brain
-Symptoms from confusion to convulsions and coma
What are the causes and S/Sx of Hypokalemia?
Causes:
-Vomiting, diarrhea, drugs, hormones, renal abnormalities, insulin therapy, inadequate intake
Symptoms:
-electrocardiogram (ECG) changes (flattened T waves “no pot, no T,” U waves) and skeletal muscle weakness
Treatment:
-replacement (IV or PO)
What are the causes of Hyperkalemia?
> 5.5mEq/L
Causes:
-abnormal kidney excretion, abnormal cellular potassium release (i.e. cell lysis), or abnormal distribution between the intra- and extracellular space.
-Chronic far better tolerated than acute rise
What is acid-base balance?
The balance between plasma HCO3- and PCO2 in the extracellular space.
