URINARY SYSTEM - Weebly
URINARY
SYSTEM
LECTURE 1
URINARY SYSTEM ~ RENAL SYSTEM
KIDNEY
URINARY BLADDER
URINARY TRACT ~ URETERS & URETHRA
URINE & URINATION ~ Processes
Filtration
Reabsorption
Secretion
KIDNEY ~ Water purification plant
Major excretory organ ~ makes & excretes “urine”
Entire blood volume passes thru kidney 60x per day
50 gallons of blood filtered daily
99% of volume retained in blood
1% of volume eliminated as urine
Filters toxins, ions, nitrogen wastes ~ mostly urea ~ NH4
Regulates volume & composition of blood ~ controls BP
Maintains balance between water & salts ~ Na+ Cl- K+
Maintains acid & base balance ~ pH control
Endocrine Function: Erythropoietin & Renin
KIDNEY ~ ANATOMY
Bean shaped & paired
Left kidney slightly superior to right kidney ~ due to liver
Capped by adrenal glands
Located retroperitoneal in the lumbar abdominal cavity
Renal Hilus ~ Concave medial surface
Renal Artery enters ~ O2 & nutrients
Renal Vein exits ~ CO2 & purest blood in body
Ureter exits~ carries urine to bladder
Adipose Capsule ~ Adipose Tissue
Outer layer of fatty tissue ~ Holds kidney in place
Cushions against contusions & traumatic blows
Renal Fascia
Outermost layer of dense fibrous connective tissue
Completely surrounds kidney & adipose tissue
Also surrounds adrenal gland
Anchors kidney to surrounding structures
Renal Capsule
Fibrous supporting tissue capsule which adheres to surface of kidney
Provides strong barrier against infection
Renal Sinus
Internal cavity within kidney ~ covered by capsule
Surrounds entire urine collecting area
Renal Cortex
Superficial internal region ~ Light in color
Contains “Nephrons” ~ Structural & functional
units of kidney
Renal Medulla
Deep to cortex ~ Darker & reddish brown
Also contains part of Nephrons
Renal Pyramids ~ Medullary Pyramids
16 -18 cone shaped tissue within renal medulla
Bases point toward Renal Cortex
Apex Cones point toward urine collecting areas
Drains thru renal papilla into minor calyx
Renal Columns
Area of renal medulla between renal pyramids
Renal Lobe
Consists of pyramid, cortex, & column
Minor Calyces ~ initial urine collecting area
Encloses renal papillae of the pyramids
Collect urine & empty it into major calyces
Site of Kidney Stone Formation
Major Calyces
Branching regions of the renal pelvis
Collect urine draining from renal pyramids
Via Minor Calyx
Renal Pelvis
Large urine collecting area within the renal sinus
Continuous with ureters ~ urine flows to bladder
Ureters
Tubes ~ carry urine between kidney & bladder
Kidney Stones break off ~ block ureters ~ painful
KIDNEY - BLOOD SUPPLY
Kidneys receive 25% of total cardiac output each minute via Renal Arteries
90% of blood is “filtered” in nephrons - filters 50 gal/day
10% of blood supplies kidney tissue with O2 & nutrients
Abdominal Aorta Abdominal Vena Cava
( (
Renal Artery Renal Vein ~ “purest blood”
( (
Interlobar & Interlobular Peritubular Capillaries
“True Capillaries”
- - - - - - - -(- - - - - - - - - - - - - - - - - - - - - - - - -(- - - - - - - - - - - - - -
NEPHRON
“Afferent” Arterioles “Efferent” Arterioles
( (
( ( GLOMERULI ( (
(SPECIALIZED FILTERING CAPILLARIES)
RENAL NERVE SUPPLY ~ Supplied via renal nerves
Sympathetic Stimulation regulates renal blood flow & pressure via dilation/constriction of renal arterioles
“VASOMOTOR ACTIVITY”
NEPHRONS > 1,000,000 in each kidney
Microscopic FILTERING units in Cortex & Medulla
FORM THE “FILTRATE” & MAKE URINE
Carries out the 3 processes of making URINE
1. Glomerular Filtration ~ filters blood
2. Tubular Reabsorption ~ primarily water & sodium
3. Tubular Secretion ~ secretes ions, H+, HCO3-, toxins,
drugs & nitrogenous wastes
“FILTRATE” = Water & solutes flowing thru the kidney prior
to urine formation
Same as blood plasma except NO PROTEINS
Proteins too large to pass filtration membrane
EMPTIES into “collecting ducts” as URINE
“URINE” = Mostly Water ~ 95%
Solutes ~ 5%
Includes: Toxins, drugs, ions, H+ & HCO3- &
NITROGEN WASTE
Elimintes Nitrogen Waste ~ UREA, Uric Acid, Creatinine
Regulates Blood Volume, Composition & pH
Regulates Water Retention & Blood Pressure
TYPES OF NEPHRONS
CORTICAL NEPHRONS ~ 85% of nephrons
Mostly in cortex ~ small portion dips into medulla
Mostly “THICK SEGMENTS” ~ NOT permeable to water
“Reabsorption” of solutes into blood ~ retains Na+
“Secretion” of solutes from blood into filtrate
Some “THIN SEGMENTS” ~ permeable to water
“Reabsorption” of H2O back into blood ~ retains H2O
JUXTAMEDULLARY NEPHRONS ~ 15% of nephrons
Located at mostly in medulla ~ LOH deep in Medulla
Many “THIN SEGMENTS” ~ Very permeable to water
MAJOR area for H2O reabsorption ~ retains H2O
Some reabsorption of solutes into blood ~ retains Na+
NEPHRON ~ Components & Specific Function
1. Renal Corpuscle ~ “Filtration” Only
2. Proximal Convoluted Tubule ~ Reabsorption Mostly
3. Loop of Henle ~ Reabsorption Mostly
4. Distal Convoluted Tubule ~ Secretion Mostly
Last Resort Reabsorption ~ ALDOSTERONE
5. Collecting Duct ~ Secretion Mostly
Last Resort Reabsorption ~ ADH
NEPHRON CAPILLARY BEDS ~ “Microvasculature”
Nephron surrounded by extensive special capillary beds
90% of blood filtered in renal corpuscle as FILTRATE
99% of filtrate is reabsorbed by the renal tubules
1% of filtrate goes to form final URINE
10% of blood goes to renal tissue as nutrients & O2
GLOMERULAR CAPILLARIES ~ in renal corpuscle
“Filtration Beds”
PERITUBULAR CAPILLARIES ~ surround tubules
“Reabsorption & Secretion Beds”
RENAL CORPUSCLE
GLOMERULUS
Glomerular Capillary Beds ~ “filtration membrane”
Form “initial” Filtrate via diffusion ~ “filtered blood”
Filtrate Passes into Bowman’s Capsule
BOWMANS CAPSULE ~ surrounds glomerulus
Continuous with & forms renal tubules
Collects the “initial filtrate” from blood
Passes “initial” filtrate into tubules for filtering
“Filtration Membrane” ~ Glomerulus Filtration Beds
Capillary Side ~ Endothelium with “fenestrations”
Tubule Side ~ Endothelium with “filtration slits”
Composed of large Podocyte Cells
Fenestrations & Filtration Slits ~ form filtrate
Permits free passage of water & solutes
smaller than plasma proteins via diffusion
Small particles pass ~ ions, H2O, small solutes
Blood, WBC, & proteins ~ too large to pass
FILTRATION dependent on “Net Filtration Pressure” ~ NFP
Movement from high pressure to low pressure
Movement from high solute conc. to low solute conc
Glomerular Capillaries
Only place with both afferent & efferent arterioles
Glomerulus ~ Fed by afferent arteriole ~ 100% in
Glomerulus ~ Drained by efferent arteriole ~ 10% out
Normal Capillaries = 40 mmHg in 20 mmHg out
Glomerular Capillaries = 60 mmHg in 30 mm Hg out
Efferent arterioles have smaller diameter
than afferent arterioles because of afferents & efferents
Causes “back pressure” into afferent arterioles
Higher blood pressure ( ( Capillary Hydrostatic Pres.
( capillary hydrostatic pressure ( ( filtration thru
Filtration membrane in glomerular capillaries(
( GLOMERULAR FILTRATION RATE (GFR)
URINE FORMATION PROCESSES
GLOMERULAR FILTRATION ~ measured as “GFR”
Forms the “initial” filtrate in the glomerulus
Glomeruli efficiently filters of blood ~ BY DIFFUSION
Passive, non-selective process ~ no ATP required
Materials move from high pressure to low pressure
Filtrate (solutes & fluid) forced into Bowman’s Capsule by HYDROSTATIC PRESSURE (BHP)
Determined by Net Filtration Pressure (NFP) ~ 10 mmHg
Glomerular Hydrostatic Pressure ↓ 60 mmHG
Blood Colloid Osmotic Pressure ↑ 32 mmHG
Capsule Hydrostatic Pressure ↑ 18 mmHG
Glomerular Hydrostatic Pressure ~ most significant
Blood Colloid Osmotic Pressure ~ in glomerulus
Pressure generated by blood to draw water in to it
Depends on solute concentration of blood
H2O moves from low to high solute concentration
Capsule Hydrostatic Pressure ~ in Bowman’s Capsule
Pressure exerted by fluids within Capsule
URINARY
SYSTEM
LECTURE 2
RENAL TUBULES ~ Further Process the Filtrate
1. Proximal Convoluted Tubule ~ PCT
2. Loop of Henle ~ LOH
3. Distal Convoluted Tubule ~ DCT
4. Collecting Ducts ~ CD ~ not really a renal tubule
“Peritubular Capillaries” ~ True Capillaries
Continuation of efferent arterioles which drain glomeruli
Surround & and closely follow renal tubules
Supply nephrons & renal tissue with O2 & Nutrients
Highly specialized for reabsorption & secretion ~ pores
Area of “reabsorption” of selected filtrate into blood
Area of “secretion” from blood into filtrate
Empty into Venules - - -> Renal Vein - - - > Vena Cava
Vasa Recta ~ surround Juxtamedullary Nephrons only
Mesh of thin straight vessels around Loop of Henle
Deep within the medulla
A major area for H2O & solute reabsorption in LOH
Further Concentrates Filtrate (Urine)
TUBULAR REABSORPTION & SECRETION
Movement of solutes & H2O between blood & tubules
Via “peritubular capillaries
Blood “reabsorbs” substances from tubule filtrate
Blood “secretes” substances back into tubular filtrate
Movement maintains equal concentration with blood
Tubular Reabsorption ~ “Reclaimation” Process
Movement of solutes or H2O from filtrate into blood
Transport may be “Active or Passive”
PASSIVE Tubular Reabsorption ~ NO ATP
Diffusion of ions & water into blood
Solutes (Na+ Cl- K+) move from high to low conc.
H2O moves from low solute to high solute conc.
Passive transport follows active transport of Na+
Na+ ~ establishes concentration gradient
Na+ pulls other solutes with it . . . H2O follows
Solutes first diffuses from filtrate into tubule cells
Then solutes diffuse into peritubular capillaries
Filtrate is concentrated as H2O is reabsorbed into blood
ACTIVE Tubular Reabsorption ~ requires ATP
Movement against concentration gradient
Na+ passively diffuses into tubule cells . . . then
Na+ is “ACTIVELY” pumped into peritubular capillaries against a gradient
Na+ K+ exchange pump
OTHER “Actively” Transported Solutes
Glucose, some other ions, & vitamins
Secondary Active Tubular Reabsorption
Protein carriers co-transport Na+ & GLUCOSE
100% of GLUCOSE is reabsorbed into blood
TUBULAR SECRETION ~ ACTIVE process ~ requires ATP
Adds solutes back to filtrate from blood
Removes undesirable Nitrogens & waste from blood
UREA (most prevalent solute in urine) ~ ammonia
Creatinine ~ nitrogen from muscle metabolism
Drugs . . . Toxins . . . Other Metabolites
Other Ions ~ Na+, K+, Cl- secreted as needed
Excess H+ or HCO3- ~ to maintain acid-base balance
RENAL TUBULE FUNCTIONS
Proximal Convoluted Tubule ~ PCT
Coiled tubule ~ continuous with Bowman’s Capsule
Confined to Renal Cortex
60-70% OF All FILTRATE IS REABSORBED IN PCT
65 % of Na+ ~ reabsorbed
65 % of water follows Na+ in PCT ~ Reabsorbed
100% Glucose Reabsorbed
50% Urea Reabsorbed
50% Urea Secreted
Loop of Henle ~ LOH
Proximal Convoluted Tubules Dip Down into Medulla
Descending Limb
Proximal ~ Thick Segment ~ Na+ Reabsorbed
Distal ~ Thin Segment ~ 15% H2O Reabsorbed
Ascending Limb
Thin Segment ~ 15 % H2O Reabsorbed
Thick Segment ~ 25 % Na+ & 40% K+ Reabsorbed
Distal Convoluted Tubule ~ DCT
Confined to Renal Cortex only
Reabsorption of Na+ & H2O Only ~ Aldosterone
Secretion of ions, H+, drugs, Urea, Creatinine
Has specialized cells that monitor filtrate concentration & hydration needs of body ~ regulates blood volume
Macula Densa ~ chemo . . . baro . . . osmoreceptors
Juxtaglomerular Apparatus ~ Secretes RENIN
Reabsorption of Na+ & H2O . . . depends on body needs
Nearly all water & Na+ can be reabsorbed if needed
Reabsorption is hormonal influenced
Aldosterone works here . . . ADH starts working here
Aldosterone ~ ( reabsorption of remaining Na+ ~ DCT
( water follows Na+
MAJOR SECRETION ~ DCT
UREA ~ MOST Creatinine
H+ if acidotic HCO3- if alkalotic
Ions . . . Toxins . . . Drugs
JUXTAGLOMERULAR APPARATUS ~ in DCT
Surround distal convoluted tubules
Macula Densa Cells
Epithelial cells around distal convoluted tubules
Chemoreceptors . . osmoreceptors . . baroreceptors
Resond to solute concentration of the filtrate
Cause Juxtaglomerular cells to secrete RENIN if. . .
Osmolarity of urine too low (urine is dilute) or
Blood pressure decreases or blood loss
Juxtaglomerular Cells
Special cells of the afferent arterioles mostly
Secretes: Renin & Erythropoietin
Renin converts angiotensin 1 to angiotensin 2
Angiotensin 2 stimulates release of aldosterone from adrenal cortex
Aldosterone stimulates reabsorption of sodium
Water follows sodium
Urine becomes more concentrated
Blood pressure increases (vasoconstriction & increased volume)
COLLECTING DUCTS ~ Part of “urine collecting” system
Located both in Renal Cortex & Renal Medulla ~ MANY
Receives Filtrate (not yet urine) from all nephron tubules
Last resort area to concentrate or dilute filtrate . . .
before it becomes urine
Makes final adjustments to concentration & volume of
urine ~ concentrates or dilutes urine . . . as needed
Reabsorption of water ~ Hormone Dependent ~ ADH
Anti-diuretic Hormone ~ ADH ~ posterior pituitary
( permeability of collecting ducts to water - - ->
( reabsorption of water - - - >
( fluid & vascular volume - - > increased BP
Final Reabsorption of Na+, K+, H+, HCO3- . . . as needed
MAJOR SECRETION of ions, acids, drugs, toxins
UREA Creatinine H+ HCO3-
Filtrate is now called “URINE”
Merges into Papillary Ducts for urine flow to bladder
PAPILLARY DUCTS ~ starts urine flow
Fusion of collecting ducts ~ delivers urine to Minor Calyx
---> Major Calyx ---> Renal Pelvis ---> Ureter ---> Bladder
REGULATION OF RENAL BLOOD FLOW
Intrinsic & Extrinsic Neural/Hormonal Feedback Mechanisms
Maintains constant renal blood flow & glomerular filtration
Blood Pressure ~ is the major regulating factor of GFR
Dilation or Constriction of renal arterioles affects GFR
Afferent Arteriole Dilation - - -> more flow >( GFR
UNIQUE
Afferent Arteriole Constriction - > less flow > ( GFR
REGULATING FACTORS: Have Opposite Effects
Systemic Vasodilation causes low BP ( GFR
Renal Afferent Arteriole Dilation causes ( GFR
Systemic Vasoconstrictors causes high BP ( GFR
Renal Afferent Arteriole Constriction causes ( GFR
RENAL AUTOREGULATION ~ “INTRINSIC” ~ kidney only
Controlled by macula densa baroreceptors of JXT (JGA)
( blood pressure ( decrease glomerular filtration ( GFR
( intrinsic reflex afferent arteriole dilation to ( GFR
SYMPATHETIC REGULATION~ “EXTRINSIC”
Baroreceptors ~ sense changes in blood pressure
( blood pressure ~ stimulates systemic sympathetic
release of epinephrine / NE
( constriction of efferent arterioles ( ( GFR
HORMONAL REGULATION ~ Renin-Angiotensin-Aldosterone
Regulates fluid volume & blood pressure
START DROP in blood pressure sensed by Baroreceptors
( blood pressure ( decreased GFR (
RENIN released by Juxtaglomerular cells
( activates Angiotensin I ( Angiotensin II
Potent vasoconstriction ~ efferent arteriole
( Angiotensin I & II ( ALDOSTERONE release
from adrenal cortex
( Aldosterone ( Na+ retention in DT and CD
( Water & Fluid Retention
( Increases Blood Volume
( Increases Systemic Pressure
( Increases Glomerular Filtration Rate
URINE FORMATION ~ OSMOLALITY
OSMOLALITY of a solution determines OSMOSIS
Osmosis ~ movement of water from low solute
to high solute concentration when only
water can move across membrane
Dependent on # of particles in a liter of solution
Solute particles per liter ~ mili-osmoles/Liter
Kidneys ~ Maintain concentration of blood ~ at 300 mOsm/L
300 (mOsm) x 1000 = 300,000 particles per liter
Hyper-osmolality ~ more than 300 mOsm/L
Hypo-osmolality ~ less than 300 mOsm/L
Osmolality ~ increases as filtrate moves from
Glomerulus (300 mOsm/L) same as blood (
Descending Loop of Henle (400 – 1200 mOsm/L) ( HYPER
Ascending Loop of Henle (1200 – 100 mOsm/L) (
Distal convoluted tubule (100 mOsm/L) HYPO-osmolar
Collecting Duct ~ urine concentrates as solutes secreted
& H2O reabsorbed
Urine could have osmolalities range of 65 –1200 mOsm/L
URINE FORMATION PROCESS ~ SUMMARY
“Medullary Osmotic Gradient” ~ changes in Tubule mOsm
“Countercurrent Mechanism” ~ opposite movement
Fluids moving in opposite directions in LOH
Filtrate in descending loop moves toward renal pelvis
Filtrate in ascending loop moves toward renal cortex
Change in gradient ~ increases as filtrate moves
“MULTIPLIER EFFECT” ~ countercurrent multiplier
GLOMERULUS
Filtrate formed ~ Osmolality = to blood ~ 300 mOsm
PROXIMAL CONVOLUTED TUBULES
60% Na+ ion reabsorption from glomerular filtrate
65% water reabsorption
Net Effect = Blood & filtrate Osmolality remains
constant ~ 300 mOsm
DESCEDING LIMB~ Loop of Henle ~ “thin” portion
15% water reabsorption into blood
This concentrates filtrate (( mOsm) ( hyper-osmolality in Loop of Henle ~ 1200 mOsm
ASCENDING LIMB ~ Loop of Henle ~ “thick” portion
Impermeable to H2O
Na+ & Cl- actively reabsorbed into blood
Filtrate becomes more dilute as more Na+ and Cl- passively move out of filtrate since water cannot move
Filtrate becomes hypo-osmolar as it moves into distal tubules and collecting ducts
Filtrate ~ 100mOsm
DISTAL CONVOLUTED TUBULES ~ DCT
Starts process of Final Adjustments to filtrate
Many substances “actively” SECRETED into filtrate
UREA & Creatinine
Drugs & Toxins
Excess ions H+ HCO3- K+
Not much Na+ of Cl- or water movement normally
Unless stimulated by Renin & Aldosterone
Aldosterone enhances Na+ reabsorption
ADH ~ starts working here ~ H2O reabsorption
Both Aldosterone (mostly) & ADH (starts) in DCT
Filtrate ~ 100 – 300 mOsm
URINE FORMATION PROCESS ~ SUMMARY
COLLECTING DUCTS
Final Area to concentrate urine & make final adjustment
Last place to reabsorb Na+ & H2O
“Active” Secretion
UREA & Creatinine
H+ HCO3- K+
Drug Metabolites & Toxins
Aldosterone ~ last place to reabsorb Na+
Anti-Diuretic Hormone ~ ADH ~ Posterior Pituitary
Effects permeability of water in collecting ducts
Affects final concentration of urine & blood volume
( ADH ( dilutes urine ~ more urine ~ polyuria
No water reabsorbed ~ Diabetes Insipitus 1.010
( ADH ( concentrates urine ~ less urine
Water reabsorbed in response to stimuli requiring increased blood & tissue fluid volume
EG: Blood Loss, dehydration, ( BP
URINARY
SYSTEM
LECTURE 3
RENAL CLEARANCE & FUNCTION TESTS
Provides information ONLY about renal function & the
course of renal disease
Glomerular Filtration Rate ~ GFR
Volume flow rate ~ ml/min
Measures 24 hr. kidney clearance of plasma solutes
BUN ~ Blood Urea Nitrogen
Nitrogen waste ~ UREA most solute in urine
Normally secreted ~ small amounts reabsorbed
Indicates reversible glomerular problems ~ retained
Serum Creatinine & Urine Creatinine
Nitrogen waste product from muscle metabolism
Normally secreated & not reabsorbed ~ serum creatinine
May indicate irreversible glomerular problems if serum creatinine is high & urine secretion is low
Must compare serum creatinine & urine creatinine clearance
Good = low serum creatinine high urine creatinine
OK = high serum creatinine high urine creatinine
Bad = high serum creatinine low urine creatinine
URINE COMPOSITION
Urinalysis ~ analysis of urine ~ Covered in Laboratory
Aid to diagnose body condition . . . not just renal system
Significant indicators: Proteins Bacteria
Glucose pH
Acetone Specific Gravity
Blood Pus
URINE CHARACTERISTICS
93-97% Water 5% Solutes
Volume ~ 1200 ml/day to 1800 ml/day
Color ~ clear to pale yellow
Yellow pigment ~ urochrome
Due to hemoglobin/bile destruction
( concentration ( ( yellow color
Foods, pus, blood ~ may change color
Odor ~ Slightly ammonia due to urea & Nitrogen
Fruity if acetones present ~ diabetes mellitus
pH ~ Slightly acid ~ pH~ 6.0 (Range 4.4-8)
High protein diet causes more acid urine
Bacterial infection causes more alkaline urine
Specific Gravity ~ 1.003-1.030 (water = 1.000)
Slightly heavier than water ~ due to “solutes”
1.010 indicates inability to concentrate urine
“isosthanuria” ~ Diabetes insipitus ~ NO ADH
> 1.035 characteristic of Diabetes mellitus or severe dehydration ~ glucose adds weight to H2O
Normal Solutes Present in Urine
Nitrogenous Waste Products
Urea Uric acid Creatinine
Sodium, Potassium, Sulfate & Phosphate
Abnormal Urine Components Cause
Glucoseuria Glucose (trace ok) D. Mellitus
Proteinuria Protein (trace ok) Diet
Ketonuria Ketones (none) Wasting
Hemoglobinuria Hemoglobin (none) Hemolysis
Bilirubinuria Bilirubin (none) Liver
Hematuria Erythrocytes (none) Trauma/Stones
Pyuria Leukocytes (none) Infection
Bacteuria Bacteria (none) Infection
OTHER RENAL SYSTEM ORGANS & Structures
URETERS ~ Transitional Epithelium Mucosa
Two Slender tubes ~ carry urine from each kidney to
urinary bladder
Move urine by peristalsis ~ contraction of muscle layers
Full bladder causes compression of ends of ureters
Prevents back flow of urine into ureter
“Urolithiasis” ~ Extreme pain during movement of sand
or calculi from kidney to bladder
URINARY BLADDER
Distendable muscular sac posterior to pubic symphasis
Stores Urine ~ 500 to 1000ml in LUMEN (opening)
Two inlets: 2 ureters ~ one in from each kidney
One outlet: 1 urethra out through penis
Bladder Wall: Transitional Epithelium ~ Mucosa
Detrusor Muscle ~ “involuntary” & powerful
Longitudinal & Circular smooth muscles layers
Contraction Compresses & empties bladder
Trigone ~ funnel area for urine ~ connects to urethra
Prostate Gland ~ surrounds urethra below “trigone”
URETHRA
Thin Muscular tube ~ moves urine from bladder out of body
Male: Through penis
Female: Empties into vulva in front of cervix
Anterior to vaginal opening ~ posterior to clitoris
Internal Urethral Sphincter
Extension of bladder detrusor smooth muscle
Involuntary smooth muscle sphincter ~ surrounds urethra at bladder / urethra junction
Sympathetic ~ constricts ~ bladder filling
Parasympathetic ~ relaxes ~ bladder emptying
External Urethral Sphincter
Voluntary skeletal muscle surrounds urethra
Voluntary control to complete urine release
Male Urethra ~ travels entire length of penis
Prostatic Urethra ~ passes through prostate ~ 1”
Membranous Urethra ~ from prostate to penis ~ 1”
Spongy Urethra ~ penile urethra ~ 5”
External Urethral Orifice ~ Meatus ~ tip of penis
MICTURATION ~ URINATION
“Process of Emptying Bladder”
Bladder Volume ~ 200 ml causes stretch of bladder wall
Distension in bladder stimulates visceral reflexes
Storage Reflex ~ sympathetic “filling reflex”
Sympathetic Reflex ~ via lumbar spinal nerves
Internal & external sphincters contract~CLOSE
Detrusor Muscles Relax ~ ALLOWS FILLING
Voiding Reflex ~ parasympathetic “emptying reflex”
Awareness when stimuli reach sensory cortex
Parasympathetic Reflex ~ via sacral “pelvic nerves”
Stimulates Detrusor Muscle Contraction
Inhibits or relaxes internal sphincters
Inhibits sympathetic outflow to external sphincter
causing relaxation
MICTURATION ~ can be delayed voluntarily since external
sphincter is voluntarily controlled . . . to a point
Control lost when urine bladder volume reaches 500 ml
Children < 2yrs old ~ NO voluntary control
Spinal cord not fully developed until age 4
RENAL SYSTEM ABNORMALATIES
Glomerulonephritis
Inflammation of the glomeruli ~ clogged glomeruli
Many causes ~ could be an autoimmune disease
Hemolytic Anemia ~ E.coli toxins in petting zoo
Damaged filtration & increased permeability to proteins
Polycystic Kidneys
Inherited condition
Swollen cysts occur along renal tubules
Compresses adjacent nephrons and vessels
Deteriorated renal function ~ insidious symptoms
Treat: nephrectomy . . . dialysis . . . kidney transplant
Bladder Cancer
3% of all cancer ~ 3x more common in men
Incidence highest among cigarette smokers
85% cure rate if local & non-metastatic
Usually terminal if generalized & metasticized
Spreads via regional lymph nodes
Renal Failure & Insufficiency ~ common with age
Kidneys unable to perform excretory function
Reduced Filtration ~ reduces adequate normal urine
production . . . nitrogens build
All systems affected ~ many symptoms ~ many causes
Acute Failure ~ filtration stops abruptly ~ SERIOUS
Chronic Failure ~ gradual deterioration ~ irreversible
Treatment: Remove Causes
Dialysis
Kidney transplant ~ best in long term
Kidney & Bladder Stones ~ Calculi ~ very common in FLA
Nephrolithiasis ~ kidney stones ~ pain ??? ~ blood
Urolithiasis ~ stones in ureters ~ extremely painful
Cystolithiasis ~ Bladder Stones ~ pain??? & blood
Usually: calcium deposits, magnesium salts, others
Diagnosis: Blood in urine ~ painful in urolithiasis
Could cause urinary blockage ~ SERIOUS
Treatment: Most pass on own
Lithotripsy ~ ultrasound
Surgery
Removal via catheter
Diabetes insipidus
Inability of kidneys to concentrate urine ~ SG < 1.010
1.010 = isosthanuria
Little or no ADH release No Glucose in Urine
Cause: Tumor or trauma to hypothalamus
Diuresis ~ elimination of excess volume of urine
Diuretics ~ Chemicals that enhance urinary output
Frequently used drugs for hypertension ~ Lower
blood pressure
Most inhibit Na+ and K+ retention & reabsorption
Alcohol ~ inhibits ADH causing profuse water loss
Caffeine ~ is hypertensive, stimulates glomerular
filtration, & elimination of Na+
Aging
30-40% loss of nephrons between ages 25-85
Urinary Incontinence ~ lost muscle tone ~ CAN’T HOLD
Urinary Retention ~ prostate enlargement ~ CAN’T GO
Incontinence
Inability to “voluntarily” control micturation
Urine leaks out after coughing or sneezing
Caused by: Trauma ~ childbirth
Spinal or neural injury ~ paralysis
Stress
Lost muscle tone with age
Urinary Retention
Bladder unable to expel its contents
Prostate Enlarged ~ most common cause
Sympathomimetic Drugs ~ cold medications
Following Anesthesia
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