Kidney Secretes Hormones
A. renin(digests circulating proteins),
B.1,25 dihdroxy-Vit D(active Vit D) secreted in proximal tubule -Vit D job to reabsorb ca and phosphate from Gut if you have renal failure you cant secrete this Active Vit D and might have probe absorbing ca
C. Erythropoietin
-problem with kidney means Anemia
Kidney Excretes Waste Products(urea, creatinine)
Responsible Water Balance
Acid/Base Balance -HCL from red meat we have to get rid of Hydrogen Ions in urine
Nephrons
-most are restricted to cortical region they do have loop of hence that dip into Medullary
-Very small percentage of nephron have long loop of henle that dip into Medulla(these create osmolar gradient)
Osmolar Gradient
-in the interstitum at beginning of medulla solution is isotonic 300 similar to the ECF
-as you go down to tip of loop of hence osmolarity can go to as much as 1200 if person was super dehydrated
-once you generate gradient permits ADH while acting on collecting duct allows passive reabsorption of water
Autoregulation and Renal Function Curve
-if Bp increases than Kidney VC in order to maintain RBF constant
-if BP drops than kidney dilate to maintain bf
-It nots that kidney really cares about BF its just trying to maintain GFR (2 mechanisms)
1. Afferent Arteriole does that vc/vd in response to BP
2. Myogenic Response to Smooth M stretch -if you stretch smooth muscle responds by greater constriction that maintains flow if you change perfusing pressure -Tubular Glomerular Feedback-->If GFR increases you deliver more Na/Cl to distal tubule which is monitored by cell called macula densa that sends signal to afferent arteriole which increase or decrease resistance -if you you deliver to much NACL to distal tubule causes constriction of afferent, bringing GFR back in line
Normal GFR 120Ml/Min
-if person loses kidney there GFR goes to 60
-however chronically it is compensated and they only lose 25% GFR bc they increase P(gc)
TF/P=1
-concentration of Bowman capsule is same as concentration in Plasma means its freely filtered
-Sodium/Potassium/Glucose/AA/Inulin/PAH
TF/P=.7 which is 1
-if ratio is greater than 1.2 in bowmans capsulee this is a distractor not possible bc nothing can be secreted into bowmans.
Filtration Fraction
GFR/RBF
-GFR usually 120
-RBF 600(plasma cn)
FF=20% this means all FF stuff will be 20% filtered(Na/k/Glucose)
-so if you raise plasma concentration of Glucose so there is more Glucose per ml of plasma you will filter more Glucose ie more of that 120 will be Glucose even though its still 20%
-So FF is technically the % of fluid I filter in Bowmans capsule but also applies to any freely filtered substance. So if I change FF I change the percentage of the fluid I filter and of the substance I filter
Determinants of GFR
-main factor is Glomerular Capillary Pressure-->so if it increases you have increase in GFR
-also keep in mind if you change plasma protein concentration can also affect the more protein the less GFR
-step might ask what happens to GFR
Factors Affecting Filtration Fraction
Remember these are Done on Percentage Base So higher percentage might be filtered doesn't mean more overall
-if I have very fast flow thru glomerular cap dillary bc fluid tends to spend very little time in cap you tend to have very little filtered.
-If flow slows down than plasma spends more time in glomerular capillaries and more is filtered so FF increases.
Effect of Sympa Nervous System dominant affect on Afferent(VC) but also some Efferent raise renal resistance
Renal plasma Flow decreases
GFR decreases
FF increases(bc flow slows down more filtered)
Also because of this FF increase the proteins leaving Glomerular become more concentrated this also promote reabsorption
Forces promoting reabsorption in the peritubular capillary increases
Bc afferent and efferent constriction causes downstream decrease in pressure. So there will be less
