pgu1 intruduction to urinary system
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UrinaryUrinary SSystemystem
IntroductionIntroduction
Dr Sami Abdo Radman
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Urinary systemUrinary system
Includes:
Two kidneys,
Two ureters, The urinary bladder,
Two sphincter muscles, and
The urethra
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Urinary System Anterior/Posterior Views
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Costovertebral Angle (renal angle)
Costovertebral Angle
T12
T11
L112th Rib
R. Kidney L. Kidney
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Kidney anatomy
Kidney is reddish-brown
Lie in the superior lumber region of the posteriorabdominal wall
weight about 300 g Looks like a bean
Approximately 4 inches x 2 inches
Extend from the level of the 11th or 12th thoracicvertebra to the 3rd lumber vertebra
Hilus indentation where blood vessels andstructures enter or exit the kidney
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Kidney anatomy
Two parts :
Cortex: Glomerular apparatus
Medulla:
Consists of about 1 million
filtering units called nephrons(basic structural and functional
unit)
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Renal Medulla
Dark, triangular structure
Form small cone shaped
regions called renal
pyramids Each pyramid is separated
by renal columns
The lower ends of the
pyramids point to the renal
pelvis
5-11 pyramids in each
kidney
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Renal pelvisRenal pelvis
The major function of the renal pelvis is toact as a funnel for urine flowing to the ureter.
The renal pelvis represents the funnel-likedilated proximal part of the ureter.
It is the point of convergence of two or three
major calices. Eachrenal papilla is surrounded by a branch
of the renal pelvis called a calyx.
Infection of renal pelvis is called pyelitis
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UretersUreters
Urine is collected in the renal pelvis
renal pelvis connects to the ureters,
which carry urine to the bladder. The ureters are about 200 to 250 mm
long.
Smooth musculartissue in the walls ofthe ureters peristaltically force the urine
downward.
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Urinary bladderUrinary bladder
The urinary bladderis a hollow muscular organshaped like a balloon.
It is located in the pelvic fossa and held in place byligaments attached to the pelvic bones.
Located behind the symphasis pubis The bladder stores urine - up to 500 ml of urine
comfortably for 2 to 5hours.
Sphincters (circular muscles) regulate the flow of
urine from th
e bladder. Internal urethral sphincter= in the beginning of urethrasmooth muscle not under ourvoluntary control
External urethral sphincter= skeletal muscle we cancontrol it
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UrethraUrethra
The urethra has an excretory function in both sexes,to pass urine to the outside
A reproductive function in the male, as a passage for
sperm. The external urethral sphincteris a striated smooth
muscle that allows voluntary control overurination.
Urethral sphincters:
Internal External
In males the internal and external urethral sphinctersare more powerful, able to retain urine for twice as
long as females
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Nephron
Each kidney contains about 1 million
nephron units
The number does not increase after birt
h
They cannot be replaced if damaged
2 parts
Renal curpuscles (Glomerulus, Bow
manscapsule)
Renal Tubules
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Renal curpuscles
Glomerular capsule (Bowmans Capsule) C shaped capsule surrounding the
glomerulus
Glomerulus cluster of capillaries Renal Tubules
Proximal convoluted tubule
Loop ofHenle ascending and descendinglimb
Distal Convoluted tubule
Collecting duct
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Renal Vasculature
Receives blood from the renal artery
Renal artery branches into the afferent arterioles
Afferent arterioles feed into Bowmans capsule
The efferent arterioles exit Bowmans capsule
The efferent arterioles form the peritubular
capillaries
The peritubular capillaries empty into thevenules, large veins, and then into the renal
veins
.
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Function of urinary systemFunction of urinary system
Excretion
Keeping homeostasis
Keeping acid-base balance PH
Regulation of blood pressure (rennin)
Formation of RBCs (erythropoiesis) by secretion of erythropoetin)
Vitamin D synthesis
Excreted products:
Product of the metabolism (It clears urea, a nitrogenous wasteproduct)
Water
Hormones Vitamins
Toxic substances
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Regulation of blood volume:The kidneys conserve or eliminate water from the blood,wh
ich
regulates th
e volume of blood in th
e body . Regulation of blood pressure:
Adjusting the volume of blood in the body (by regulatingthe quantity ofwater in the blood
Action of the enzyme renin. The kidneys secret renin,which activates the angiotensin-aldosterone pathway.
Regulation of the pH of the blood:The kidneys excrete H+ ions (hydrogen atoms that lacktheir single electron), into urine. At the same time, thekidneys also conserve bicarbonate ions (HCO3-), whichare an important buffer ofH+.
pH 7.4.
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The process of separating wastes from the
body fluids and eliminating them, is known
as excretion
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Formation of Urine
Three processes are involved in urine
formation
Glomerular filtration
Tubular reabsorption
Tubular secretion
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(1)GlomerularFiltration
The diameter of the afferent (incoming) arteriole isgreater than the diameter of the efferent arteriole
The pressure of the blood inside the glomerulus isincreased due to the difference in diameter of the
incoming and out-going arterioles. This increased blood pressure helps to force the
following components of the blood out of the glomerularcapillaries:
Most of the water ;
Most/all of t
he salts ; Most/all of the glucose ;
Most/all of the urea .
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Blood cells and plasma proteins are not filteredthrough the glomerular capillaries.
. Presence of cells and protein indicate a kidney
dysfunction The water and salts that have been forced out of
the glomerular capillaries pass into the Bowman'sCapsule and are called the glomerular filtrate.
Renal blood flow= 1200- 1300 ml/ min, (cardiacoutput=5600 ml/min)
This glomerular filtrate is formed at a rate ofabove 125 cm3 (mL) per minute (glomerularfiltration rate) =7.5L/h =180L/day
This volume is approx. 20% of the plasmadelivered during that time
Urine volume=1L/day (depends on )
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(2)Tubular Reabsorption
Only about 1% of the glomerularfitrate
actually leaves the body because the
rest (the other 99%) is reabsorbed intothe blood while it passes throughthe
renal tubules
Most of the volume of the fitratesolution is reabsobed in the proximal
convoluted tubule (PCT)
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(3)Tubular Secretion
Substances being added to the tubular
fluid from the efferent arterioles
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CLEARANCECLEARANCE
The GFR can be measured by measuring the
excretion and plasma level of a substance that
is freely filtered through the glomeruli and
neither secreted, nor reabsorbed by thetubules
Amount per unit of time
GFR = (UX) V/ P
X
(UX) = concentration ofX in the urine
V= urine flow per unit of time
PX = concentration ofX in the plasma
Eg . Inulin
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CLEARANCECLEARANCE
Example:
UIN=35 mg/Ml
V= 0.9 mL/min PIN= 0.25 mg/Ml
CIN=350.9/0.25 = 126ml/min
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(Micturition)(Micturition)
The process of disposing urine from theurinary bladder through the urethra to theoutside of the body.
The process of urination is usually undervoluntary control.
Urinary incontinence is the inability to controlurination, and is more common in women
than men. Urinary retention refers to the inability to
urinate.
Enuresis nocturnia = incontinence during the
night
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Urine Characteristics
Amount 1500 ml in 24 hours
pH average 6.0
Specific Gravity heavier than water(1.001-1.035)
Color yellow (amber, straw colored,
concentrated, orange, brow
n, red,sediment, clear or cloudy)
Dehydrated = deep yellow, dark
Overhydrated = pale yellow, colorless
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Light yellow color of urine is due to a
pigment called uroch
rome Urochrome is formed from the breakdown
ofhemoglobin in the liver
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Urine Testing
Urinalysis
Microscopic exam
Culture and sensitivity Urine dipstick
Urine Drug and alcohol screening
24 hour urine testing
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Abnormal Constituents ofUrine
Albumin (protein)
Glucose
Red blood cells Hemoglobin
White blood cells
Ketone bodies Bilirubin
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