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Filtration - Anatomy + Function of the Glomerulus
Terms in this set (23)
What are the functions of the kidney?
Filtration of blood
Detoxification (incl drugs)
Regulation of blood pressure
Regulation of blood pH
Regulation of haematopoiesis
Making vitamin D
What is the input pressure of the filtration system?
What is the finest filter in the kidney?
The slit diaphragm.
Fine filter between the foot processes of the podocytes.
3% of the total area is the slit = major resistance to fluid flow.
Describe the movement of particles across the slit diaphragm.
Proteins and small solutes on the blood side. Small solutes move across to the filtrate side.
Big molecules will still be on one side - so osmosis works against you and we need the pressure from the heart to work against this.
What is the effect of restricting the afferent arteriole on the blood supply and filtration?
•Blood pressure in capillaries drops
•Filtration rate drops
What is the effect of restricting the efferent arteriole on the blood supply and filtration?
•Blood pressure in glomerular capillaries rises
•Filtration rate rises
What role does pinocytosis play in filtration?
Pinocytosis = ingestion into the cell by budding of vesicles.
Pinocytoses small molecules trapped in the filter to unclog it.
Additional filters are required to keep bigger molecules out.
Describe the structures between the blood and the slit diaphragm.
Fenestrated endothelial cells.
GBM = glomerular basement membrane
- lamina rara interna.
- lamina densa
- lamina rara externa.
Podocytes with slit diaphragm.
How are the fenestrated endothelial cells cleaned?
By blood flow and phagocytes.
How is the GBM renewed?
By mesangial cells.
How are the podocytes and slit membrane cleaned?
By pinocytosis by podocytes.
What is the glomerulus?
Knot of capillaries. Can also be used to describe the renal corpuscle.
Describe the structure of a renal corpuscle.
Knot of capillaries surrounded by visceral epithelium with mesangial cells in the spaces between.
Surrounded by capsular space, then parietal epithelium, then Bowman's Capsule.
Afferent arteriole supplies, glomerular capillaries run through then efferent arteriole drains blood from renal corpuscle.
Proximal convoluted tubule drains the filtrate from renal corpuscle.
How many renal corpuscles are in one adult kidney?
50,000 - 1,000,000
What is the blood flow to the kidneys (litres / min)?
What is the plasma flow to the kidneys?
What is the rate of filtration through the glomerulus?
What percentage of the plasma is removed as filtrate?
How can the glomerular filtration rate be clinically measured?
Creatinine is produced at a relatively steady rate and is excreted. So can measure filtration rate with concentration of creatinine in urine and plasma.
GFR = clearance = (urine conc x urine flow rate) / plasma concentration = UV/P
What are the ranges of GFR?
100 = normal.
40-100 = reduced reserve, asymptomatic.
<40 = renal impairment, worrying, very unwell. >20 = end stage renal disease, need support or will die.
How does dialysis prevent loss of wanted small molecules in the blood?
Fresh dialysate contains lots of these wanted small molecules so there is no net loss.
What must the dialysis machine do other than clean the blood?
Must also control other functions of the kidney: blood pressure etc.
What is the alternative to dialysis and what are the problems with it?
Alternative = transplantation.
Social: theft, selling illegally
Tumours: immunosuppressants to prevent rejection
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