Renal Flashcards
Driving force for facilitators and diffusion
Electrochemical gradient
How is the electrochemical gradient made?
Na+/K+ ATPase pumping in 2K+ and pumping out 3Na+
Absorption of Na+ causes what in the lumen?
Osmotic and electric gradient between lumen and interstitium
How does osmolarity effect H2O movement?
Water follows solutes to keep the solutions iso osmotic
H2O moves via what type of pathway?
Transcellular and paracellular pathways in leaky tight epithelia
ONLY transcellularly in tight tight epithelia
Na transport in tight tight epithelia
ENaC which is driven by Na+/K+ ATPase activity/electrochemical gradient
only transcellular
Salivary acinar cells produce …. fluid
iostonic (same concentrations of NaCl as our blood)
In secretory epithelia, what is the additional transporter?
Name, where, what it does
Na+/H+/2Cl- cotransporter
Basolateral membrane
Pumps them all into the cell, builds up Cl- gradient inside
What is the electric and osmotic effect of Cl- movement into the lumen?
Negative lumen potential, pulls Na+ paracellularly and therefore creates the osmotic gradient and pulls water paracellularly and transcellularly
What is the mechanism of water secretion in leaky secretory epithelia?
Na/K ATPase generates the electrochemical gradient using ATP as a primary active transporter
Na+/K+/Cl- are all pumped into the cell using NKCC1
Na and K are pumped back out to the interstitium
Cl- conc increases inside the cell, creating a conc gradient
Cl- facilitators on the apical side (CTFR) allow Cl- to flow down its conc gradient into the lumen
Cl- conc increases in lumen, causing a build up of negative charge
Na+ flows paracellularly into lumen to balance charge
This creates an osmotic gradient between lumen and interstitium and pulls water paracellularly
Na transporters in leaky epithelia
SGLT1 and SGLT2
Which parts of the nephron have leaky epithelia?
PCT and thinDL
Leaky absorbative epithelia function is to:
Absorb glucose using the sodium gradient on the apical side of the cell
Main function of the kidney
Maintain blood pressure via water and ion homeostasis
Main function of the kidney
Maintain blood pressure via water and ion homeostasis
Filter blood from waste products and drugs
What is in normal urine?
95-98% water creatinine Urea H+, NH3 Na+, K+ drugs
How much urine do we make a day?
1.5L/day = 1mL/min
What is in pathological urine?
Glucose Protein Blood Haemoglobin Leukocytes Bacteria
The juxtaglomerular
Juxtaglomerular cells and macula densa with the afferent arteriole
What type of capillary endothelium is in the filtration barrier?
Fenestrated endothelium
What is the filtration barrier composed of?
Fenestrated capillary endothelium
Basement membrane
Epithelial podocyte
What are the driving forces for filtration?
Glomerular capillary blood pressure
Osmotic force due to the proteins in plasma
What is the net glomerular filtration pressure?
Pgc - Pbs - OsmF
= 16mmHg
Which filtration driving force/ pressure at PCT is the highest?
Glomerular capillary blood pressure (60mmHg)
Which forces are opposing filtration?
Fluid pressure from Bowman’s space
Osmotic force due to the proteins in plasma
Filtration at the kidney results in a hypo, iso or hyper-osmotic primary filtrate?
Iso-osmotic
What are the substances suitable for determining the filtration rate?
Inulin
Creatinine
Clearance definition
Volume of plasma that was cleared from a substance per unit time
Clearance equation
C = (UxV)/P Clearance = (Conc of substance in the urine x urine output) / concentration of substance in plasma
GFR approx value
132mL/min
7.9L/h
What makes something a good substance for determining the filtration rate?
Something that is: Freely filtered NOT reabsorbed NOT secreted NOT metabolised NOT toxic
What is filtration at the kidney?
Filtered at the filtration barrier
- everything is slightly filtered at the barrier
What is secretion at the kidney?
Active transcellular secretion of substances into the urine from the PCT
Usually secretion of drugs
Substance is fully secreted so there is no more of it in the blood
What is re-absorption at the kidney?
Re-uptaking things that are filtered either partially (K+, Na+) or fully (glucose)
