CH 26 Flashcards
Role of kidneys
- Removes waste (Toxins, muscle break down, protein break down)
- Regulation of pH and ions
- Regulation of blood volume
- Regulation of BP
- Regulation of blood osmolarity (Thickness)
- Production of hormones
Reducing blood volume also reduces
BP
If one kidney is removed, other kidney can compensate up to
80%
Retroperitoneal:
Describing location, posterior to peritenium, does not have membrane on the top
- Typically ribs 11-12 protect at the back (Floating ribs
- T12-L3 vertabrae is level of kidneys
Renal Hilum:
indentation in side
Central area where blood vessels and lymph comes in (Lots of bloods supply)
Kidneys use how much cardiac output
20-30%
3 layers of tissue around each kidney
i) Renal Capsule
ii) Adipose Capsule
iii) Renal Fascia
Renal Capsule
smooth dense irregular Connective Tissue (Shape and protection)
ii) Adipose Capsule
mass of fatty tissue (Protection from impact)
Renal Fascia
thin dense irregular CT (Anchors kidney in position in abdominopelvic cavity)
Renal Cortex
Outer kidney, lighter colour
Renal Medulla:
Darker red, formed into pyramids (8-18 pyramids per kidney)
- Cortex flows bw pyramids, called a column in these locations
Renal papilla
Skinny End/apex of each renal pyramid
Renal Columns
Region bw the pyramids
Nephron
Functional part of the kidney, forms and determines conc. of urine (Born with a #, don’t get any more)
Path of urine
Collecting duct – papillary duct, - minor calyx – major calyx – renal pelvis – ureter – urinary bladder (Outside the kidney)
What do kidneys work hard at in filteration
dealing with proteins
Path of blood flow in kidneys
Afferent Arterioles (Incoming, blood supply into each individual nephron)
Glomerular Capillaries (capillaries in each nephron where filtration of blood begins)
Efferent Arterioles (Blood is leaving the nephron)
Peritubular Capillaries/Vasa Recta (Capillaries that surround the nephrons – providing nephrons with their own blood supply)
Two parts of nephron
Renal corpuscle
Renal tubule
Renal Corpuscle
(where blood plasma is filtered)
- The ball-looking structure
i) Glomerulus (capillary network) ii) Bowman’s Capsule (glomerular capsule) – outer capsule
Renal Tubules
Proximal Convoluted Tubule
Loop of Henle
Distal Convoluted Tubule
Proximal Convoluted Tubule
- Closed to corpusal
Loop of Henle
Descending element of renal tubules
DCT
- Farthest away from the capsule
Cortical nephrons
Most common (80%)
- Most of the nephron will be in the cortex
- Short loop of Henle is in the medulla
- Juxtamedullary Nephrons
(Same structure as corical)
- Closer to the medulla
- Long skinny loop of Henle, significant for determining final composition of urine (Conc. Or diluted)
Layers of th glomerular capsule
Visceral layer
Parietal Layer
Visceral Layer of glomerular capsule
- On top of the capilleries
- Podocytes
Podocytes
A certain cell with fingerlike extension that lays on top of capillaries in the glomularis
Eventually have ability to determine what leaves blood and goes into urine
Parietal layer of Glomerular capsule
Capsule (bowmans) Space
- The actual space inside the capsule
- When plasma leaves capillary and enters capsular space it is called filtrate
- Plasma proteins should not be in filtrate, bc they normally cannot fit out of capillaries
Macula Densa cells
Part of the tubule (The ascending limb) that comes close to the capsule
o Touch afferent arteriole
o Play role in determining if afferent arteriole dilates or constricts
Juxtaglomerular Cells
Part of the wall of the afferent arteriole
o Basically modified smooth muscle cells
o Typically would find some in efferent arteriole as well
Juxtaglomerular Apparatus
o Macula Densa and juxtaglomerular together are referred to as juxtaglomerular apparatus – major BP regulators
Principal Cells
Found in last part of distal convoluted tubule and collecting duct
o Primarily responsible for determining final concentration of urine (Thick or thin)
o Have receptors (Protein is inserted into those cells) for antidiuretic hormone.
- Intercalated Cells:
found mainly on collecting ducts and distal convoluted tubule.
o Monitor pH of the urine (Typically slightly acidic)
o Hanging on to bicarbonate or letting nitrate out allows for regulation of pH
Filtration
Something that was in the blood is now in the capsular spae (Now called filtrate)
How much filrate produced by a healthy person per day?
150-180L
How much filtrate reabsorbed into the bloodstream
99%
Stages of urine production
i) Glomerular Filtration
ii) Tubular Reabsorption
iii) Tubular Secretion
What occurs in Glomerular Filtration
Filtrate moves from From blood into capsular space
What ocurs in tubular reabsorption
Fluid or substances going from tubules back into the capillaries (Vasa recta or peritubular capillaries)
What occurs in tubular secretion
More things moving from the capillaries back into the tubules.
Hyper hydrated
blood volume is enough therefore more water is excreted in the urine
- Glomerular Filtrate
Any fluid and solutes that end up in the capsular space
- Filtration Fraction
What percentage of the blood that came into the capsule ends (from afferent arteriole) up as filtrate.
o Typically, from 16-20%
3 Components of filtrate membrane
i) Glomerular endothelial cells with fenestrations
* Mesangial Cell
ii) Basal Lamina
iii) Podocyte
Fenestrations
: Holes/openings in the linings of the capillaries, fluid and some solutes can begin to pass through.
Specifically of glomerular endothelial cells
Parts of Podocyte
- Pedicels: The fingers of the podocyte
- Filtration Slits (Space): The space bw the pedicels
- Slit (Filtration) Membrane: Final filtration layer – small amino acids, water soluble vitamins, hormones can all make it through; proteins cannot get through this membrane
principals of filtration
- Capsular capillaries = large surface area for filtration
- Filtration membrane is thin and porous
- Glomerular capillary BP is high – to drive filtration: #1 factor determining how much filtrate is formed
Glomerular filtration depends on which three main pressures?
Glomerular Blood Hydrostatic Pressure
Capsular Hydrostatic Pressure
Blood Colloid Osmotic Pressure
Glomerular Blood Hydrostatic Pressure (GBHP)
– promotes filtration
~ 55 mmHg
- Basically your blood pressure – in the afferent arteriole
CHP (Capsular Hydrostatic Pressure)
resists filtration
~ 15 mmHg
- Pressure produced by fluid already yin capsular space (Says “We’re full, we don’t want more fluid here”)
BCOP (Blood Colloid Osmotic Pressure)
resists filtration
~ 30 mmHg
- Colloid is particle in plasma (plasma proteins)
- Don’t want water to leave
- Resisting filtration
- Maintaining osmolarity (Blood thickness)
How would net filtration pressure be calculated
(NFP) = GBHP-CHP-BCOP
~ 10 mmHg
- Typical under resting conditions
GFR
Glomerular Filtration Rate (GFR)
- Way to measure the efficiency of kidneys
Amount of filtrate formed in both kidneys (all renal corpuscles) each minute
Average GFR in adults
= 125 ml/min (males)
= 105 ml/min (females)
GFR regulation works by two main processes
i) Adjusting blood flow in and out of glomerulus (adjusting afferent arteriole)
- Increase blood flow in, increase GFR
ii) Altering glomerular capillary surface area for filtration.
- Allow it to filter more or less
Renal Autoregulation of GFR
- Nephrons control blood flow and therefore control GFR
- myogenic and tubuloglomerular feedback
Myogenic (muscle) mechanism
- High BP is problem
- Causes stretch in wall of afferent arteriole
- This causes myogenic constriction of arteriole walls.
- Narrows lumen
- Reduces blood flow
- Drops GFR back to normal (Occurs in seconds)
- Tubuloglomerular Feedback
- Tubule creates the change
- Slower (Minutes) than myogenic
If high BP is problem - Filtrate moves quickly when high BP through tubules,
- water and sodium cannot be reabsorbed bc of fast rate (this is monitored by macula densa cells)
- Less Nitric Oxide (dialator) released by juxtaglumular apparatus
- Constricts afferent arteriole, reducing blood flow, reducing rate of arteriole tubule flow
- When flow slows down, reabsorption rate is back to normal
What does low sodium mean in relation to BP?
Less water absorbed into blood therefore lower BP
Neural regulation of GFR
Autoregulation occurs during parasymp. dominance
Increase in stress results in less blood flow to kidneys and thus lower GFR
Hormonal regulation of GFR
Takes longer and lasts longer
Angiotensin ll reduces GFR by Constricting afferent and efferent arterioles
Atrial Natriuretic Peptide (ANP) (increases GFR)
How does angiotensin ll affect GFR
reduces GFR by Constricting afferent and efferent arterioles
- Atrial Natriuretic Peptide (ANP) affect on GFR
- Hormone released by heart when BV is too high, increase GFR when ANP goes up
- Increases filtration on the filtration membrane using the mesengeal cells
What part of the renal tubules determines final composition of urine
collecting duct
What does reabsorption imply?
back into peritubular capillaries
What does secretion imply?
From blood supply (capilleries) back into tubules
Which part of tubule does most of the reabsorption?
mostly through the Proximal Convoluted Tubule with more distal tubule cells “fine tuning” – in collecting ducts.
Paracellular reabsorption
Filtrate moves bw cells of tubule
Transcellular reabsorption
Filtrate moves through individual cells of tubule
Components of tubule wall
INNER
* Apical Membrane
- The fingers that faces into the filtrate/urine
* Tight Junctions
- Spaces that weld individual cells together
* Basolateral Membrane
- Faces interstitial fluid
OUTER
Transport mechanisms of filtrate
Primary active transport
- ATP required
Secondary Active transport
- Indirectly using energy (Moving down the gradient)
Any time a pump is present, the form of transport must be
Active transport
Transport maximum
Cerntain # of transporters on tubule, once all are full you’ve reached the TRANSPORT MAXIMUM of the solute
therefore substance stays in the urine and is not reabsorbed (Glucose in urine in diabetes)
- Obligatory H2O Reabsorption
- Water is absorbed along with solutes (normally sodium)
- 90% of h20 reabsorbed done so in obligatory fashion
- When solute is reabsorbed, water will follow
- Reason why hypertension person tries to reduce their sodium (More sodium more blood plessure)
- Facultative H2O Reabsorption
- Remaining 10% of any water not reabsorbed with solutes
- Primarily collecting ducts (end of tubule)
- Under influence of antidiuretic hormone
- used for Fine tuning final composition of the urine
Glucosuria
Glucose in urine
- Usually, a problem when all glucose transporters for reabsorption are full
Urine formation (6 steps)
Step 1: Glomerular filtration produces a filtrate resembling blood plasma but containing few plasma proteins.
Step 2: In the PCT, 60-70 percent of the water and almost all of the dissolved nutrients are reabsorbed. The osmolarity of the tubular fluid remains unchanged.
Step 3: In the PCT and descending loop of Henle, water moves into the surrounding interstitial fluid, leaving a small fluid volume of highly concentrated tubular fluid.
Step 4: The ascending limb is impermeable to water and solutes. The tubular cells actively pump sodium and chloride ions out of the tubular fluid. Because only sodium and chloride ions are removed, urea now accounts for a higher proportion of the solutes in the tubular fluid.
Step 5: The final composition and concentration of the tubular fluid will be determined by the events under way in the DCT and the collecting ducts. These segments are impermeable to solutes, but ions may be actively transported into or out of the filtrate under the control of hormones such as aldosterone.
Step 6: The concentration of urine is controlled by variations in the water permeabilities of the DCT and the collecting ducts. These segments are impermeable to water unless exposed to antidiuretic hormone (ADH). In the absence of ADH, no water reabsorption occurs, and the individual produces a large volume of dilute urine. At high concentrations of ADH, the collecting ducts become freely permeable to water, and the individual produces a small volume of highly concentrated urine.
How much filtrate produced in glomerular filtration
120-180L
Hormones causing a reabsorption of electrolytes
Angiotensin ll
Aldosterone
Hormones causing H2O Absorption
ADH (Antidiuretic hormone)
Aldosterone
Both have minor effects
What is the active from of angiotensin and how is it converted to this?
Angiotensin ll is the active from, converted by Angiotensin converting enzyme (ACE)
RAA
Renin Angiotensin ALdosterone system
Job of Aldosterone
Decrease ADH = dilluted urine
Affects of angiotensin ll
Stimulates release of ADH (reabsorption of H2O)
Stimulates Aldosterone
Reabsorption of solutes and water in PCT
Decreases GFR via vasoconstriction of afferent arteries
Atrial Natriuretic Peptide affects
) Inhibition of H2O reabsorption in PCT and collecting duct
2) Decreased aldosterone release
3) Decreased ADH release
ALL stimulate secretion of Na into urine and therefore increase output
What hormone is primarilly responsible for facultative reabsorption
Antidiuretic hormone (Vasopressin)
Vasopressin AKA
Antidiuretic hormone
How does Antidiuretic hormone work
Increase in osmolarity (stimulus)
Osmoreceptors in hypothalamus detect change
increase ADH release in blood
Increase permeabiilty of cells in DCT and collecting duct (by increasing aquaporin -2)
Facultative Water reabsorption
osmolarity normal
Parathyroid hormone (PTH)
Decreased blood calcium
parathyroid releases PTH
Causes:
- DCT reabsorb more Ca into blood
- Inhibits HPO4 reabsorption into PCT = increased phosphate excretion
Where does the antidiuretic hormone work?
Collecting ducts
How does osmolarity change throughout renal tubule
Increase decending loop of Henle
Decrease ascending loop of Henle
decrease along rest of the pathway
How does ADH affect permeabiliy of collecting ducts
When ADH is low, ducts are impermeable to H2O so tubular fluid becomes more dilute
Why would urine become conc.?
Fluid Intake is low or loss is high
kidneys conserve H2O but still rid excess wastes and ions
ADH critical
BUN
Blood Urea Nitrogen blood test
- Increase in blood N means GFR has come down
Plasma Creatine blood test
- If blood creatinine level went up dramatical GFR level is not as functional/efficient as it should be
Renal Plasma clearance
“Volume of blood cleaned of a specific substance per unit of time”
Every substance has different renal plasna clearance
Hemodialysis
“Artificial blood cleansing by separating elements through a semi permeable membrane”
must happen every 2-4 days in cases of kidney failure
CAPD
(Continuous ambulatory Peritoneal Dialysis)
- Peritoneal cavity is viewed as membrane for filtering (filter put in cavity which cleanses blood)
Urine transportation from kidneys
Collecting ducts - papillary ducts - Minor Calyces - Major calyces - Renal pelvis - Ureters - Urinary Bladder - Urethra
Wall of bladder
Detrusor muscle
- Begins to contract when certain level of urine is reached
- Trigone
Part of bladder, triangle before the exit to exterior
- Internal Urethral sphincter
- Under parasympathetic control (non voluntary)
- External Urethral Sphincter
- Voluntary control
- Where is urethra is leaving internal and becoming external
Micturition Reflex
Bladder contraction
Describe process of Micturition Reflex
When volume of urine greater than 200-400 mL
Stretch receptors send signals up spine to Micturition center (S2-S3) triggering reflex
PS reflex cause contraction of detrusor muscles and relaxation of internal urethral sphicter
Simultaneously somatic motor neurons in external sphincter are inhibited
What occurs to kidneys with agin
Shrink, decreased renal blodo flow (50%)
Decline in filtration rate
Thirst and age
Thirst sense diminishes, not as sensitive (osmoreceptors and hypothalamus)
- Polyuria
Excessive urination
- Dysuria
Pain during urination (infection, disease, UTI)
- Stress Incontinence
Unwanted release of urine due to coughing, laughing, sneezing, excersise
UTI
Bladder, urethra – link bw bladder infection and kidney infection with decline in cognition
