Basic Renal Structure and Function Flashcards
Kidney percentage of O2 and CO
O2 about 7%
CO 20-25%>> brain
Kidneys are OVer perfused because the extra blood is used for functions other thanjust keeping thekidney alive.
O2 is high (relative to 1% weight) because of all the active tranport needs of the kidneys
3 main kidney functions- how
1 Maintain a relatively Constant EC Environment- This is accomplished by the excretion in urine of many waste products of metabolism (e.g., urea, creatinine) as well as any excess water and solutes that arise from dietary intake. In short, kidneys adjust the content and volume of urine as dietary
and metabolic challenges arise in order to keep the extracellular environment relatively constant.
- Generatin of Hormones- Involved in production of renin and prostaglandin and erythopoitein that stimulates RBC production. ALso activating Vitamin D
- Miscellaneous- gluconeogensis and catabolims of peptide hormones
What ways does the kidney maintain EC constant
- Regulation of water and electrolyte composition of blood- ensures input=output especially for salts and water
- Control of blood osmolality (moles of osmotic particles/liter)- this is mainl y done by controlling NaCl
- Elimination of Metabolic waste from blood- for instance removal of uric acid to avoid gout (-uria means abnormal amounts in urine)
- Eliminatio of other substances from blood (exogenous drugs)- drugs often eliminated from body– peniciliin can be given often because we exrete it quikcly. Pyrogens (proteins released during fever) canbe reduced in the blood by increasing urine flow so hydration is important for fevers
- Regulatin of acid-base- acidic urine removes the H+ that can’t be neurlized by bicarb. Unless the kidney itself isdamage it normally compensates for imbalances in pH caused by other illnessed keeping te body at 7.4
- Regulation of BP- regulate BV by changing overal body water content. increase BV—> increase CVP—> increase CO (also through hormones)
Explain the kidneys functions in homrones production
- Hormonal regulation of BP- kidneys secrete renin which ultimately increase angio II— a vasoconstrictor
- Makes erythropoiten- low blood O2 stimulates more RBC production by the interstitial cells in renal cortex. Erthropoiten stimulates RBC precurosors in the bone maros to mature. This can counter anemia.
** done in blood doping too to improve atheletic preformance with possible side effects of thickening blood**
- Production of active Vitamin D (calcitriol)- Vitamin D produced in skin and by diet. It is activated by two hydroxylations– one of which is in the kidney (other in liver). Calcitrol promotes Ca2+ uptake in the GI tract so vital in keeping Ca2+ levels normal. Low Vitamin D leads to Rickets and osteoporosis
Parts of a kidney
think of the pathway of urine flow
- Outer cortex and medulla
- Medulla further divide dinto inner and outer medulla
- Nephrons- functional unit in both the cortex and medulla
- Ther are 8-18 conical regions calls renal pyramids that have apexs call papilla that project into the minor calyx.
- Renal pyramids—> Minor calyx act a collecting cup for urine forming and empty into the majoy calyces —->renal pelvis drains into —-> ureter—>bladder.
parts of a nephron
Each nephron consists of a
- glomerulus (with BC is called Renal Corpuscle)
- Bowman’s capsule
3proximal tubule
- loopof Henle
- distal tubule
6 collecting duct (multiple nephrons may share a CD)
What happens at the renal corpuscel
At renal corpsucle (BC + glomeruls) this is the site of filtraiton of the blood and the filter fluid enters the BC and goes through the rest of the nephron.
As you travel down the nephron we have secretion and reabsorption and the end product is urine.
Explain the pathway of renal circulation
Renal artery–> Interlobular arteries– arcuate/arciform arteries—> interlobular arteries (radiate towards renal corpuscle)
The interlobular narrow —> afferent arteriole—> ball of glomerular capilllaries
Explain the importance of parallel blood flow
It means that one interlobar feeds many glomeruli so change in flow locally to one glomerulsu will not affect nerighboring glomeruli
Dicuss path of blood after glomerulus
Glomerulus coalesce to make efferent arteriole which carry blood to a second capillary bed called the peritubular capillaries either the vasa recta in jxtamedullary nephrons or branching peritubular in corticol nephrons
What are the two types of neprhons and their major differnece
Corticol (superfiicla)- high in cortex, have a short loop of henle that doesn’t reach inner medulla, have branching peritubular capillary network
Juxtamedullary nephrons- arise in cortex but close to cortex medulla boundry, have long loop of henle that goes into inner medulla, have vasa recta which are loop like peritubular capillaries
Explain features of glomerulus that benefit its function (think larger scale)
Extensive branching of the glomerular capillaries maximizes their surface area for filtration.
The endothelium of the glomerular capillaries is fenestrated to promote filtration.
Encompassed by the BC that gather filtrate and is the start of the nephron
Explain the 3 layers of the glomerulus
- *Filter Layer 1 : the capillary endothelial cells (form holes of ~70 nm)**—This layer is fenestrated to allow filtratio. Fenestrations are too small for RBC but wide enough for most plasma proteins.
- *Filter Layer 2 : the glomerular basement membrane (charged barrier)-**- this layer has a net negative charge (as do plasma proteins) so although they pass through enothelial cells. So generally anything greater than 3nm with a charge isn’t filtered (like albumin and Hb)– note that even with a charge it doesnt affect small negatively charged particles like Cl- (.2nm)
- *Filter Layer 3 : the podocytes (form slits of ~8 nm)**- considered visceral of Bowman’s capsule. These cells have “foot processes” that inter-digitate to form “slit-like holes” or “filtration slits”. These slits do not permit the filtration of molecules in plasma with dimensions greater than ~8 nm.
explain function (2) and location of medangial cells
They re embedded in the mesangial matrix (MM). These phagocytic cells are not part of the filtration pathway, but instead serve a “cleansing function” in the renal corpuscle.
Also, their contraction status (under autonomic control) can regulate total filtration.
- Phagocytes
- Can control contraction and regulate filtration
What happens with distruction of of the Glomerular basment membrane
Loss of GBM negative charge results in filtration of relatively large
plasma proteins. This produces proteinuria (increased concentrations of plasma proteins in urine).
Remember that the first layer allows negative charges through and the GBM is what stops negative charges like albumin and Hb.
