9. Renal Flashcards
what are the 3 stages of urine production
glomerular filtration/ ultrafiltration
selective reabsorption
tubular secretion
• To initiate the RAAS system one of three things needs to occur:
- Macula densa cells in the distal convoluted tubule detect less NaCl in the tubule
- Sympathetic stimulation
- Little/ no arterial stretch (Low blood volume due to a lack of sodium ions)
- If any of these three things occur the JUXTAGLOMERULAR cells (in afferent arterioles) are stimulated to release the enzyme renin
what does renin do?
enters the blood and here it cleaves the large plasma protein angiotensinogen (produced by the liver) into a smaller polypeptide called Angiotensin I
what is the role of angiotensin I
• The enzyme ACE (angiotensin converting enzyme) which is produced in the lungs is released and cleaves Angiotensin I further to form the active agent of the RAAS system Angiotensin II.
what is the role of angiotensin II
- Stimulates the cells of the zona glomerulosa in the adrenal cortex of the suprarenal/adrenal glands to secrete the steroid hormone ALDOSTERONE
- Acts as a vasoconstrictor which leads to increased pressure and an increased glomerular filtration rate due to vasoconstriction at the efferent arteriole
- Stimulates thirst
- Increases sodium ion reabsorption in the Proximal Convoluted Tubule
- Stimulates ADH release resulting in water retention
what is the role of aldosterone
o Acts on the principal cells of the collecting duct
o Stimulates the transcription of Epithelial Sodium Channels leading to increased sodium and water reabsorption
o Acts slower than ADH as it induces change in gene expression and protein synthesis
o As Sodium ions enter the principal cells they are exchanged for Potassium ions
what is ADH (vasopressin)
o Acts on the principal cells
o Binds to the adenyl-cyclase couple vasopressin receptor and results in the insertion of aquaporin 2 into the apical membrane of DCT and Collecting Duct cells
o This increases water permeability and thus reabsorption resulting in more concentrated urine
o It also increases the UREA permeability of the collecting duct
factors affecting secretion of ADH
o Hypothalamic osmoreceptors – these monitor osmolarity and control the release of ADH accordingly. Increased osmolarity = increased ADH secretion.
o Alcohol – decreases secretion
o MDMA – increases secretion
o Baroreceptors – monitor pressure and adjust secretion accordingly
what can GFR be affected by
age (increasing age decreases GFR)
gender (slower decline in women)
ethnicity
what is a pre renal cause of kidney injury
decreased blood flow to kidney
what is a renal cause of kidney injury
when something goes from with the kidney itself e.g. tubules - acute tubular necrosis
what are post renal cause of kidney injury
obstruction/ damage of urinary tract below the kidney
what are the 2 most common causes of chronic renal failure
diabetes
high blood pressure
what are some major complications of chronic renal failure
- Bone weakness and fractures
- Increased susceptibility to infections and bleeding (ESRD)
- Sexual dysfunction and impotence
- Nervous disorders like seizures and delirium
- Anaemia
What is Chronic Kidney Disease of unknown origin (CKDu)?
steep increase in agricultural communities of chronic kidney disease
