Kidney Flashcards
1
Q
Kidney
A
- closely related to cardiovascular system since both deal heavily w/bodily fluids
- eliminates Nitrogenous waste via urea in the urine (given normal protein turnover)
- water balance
- pH balance
- [solutes] in extracellular fluid, including Na, K, Cl
2
Q
Dehydration - places of water loss
A
- dehydration is a huge threat to our existence and places of water loss are:
- kidney
- GI
- skin - general water loss via transpiration and sweating
- respiration - when exercise and increase RMV you lose water
- to help with this: kidney can make a concentrated urine to help w/dehydration
- osmolarity of urine (most we can concentrate the urine) is 1200 mOsm urine
- osmolarity is colligative property of a solution - depends on ratio of total number of solutes to solvent in the solution
- vs. molarity is of specific substance
3
Q
To make 1200 mOsm urine
A
- blood plasma has osmolarity of about 300 mOsm
- what we generate is U/P ratio of urine to plasma
- U/P ratio = 1200/300 = 4 (we concentrate our urine 4 fold over the plasma; take solutes and urea and want to eliminate and can concentrate in small volume of water to lose little water); to increase osmolarity you increase solutes not the water
- squirrel has U/P ratio of 9
- hopping mouse has ratio of 22 (extremely dry dessert)
- they win U/P contest; extremely concentrated urine
4
Q
Kidneys make 1% body wt
A
- about the size of fist toward your back wall in abdominal cavity
- but they get 20% of your cardiac output
- if CO is 6L/min x 20% that’s 1200 mL blood/min going to kidneys
- massive amount
- blood is roughly 50/50 plasma to rbc
- if we take 1200 mL x 0.5(%plasma) we have 600 mL of plasma/min coming to kidneys
- kidneys work on plasma not RBC portion
- if CO is 6L/min x 20% that’s 1200 mL blood/min going to kidneys
5
Q
Urinary System
A
- generate urine that goes down the ureters and store in urinary bladder and release thru the urethra
- bladder is storage tank, don’t manipulate urine in the bladder
- kidney stones usually form in ureter and are extremely painful, some smooth muscle around here
6
Q
Kidney circulation
A
- circulation off aorta to kidney and that is how we get 20% CO
7
Q
Kidney Morphology
A
- region on outside - cortext
- region toward center is medulla (sectioned into regions)
- then renal pelvis collects urine to go down ureter
- we have cortical region, medullary region and we change osmolarity btwn 2 regions and that helps make a concentrated urine
- nephron is functional unit of the kidney - some in cortical and some in medullary region
- each nephron has its own circulation and about 1 million per kidney
- vasculature is very extensive and each kidney gets its own circulation - renal artery and renal vein
8
Q
Circulation to nephron
A
- as circulation comes in, we branch off
- each structure represents a capillary vein that goes to each nephron
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9
Q
Nephron
A
- structures upward are cortex and below line are in medulla
- see bowman’s capsule and then into proximal tubule which leads to a structure deep into the medulla and then back up
- and this loop is loop of Henle - important for setting up osmotic gradient
- as go from cortex down into medulla in loop of henle with proximal tubule above: from 300 mOsm(in extracellular fluid) to 1200 mOsm deep in medulla
- osmotic gradient allows us to reabsorb water out of collecting duct if we need to and helps give us concentrated urine
- rate of fluid flow is critical and have fluid moving thru loop of henle all the time
- and then go to the distal tubule and then leads down into the collecting duct to the renal pelvis and then out to bladder
- then look at blood flow to the nephron
10
Q
Blood Flow to Nephron
A
- blood flow comes into afferent arteriole and forms a capillary bed in bowman’s capsule called the glomerulus
- and then blood leads the vessel from the efferent arteroile - which leads to the capillary bed called peritubular capillaries
- special branch of peritubular bed that comes down into the medulla and that is called the vasa recta - brings blood into medulla and when want to reabsorb water we need to put it in the circulation
- blood from peritubular bed goes out the renal vein
- nephron is btwn cortical and medullary region and then have laid on top the circulation
- bring blood to each nephron which has glomerulus and peritubular capillaries
11
Q
Kidney Basic Functions - Nephrons 4 jobs
A
- filtration, reabsorption and secretion
- spring cleaning - throw everything out in trash except huge things and then go into trash and take some stuff out
12
Q
Filtration
A
- happens in the glomerulus, in capillary bed - we create a filtrate
- but things in the trash; anything in filtrate or into the nephron is headed to become urine unless we do something to it
- we create a filtrate and then we realize we might like some of it so we reabsorb (mostly occurs in proximal tubule - take Na+ or glucose back in)
- big stuff does not get filtered - never go into Bowman’s capsule and out of efferent arteriole: RBC, WBC, proteins (come out of efferent arteriole
- glucose, Na+ and K+ do get filtered out and goes into Bowman’s capsul and then into proximal tubule might reabsorb and reduce filtrate by taking back 75-90% of filtrate
- GFR = glomerular filtration rate = 120 mL/min (all nephrons working all together)
- whatever is filtered goes thru Bowman’s capsule
- we have 600 mLplasma/ min into kidney overall; what gets filtered is plasma
- in nephron we filter 120 mL/min into Bowman’s capsule, so not all the plasma gets filtered out; we take about 20%
- beauty of the system - good way to get rid of toxins
13
Q
Reabsorption
A
- takes place in proximal tubule we take back what we want here (take back stuff that we had originally filtered out at glomerulus) as we reabsorb into the peritubular capillaries
- takes back 75-90% of filtrate
- by taking things back in, we take back what we need
- that is how we set the electrolyte concentration (Na, K, Cl) since we take these back and so we set electrolyte concentration
14
Q
Secretion
A
- we have ability to actively secrete into tubule
- in the tubules we have the ability to actively secrete into the tubules from the peritubular capillaries
- way our body handles drugs is this way
15
Q
Excretion
A
what ends up in urine
16
Q
Capillary Bed
A
- we’ve taken normal functions of capillary bed - one end filtration, other end absorption but in kidney we’ve separated 2 functions
- glomerulus for filtration only
- peritubular capillary bed: reabsoption only
- can control/regulate these functions together and individually
18
Q
Long Nephrons
A
- juxtamedullary nephrons - mostly in the medulla and very low and help us with water balance
- cortical nephrons - mostly in cortex and they focus on salt balance
19
Q
Summary
A
- efferent arteriole and then into glomerulus we filter and create filtrate and in proximal tubule we reabsorb into the peritubular bed
- and can secrete back into the tubule and then end up with excretion
20
Q
At Bowman’s Capsule and Glomerulus
A
- smooth muscle around efferent arteriole, and have glomerulus where capillaries are surrounded by special cells called podocytes taht wrap around capillaries
- we filter and bring fluid out in proximal tubule
- podocyte - do size selectivity, keep big molecules in and small molecules push out
- have capillary w/endothelial cells in capillary which create pores thru which we filter
- the podycytes w/fingerlike projections do size selectivity here
- have cells that can contract and can be called into play too called mesangial cells
21
Q
Capillary forces in filtration
A
- hydrostatic pressure - blood pressure
- have oncotic pressure which is 30 mm Hg
- have fluid pressure of 15 mm Hg
- net filtration pressure is 10 mm Hg and all we get is filtration
- we filter out fluid and leave in wbc, rbc, and proteins
- in efferent arteriole going out, it has higher concentration of protein then normal because they were not filtered out at bowman’s capsule
22
Q
Reabsorption takes place in Proximal Tubule and reabsorption into Peritubular bed
A
- actively transport Na+ and anions like Cl- follow
- water follows sodium
- active pumps that move sodium in and chloride follows
- if bring water in then the concentration of other solutes increases
- sodium is key to getting this to go; brings in sodium to proximal tubule thru channel from tubule lumen and then pump into interstitual fluid and exchange for K+
23
Q
Glucose Absorption
A
- symporter - glucose and Na+ together into proximal tubule from tubule lumen (become urine unless do something into it) and then glucose transporter into interstitual fluid in the circulation
- S-GLT2 in kidney
- S-GLT1 in intestine
- Na+ - K+ pump to pump Na+ out so gradient for sodium inside cell of proximal tubule
24
Q
Filtration and Reabsorption
A
- afferent arteriole, filtration and then efferent arteriole
- we filter out 20% of what comes into afferent arteriole
- at end we reabsorb 19% so 80% of what comes in goes into efferent arteriole and filter 20% but get most of that back
- 1% of the volume that we filter gets excreted, so very small percent of what we actually filter gets excreted
- GFR w/all nephrons in both kidneys is 120 mL/min is urine unless you do something to it
- we end up excreting about 1% of what we filter or less which gives us about 1mL/min and your bladder holds 400 mLs so gives you like 400 min
