Renal Flashcards
(88 cards)
What are the 4 main functions of the kidney?
- It’s a homeostatic organ that mainly works to control electrolyte/mineral/body fluid content via the production of urine
- Excretes waste products via urine
- Endocrine organ that secretes calcitriol (calcium production), EPO (RBC production), and renin (BP control)
- Acid/Base modulator
Whats the indicator dilution method? Function?
It’s used to find the volume of a body fluid
You inject a known quantity of a substance into the body that latches onto a specific bodily fluid…then after it has equilibrated in the body, you remove blood sample and measure concentration in plasma sample
use C= Q/V to find the volume
ex: radioactively labeled RBCs for polycethemia diagnosis
What is hematocrit?
It’s the number of RBCs in the blood
Whats the major source of intake and output?
Intake = Drinking Output = Urination
What’s the main regulator of volume in the body? Regulator of osmolarity?
Volume = Sodium content (higher Na = hypervolemia & lower Na = hypovolemia)…this is why sodium sensors in the body tend to be pressure sensors…HOW RENIN-ANGIOTENSIN WORKS
Osmolarity = Water content (higher water = hyposmosis & lower water = hyperosmosis)…this why water sensors are primarily osmosensors…HOW VASOPRESSIN WORKS
What is the importance of inulin and paraminihippuric acid? What can they help to estimate?
Inulin: Doesn’t get reabsorbed or secreted so it’s a good measure of GFR
PAH: Gets completely secreted and thus can be a good estimate of RPF
Describe the tripartite filtration barrier? (Layers, different components and the stuff
the capillary endothelial cells have large openings called fenestra that allow for particles to pass through…then you have the thick basal lamina (basement membrane). Outside of this you have the podocytes which have processes that attach to the outside of the basement membrane
B/w the podocyte processes, you have large filtration slits that are covered by extracellular matrix materials and the slit diaphragm…this provides further filtration on top of the filtration slits
What is the filtrate that comes out of the glomerulus missing from the normal plasma?
PROTEINS are NOT allowed to pass through the fenestrated openings of the capillaries and also through the filtration slits
What is the primary factor by which the glomerulus filters? secondary factor?
1st is size so bigger don’t get in (AKA proteins)
2nd is charge (neutral or positive is perfect)
What are the size limits for a molecule being filtered? When does charge play a role?
If it’s s between 4-8 nm then charge comes into play and partially filtered…note that the filtration slit is negatively charged and thus they repel negatively charged proteins and attract positively
What can be one reason for early albuminuria in the urine
If you albumin lose their negative charge, then they’ll pass through the filtration slits more easily and thus be found in the urine at higher concentrations than normal
Describe the process of using creatinine? What does it help you assess/measure?
Creatinine is a by product of muscle metabolism and is found in produced at nearly a constant rate
Thus, you can normally use it to measure GFR. People tend to just look at the creatinine level in the blood and see if it’s low (Higher than normal GFR) or high (Lower than normal GFR)
Why can creatinine be a flawed means of measuring GFR?
B/c it is also secreted to a certain extent. Thus, the actual plasma concentrations will be lower than normal
Also, creatinine is a good predictor when you have really low GFR and a poor predictor at high GFR…therefore it can be a good indicator but only when you’re in really deep shit
What is cystatin C and what can it be used to measure?
This can be used to assess GFR and is much better than creatinine
HOWEVER, you can’t use it for clearance since it is fully broken down in the nephron tubules
What are the two factors that affect GFR? Go in depth
- Starling Forces determine the level of filtration…so if you have more hydrostatic pressure in the glomerular capillaries then you will be favoring filtration. But if you increase the oncotic pressure of the glomerular capillaries, increase the hydrostatic pressure in the bowman’s capsule, or decrease the hydrostatic pressure in the glomerular capillaries, then you will favor reabsorption. MAJOR DRIVING FORCE IS THE HYDROSTATIC PRESSURE IN GLOMERULAR CAPILLARY
- RPF. if you increase RPF, then you decrease the likelihood of reaching filtration equilibrium b/c you’ve also increased the pressure inside the glomerular capillary. If you decrease RPF, then you increase the chance of reaching filtration equilibrium before the capillary is done and thus create areas of wasted capillary.
What is filtration equilibrium?
This is the point where you no longer undergo filtration b/c the oncotic pressure in the glomerular capillary = hydrostatic pressure in the capillary…can happen if you continue to concentrate the blood by undergoing filtration or if you decrease the pressure of the blood flowing through the capillary
What are the conditions of FF, GFR, and RPF at filtration equilibrium?
At filtration equilibrium, the FF is constant and GFR is direction proportion to RPF
As, RPF increases FF decreases b/c while GFR increases it does so at a much slower rate
What are the two factors that allow for increased reabsorption in the peritubular capillaries?
- The pressure in the peritubular capillaries is super low b/c it has dropped once in afferent arterioles before enter the glomerular capillary and again in the efferent arteriole
- The blood has been soo thoroughly filtered that it is mostly made up of proteins and has a very high colloid oncotic pressure at that point
How is glomerular capillary pressure mainly controlled?
Via afferent arteriole vasoconstriction b/c this reduces both Pressure and RPF
The efferent only vasoconstriction actually increases pressure initially before the reduced RPF kicks into effect and causes the pressure to drop
Vasoconstricting both causes a reduction in RPF but also an increase in the pressure
What is autoregulation? What are the two ways in which it is controlled?
Autoregulation is when you hold your GFR and your RPF at a constant level over a certain range of blood pressure (90-160 mm Hg)
- Myogenic response…stretch activating calcium channels open up…vasoconstricts the afferent arterioles
- Macula densa senses flow in the afferent arteriole when the DCT touches it. If the flow is high, then it increases delivery of NaCl to the macula dena. This causes secretion of adenine from the macula densa into the afferent arteriole. This adenine secretion vasoconstricts the afferent arteriole and reduces the
Describe the Renin-Angiotensin system effects in autoregulation
Major effect: Increase salt reabsorption through aldosterone release. Also, produces angiotensin II that constricts both the efferent and afferent arterioles. This reduces the GFR slightly and severely decreases the RPF. Also, greatly increases the FF, which increases the oncotic pressure in the pretubular capillaries (due to high protein content)…this promotes reabsorption!!!!
Reduces surface area for filtration and decreases the Kf and thus the rate of filtration
Describe the effects of the sympathetic nervous system in autoregulation
As BP decreases, baroreceptors in the carotid and aortic arches fire slowly and trigger the SNS to constrict afferent and efferent arterioles. This decreases RPF, increases FF, and increases oncotic pressure in peritubular capillaries
Also causes secretion of renin and production of angiotensin II
Describe the effects of the ANP and Prostaglandins
ANP
- opposes renin-angiotensin system and is secreted by atrial myocytes when it stretches due to increased BP in the body
- Vasodilator that acts on both AFFERENT & EFFERENT ARTERIOLES to increase GFR and thus increase Na excretion
- Inhibits aldosterone & renin secretion
Prostaglandins
- Vasodilators made in the kidney in response to angiotensin II & increased sympathetic activity
- Helps to limit its effects and turn it off
Whats the difference b/w a moderate and maximal sympathetic activity?
Moderate: causes a small decrease in GFR and helps sodium reabsoprtion
Maximal: favors constriction of the afferent arteriole (NOT BOTH) and thus reduces GFR by a lot as well and almost shuts down the kidney…this is what people in shock have when they lose a lot of blood…stop filtrating the blood well