deck_17307781 Flashcards
urinary system maintains homeostasis by regulating the ____ and ____ of blood
volume & composition of blood
concentration of urine
855–1355 mOsm/L
kidneys excrete ____, especially ____
solutes
esp metabolic wastes
E.g. of metabolic wastes
Urea
Creatinine
Uric acid
urea
Most abundant organic waste
By-product of amino acid breakdown
creatinine
By-product of creatine phosphate breakdown in muscles
Uric acid
Formed during recycling of nitrogenous bases of RNA
three processes involved in urine formation:
1) filtration
2) reabsorption
3) secretion
____
secretion vs filtration?
“Filtration occurs in the glomerulus, while secretion occurs in the proximal and distal convoluted tubules.” (AI)
“secretion is the movement of solutes from the bloodstream into the filtrate.”
filtration
blood hydrostatic pressure forces water and solutes across the membranes of the glomerular capillaries into the capsular space
filtration ONLY happens in ____
ONLY happens in the glomerulus
The resulting fluid that enters the capsular space is _____
the glomerular filtrate
filtration occurs through ___
the filtration membrane
filtration membrane consists of
1) fenestrations of glomerular endothelial cells (capillaries)
2) basement membrane (collagen fibres & proteoglycans)
3) filtration slit = space between pedicels of podocytes
what is too big to cross the GLOMERULAR (capillary) ENDOTHELIAL CELLS?
blood cells & proteins too big too cross
what is too big to cross the BASEMENT MEMBRANE?
large negatively charged proteins do not fit
what fits through the filtrations slits
water, glucose, vitamins, amino acids, very small plasma proteins, ammonia, urea, & ions fit
NET FILTRATION PRESSURE
(NFP)
Glomerular Blood Hydrostatic Pressure (GBHP)
+
Capsular Hydrostatic Pressure (CHP)
+
Blood Colloid Osmotic Pressure (BCOP)
Glomerular Blood Hydrostatic Pressure (GBHP) =
55 mmHg
blood pressure in glomerular capillaries
Pro-filtration
Capsular Hydrostatic Pressure (CHP) =
15 mmHg
hydrostatic pressure pushing against filtration membrane by fluid already in capsular space
Anti-filtration
Blood Colloid Osmotic Pressure (BCOP) =
30 mmHg
osmotic pressure of large proteins pulling water into capillaries
Anti-filtration
so NFP is …
(GBHP) – (CHP) – (BCOP)
(55 – 15 – 30)
= 10 mmHg (under normal circumstances)
therefore, NFP dictates …
NFP dictates how much will move in which direction
filtration will stop if (for instance) …
*** Filtration stops if GBHP drops below 45mmHg
b/c in this example, opposing pressure = 45mmHg
Filtration Fraction (FF)
note two concepts
Renal plasma flow (RPF)
Filtration fraction (FF)
Renal plasma flow (RPF) =
volume of plasma that moves through the kidneys per unit time
Filtration fraction (FF) =
is the fraction of RPF that becomes GLOMERULAR FILTRATE
recall – what is glomerular filtrate?
The resulting fluid that enters the capsular space
normal Filtration Fraction (percentage)?
Normal FF = 16-20%
what is daily GLOMERULAR FILTRATE (avg)
Daily glomerular filtrate = 150L - 180L
what percentage of glomerular filtrate is RETURNED to bloodstream?
therefore, how much urine is actually produced?
99% of filtrate is returned to bloodstream
by tubular REABSORPTION
Therefore, 1-2L of urine produced daily
Glomerular Filtration Rate (GFR)
amount of filtrate formed per minute in all the renal corpuscles of both kidneys
normal glomerular filtration rate
Normal is 105-120 ml/min
Glomerular Filtration rate is DIRECTLY proportional to ____
Net Filtration Pressure
(NFP)
(Increased Net Filtration Pressure (NFP) INCREASES Glomerular Filtration Rate (GFR) )
how is Kidney function tested?
via eGFR (estimated)
what values indicate kidney disease vs kidney failure
An eGFR of <90 usually indicates kidney disease
An eGFR of <15 usually indicates kidney failure
what is the problem with GFR getting too high
If GFR ever gets too high, needed substances pass so quickly through renal tubules that they can’t be reabsorbed & are lost in urine
what is the problem with GFR getting too low?
If GFR ever gets too low, metabolic wastes will not get filtered from the blood and into the renal tubules
what THREE regulatory mechanisms are in place to maintain GFR?
1) Renal autoregulation
2) Neural regulation
3) Hormonal regulation
1) RENAL AUTOREGULATION (to maintain GFR)
involves TWO important structures …
Mesangial cells
Juxtaglomerular Apparatus (JGA)
renal autoregulation involves TWO important mechanisms
Myogenic mechanism (faster)
Tubuloglomerular feedback (slower)
Mesangial cells (of renal autoregulation, of GFR)
mesangial cells lie between ___
Lie between adjacent GLOMERULAR CAPILLARIES
mesangial cells control ____
capillary diameter and rate of blood flow
Juxtaglomerular Apparatus (JGA)
(of renal autoregulation, of GFR)
a specialized structure where the distal convoluted tubule meets the afferent arteriole
main function is to regulate blood pressure and the filtration rate of the glomerulus
Juxtaglomerular Apparatus (JGA) structures
Macula densa
Juxtaglomerular cells (granular cells)
Extraglomerular mesangial cells
macula densa
Specialized cells in the DCT
detectÂchanges in tubule NaCl concentration
—> therefore detects changes in GFR
Juxtaglomerular cells (granular cells)
Specialized cells in the AFFERENT arteriole
Secrete RENIN in response to low BP
–> + renin = +BP
Extraglomerular mesangial cells
can affect blood flow through the arterioles
Myogenic mechanism (faster type of renal autoregulation)
stretch receptors in afferent arterioles respond to increased or decreased blood pressure (BP)
Smooth muscle of afferent arteriole constricts or dilates to increase or decrease GFR to what it was previous to BP change
Tubuloglomerular feedback (slower)
Uses the juxtaglomerular apparatus
with the tubuloglomerular feedback, when BP is increased, GFR is increased
THEREFORE, in response, in order to DECREASE GFR, the following takes place:
macula densa cells (of JGA) detect increased concentration of Na+, Cl-
Macula densa cells release a vasoconstrictor (adenosine)
Afferent arterioles vasoconstrict = DECREASED GFR
with the tubuloglomerular feedback, when BP is decreased, GFR is decreased
THEREFORE, in response, in order to INCREASE GFR, the following takes place:
Macula densa cells (of JGA) detect decreased concentration of Na+, Cl-
Macula densa cells release vasodilators (nitric oxide)
Afferent arterioles vasodilate = INCREASED GFR
(Also, signal for juxtaglomerular cells to release RENIN which will work to get BP up (more later))
NEURAL REGULATION of GFR
at rest, not much sympathetic ANS stimulation
renal autoregulation prevails
neural autoregulation of GFR during fight-or-flight (stress) response
during fight-or-flight, sympathetic ANS fibres release norepinephrine to cause vasoconstriction of afferent arterioles
= DECREASED GFR
(no need to produce urine when in dangerous scenario)
If (overall systemic) blood pressure is very low (MAP < 65 mmHg) what happens to neural regulation of GFR?
sympathetic NS is activated
Increases BP systemically to make sure important tissues are perfused
vasoconstriction of afferent arterioles to conserve blood elsewhere = DECREASED GFR
—> Sacrifices GFR
(Also causes release of RENIN)
3) Hormonal Regulation of GFR
(important components)
Angiotensin II
ANP (Atrial Natriuretic Peptide)
Angiotensin II
Part of RAA system (renin-angiotensin-aldosterone system)
Increased in response to renin (from JGA)
FYI:
(Aim is to get blood pressure up without increasing GFR too much, so it will maintain or slightly increase GFR)
(—> vasoconstrictor = narrow afferent and efferent arterioles)
—> *also increases reabsorption (more later)
ANP (Atrial Natriuretic Peptide)
secreted by heart cells when blood in atria stretch walls
relaxes mesangial cells = INCREASES surface area of glomerulus = INCREASES GFR
—> *also limits reabsorption (more later)
REABSORPTION
Movement of solutes and water from renal tubules into the blood
(peritubular capillaries or vasa recta)
reabsorption can either be ___ or ___
paracellular
or transcellular
transcellular reabsorption utilizes …
primary and secondary active transport
primary active transport
moves solute across membrane with a pump using ATP (ie. Na+/K+ATPase)
secondary active transport
electrochemical gradient causes the movement of 2 ions across membrane; one ion moves with its gradient and other moves against its gradient
symporters: move 2 or more ions in same direction
antiporters: move 2 or more ions in opposite directions
MOST REABSORPTION takes place in
Proximal Convoluted Tubule (PCT)
what can get reabsorbed in PCT?
> 99 percent of glucose,
amino acids,
other organic nutrients
Sodium,
potassium,
bicarbonate,
magnesium,
phosphate,
sulfate ions
Water (about 108 liters each day)
Glucose Amino Acid Reabsorption from THE PCT
Various Na+ symporters in APICAL MEMBRANE reclaim:
—> 100% of filtered glucose & amino acids, HPO42, SO42-, & lactic acid
most use FACILITATED DIFFUSION to cross BASOLATERAL MEMBRANE and flow into interstitial fluid, and then PERITUBULAR CAPILLARIES
except for Na+ which crosses basolateral membrane via ___
via sodium-potassium pump (ATPase)
Bicarbonate Reabsorption from THE PCT
Antiporters move H+ from cytosol to lumen, and Na+ from lumen to cytosol
supply of H+ maintained by CO2 flowing into cell
—> Recall CO2 + H2O —> H2CO3 —> H+ + HCO3-
(this process also reabsorbs 80-90% of filtered HCO3-)
Water reabsorption from PCT is via
Via osmosis (obligatory water reabsorption)
& PARACELLULAR REABSORPTION (passive process through leaky tight junctions)
this is d/t solutes increased of osmolarity of cytosol, interstitial fluid, and then peritubular blood
—> Water follows the solutes
also,
tubule cells in PCT & descending limb of nephron loop have high amount of aquaporins in APICAL & BASOLATERAL membranes
remaining reabsorption from PCT
50% of filtered:
—> Cl-
—> urea
variable amount of filtered:
—> Mg2+
—> Ca2+
—> HPO42-
Secretion @ PCT
H+ is released into the lumen via Na+/H+ antiporters
H+ secretion controls blood pH
Also, substances eliminated from the body:
—> NH4+ and some medications
OVERVIEW OF reabsorption & secretion @ THE PCT
Reabsorption:
100% of filtered glucose, amino acids, HPO42, SO42-, & lactic acid
85-90% of filtered bicarbonate
65% of filtered H2O
65% of filtered sodium, potassium
50% of filtered chloride, urea
Secretion:
Ammonium (NH4+) and some medications
Nephron loop and reabsorption/secretion
why is fluid in nephron loop different from original filtrate
there is LOTS of ____ but VERY LITTLE ____
fluid here is quite different from original filtrate b/c glucose, amino acids & other nutrients are removed
enters this part of tubule more slowly d/t less H2O in fluid
Lots of reabsorption, VERY LITTLE TO NO SECRETION
reabsorption @ NEPHRON
what percentage of H2O?
ONLY IN WHICH part of the nephron loop?
15% of filtered H2O
in descending limb only
ascending limb impermeable to water
other substances reabsorbed @ nephron loop
20-30% of filtered Na+ & K+
35% of filtered Cl-
10-20% of filtered HCO3-
variable Mg2+ & Ca2+
REABSORPTION & SECRETION
(@ EARLY DISTAL CONVOLUTED TUBULE)
Why does fluid (filtrate) begin travelling slowly at this point?
Fluid travelling very slowly, as 80% water reabsorbed
what else reabsorbed @ DCT?
10-15% of remaining water via osmosis
5% of Na+ & Cl-
PTH acts here to reabsorb Ca2+
secretion @ EARLY DCT
none
Late Distal Convoluted Tubule and Collecting Duct
(reabsorption & secretion)
what percentage of water/solutes have been returned to blood at this point?
90-95% of water and solutes have been returned to blood
H2O and solute reabsorption & secretion here depend on body’s needs
reabsorption @ LATE DCT involves two cells
Principal cells & Intercalated cells
principal cells of late DCT – responsible for …
reabsorb Na+ & H2O
(Secrete K+)
intercalated cells of late DCT – responsible for …
(reabsorb K+)
reabsorb HCO3- to regulate pH
two hormones involved with increasing blood volume (@ DCT)
ADH
Aldosterone
ADH (@ late DCT)
ADH stimulates formation of aquaporins to reabsorb H2O
Aldosteron (@ late DCT)
stimulates reabsorption of Na+, Cl-, & H2O
Late Distal Convoluted Tubule and Collecting Duct
SECRETION
Principal cells: secrete K+
Intercalated cells: secrete H+
Urea
Hormonal Regulation of Tubular Reabsorption & Secretion
Many hormones play a role in regulating the amount of solute and water that is reabsorbed or secreted in the tubules
which hormones play a role in regulation of reabsorption & secretion
1) Renin-Aldosterone-Angiotensin System (RAAS)
2) Antidiuretic Hormone (ADH)
3) Atrial Natriuretic Peptide (ANP)
4) Parathyroid Hormone (PTH)
5) Calcitonin
1) Renin-Angiotensin-Aldosterone System (RAAS)
Angiotensin II
Already discussed: REDUCED GFR via vasoconstriction of afferent arterioles
—>
INCREASED reabsorption of Na+, Cl- and therefore H2O via Na+/H+ antiporters in PCT
—>
stimulates adrenal cortex to release ALDOSTERONE
Aldosterone
acts on principal cells to reabsorb more Na+, Cl-, and therefore H2O
2) Antidiuretic Hormone (ADH)
osmoreceptors in hypothalamus respond to low blood volume by stimulating posterior pituitary to release ADH
—>
Also released in response to angiotensin II
principal cells INCREASE number of aquaporins on apical surface to reabsorb more H2O
—>
REDUCED ADH = dilute urine
INCREASED ADH = concentrated urine
3) Atrial Natriuretic Peptide (ANP)
atrial cells in heart release ANP in response to increased stretch due to elevated BP
Already discussed: relaxes mesangial cells = INCREASE surface area of glomerulus = INCREASE GFR
inhibits reabsorption of Na+ and therefore H2O in PCT & collecting duct
**(also, suppresses secretion of ADH & aldosterone )
4) Parathyroid Hormone (PTH)
REDUCED blood Ca2+ = parathyroid glands release PTH
cells in early DCT INCREASE Ca2+ reabsorption = INCREASED blood Ca2+
5) Calcitonin
INCREASED blood Ca2+ = parafollicular cells (C cells) release calcitonin
REDUCED Ca2+ reabsorption in the distal tubule = REDUCED blood Ca2+
TWO TYPES OF WATER REABSORPTION
1) Obligatory water reabsorption
2) Facultative water reabsorption
1) Obligatory water reabsorption
Occurs in locations where water movements cannot be prevented
Rate cannot be adjusted
Recovers 85 percent of filtrate
where does obligatory water reabsorption take place?
PCT and descending limb of nephron loop
2) Facultative water reabsorption
Allows precise control of water reabsorption by ADH
Adjusts urine volume by reabsorbing a portion (or all) of the remaining 15 percent of filtrate volume
where does facultative water reabsorption take place?
Occurs in the DCT and collecting tubule
NORMAL URINE volume
Normal volume is about 1200 mL/day
NORMAL URINE osmotic concentration
Normal osmotic concentration of 600 - 1500 mOsm/L
urine values differ …
Values differ from person to person and from day to day
(Kidneys alter their function to maintain homeostasis)
The production of dilute urine
..
dilute urine is produced in the absence of ____
produced in the absence of ADH
No ADH =
Err:509
kidneys produce dilute urine b/c …
= no aquaporins = less water reabsorption
therefore
—>
urine up to 4X more dilute than blood plasma
(As low as 80 mOsm/L compared to 300 mOsm/L of blood)
Causes of dilute urine
Over hydration
Diabetes insipidus (more later)
Renal failure
The production of concentrated urine
produce with ____
Concentrated urine is produced in the presence of ADH
kidneys produce concentrated urine b/c large amounts of water are reabsorbed from the tubular fluid into the interstitial fluid
—>
therefore increasing solute concentration of the urine (urine up to 5X more concentrated than blood plasma)
THE COUNTERCURRENT MULTIPLICATION SYSTEM
A system in the nephron loop of juxtamedullary nephrons that allows the kidneys to produce concentrated urine
countercurrent multiplication system generates ____
enables you to ____
generates anÂOSMOTIC GRADIENTÂin the renal interstitial fluid
—> enables you to reabsorb water from the tubular fluid and produce concentrated urine
(So don’t unnecessarily lose water in the urine)
nephron loop — thin descending limb
permeable to ____
impermeable to ____
permeable to H2O
impermeable to Na+, Cl-, K+
juxtamedullary nephrons BV
vasa recta
nephron loop – THICK ascending limb
permeable to Na+, Cl-, K+
Impermeable to H2O
how is Na+, Cl-, K+ pumped out of THICK ascending limb?
Pumped out of tubule due to Na+-K+-2Cl- cotransporters
D/t to the DIFFERENCE in permeability b/w thin/thick limbs, we establish _____ in the _____
we establish an osmotic gradient in the renal medulla
why is it called the “countercurrent multiplication system”
Countercurrent because the thin and thick limbs run in opposite directions to each other
Multiplication because the osmolality of the renal medulla increases or â€multiplies†the deeper you go
osmolality vs osmolarity
Osmolarity is the number of milliosmoles of solute per liter solution. This differs from osmolality (osm), which is the milliosmoles of solute per kilogram of solution.
what does thick ascending limb do?
actively pumps Na+, Cl-, and K+ in the interstitial space of the renal medulla
what happens to renal medulla in this area (of the thick ascending limb?)
Why?
it makes the renal medulla â€salty†or hypertonic in this area
Because the thick ascending limb is impermeable to water
what does salty medulla lead to?
This allows for passive water absorption in the thin descending limb (obligatory) and the collecting duct (in the presence of ADH)
NOTE WHAT UREA DOES IN COUNTERCURRENT MULTIPLICATION SYSTEM
it is reabsorbed in the collecting duct, but secreted in the ascending limb
—>
(Goes back)
“recycled†in a process called urea recycling
what is the purpose of urea recycling?
Also helps maintain the osmotic gradient in the renal medulla
(Helps reabsorb water passively)
Countercurrent exchange
is the process by which solutes and water are passively exchanged between the blood of the vasa recta and interstitial fluid of the renal medulla
Helps to reabsorb water without “washing away†the osmotic gradient we worked so hard to set up
the vasa recta is called ____
because ____
the vasa recta is called the countercurrent exchanger
b/c the descending and ascending portions also run opposite of each other and they exchange solutes and H2O
vasa recta also supply ____ with _____
Vasa recta also supply the renal medulla with oxygen and nutrients
Pathology
..
Diabetes Insipidus
An inadequate response to ADH
or inadequate production of antidiuretic hormone (ADH)
insipidus
“lacking flavour or zest”
types of diabetes insipidus
Central DI (diabetes insipidus)
Nephrogenic DI
Central DI
inability of the posterior pituitary/hypothalamus to secrete ADH
nephrogenic DI
defects in ADH receptors
DI SSx
excretion of large volumes of dilute urine
with resulting dehydration and thirst
what happens if DI not treated
can experience SSx of dehydration
—> Feeling dizzyÂor lightheaded, nausea, fainting, fatigue
—> Having a dry mouth, lips and eyes
—> Difficulty performing simple mental tasks
DI, Epidemiology
what is rate?
Who can it affect? (age)
Rare: It affects about 1 in 25,000 people worldwide
People of all ages can develop diabetes insipidus
Etiology, central DI
Damage to the hypothalamus/posterior pituitary during surgery or due to head injury
Non-functional brain tumours
Genetic mutations
Autoimmune destruction of cells that make ADH
nephrogenic DI, etiology
medications (lithium, tetracycline)
Inherited genetic mutations
Central DI, Tx
Desmopressin (synthetic vasopressin or ADH)
Nephrogenic DI, Tx
Thiazide diuretics (?)
In the absence of ADH (receptors?), these (anti-?)diuretics decrease urinary output by decreasing GFR
DI, Px
Usually good if managed well and those affected drink enough water
LECTURE 3
..
Normal Urine Composition
..
normal urine volume
normal urine osmolarity
Normal volume is about 1200 milliLiters/day
with an osmotic concentration of 1000 milliOsmole/L
what can changes in urine indicate?
Changes in urine can be tested and measured to show abnormalities in the urinary system
or abnormalities elsewhere
urine water composition
95% of total urine volume
remaining 5% of urine composition
Electrolytes
“Solutes derived from cellular metabolism”
Exogenous substances such as drugs
Small quantities of fatty acids, pigments, enzymes and hormones
what are “Solutes derived from cellular metabolism” ?
UREA from protein breakdown
CREATININE from creatine phosphate breakdown in mm. fibres
URIC ACID from nucleic acid breakdown
UROBILINOGEN from hemoglobin breakdown
Urinalysis
sample of urine is taken and individual substances are analyzed
what substances are analyzed in Urinalysis
RBC
WBC
nitrites
leukocyte esterase
proteins
glucose
among others…
what does RBC in urine indicate
may indicate infection or kidney stones, but blood could be from other sources
what does WBC in urine indicate
may indicate infection in urinary tract
what does nitrites in urine indicate
some bacteria convert nitrates to nitrites, could indicate infection
what does leukocyte esterase in urine indicate
indicates infection
what does proteins in urine indicate
may indicate kidney disease
what does glucose in urine indicate?
may indicate diabetes mellitus
blood tests to evaluate kidney function
Blood Urea Nitrogen (BUN) (test)
Plasma Creatinine (test)
inulin clearance (test)
PAH clearance (test)
Blood Urea Nitrogen (BUN) (test)
measures blood nitrogen
—>
(part of urea resulting from the catabolism and deamination of amino acids)
(rises steeply with severe decreases in GFR that can happen with renal disease )
Plasma Creatinine (blood test)
measures plasma levels of creatinine
—>
(result from the catabolism of creatine phosphate in skeletal muscle cells)
rises steeply with severe decreases in GFR that can happen with renal disease
Plasma creatinine blood test is used to estimate ____
Used to estimate GFR (eGFR)
Inulin Clearance (blood test)
measures volume of blood that is cleansed of inulin (per?) unit of time
measures how efficiently the kidneys are removing inulin from the blood
high renal clearance
High renal clearance = efficient filtration and excretion
low renal clearance
Low renal clearance = inefficient filtration and excretion
what is inulin?
How does it pass through kidneys?
why is it gold standard for eGFR?
Inulin (plant polysaccharide) passes through the kidneys with no amount of inulin secreted or reabsorbed.
—> therefore, clearance rate = GFR (can be used clinically to determine GFR)
(Gold standard for estimating eGFR, but not always accessible in a clinical setting)
PAH clearance test (blood test)
measures the amount of plasma that passes through the kidneys in one minute (typically 650 mL/min)
(PAH (para-aminohippuric acid) is used to measure renal plasma flow b/c when administered via IV it is filtered and secreted in 1 single pass)
kdiney failure
..
kidney failure occurs when ____
when the kidneys cannot filter wastes from blood and can no longer maintain homeostasis
what happens to GFR during kidney failure?
drops too low
what are some ways kidney failure impair body systems?
Decrease in urine production
Rise in blood pressure
(d/t blood volume?)
Anemia from decline in erythropoietin production
CNS problems (sleeplessness, seizures, delirium, and coma)
Chronic kidney failure
describe
Kidney function deteriorates gradually
—>
Associated problems accumulate over time
can chronic kidney failure be reversed?
No.
Progression can be slowed, but the condition is not reversible
management of chronic kidney failure involves ____
Management involves restricted water, salt, and protein intake
restricting water, salt, proteins helps slow progression of chronic kidney failure by _____
Reduces strain on urinary system
—> reduce Volume of urine produced
—> reduce Amount of nitrogenous waste generated
what is a common complication of reduced renal function?
Acidosis
how can acidosis during renal failure be countered?
can be countered by ingesting bicarbonate ions
what are most common causes of chronic kidney failure?
Diabetes and hypertension are the most common causes
Acute Kidney Injury (AKI)
..
what happens during AKI?
Kidney function deteriorates rapidly in just a few days
(May be impaired for weeks)
AKI is a sudden ____
Sudden slowing or stopping of filtration (GFR)
AKI is caused by
toxic drugs,
renal ischemia,
urinary obstruction,
trauma
AKI can also be caused by
Allergic response to antibiotics or anesthetics in sensitized individuals
can partial or complete function be recovered following AKI (acute kidney injury) ?
YES.
(only if patients survive the initial incident)
Dialysis, define
“What is dialysis? Dialysis is a treatment for people whose kidneys are failing. When you have kidney failure, your kidneys don’t filter blood the way they should. As a result, wastes and toxins build up in your bloodstream. Dialysis does the work of your kidneys, removing waste products and excess fluid from the blood.”
“through” + “decompose”
dialysis (from class notes)
Process of passive diffusion across a selectively permeable membrane
hemodialysis
Uses an artificial membrane as an alternative to the kidney’s normal membrane around the glomerulus
Regulates the composition of blood using a dialysis machine
Membrane pores allow diffusion of ions, nutrients, and organic wastes, but not plasma proteins
Dialysis fluid containing specific concentrations of solutes is run on the other side of the membrane
is dialysis a cure?
no
Dialysis relieves renal failure symptoms, but is not a cure
what is the ultimate treatment for kidney failure?
Kidney transplant is the only real cure for severe renal failure
patient survival 2 years post-transplant
> 90 percent at 2 years after the transplant
what increases success rate of transplant?
Close relative donor increases success rate
post-transplant complication?
immune response to transplant
Immunosuppressive drugs are necessary to reduce rejection of transplant
urinary tract
..
urinary tract functions
transports urine
Stores urine
eliminates urine
urinary tract components
ureters
urinary bladder
urethra
ureters
receive urine from the kidneys
Conduct urine to the urinary bladder by gravity and peristalsis
urinary bladder
receives and stores urine
contraction of muscle in walls drives urination
urethra
conducts urine from the bladder to outside the body
In the penis, also conducts semen
ureters transports urine from ___ to ___
transport urine from renal pelvis —> bladder
ureters, app length
Paired muscular tubes extending from the kidney to the urinary bladder
(about 30 cm)
ureters positioning & attachment
Retroperitoneal and attached to the posterior abdominal wall
ureters three layers (histology)
mucosa
muscularis
adventitia
ureter mucosa structure
transitional epithelium (urothelium)
ureters muscularis (structure)
2 layers of smooth muscle for peristalsis
ureters adventitia
outer connective tissue layer
anchors ureters to wall of peritoneum
urinary bladder, location
Located posterior to pubic symphysis
urinary bladder, filled by ___ and drained by ___
Filled by the ureters and drained by the urethra
bladder, dimensions
Dimensions vary with state of distension
bladder, position vs peritoneum
outside the peritoneal cavity
subperitoneal
bladder, attachment to pelvis (inc. pubis)
supporting ligaments:
Lateral umbilical ligaments
Middle umbilical ligament
umbilical define
- : of, relating to, or used at the navel.
- : of or relating to the central region of the abdomen.
in this case, possibly referring to 2.
urinary bladder – rugae
Folds in the bladder lining that disappear with expansion as the bladder fills
urinary bladder – ureteric orifices
Two (one for each ureter) on the posterior inferior surface
Slit-like shape helps prevent backflow of urine into ureters with bladder contraction
urinary bladder – internal urethral orifice
Where urine leaves the bladder and enters the urethra
bladder, TRIGONE
Triangular area bounded by the two ureteral openings and the entrance to the urethra
trigone define
“a smooth triangular area on the inner surface of the bladder limited by the apertures of the ureters and urethra.”
Neck of the urinary bladder
what does neck “ contain?
Surrounds the urethral opening
Contains a muscular INTERNAL URETHRAL SPHINCTER
is internal urethral sphincter voluntary?
involuntary smooth muscle
External urethral sphincter
male vs female location
Located distal to prostate in males
In females, located in similar location to males, at pelvic floor boundary
is external urethral sphincter voluntary or involuntary?
Under voluntary control
Must be voluntarily relaxed to permit urination
urinary bladder, layers
mucosa, submucosa, muscularis, and connective tissue layers
urinary bladder vs ureters — layers
bladder also has SUBMUCOSA
bladder, mucosa
Contains rugae
Lined with transitional epithelium (urothelium)
Both allow for expansion to hold urine
do ureters also have transitional epithelium (urothelium)
yes
bladder, muscularis – three layers
Inner longitudinal layer
Circular layer
Outer longitudinal layer
what are the three muscular layers of bladder called?
Collectively, the layers form the DETRUSOR muscles
detrusor etymology
detrus-
–> “thrust down”
urethra — from ____ to ____
Extends from the
A) neck of the urinary bladder
—> to the
B) exterior of the body
urethra, male vs female
(length/function)
Male urethra is longer and transports semen as well as urine
female urinary tract
4cm long
Opens into orifice between clitoris & vagina
male urinary tract
20cm long
also carries semen
tube passes through prostate
three sections of male urinary tract
prostatic urethra,
membranous urethra,
spongy urethra
internal lining of urethra
stratified epithelium that varies by location
urethra lining “at neck”
(below neck of bladder?)
“Transitional at the neck”
urethra lining at midpoint
Stratified columnar
urethra lining near external urethral orifice
Stratified squamous
lamina propria of urethra
Thick, elastic lamina propria
aside note: SEROSA vs ADVENTITIA
“Serosa covers intraperitoneal structures and is continuous with the parietal peritoneum. It is thin and consists of a double wall of simple squamous epithelium.”
“Adventitia covers retroperitoneal structures. It is made of fibrous connective tissue and fixes structures in place.”
____
“Some parts of the digestive tract have an adventitia as outer layer instead of a serosa.”
note longitudinal folds in mucous membrane of URETHRA
Mucin-secreting cells in the epithelial pockets
micturition
.
micturition define
process where urine is expelled from the body.
micturition etymology
From Latin micturio (“to urinateâ€).
urine storage reflex
Stretch receptors of urinary bladder wall distort as it fills
Afferent impulses stimulate sympathetic stimulation to detrusor and stimulate contraction of internal urethral sphincter
Pontine storage center decreases parasympathetic activity and increases
somatic motor nerve activity
of external urethral sphincter
sympathetic/parasympathetic nervous system, external urethral sphincter, detrusor mm
“parasympathetic fibers produce contraction of the detrusor muscle by acting at M3 receptors; and sympathetic innervation inhibits detrusor contraction through β3 receptors, and contraction of the internal urethral sphincter by α1 receptor activation.”
Micturition reflex (urination)
Coordinates the process of urination
is micturition reflex local or via CNS pathway?
BOTH.
Local reflex pathway
+
Central pathway through the cerebral cortex
Urine voiding reflex
through pontine micturition center
Afferent information of sensation of bladder fullness relayed to the THALAMUS
at what bladder volume do stretch receptors signal CNS?
200-400mL
—>
Stretch receptors signal spinal cord & brain when volume 200-400ml
projection fibres relay information to ____
CEREBRAL CORTEX
Projection fibers relay the information to the cerebral cortex
—>
For voluntary relaxation of the external urethral sphincter
—> Causes contraction of the detrusor muscle and relaxation of the internal urethral sphincter
—> Since pressure is already increased, relaxing the sphincters leads to urination
URINARY DISORDERS
…
primary signs of urinary disorders
changes in volume and appearance of urine
changes in volume and appearance of urine — E.g.
Polyuria
Oliguria
Anuria
Polyuria
Excessive urine production
Results from hormonal or metabolic problems
—> Possibly DIABETES or GLOMERULONEPHRITIS
Oliguria
Reduced urine production (50–500 mL/day)
Anuria
Severely reduced urine production (0–50 mL/day)
when does urination indicate potentially serious problem?
Oliguria and Anuria
indicate serious kidney problems and potential renal failure
changes in frequency as sign of urinary disorders
Increased urgency or frequency
Incontinence
Increased urgency or frequency
Can be from irritation of the lining of the ureters or urinary bladder
urgency/frequency – potential causes
UTI, prostatitis, diabetes, kidney stones, etc.
incontinence
Inability to control urination voluntarily
incontinence types
stress incontinence
urge incontinence
overflow incontinence
stress incontinence
periodic involuntary leakage
urge incontinence
inability to delay urination
overflow incontinence
continual trickle of urine from full bladder
Urinary retention
Initially normal renal function
Urination does not occur
males and urinary retention, vs prostate
(Urination function reduced (?))
In males, commonly results from enlarged prostate gland and compression of prostatic urethra
pain and urination
Pain in the superior pubic region
—>
Associated with urinary bladder disorders
Pain in the superior lumbar region or in the flank that radiates to the right or left upper quadrants
Associated with kidney infections (pyelonephritis)
Also associated with kidney stones (renal calculi)
pyelonephritis
Pyelo: a prefix that means that a term is related to the renal pelvis, e.g. pyelonephritis, pyelogram.
Dysuria
Painful or difficult urination
Can occur with cystitis or urethritis or urinary obstructions (possibly enlarged prostate in males)
systemic/clinical signs of urinary system disorders
Commonly develops when urinary system is infected with pathogens
Cystitis (bladder infection)—usually low-grade fever
Pyelonephritis (kidney infection) can produce very high fevers
cystitis vs pyelonephritis fever intensity
Pyelonephritis can produce very HIGH fevers
