Session 3 Flashcards
(18 cards)
Through what artery does blood enter the glomerulus?
Describe structure of glomerulus
What are podocytes?
Renal afferent arterioles
Fenestrated capillaries with a specialised selective 1 cell thick BM
Specialised epithelium again aiding specificity in filtration. They use foot processes then the gaps between adjacent form a slit diaphragm.
Name of artery leaving the glomerulus?
Structure and function of bowman capsule?
Role of mesangium?
Renal efferent arterioles
Layer of epithelial cells, gelatinous, glycoproteins and negatively charged draining blood into proximal tubule
Full of mesangial cells that support the glomerulus capillaries by forming a basement membrane like matrix.
Body fluid compartment distribution?
Predominant cations and anion in ECF?
60% water. 2/3 intracellular. 1/3 extra cellular.
Of ECF- 75%interstitial and 25% intravascular.
Sodium and chlorine
What causes the hydrostatic pressure inside the glomeruli?
4 things filtered through fenstrations?
The diameter of the afferent arterioles is greater than the efferent.
Water, urea, glucose, salts
Define ultra-filtrate and how much produced per day?
What happens if NaCl concentration in filtrate decreases?
Plasma without the cells and large organic molecules. 180L per day.
Macula Densa is sensitive to the decrease,it increases renin secretion from juxtaglomerular cells.
What happens to the ultra-filtrate once it enters the kidney nephron tubules?
99% of water urea glucose AA’s are reabsorbed back into circulating plasma.
Describe reabsorption in the proximal convoluted tubule
All the glucose and some water is reabsorbed. Sodium also moves out through the cells in the PCT, using symporters on the apical membrane. Symporters are dependent on the 3Na-2K-ATPase transporter on the basolateral membrane. After solute movement majority of water then moves out my osmosis.
Describe and role of tubular secretion?
H+,K+,NH4+ etc secreted by epithelial cells and added to ultra-filtrate to maintain the optimum pH.
Why is auto regulation important?
Maintains GFR allowing optimum solute plasma/ultrafiltrate concentration.
Protects glomeruli from increased perfusion pressure causing structural damage.
Describe the myogenic autoregulation response
Afferent arterioles response to changes in pressure, the smooth muscle has non-selective cat ion channels in vascular smooth muscle. Upon depolarisation ca2+ will rush in causing contraction.
Contraction will decrease GFR as less blood available to be filtered.
Describe the tubuloglomerular feedback system
Macula densa cells in ascending limb sense change in salinity (increase in GFR) causing a contraction of the afferent arterioles thus reducing GFR.
Normal GFR?
Normal total glomerular filtrate per day?
Define renal clearance
90-120ml/min
180L/day
Volume of plasma cleared of a substance per unit time.
Clearance equation?
Work out clearance if substrate at conc in urine at 100 mg/ml and urine flow rate of 1ml/min. And plasma conc is 1 ml/min.
Cx= Ax/Px
Ax= amount of substance eliminated from plasma.
Px=plasma conc of substance.
100(1)=100 (Ax)
100%1=100ml/min
Hat must be the case to measure renal clearance?
If all true relationship between amount excreted to urine compared to amount filtered by kidney?
Freely filtered by glomerulus
No secretion/reabsorption at renal tubule.
They are the same.
Why is insulin a surrogate for GFR?
Why dont we use insulin?
Alternative?
It’s exogenous, not secreted absorbed at renal tubule and freely filtered.
Catheter and constant IV drip.
51 Cr EDTA
Best endogenous source for measuring insulin and why?
What measurements are taken for creatinine clearance measurement?
Why is GFR usually a 10-15% overestimate?
Creatinine as freely filtered and on,y a bit secreted at renal tubule however changes in people depending on age/ethnicity and diet so can vary a bit.
Urine collection every 24 hours and a plasma collection.
Due to some secretion into the renal tubule.
What happens to plasma creatinine levels as kidney function falls?
They increase in creatine is filtered and excreted by the healthy kidney.
Serum creatinine in US =Mg/dl
In England=umol/L
Convert to Mg/ml
Mg/dl= umol/l % 88.4
Mg/ml= Mg/dl % 100
