Week Three - Filtration Of Glomerulus Flashcards
(23 cards)
Where are the cortical nephrons?
Outer 2/3 of cortex
Wh is the diameter or the afferent arterioles bigger than the efferent
To maintain high pressure - opposite to normal system.
Which is sympathetic rich, cortical or juxtamedullary nephrons?
Cortical
What are the three layers of the filtration barrier in the glomerulus and explain their function,
1 capillary endothelium which is permeable to water salts and glucose
2 basement membrane which is permeable to small proteins but has negative glycoproteins within and therefore repels proteins
3 podocyte later which forms filtration slits and ultimately defines the maximum size too molecules that can fit through
Why might proteinuria occur in general terms?
The disease process may remove the negative charge on the filtration barrier and so proteins are more readily filtered.
What are the three forces that result in the overall driving force of plasma filtration. Explain each.
1) the hydrostatic pressure in the capillary - this is regulated
2) the hydrostatic pressure of the bowmans capsule - pushes back as more filtrate moves across
3) the oncotic pressure of the capillary - pulls back as water molecules leave the capillary and the proteins are left behind
What is autoregulation and how does it work in the kidneys?
Maintains blood pressure writhing tight physiological limits - 80-180mmHg
If systemic BP goes up, the afferent arterioles will constrict to limit the blood flow to the kidneys. Vice versa. Myogenic response.
What is involved in tubular glomerular feedback?
Increase in art pressure = increase glomerular capillary pressure = increase in renal plasma flow = increase GFR = increase NA+ and cl- in distal tubule… Macula densa cells sense this via NaK2Cl cotransporters. They stimulate the juxtaglomerular apparatus to release adenosine for constriction, as in this case IOT reduce blood flow, or prostaglandins for dilation
What does reabsorbtion In the proximal tubule mean and what is the driving force?
Reabsorbtion of the water and solutes back in to the capillary. This is called bulk transport. Driving force is thick reader oncotic pressure in the caps pulling back.
What are the main sodium transporters in the PCT used to drive bulk transport?
Na-H anti porter and the Na- glucose symporter
How does the cotransport system in the PCT to remove glucose and sodium?
All hinged on the nak atpase which activity tranports sodium out of the tubule cell and moves it in to the interstitial space.
This decreases the amount of sodium inside the tubule cell and this pulls sodium, and, via the stored energy, glucose through from the lumen. Glucose then moves down its concentration g until it too is in the interstitial space. Both then move down their concentration gradient in to the peritubular tubule.
Secretion in the PCT offer s awesome entry for solutes to enter the tubule lumen. What is secreted?
Protons, potassium and organic anions
How are cations and anions secreted in the PCT.
Use gradient set up by the sodium potassium atpase and then uses a sodium hydrogen exchanger which then drives and a H+Organic cation exchanger
What are the normal adult glomerular filtration rates?
Males - 115-125 ml/min
Females - 90-100 ml/min
What is the renal plasma flow?
The volume of plasma that passes through the kidney in mls per minute
To work out take the volume of haematocrit away from the total blood volume which normally leaves about 55%. The amount of blood that goes through kidney is 1.1l therefore
0.55 X 1.1L/min = 605ml/min of plasma = Rpf
If the renal plasma flow is 605ml/l, how much is actually filtered and the fore what is the GRF.
20% X 605 =125ml/l
What is the filtration fraction?
GRF/RPF
What is renal clearance?
The volume of plasma that is completely cleaned of a particular substance by the kidneys per unit time
C = concentration of it in urine X urine volume
/ concentration of it in plasma
Indicates how well the kidney is working
What are the three requirements in order Thor the renal clearance to equal the GFR.
Substance must be freely filtered, non reabsorbed and non secreted. Eg inulin or creatinine although small amounts of creatinine are secreted.
What is eGFR?
Cockcroft-gault formula which takes in to account a patients age and weight
What is the filtered load?
The concentration of the substrate in the plasma X the GFR therefore how much of the substrate is filtered in a minute
What is the transport maximum?
The amount that can be filtered before it starts spilling over. Eg tm of glucose is 375mg/min in males. If pt has plasma glucose concentration of 400mg/100ml then filtered load will be 500mg/min (400mg per 100ml and we filter 125ml) therefore 125mg/ml over and so this amount of glucose will be lost in urine
What are the names of the arteries as they leave the renal artery until they reach the renal vein?
Renal art, segmental art, interlobar art, arcuate art, interlobular art, afferent art, efferent art, peritubular capillarys and vasa recta, interlobular veins, arcuate veins, interlobar veins, segmental and then renal vein
