Renal BF and Glom Filtr-Rao Flashcards
Functions of the kidney? (5)
- Ridding the body of metabolic by-products (urea, creatinine, uric acid, sulfate, phosphate) 2. Excrete toxins and foreign substances (medications, diet) 3. Ability to balance daily intake of salt and water with their excretion in the urine. 4. Acid base balance 5. Endocrine functions (EPO production, conversion of Vit D3 to calcitrol)
A functional kidney is crucial for the maintenance of ___________.
body homeostasis
How can renal failure lead to death? (steps)
Renal Failure–> Loss of ability to balance salt and water–> Edema (retention of fluid)–> Increased work load of heart–> Heart failure and pulmonary edema (these can be complicated by hyperkalemia or acidemia)–> death
What is End-stage renal disease? Treatment?
little or no kidney function, cannot survive without hemodialysis or kidney transplant
What is the functional unit of the kidney? How many per kidney?
Nephron; nearly 1 million per kidney
What are the two types of nephrons and their relative frequencies?
- Cortical (Superficial) 85%
2. Juxtamedullary 15% (these extend all the way into the inner medulla)
The kidney receives how much of the body’s cardiac output?
20%
What is unique about the vasculature structure kidney/nephron?
There are two sets of capillaries
Path of blood in the kidney?
RA–Interlobar aa–Arcuate aa–Radial/Interlobular aa–Afferent Arteriole–Glomerular capillary bed– Efferent Arteriole– Peritubular capillary bed– Renal V
The afferent arteriole forms what? The efferent arteriole forms what?
Aff– Glomerular cap bed
Eff– Peritubular cap bed
In JM nephrons, what supplies blood to the medullary region?
Vasa recta
Due to the unique structure of the renal vasculature, what is very different than very different compared to vasculatures elsewhere in the body?
The Vascular Pressure Profile is very different.
What about the vascular pressure profile is different in the renal vasculature?
The arteriovenous pressure drop occurs in 2 steps (unique to this organ), maintaining high hydrostatic pressure in the glomerular capillary. (Look at graph and diagram–resistance in aff and eff arterioles with low resistance in glom capillaries)
Describe the Oncotic pressure throughout the renal vasculature?
The oncotic pressure is steady/constant, then gradually increases in the glomerular capillaries bc of filtration, and then it lowers back down to normal (~20) by the time it reaches the renal vein (look at graph)
What are the three processes that occur in the nephron that contribute to urine formation?
- Glomerular Filtration
- Tubular Reabsorption
- Tubular Secretion
What are the four different types of substances that can filter into the tubules?
- Freely filtered, not reabsorbed or secreted (inulin)
- Freely filtered, partly reabsorbed, not secreted (urea)
- Freely filtered and completely reabsorbed (nutrients–glc, organic acids)
- Freely filtered, not reabsorbed but secreted from tubules
What is the summary equation of urinary excretion?
Excretion = Filtration-Reabsorption+Secretion
Why is it useful to filter large amounts of body fluids and solutes and reabsorb most of them back into the body? (2)
- Allows kidneys to rapidly remove waste products from the body that depend primarily on glomerular filtration for excretion
- Allows all body fluids to be filtered and processed several times each day.
(kinda 3. quickly remove products that are continuously made thruout the day.
Compostition of filtrate (vs. plasma)?
A. Similar to plasma but without large proteins (almost no albumin, globulin, or Hgb)
B. Low level of some small molecules bound to proteins (calcium and fatty acids)
C. 4-5% more anions and 4-5% less cations (due Gibbs Donnan Effect–cations stay in plasma, anions go due to attraction vs repulsion effect of the large negatively charged proteins in the plasma)
What is the average GFR? What are two things that cause the GFR to decrease?
average GFR= 130ml/min (180L/day)
GFR decreases with age and renal disease
What is the filtration fraction?
FF= GFR/RPF= 130/670= 19.4% on average
How do factors that affect GFR and RPF affect FF?
a. Factors that reduce GFR reduce FF (uretral obstruction)
b. Factors that reduce RPF increase FF (renal artery stenosis)
What are the three filtration barrier of the glomerulus?
- Capillary endothelium (much leakier than capillaries of other organs)
- Basement Membrane (just below the endothelial monolayer, its a clear meshwork of collagen and proteoglycan fibrils–has a negative charge)
- Epithelium or Podocyte monolayer (extend pedicels, forming slit pores; the major barrier of proteins)
What two factors affect the filterability of solutes?
- Size selectivity (glomerular pores=8nm/80Angstroms)
2. Charge selectivity