Filtration basics Flashcards
Define glomerular filtration
when water and many solutes found in the blood move across the wall of the glomerulus, into the glomerular (Bowman’s) capsule and into the convoluted tubules
Define tubular reabsorption
water and solutes in the tubular system can get reabsorbed back into the blood stream
Define tubular secretion
b/c the the peritubular capillaries and the vasa recta are around the tubular system unwanted material that remained in the blood after it traveled through the glomerulus can be pushed into the filtrate
What are the 3 layers of filtration in the glomerulus and what do they prevent from passing through
- Fenestrated epithelial cells of the capillary=prevent RBC’s
- Basement membrane of capillary = prevents large proteins
- Slit membranes between pedicels(foot projections of podocytes)=prevents most other proteins
What are mesangial cells and what is their function
specialized cells that are interspaced between the loops of the glomerulus and wrap around the glomerulus vessels that regulate the surface area available for filtration.
contracted=less surface area
relaxed=more surface area
True or False the pressure in the glomeruli is lower compared to other body capillaries
False, pressure in the glomeruli is higher than any other capillary in the body.
Why is the pressure in the glomeruli higher than any other capillary
More pressure is needed for blood to get out of the glomeruli, this is because there is more surface area, larger fenestrations, and the efferent artery is smaller than afferent artery
This back pressure is also needed to create a filtering pressure
What are the 3 pressures that make up the Net Filtration Pressure (NFP)
NFP=GBHP-CHP-BCOP
GBHP=Glomerular blood hydrostatic pressure= Pressure in the glomerulus that pushes outward into capsular space. From blood pressure and constriction of afferent and efferent arterioles (55 mmHg usually)
CHP=Capsular hydrostatic pressure= pressure of filtrate in the capsule, pushes back (15 mmHg usually)
BCOP=Blood colloid osmotic pressure=pressure d/t protein in the blood that tries to keep fluid in glomerulus (30 mmHg usually)
What is the usual NFP in normal healthy kidneys
10 mmHg
What does it mean if NFP is positive
filtration is occurring, and urine is being made
What does it mean if NFP is negative and when could this occur
No filtration
Could happen if there is a renal obstruction, like a kidney stone, this obstruction causes capsular hydrostatic pressure (CHP) to rises and eventually overcome the GHBP
What is hydronephrosis
NFP overcomes GHBP and kidneys retain fluid, and eventually can cause nephron destruction
