Kidney Flashcards
How many nephrons are there in a kidney?
1 million nephrons per kidney
What are the eight functions of the kidney?
Short term blood pressure control - RAAS system
Haematopoiesis stimulation - EPO
Serum calcium and phosphate increase - Activation of vitamin D to Calcitriol
Acid base balance - acid excretion and bicarbonate reabsorbtion/regeneration
Drug metabolism: Morphine, insulin, paracetamol and others - the kidneys contain P450 enzymes, and has a minor contribution to drug metabolism
Filtration of uraemic toxins - urea and ammonia (two most important)
Regulation of electrolytes
Urine production and concentration - Fluid homeostasis
What is urea?
A non-toxic waste product of amino acid break down, formed from ammonia (toxic) by the liver.
Functions:
Excretion of ammonia - excess nitrogen
Water reabsorption - Osmolar agent in the countercurrent multiplier
It could be used to estimate kidney function since it is excreted by the kidney but urea excretion is heavily influenced by protein turnover (increases urea production) and state of hydration (increases urea reabsorption to increase water reuptake).
What is creatinine?
A breakdown product of creatine phosphate in the muscles due to muscle use. It is produced in muscle at a rate dependent on muscle bulk (consistent), and is excreted unchanged by the kidneys - a good indication of kidney function.
10% of creatinine is derived from dietary sources, mostly from meat, and a higher muscle mass can also increase concentrations - therefore diet and muscle bulk can skew the calculation of eGFR.
USES:
Monitor progression of AKI and CKD
Monitor treatment of AKI and CKD
What are the three functional layers of the vascular kidney glomerulus threshold?
The capillary loops - vascular endothelium
Glomerular Basement membrane (negatively charged)
Podocytes - visceral layer
(Outside this: intracapsular space filled with ultrafiltrate and then Parietal epithelium forms the outer boundary of the Bowman capsule)
- these are the functional layers around each capillary bundle.
- the bundles are stuck together with mesangial cells, kind of like the stem from which the capillary flowers blossom
- this only allows positively charged or small molecules across the layers
How large are the kidneys and where are they?
Roughly the size of a fist - 11cm M or 10cm F
Lie on the transverse processes of T12-L3 and the R is lower than the left due to the liver pushing it down
Where is the kidney’s peritoneum?
The kidneys are retroperitoneal, so only their anterior surface are covered in peritoneum.
What are the protective layers for the kidney?
Perirenal fat and posteriorly the erector spinae muscles
What is the pathway of drainage after the collecting duct?
Papillary duct in renal pyramid
Minor calyx
Major calyx
Renal pelvis
Ureter
Urinary bladder
Where do the renal veins drain?
Both drain to the superior vena cava.
At what age do we start to lose kidney function?
Age 35 - every year there is a 1% loss in kidney function
What are the two types of nephron?
Cortical nephrons - 85% they have a short LOH that goes in to the medulla
Juxtamedullary nephrons - 15% they have a long LOH that goes in to the medulla
“Juxtamedullary” - because the glomerulus is close to the renal medulla
What type of cells make the proximal convoluted part of the nephron?
Columnar and cuboidal cells with a brush border made of microvilli
The PCT is the surface where most of the reabsorption occurs, so it has a high concentration of mitochondria and a large energy requirement.
What kind of epithelium makes up the LOH?
Squamous epithelium
Reminder: water then salt, like making pasta - the descending limb is permeable to water and the ascending limb is permeable only to salt and urea
Which part of the nephron senses reduced glomerular filtration?
The macula densa cells of the juxtaglomerular apparatus, they respond to the composition of the fluid in the PCT lumen
