L04: Glomerular Filtration Flashcards
What is a nephron
A functional unit of the kidney
What are the structures of a nephron
afferent arteriole Efferent arteriole Glomerulus Bowmans space Proximal tubule Loop of henle- descending and ascending limb Distal tubule Collecting duct
What is bulk flow
Movement of substances as water flows
What flow does filtration have
Bulk flow
If there is bulk flow, then what determines the movement of water into the bowmans space
1) hydrostatic pressure
2) oncotic pressure
What is the hydrostatic pressure
Pressure in the capillaries that is generated by the heart
What is the oncotic pressure
The pressure generated by proteins present in the capillaries
Describe the filtration process that occurs in the glomerulus
1) hydrostatic pressure drives the water out from the glomerulus to the bowmans space
2) as proteins are left behind in the capillaries this creates an oncotic pressure which causes the fluid to be drawn back in.
3) bowmans pressure also drives fluid back into the glomerulus
4) overall the difference between the pressures causes a net perfusion pressure which causes the fluid to move from the capillaries to the bowmans space.
What happens to the efferent arteriole when it leaves the glomerulus
Joins the portal vein and to another capillary bed that surrounds the loop of henle of the nephron.
What are the layers of the glomerulus
1) endothelial cells
2) basement membrane
3) podocytes with filtration slits.
What are podocytes
The epithelial cells of the bowmans capsule
How are filtration slits formed
From the processes of the podocytes
Which molecules are easily filtered at the bowmans structure
Small
Positively charged
What passes into the bowmans space to become the filtrate
Sodium Potassium Chloride Bicarbonate Glucose Urea Calcium Magnesium
How is the blood flow controlled/regulated to allow filtration
change the diameter of the afferent and efferent arterioles
How do we increase the blood flow by regulating the diameters of the arterioles
Vasodilation of afferent arteriole
Vasoconstriction of efferent arteriole
What does GFR stand for
Glomerular filtration rate
Which substance can be used clinically to measure GFR
Creatine
Why is creatine a good substance to use for measuring GFR
Creatinine can become filtered and it not reabsorbed so it will become excreted into the urine.
What equation do we use to measure the rate of creatine filtered
(Concentration x volume)/ time
How do we measure the GFR using the creatine equations
GFR= creatine excretion rate / creatine in plasma
Which factor causes the decrease in GFR
Ageing
What is proteinuria
Protein in the urea
What does proteinuria suggest
Glomerular damage
What can glomerular damage lead to
Glomerular nephritis
What is a congenital nephrotic syndrome
Genetic disorder that leads to defects of the glomerular barrier which therefore leads to proteinuria
Which layers of the glomerular barrier are charged
Endothelial cells
Basement membrane
What is the charge of the endothelial cell and basement membrane
Negative
What creates the negative charge in the endothelial cells
Negatively charges glycocalyx
What does the negatively charged glyco-calyx repel
Negatively charged proteins
What does the negative charge in the basement membrane repel
Negatively charged proteins
