Normal Renal Physiology I Flashcards
Where is the kidney located in the abdominal space?
Ribs and muscle surrounds kidneys from the posterior aspect.
Diaphragm is wedged close to the midline of the kidney.
Much of the kidneys are behind anterior thoracic and abdominal structures (lungs and abd organs).
What are the surgical approaches usually taken to access the kidneys?
Often accessed through the retroperitoneal approach from the side flank.
Posterior aspect accessed sometimes for needle insertion into renal pelvis for drainage in radiology settings (nephrostomy tubes)
Anterior approach is difficult due to intestinal contents in the way
Posterior approach is difficult due to the ribs, muscles, and diaphragm in the way.
What are nephrostomy tubes used for?
Most commonly used for urinary drainage.
Other uses:
To remove or dissolve renal calculi
To obtain direct access to the upper urinary tract
To diagnose ureteral obstruction, filling defects, etc.. via antegrade radiography
To deliver chemotherapeutic agents to the renal collecting system
To provide prophylaxis after resection for local chemotherapy in patients with tumors of the renal pelvis
What is the general pathway of blood as it travels through the kidneys?
Arterial blood –> Renal arteries –> Glomeruli (Bowman’s Capsule) –> Nephrons –> Papilla –> Renal pelvis (major and minor calyces) –> Ureter –> Bladder
What are papilla?
groups of collecting ducts from the nephrons
What is the general role of glomeruli in the kidneys?
Initial filtration of renal blood
What are the two major populations of nephron cells in the kidneys?
Cortical nephrons = out near the peripheral of the kidney (short nephrons)
Juxta-Medullary nephrons = projections dive deep down into the kidneys (major role in urine composition)
Explain the anatomy of the glomeruli and the flow of blood through there.
Afferent arterioles enter the glomeruli and bundle up around multiple potocytes (Cells of Bowman’s capsules).
Potocytes have finger-like projections which form a filtration barrier that allows smaller molecules and fluids to flow into Bowman’s space (btwn Bowman’s capsule and glomeruli).
What is the Bowman’s capsule and Bowman’s space?
Bowman’s capsule = endothelial lining of Bowman’s space.
Bowman’s space = directly connected to proximal tubule of nephron (initial part of nephron) and is btween Bowman’s capsule and nephron
Where are macula densa and what are there function?
Maculate densa = cells that are part of the distal tubule of the nephron
Rests between the renal artery and renal vein
-They sample the composition of the filtrate at this point and will send signals to the afferent/efferent arterioles to influence their vasculature in response
What percet of our total body weight is composed of water?
60%
Of our total water weight, how much is in the intracellular and how much is in the extracellular space?
2/3 of our total body water is accounted for by intracellular space while 1/3 is extracellular space.
What fluids make up our extracellular space?
Extracellular fluids are broken up into two components: plasma and interstitial fluids (space btwn cells).
3/4 of extracellular fluids = in plasma space (blood, plasma, etc..).
1/4 = interstitial space
What exactly causes edema at the level of the extracellular fluid space?
It comes from excess ECF in the interstitial space.
It is much more common during trauma due to the presence of leaky vessels (vessels become more permeable to allow for cellular repair around traumatized sites)
Explain how NS and LR redistributes fluid-wise in the body and how this manifests clinically,
LR and NS have about the same ionic composition w/ plasma.
Therefore, only about 1/3 about what we give will go into the plasma.
Only about 3/4 of this volume will stay in the plasma.
This is why BP will rise transiently when you give fluids, but will drop when the fluids are redistributed if you discontinue your drip prematurely.
How much of your total body weight does intracellular fluids make up?
40%
(total body water is 60^% of tbw and 2/3 of it is intracellular while 1/3 of it is extracellular)
What is transcellular space and how much of our fluid capacity does it make up?
It is the fluids that are constantly in flux between cells as they travel down their osmotic gradient.
Makes up 1-2 L (out of 70L of a 70 kg pt)
What is the osmotic effect of giving D5W?
When we give D5W, its actually like giving free water (its hypotonic as it has no ions - body is pulling the glucose from the administered fluid) and will result in fluid being pulled into intracellular space, possibly causing cell lysis if given too quickly.
What ions predominantly make up the intracellular space?
The extracellular space?
ICF: K+, PO4- (used in ATP generation), organic anions
ECF: Na+, Cl-, HCO3-
What causes thirst?
Decreased blood volume or ion content increases
(up osmolality, down blood volume, down blood pressure, up angiotensin II all cause thirst)
At what range of MAP does autoregulation of GFR occur?
80-180 mm Hg
< ~50 mm Hg, regulation suffers
This process involves feedback from afferent and efferent renal arterioles as well as intrinsic signals from the macula densa.
Why is maintaining blood osmolality important?
So the blood does not become too thick or diffuse
What are the two main molecules that affect serum osmolality?
Na+ and glucose
Where are the brain’s “osmolality sensors” located?
the hypothalamus
Where is ADH secreted? where does it act? what does it do?
secreted from hypothalamus; acts on distal convoluted tubule; creates aquaporins that allow water to travel out of the tubule
