The Urinary System

Kidney functions Other system organs

General system anatomy

Kidney str & fxn Nephron – basic fxnal

unit of the kidney

Overview

Kidney Functions Filter 200L blood/day to eliminate:

Toxins Metabolic wastes Excess ions

Regulate blood volume ~ 5 L

Regulate chemical makeup of the blood 300 mmoL concentration of solutes (i.e. sodium,

potassium, zinc) Maintain the proper balance between H20 & salts,

and acids and bases.

Other Kidney Functions Gluconeogenesis

Production of renin

Production of erythropoietin

Activation of vitamin D

Other Urinary System Organs

Urinary bladder – provides temp. storage reservoir for urine

Paired ureters – transport urine from the kidneys to the bladder

Urethra – transports urine from the bladder out of the body

Ureters Slender tubes-carry urine: kidneys to the bladder Ureters enter the base of the bladder through the

posterior wall As bladder pressure increases (increased urine

volume in bladder), distal ends of ureters get closed off & prevent backflow of urine into ureters.

Tri-layered wall Epithelial mucosa Smooth muscle Fibrous connective tissue

Ureters actively propel urine to the bladder via response to smooth muscle stretch

Urinary Bladder Smooth, collapsible, muscular sac that temporarily

stores urine

Lies on the pelvic floor posterior to the pubic symphysis

Males – prostate gland surrounds the neck inferiorly

Females – anterior to the vagina and uterus

Trigone – triangular area outlined by the openings for

the ureters and the urethra

Clinically important because infections tend to persist

in this region

Urinary Bladder The bladder wall has three layers

epithelium

muscular layer

fibrous layer

The bladder is distensible &

collapses when empty

As urine accumulates, the bladder expands without

significant rise in internal pressure

Bladder Cancer 60,000 cases a year in the US

13,000 deaths per year 4 times more likely to occur in men Most frequently b/w 60-70 yrs of age

Causes ? Environmental exposures

High rates in employees in chemical and rubber plants

Prognosis for metastatic bladder cancer is poor Spreads to bone, lymphatic system

Tissue engineering: Bladder

Bladder disease

Increased pressure in poorly functioning bladder

leads to kidney damage

Reconstruction w/ small intestine tissue

Grow own bladder cells in culture for 7-8 weeks

Attached ‘new bladder’ to old bladder in 7, 4-19 yr old

children

2-5 yrs later: improved bladder function in all

subjects

Urethra Muscular tube that:

Drains urine from the bladder Moves urine out of the body

Sphincters keep the urethra closed when urine is not

being passed

Internal sphincter – involuntary sphincter at the

bladder-urethra junction

External sphincter – voluntary sphincter surrounding

the urethra as it passes through the urogenital

diaphragm

Levator ani muscle – voluntary urethral sphincter

The female urethra is tightly bound to the anterior

vaginal wall

External opening lies anterior to vaginal opening and

posterior to the clitoris

The male urethra has 3 named regions:

Prostatic urethra – runs within the prostate gland

Membranous urethra – runs through the urogenital

diaphragm

Spongy (penile) urethra – passes through the penis

and opens via the external urethral orifice

Prostate Gland Surrounds Urethra

Prostate Gland: Size of walnut

Surrounds neck of urinary

bladder and urethra

Secretes fluid that forms part

of semen

Benign Prostate Disorders Infection Inflammation Enlarged prostate

High blood levels of PSA Impotence Incontinence and or retention

S&S of prostate disorders Interference of flow Change in urinary freq. urination Pain

Prostate CA

Increased likelihood with enlarged prostate

(hypertrophy).

60% of prostate cancers discovered remain localized

5 yr survival = 100%

10 yr survival = 68%

15 yr survival = 52%

In past 20 yrs survival has increased from 67-93%

Other Considerations PSA check annually after age 50 High risk males should begin screening

earlier Risk factors

Age Race

African Americans are 61% more likely to get prostate CA & 2.5x more likely to die from dx

Diet: high fat / low fiber Obesity Environmental exposures

Kidney Location & Structure Bean-shaped

extends from T-12 to L-3. R kidney hangs lower than left.

crowded by the liver

Layers of Tissue Support Renal capsule – fibrous capsule surrounding kidneys

that gives support & helps prevent infection

Adipose capsule – fatty mass that cushions the kidney

and helps attach it to the body wall

Renal fascia – outer layer of dense fibrous connective

tissue that anchors the kidney

Internal Structure of Kidney Cortex – the light colored, granular superficial region

Medulla – exhibits cone-shaped medullary (renal)

pyramids

Pyramids are made up of parallel bundles of urine-

collecting tubules

Renal columns are inward extensions of cortical tissue

that separate the pyramids

Pyramid plus its surrounding capsule, constitute a

lobe

Large blood flow to kidney:~25% (1200 ml) of BF from heart into

systemic circulation, flows through the kidneys per minute.

The Nephron Nephrons: stral & fxnal units of the kidneys that form

urine: Glomerulus: a capillary bed associated with a renal

tubule Bowman’s capsule: cup-shaped end of a renal tubule

that surrounds glomerulus. Renal corpuscle – the glomerulus and its Bowman’s

capsule Glomerular endothelium –epithelium that allows

solute-rich, virtually protein-free filtrate to pass from the blood into the glomerular capsule

Renal Tubule Proximal convoluted tubule (PCT):

Composed of cuboidal cells with numerous microvilli

and mitochondria

Reabsorbs water and solutes from filtrate and

secretes substances into it

Loop of Henle: a hairpin-shaped loop of the renal tubule

Distal convoluted tubule (DCT):

cuboidal cells w/o microvilli that function more in

secretion than reabsorption

Nephrons Cortical nephrons – 85% of nephrons; located in the

cortex

Juxtamedullary nephrons:

Located at the cortex-medulla jxn

Have loops of Henle that deeply invade the medulla

Have extensive thin segments

Are involved in the production of concentrated urine

Capillary Beds of the Nephron

B/P in the glomerulus is high:

Kidney is very well vascularized

High density of blood vessels

Blood flow within nephron controlled by afferent

arteriole

Fluids & solutes are forced out of the blood

throughout the entire length of the glomerulus

Characteristics of Normal Urine• Complex watery (95%) solution of organic &

inorganic wastes (5%)• Color: pale, straw to amber color

– If highly concentrated:

•Hematuria / orange color–‘milky’ / turbid : infection

• Clarity: transparent• Odor: faintly aromatic; will change to ammonia

if standing too long. Some drugs and vegetables (asparagus) alter the usual odor

• pH: 5.5 – 7.0– Will turn alkaline if left standing

Characteristics of Normal Urine Specific Gravity:

Indicates concentration of urine (# of particles in it) Normal values = 1.01 – 1.03

Measured by comparing the weight of pure water vs. urine

Urine should not contain: Albumin Glucose Ketones Blood / Pus / Bacteria Calculi Bile

Normal Output

Normal voiding: 250 – 500cc

Normal 24 hour voiding: 1000

- 1500cc

Normal hourly: 30 -120cc

< 30cc / hr may indicate renal

pathology

Chemical Composition of Urine Urine is 95% water and 5% solutes

Nitrogenous wastes include urea, uric acid, and

creatinine

Other normal solutes include:

Na+, K+, phosphate, and sulfate ions

Calcium, magnesium, and bicarbonate ions

Abnormally high concentrations of any urinary

constituents may indicate pathology

Trauma, Ischemia & Kidney Damage Ischemia – decreased oxygen supply to nephron because

there is decrease in blood flow

Decreased blood flow to nephron which is chronic can

lead to Kidney Damage.

Anything that causes afferent arteriole prolonged

constriction

Renal Clearance Diagnostic Test The volume of plasma that is cleared of a particular

substance in a given time Clearance tests are used to:

Determine the GFR Detect glomerular damage Follow progress of renal dx

Renal Clearance

RCR = UV/P

RCR = renal clearance rate

U = concentration (mg/ml) of the substance in urine

V = flow rate of urine formation (ml/min)

P = concentration of the same substance in plasma

Urinary Disorders: S&S Changes in urinary frequency

or volume

Dark urine

Pain with urination

Kidneys unable to regulate

body H2O & Na+ balance

Edema (fluid retention) &

or High B/P

Urinary Tract Patho Urinalysis

General health of urinary sys Drug testing

Proteinuria Glomerular damage

Ketonuria Diabetes or starvation

Glucosuria Diabetes

Solids in urine - sediment examined. Types of cells: RBCs ; WBCs

Ability of kidneys to concentrate urine Administer ADH

become more concentrated since more fluid should be retained

Urinary Tract Infections Occurs in any portion of urinary

tract 10 - 20% of all women in US have

lower UTI at some time Limited occurrence

Effects of urea (kill bacteria) Acidic pH of urine Washing out of bacteria during

voiding Minimize urine reflux

Cystitis

Bladder inflammation

Increased urination

frequency & urgency

Pain

Cloudy urine

Blood in urine

Treatment: ABx thpy

Kidney Infection Bacterial or viral Urinary obstruction

causes backflow of urine from bladder to kidneys From blood infection Most cases in women Symptoms

Pain / Fever Increased urinary frequency

Treatment Longer use of ABx thpy

Urolithiasis Presence of stones in the

urinary tract Calculi formed by:

Calcium oxalate Calcium phosphate Uric acid

Calculi can pass through the urinary tract and/or cause an obstruction

Urolithiasis Assessment:

Acute, sharp, intermittent pain (ureteral colic)

Dull, tender ache in the flank (renal colic)

N&V, Fever & chills Hematuria / Pyuria Abd. Distention

Diagnostic Findings: KUB: visible calculi IVP: size & loc of stones Renal sonogram &

Spiral CT scan Stone Analysis –

detection of type of stone

Non-Surgical Procedures:

Extracorporeal Shock Wave

Lithotripsy

Stone dissolution

Laser impulse technology

Surgical Procedures:

Cystoscopy

Ureterolithotomy;

Pyelolithotomy; Nephrolithotomy

Polycystic Kidney Disease Genetic disorder - 500,000 cases in US Large cysts form in the kidneys Kidney hypertrophy Over time, decreasing kidney function as nephrons units

are replaced by cysts Dialysis or transplant

50% with PKD progress to kidney failure (end stage renal disease)

4th leading cause of kidney failure No cure except kidney transplant

Polycystic Kidney Disease

Acquired Cystic Kidney Disease

From long-term kidney dialysis and end-stage renal

disease

90% of people on dialysis for 5 yrs develop ACKD

Cysts may bleed

Increased risk of kidney cancer (very rare)

2 times as likely with ACKD

Diabetic Nephropathy Diabetes - Abnormally high blood glucose

Causes major problems with blood chemistry including osmotic balance

Kidneys can remove all extra glucose from bloodKidneys must work extra hard to do this

Larger urine volume as kidneys must excrete excess glucose

Diabetic Nephropathy (con’t) Prolonged high blood glucose causes nephropathy

Damage to the glomerulus and the filtering system

Proteins and blood cells that would normally not be

filtered appear in the urine

Kidney function is compromised

Diabetic nephropathy is leading cause of kidney failure

in United States

Diuretics Chemicals that enhance the urinary output include:

Any substance not reabsorbed

Substances that exceed the ability of the renal tubules

to reabsorb it

At transport max

Substances that inhibit Na+ reabsorption

Na+ drives the reabsorption of fluid

Osmotic diuretics include:

High glucose levels

H2O carried out w/ glucose

Alcohol

inhibits release of ADH

Caffeine and most diuretic drugs

inhibit Na+ reabsorption

Lasix

inhibit Na+ associated transporters

Diuretics to Treat Urinary System Dx Diuretics: increase urine volume

Aldosterone antagonists: block sodium retaining effect of aldosteroneMore sodium remains in renal tubule

More sodium excreted Where sodium goes, water goes (increased fluid

elimination Sodium and chloride reabsorption inhibitors

(thiazides)block reabsorption of sodium, potassium and

chloride Increased salt and water elimination

Treatment of Renal Failure Will develop after both kidneys are damaged

Restrict water, salt and protein intakeMinimizes volume of urine producedPrevent production of large amount of nitrogenous

waste Hemodialysis

Uses artificial membrane (replaces glomerular filtration) to filter blood.Diffusion of small ionsMinimal loss of blood protein

Dialysis fluidK+, phosphate ions, sulfate ions, urea, creatinine,

uric acid go into dialysis fluid

Treatment of Renal Failure Dialysis

15 hrs per week

Dialysis centers

Transplantation

15,000 transplants in 2003

1 yr success rate is 85-95%

Immunosupressive drugs to reduce transplant

rejection

Urinary Incontinence – Multiple Etiologies Normal effect of aging or pathology Stretching of pelvic floor during childbirth

Incontinence during sneezing and coughing (stress incontinence)

Prostate removal Neurogenic bladder dysfunction Treatment

Kegel exercises: tightening pelvic muscles as if trying to stop urination

Did you know? Infants have small bladders and the kidneys cannot

concentrate urine, resulting in frequent micturition Control of the voluntary urethral sphincter develops

with the N System about age 1 E. coli bacteria account for 80% of all urinary tract

infections Sexually transmitted diseases can also inflame the

urinary tract and result in urinary tract infections Kidney function declines with age, with many elderly

becoming incontinent