Intro to Neph Flashcards
True/False
The amount of sodium you intake on a single day will alter what the normal homeostatic function of the kidney is.
False, regardless of how much or how little the sodium, water, or potassium in take is, the kidney will still maintain it’s “single” homeostatic state.
What is the homeostatic value of sodium that the kidney tries to maintain?
140
What is the homeostatic value of potassium that the kidney tries to maintain?
4
What is the homeostatic pH that the kidney tries to maintain?
7.4
What is the functional unit of the kidney?
Nephron
What is a nephron comprised of?
Glomerulus and Tubule
Where is the afferent arterioles of the kidney coming from? Where is it going?
From the heart/outside the kidney; Going to the glomerulus.
Where is the afferent arterioles of the kidney coming from? Where is it going?
From the glomerulus; Going to the heart/outside the kidney
What are the important cells that surround the afferent arterioles?
JG cells
What is the function of the JG cells?
To make renin
What is the function of the macula densa? Where is this located?
Senses NaCl; Located in the distal convoluted tubule that comes into contact with the afferent arteriole
What do the JG cells contain?
Mechanoreceptors that sense changes in blood pressure (stretch receptors)
If blood pressure drops, what will cause your body to naturally increase BP?
Renin-Angiotensin System
Simplified Breakdown of the RAAA system?
Renin –> Angio I –> ACE –> Angio II –> Vasoconstriction/Na Reabsorption –> Inc. BP
What sensory receptors do the macula densa cells have?
Chemoreceptors
What do the chemoreceptors in the macula densa cells do?
Sense changes in the concentration of the ultrafiltrate before it goes into the DCT.
What happens when there is a DROP in Na+ concentration?
- Leads to vasodilation of the afferent arteriole –> Inc GFR and NaCL reabsorption
- Lead to renin release from the JG cells by the shrinking of the MD cells
Drop in Na+ concentration similar to drop in BP?
A drop in NaCl will leave to the constriction of which vessels?
Efferent Arterioles that will force blood to build up in the glomerulus, and causes peripheral vasoconstriction that will increase BP
The tubuloglomerular feedback mechanism is considered?
A. Autoregulated
B. Regulated based on parasympathethic activity
C. Regulated based on sympathetic activity
D. No regulatory control, extrinsic or intrinsic, it is a fixed system.
A. Autoregulated
Structure of the Glomerulus includes:
Afferent Capillary Efferent Capillary Glomerular Tuft Bowman's Capsule Endothelial Cells Glomerular Basesment Membrane Podocytes Mesangial Cell
What is the function of the glomerular tuft?
Filtering element that consists of an enclosed capillary network
Glomerulus is enclosed in what structure?
Bowman’s capsule
What IS a glomerular tuft?
Lobular structures of capillaries that are lined by endothelial cells.
What is the glomerular basement membrane made of?
Hydrated gel composed of glycoproteins that contain interwoven Collagen Type IV
This lines the inside of the capillary walls and is perforated with small fenestra (windows) that let only plasma through but retains the formed elements such as RBCs.
Endothelial Cells
What is the function of the fenestrated endothelial cells?
- Regulate coagulation, inflammation, and vasomotor tone.
- Make surface antigens, express adhesion molecules for leukocytes, and release vasodilator substances like nitric oxide.
This is an important determinant of the charged porous nature of GBM.
Glomerular Basement Membrane
If the layers of the glomerulus were compared to a PB & J sandwich the GBM would be the ________.
Jelly
True/False:
Most substances can cross the GBM
FALSE!
Most substances are too big to cross the GBM.
What can damage the GBM?
HTN and DM
What happens if there is damage to the GBM?
No longer a good filter — pts can lose things like small RBCs or smal proteins
A disorder of the GBM due to abnormal type IV collagen (by mutation on the X chromosome)
Alport’s Syndrome
How do you diagnose Alport’s Syndrome?
Microscopic Hematuria
Dz characterized by thickening and lamellation of GBM
Alport’s Syndrome
What is an effect of Alport’s Syndrome outside of the glomeruli?
Sensorineural Hearing Loss (M>F) and lens issues in the eye
What is the mesangium made of?
Mesangial Cells and surrounding matrix
Mesangial Cells are composed of?
Collagen Fibers (similar to those of the GBM)
Microfibrils provide a ________ for the glomerulus.
Cytoskeleton
________ properties play a role in the regulation of GFR.
Contractile
Mesangial matrix cushion and surround the _____________________.
Glomerular Tuft
Function of phagocytic properties of the mesangium
Clearance of macromolecules
What functions to produce the extracellular matrix?
Receptors for growth factors
T/F:
Dz can stimulate overproduction of extracellular matrix
True
When looking at the cells of a patient with diabetic nephropathy, what will you see?
Nodular mesangial expansion called Kimmelstiel-Wilson lesions/nodules.
There is also an increased mesangial matrix.
What cause proteinuria in DM?
Hyperfiltration in the nephron
How do ACE Inhibitors (or ARB) lower the pressure in the glomerulus and decreases proteinuria?
Dilates the efferent arteriole!
How many glomeruli does the renal cortex contain?
1 million
What protein is most commonly looked at in an Urinanalysis?
Albumin
Between two podocytes, what is located there?
Slit diaphragm
Function of the slit diaphragm?
“Pore”
Main structure of the glomerulus that stops large proteins like albumin from escaping into the ultrafiltrate.
If there is an issue with the podocytes, what can happen?
Nephrotic Syndrome; large amounts of protein being lost in his urine.
If a child shows up swollen and a full blood work up is done, including UA, CBC, CMP, LFTs, Cholesterol, what would be important in determining if this is an issue with the kidneys/podocytes?
Elevated Protein in Urine
Positive Oval Fat Bodies
Elevated Total Cholesterol Levels
What causes edema in a patient with podocyte dz?
Diminished plasma osmotic pressure leads to a net accumulation of extravascular fluid
Pressure caused by plasma proteins that can’t cross the capillaries (colloids).
Oncotic Pressure
Causes of edema in Nephrotic Syndrome
- Low protein plasma leads to low oncotic pressure and causes free water to shift from his vascular space to his interstitial space
- Fluid shift triggers the RA System and leads to renal salt conservation causing more fluid retention.
When comparing nephrotic syndrome with normal glomerular capillary loop on scan, you will see
An effacement of the epithelial foot processes and microvillus projections into the cytoplasm.
Most common cause (70-90%) of nephrotic syndrome in children under 10 yo
Minimal Change Glomerulopathy AKA Minimal Change Dz
Pathogenesis of Minimal Change Dz?
Exact reason for disease unclear, most likely due to abnormal regulation of T-cell’s and pathologic elaboration of circulating permeability factor. This factor my have specificity for Podocytes leading to loss of the charge barrier
Why do patients with Nephrotic Syndrome have Hyperlipidemia?
Hyperlipidemic response is triggered at least in part by the reduction in plasma oncotic pressure which directly stimulates hepatic apoprotein B gene transcription and leads to elevated VLDL and LDL.
Key features of Nephrotic Syndrome
- Peripheral Edema
- Hypoalbuminemia (Albumin < 3 g/dL)
- Hyperlipidemia
- Proteinuria (>3 g/day)
- Oval Fat Bodies in Urine
Medical condition characterized by abnormally high levels of nitrogen-containing compounds, such as urea, creatinine, various body waste compounds, and other nitrogen-rich compounds in the blood.
Azotemia
Key Features of Nephritic Syndrome
- Hypertension
- Elevated BUN/Creatinine (Azotemia)
- Edema may or may not be present
- Usually less than nephrotic range proteinuria (0.3-3 g/dL)
Diseases of the kidneys are specific to what?
STRUCTURE of the kidney. All dz of the kidneys is based on structural changes.
Why does HTN occur in Nephritic Syndrome?
Acute glomerular failure thought to be triggered by Na+ retention and volume expansion in a sick kidney that is unable to get rid of excess fluid.
Tx: Diuretics
What is a marker for glomerular injury?
Red Cell Casts
What are red cell casts?
The clumps that come out in urine due to injured glomeruli have inc. permeability and leak red cells and proteins into the proximal convoluted tubule and in the collecting ducts.
Refers to a form of red blood cell that has a spiked cell membrane, due to abnormal thorny projections.
Acanthocytes
Pathogenesis of Nephritic Syndrome
Uncertain
What causes post-streptococcal glomerulonephritis?
Secondary due to direct toxic effect on the glomerulus or the product of an immune-complex-mediated injury
How would an immune complex mediated injury work?
- Intro. antigen to the glomerulus
- Deposits of circulating immunecomplexes
- Alters the normal renal antigen, causing it to be a self antigen
Under immunofluorescence, what will you see in a patient with poststreptococcal glomerulonephritis?
Immune deposits (IgG and C3) will be widely distributed within the capillary loops and will glow bright green.
Granular, bumpy pattern.
In poststreptococcal glomerulonephritis, what will you see on a light microscope that you won’t see in Normal?
Hypercellularity due to inc. numbers of epithelial and mesangial cells, and neutrophils in an and around the glomerular capillary loops
In poststreptococcal glomerulonephritis, what will you see on a electron micrograph that you won’t see in Normal?
Pathognomonic subepithelial deposits sitting on top of the GBM with a semilunar, hump-shaped appearance.
