Formation of urine Flashcards
Glomerular filtration rate
125ml/min
Used as an indicator of renal function
What remains in the blood
Red blood cells, lipids, proteins, most drugs, metabolites
What layers does filtrate pass through to reach kidney
Pores in glomerular capillary endothelium
Basement membrane of Bowman’s capsule
Epithelial cells of Bowman’s capsule - podocytes via filtration slits
What happens to GFR when BP changes
It remains constant
Autoregulation of renal blood flow
Autoregulation persists in denervated kidneys and isolated perfused kidneys - not a neuronal or hormonal response - local effect
Is so Renal blood flow persists
Hypotheses of autoregulation
Myogenic: response to stretch of arterioles
Metabolic: renal metabolites modulate arteriolar contraction/dilation via adenosine and NO
What dilates afferent arteriole
Prostaglandins ANP, dopamine, NO kinase
What constricts afferent arteriole
symp NS, endothelin, adenosine, ADH
What dilates efferent arteriole
Adenosine, NO
What constricts efferent arteriole
Ang II
What does a drop in filtration pressure result in
Drop in GFR -> less Na+ enters proximal tubule -> macula dense sense change in Na+ levels -> stimulates juxtaglomerular cells to release renin -> Ang II
Reabsorption from proximal tubule
60-70% water, Na+, HCO3-, Cl-, K+ and urea
Complete absorption of glucose amino acids and filtered proteins
Driving force: Na+K+ATPase
What does the Na+/K+ATPase pump do to Na, Cl, phosphate and sulphate concentration in proximal tubules
Keeps concentration low (less than 30nM)
Cl- follows Na+ by facilitated diffusion
Phosphate and sulphate are co-transported with Na+
Routes of water reabsorption
Transcellular and paracellular
Transcellular routes involve aquaporin channels on apical and basolateral membranes
There are 4 types of AQP - 1 (PT), 2 (apical of CD), 3&4 (basolateral of tubular cells)
SGLT2 inhibitors
New drugs for controlling T2 diabetes - make patients excrete more glucose
How many amino acid transport processes are there
7
How are proteins reabsorbed from PT
Receptor mediated endocytosis - pinocytosis
What percentage of urea is reabsorbed passively in PT
40-50%
Specialised pumps in PT
One for organic acids
One for organic bases
Secretion of PAH into PT
Para-amino hippurate secreted into PT from blood
Can be used to measure tubular secretion
Transported with alpha ketoglutarate
