Flashcards in Structure and Function of Kidney Deck (18):
1. Describe the anatomy of the kidney and its vasculature.
cortex includes the glomerular structures while the medulla contains the tubular segments
blood supply to the glomerulus enters and exits as a artery
vascular follows: renal artery- segmental artery- inter lobar artery- arcuate artery- interlobar artery, afferent arteriole- glomerulus- efferent arteriole- peritubular capillaries and vasa recta lead to inter lobar, arcuate, inter lobar then renal vein
2. Describe the structure and function of the glomerulus.
bowman's capsule contains a parietal and visceral layer (podocytes) of glomerular capsule
blood enters and exits through the afferent and efferent arterioles
filtrate leaves via the proximal convoluted tubule
3. Explain the juxtaglomerular apparatus and tubuloglomerular feedback.
low volume state serves as a stimulus sensed by macula densa cells (sense low Na and Cl and stretch) and sympathetic nerve endings in JG apparatus
causing release of renin by juxtaglomerular apparatus of renin leading to vasoconstriction and increased Na and water retention
4. Identify the factors that regulate glomerular filtration.
hydrostatic pressure of blood arterioles is only opposed by fluid pressure within the glomerulus and the oncotic pressure of the blood
due to compensation of the arterioles, there is a fairly consistent level of renal blood flow for a wide range of MAP, very high or low BP can lead to changes in filtration
5. Explain the major transport functions of the different segments of the nephron.
proximal tubule: reabsorption of solutes and water (66% Na, 100% glucose, 90% phosphate), water is reabsorbed passively leaving isotonic filtration
loop of Henle: descending limb removes water w/o salt, ascending limb transports NaCl w/o water resulting in countercurrent multiplication
distal convoluted tubule: further reabsorption of sodium and dilution of ultra filtrate
collecting duct: cortical (Na reab, K excretion); medullary reabsorption of water
6. Describe the endocrine functions of the kidney with regard to the production of renin.
1. juxtaglomerular signal
2. efferent constriction
3. juxta release of renin (converts angiotensiongen to angiotensin I, leads to aldeosterone and ADH release action in collecting duct
6. Describe the endocrine functions of the kidney with regard to the production of 1,25-dihydroxy vitamin D3. (which cells, when and to what effect)
kidney converts to active form of vit D by alpha 1 hydroxylase
produced when Ca or Phos are low, promoting healthy bone formation, inhibiting PTH
6. Describe the endocrine functions of the kidney with regard to the production of erythropoietin. (which cells, when and to what effect)
produced when tissue have low oxygenation,
produced by the proximal tubular epithelial cells and cortical interstitial cells
increases RBC production, maturation and lifespan
7. [How would you] assess kidney function with the measure of creatinine clearance?
clearance = (U x V)/ P (don't forget units)
U= urinary concentration of substance
V= urine flow rate (mL/min)
P= plasma concentration of substance (mg/mL)
inulin(exogenous) and cystatin C (proteinase inhibitor) are expensive to test but creatinine (muscle produces) is a endogenous substance that is cheap to test but requires a 24hr. collection
7. [How would you] assess kidney function with the Cockcroft-Gault equation to estimate creatinine clearance? (What are the benefits)
avoid 24h collection
uses weight for a surrogate of muscle mass (potential for error)
and accounts for age and center
good estimate when kidneys function at a high level (measured in chronic not acute disease)
7. [How would you] assess kidney function with the Modification of Diet in Renal disease and CKD-EPI formulae to estimate the glomerular filtration rate?
MDRD is a more complex formula that is useful when the kidney is functioning at lower levels of filtration and stable creatinine (not AKI)
CKD-Epi is the newest formula (not used in AKI)
2. Describe the make up of the glomerular basement membrane.
fenestrated endothelium lines vessel
GBM acellular matrix includes type IV collagen, laminin and negatively charged glycoproteins
potocytes form visceral layer of glomerular capsule (interdigitated- adjacent cells connected by slit diaphragm 40nm) are anchored to GBM
Name 3 important components of podocytes that can be effected by mutation and cause leakage of proteins.
podocin, nephrite and actinin 4
Describe the transporters of the proximal tubule.
Na+ reabsorbed with glucose, phos and AA or exchanged for H+
basolaterally Na+ and bicarbonate are transported together; Na/K ATPase sets up sodium gradient
What is the action of anhydrase inhibitors?
disable CA inside the cell which decreases Na/H activity, blocks transport of H+ and therefore Na reabsorption
cause diaeresis and also decreased bicarb reabsorption (acidosis)
Where is the action of loop diuretics? (what channels are effected and what electrolytes are effected?)
in thick ascending limb: decreases action of NaCLK transporter, disabling channel lease to low Na reabsorption (volume loss) but also loss of Ca, Mg and K
What is the site of action of ADH
reduces aquaporins in the medullary collecting ducts