urinary system indicators of health and disease Flashcards
explain concentrating urine
Although both cortical and juxtamedullary nephrons regulate theconcentrationsof solutes and water in the blood,countercurrent multiplication (see previous lecture)in the loops of Henle of juxtamedullary nephrons is largely responsible for developing the osmotic gradients that are needed to concentrateurine.
absorbed water is returned to the circulatory system by what? and what is it?
the vasa recta
a looping capillary, which surrounds the tips of the loops of Henle in juxtamedullary nephrons.
whats the speed of blood flow through the vasa recta, and explain the impact of this
very slow
any solutes that are reabsorbed into the bloodstream have time to diffuse back into the interstitial fluid, which maintains the solute concentration gradient in the medulla.
explain the vasa recta in terms of what it lets in and out, what happens as it ascends and what it forms
Solutes in, water out, as blood flows down
(Note blood leaving is approx. iso-osmotic with normal plasma)
Reverses as ascends
Formation of concentrated urine depends on high solute concentration in interstitial fluid
Why have a loop of Henle & associated structures?
To set up a concentration gradient in medulla of kidney
To concentrate urine
- i.e., reabsorb water back into the body
The amount of water absorbed out of urine is dependent on the interstitial osmolarity gradient established by the Loop of Henle
Urine becomes concentrated as it equilibrates with interstitium in medullary collecting tubule.
Water can move out of duct in the loop of henle and associated structures via what
osmosis, saving energy
what do diuretics do and cause
Diuretics slow the renal absorption of water
cause diuresis = elevated urine flow rate
name 2 naturally occurring diuretics
Caffeine (inhibits Na+ reabsorption)
Alcohol (inhibits ADH secretion)
Different physiological mechanisms involved
what can diuretics be used to treat
to treat hypertension & oedema due to congestive heart failure & cirrhosis of liver
what are some complications of diuretics use
dehydration & electrolyte imbalances
name 3 forms of clinical evaluations for kidney function
Urinalysis
Blood screening tests
Renal plasma clearance
explain urinalysis - the kidney evaluation method
Analysis of volume, chemical & microscopic properties of urine.
Reveals much about the state of the body.
Normally adult eliminates 1-2L/day
Urine volume influenced by fluid intake, blood pressure (BP), blood osmolality, diet, body temp, diuretics, mental state & general health.
Urine normally protein free.
name the typical solutes in urine and where theyre from
Urea
- From protein breakdown
Creatinine
- From creatine phosphate breakdown in muscle
Uric acid
- From nucleic acid breakdown
Urobilinogen
- From haemoglobin breakdown
Plus fatty acids, pigments, enzymes & hormones
what abnormal constituents can be found in urine
Description of colour & appearance
Specific gravity
pH
Glucose
Ketone Bodies
RBC count
WBC count
Protein
Hormone: hCG for pregnancy.
what are some detectable abnormalities
Albuminuria
Glucosuria
Haematuria
Pyuria
Ketonuria
Bilirubinuria
what does the detectable abnormalty in urine: albuminuria mean
injury/disease of filtration membranes, increase BP, irritation of kidney cells by bacterial toxins, ether or heavy metals
what does the detectable abnormalty in urine: glucosuria mean
diabetes mellitis or stress/epinephrine
what does the detectable abnormalty in urine: haematuria mean
RBC in urine; urinary disease or kidney stones, tumours, trauma
what does the detectable abnormalty in urine: pyuria mean
WBC in urine; infection in kidney/urinary organs
what does the detectable abnormalty in urine: ketonuria mean
diabetes mellitis, anorexia, starvation, too little dietary carbohydrate
what does the detectable abnormalty in urine: bilirubinuria mean
RBC destroyed, Hb broken up to form globin + haem;
haem becomes biliverdin which then becomes bilirubin [major bile pigment]
what are urines normal values
Yellow – amber
Clear
0.75 - 2L/day
pH 7 (4.5 - 8.0)
0.1mg/ml protein
<130mg/day glucose
describe the dip stick test
Quick and simple measurement of chemical composition of urine
glucose: blue coloured = neg
brown coloured = pos
protein: cream coloured = neg
green coloured = pos
blood: orange coloured= neg
brown coloured = trace
black coloured = pos
explain what blood screening tests can detect in terms of for evaluating kidney function
blood urea nitrogen (BUN)
plasma creatine
why would blood urea nitrogen (BUN) be detected in blood screening
due to catabolism & deamination of amino acids; levels rise steeply if decreased glomerular filtration with renal disease or obstruction of urinary tract.
Strategy: minimise patient’s protein intake
why would plasma creatine be detected in blood screening
due to catabolism of creatine phosphate in skeletal muscle; high level if poor renal function.
explain renal plasma clearing for evaluating kidney function in terms of what it does
Evaluation of kidney function
Measures how effective kidneys are at removing a given substance from blood plasma
Is a calculated value
describe how to calculate renal plasma clearance
plasma clearance (ml/min) = quality of urine (ml/min) x (conc in urine (mg/ml) divided by conc in plasma (mg/ml))
high value = Indicates efficient excretion of substance in urine
what is renal plasma clearance
Is the volume of plasma per minute needed to excrete the quantity of solute appearing in the urine per minute.
when is the renal plasma clearance of a substance high
if most is cleared to the urine
- therefore., a larger volume of plasma is ‘cleared’ per minute.
what would Normal Renal Plasma Clearance
Clearance of glucose normally 0
not excreted in urine at all
filtered glucose returned to blood via tubular resorption
what is a renal plasma clearance of high creatinine look like
120-140ml/min
filtered and not reabsorbed
only a very small amount secreted, so is cleared in the urine
explain Glucose in nephron
Glucose filtered out of blood in glomerulus into capsule (in corpuscle)
All reabsorbed into blood
None secreted out of blood
None excreted into urine
Renal Plasma Clearance of Glucose is 0
explain Creatinine in nephron
Creatinine filtered out of blood in glomerulus into capsule (in corpuscle)
None reabsorbed into blood
None secreted out of blood
All excreted into urine
Renal Plasma Clearance of Creatinine is high (120-140ml/min)
what parts of the body are involved in Urine Storage, Transportation & Elimination
ureters
urinary bladder
explain Ureters
have no anatomical valve at opening into urinary bladder, but effective physiological one: as bladder fills, pressure within it compresses the oblique openings into ureters & prevents backflow of urine
explain the urinary bladders average volume it holds
700-800ml
what is micturition
urination = voiding
Occurs via combination of involuntary & voluntary muscle contractions
When bladder volume >200-400ml
- stretch receptors in wall transmit nerve impulses into spinal cord
They propagate to micturition centre in sacral spinal cord segments S2 & S3 to trigger micturition reflex:
Bladder contracts & urinary internal & external sphincter muscles relax
Learn to initiate & stop it voluntarily
Urethra = terminal portion of urinary system
explain polycystic kidney disease
Genetic
- Autosomal
Multiple cysts
Form of chronic kidney disease
Reduces kidney function
reduced kidney function from Polycystic Kidney Disease causes what
Possible kidney failure
high BP
blood vessel problems
liver cysts
how does diabetic nephropathy occur and what can eb detected
Occurs with chronic diabetes
- after 10-15 years onset
- Mostly affects those aged: 50-70
Albuminuria detected
what is Pathophysiology
Thickened glomerulus
Abnormal blood vessels
Increasing number of glomeruli destroyed
explain Glomerulonephritis
primary or secondary autoimmune disease
Characterised by inflammation of glomeruli
May present different degrees of hyalinization
- Hyalinosclerosis: total replacement of glomeruli and Bowmann’s space with hyaline.
- The hyaline is an amorphous pink, homogenous, material - combination of plasma proteins, increased mesangial matrix and collagen
Such glomeruli are atrophic
- Smaller
Lacking capillaries
- non-functional.
Urinary Tract Infection (UTI) can be what types
Urethritis
Cystitis (bladder)
Pyelitis (walls of renal pelvis near hilus)
Pyelonephritis (if also inflame renal cortex & medulla)
If chronic & affects kidney, scar tissue forms in kidney to severely impair function.
what happens at the dialysis unit in hospitals
Where blood cleaned artificially through selectively permeable membrane
describe dialysis fluids composition
similar to blood except concentration of wastes is very low.
what is renal calculi and explain
a.k.a Kidney Stones
Crystal aggregations of dissolved minerals in urine
Size can vary from grain of sand to a grapefruit!
If 2 - 3mm can obstruct ureter
Causes renal colic (pain)
kidney stones form due to what
Ingestion of excessive calcium
Scant water intake
Abnormal alkaline or acidic urine
Overactive parathyroid gland
its possible to break down kidney stones via what
with shock waves.
