The Urinary System

Glen Hookey Eric Kolker Justin Loeb Michael Ross

Uston—Period 5

Overview

Animals and Waste

• Filter body fluid for toxins and unnecessary substances

• Kidneys (bp, activation of vitamin D, erythropoietin, wastes)

• Nitrogenous waste

Transport Epithelium

• Manage solute levels

• Line many channels inside the body

• Comprised of special epithelial cells

• Can move solutes against gradient

Nitrogenous Wastes

• Three types: Ammonia, Urea, Uric Acid• Ammonia

– Highly toxic, diluted with large supplies of water

• Urea– Low toxicity, energy cost (used by mammals)

• Uric Acid– Low toxicity, water insoluble, excreted as a paste

Excretory Processes

• Filtration– One layer of transport epithelium (large molecules removed);

filtrate

• Reabsorption– Active transport (glucose, amino acids, etc.)

• Secretion– Materials added to excretory tubule

• Excretion– Expelled as urine

Filtrate/Urine Pathway

Kidney

• Filters substances form blood

• Adjusts filtrate’s composition

• Returns most substances to blood

Nephron

• Functional unit

• Packed tubules

• Surrounded by capillaries

• Filters blood

Bowman’s Capsule

• Start of Nephron• Glomerulus• Filtration into

lumen:– Water, salts

bicarbonate, hydrogen ions, urea, glucose, amino acids

Proximal Tubule

• pH maintained• Reabsorption• Reabsorbs Na+

osmosis

Loop of Henle

• Descending– Water

• Ascending– Thin & Thick

– Passive & Active

Distal Tubule

• pH regulation• Sodium, calcium,

potassium

Collecting Duct

• Subject to hormonal controls

• Diseases• Concentration of

filtrate

Urine Composition

• Excess water and solutes• Ions• Urea• Neurotransmitters• Histamine• Drugs/toxins

Osmoregulation

• Solute gradient• Bends in nephron• Membrane selective

permeability• Diffusion• Active transport• Salt

Solute Gradient

• Membrane selective permeability

• Interstitial fluid• Filtrate• Active transport• Diffusion

Nephron Overview

ProximalTubule

DescendingLoop of the henle

AscendingLoop of the henle

DistalTubule

Collectingduct

Gradient Overview

Gradient #1: Proximal tubule• Blood

– ~300 mosm/L• Interstitial fluid:

– ~300 mosm/L• Filtrate:

– ~300 mosm/L– In:

• Hydrogen ions• Ammonia

– Out:• Bicarbonate• Salt• Water• Nutrients• Potassium ions

• In cortex• Volume decreased• Osmolarity stays constant

Gradient #2: Descending Loop of the Henle

– Interstitial fluid• 300 - 1200 mosm/L

– Filtrate• 300 - 1200 mosm/L

• In– N/A

• Out– Water

– Membrane permeable only to water

– Salt concentration increases

– Water diffuses out

Gradient #3: Ascending Loop of the Henle

• Ascending loop– Interstitial fluid

• 1200 - 300 mosm/L

– Filtrate• 1200 - 200 mosm/L• In

– N/A

• Out– Salt

– Membrane permeable only to Salt

– Salt concentration decreases– Filtrate osmolarity lowered to

increase osmolarity of interstitial fluid

Gradient #4: Distal tubule

• Interstitial fluid– 300 mosm/L

• Filtrate– 100 mosm/L

– In• Potassium ions

• Hydrogen ions

– Out• Salt

• Water

• Bicarbonate

• Filtrate at lowest osmolarity

• Key role in determination of pH of urine

Gradient #5: Collection duct• Interstitial fluid

– 300 - 1200 mosm/L

• Filtrate– 300 - 1200 mosm/L– In

• N/A

– Out• Salt• Urea• Water

• Final stage• Controls final salt output• Low salt• Water diffuses• Concentrated filtrate

Regulation #1: ADH

• Antidiuretic hormone• Hormone• Activated by

hypothalamus at high blood osmolarity

• Decreases water loss– More permeability to

water

Regulation #2: RAAS

• Renin-angiotensin-aldosterone system

• Angiotensin II• Activated at low blood

pressure/volume• Decreases water loss

– Constricts capillaries– More reabsorption of

salt

Regulation #3: ANF

• Atrial natriuretic factor• Opposite of ADH and

RAAS– Triggered by high blood

pressure/volume– Inhibits NaCl absorption– Increased water loss

through urine

• Disables ADH

Ureter

• Lining of ureter

• Smooth-muscle cells contractions

• Ureter crosses bladder wall

• Ureter in Micturition

Urinary Bladder• Storage organ

• Bladder in micturition

• Brain cells

• Structure

Urethra

• Function and location

• Cells of Urethra

• External Meatus

Abnormalities of the Renal System

• Acute

• Chronic

• Congenital

Congenital Problems

• Horseshoe kidneys– Functions as one kidney

• Has to be cautious of rigorous activity

Acute Problems

• Usually reversible• Examples: stones, infections, tumors,

inflammation, acute renal failure• Detected by urinalysis or by pain and fever

Urinary Tract Infection (UTI)

• Occurs anywhere along the urinary tract (kidneys, bladder)

• Women more prone than men; shorter urethra

• Pain and fever• Treated with antibiotics

Tumors and Stones• Most tumors in kidneys

and bladder are malignant

• Smokers are prone to bladder tumors

• Stones- intensely painful• Can be passed but some

require surgery or ultrasound

Trauma

• Kidneys damaged by physical trauma

• People with one kidney have to avoid potentially dangerous activities

• Blood in urine

Chronic Kidney Failure• Dialysis (3 days a week; 4 hours)

– Cleans blood

• Only cure is transplantation