Urinary System

FUNCTION 

• Control composition and volume of blood by regulating 
• water and solute levels 
• Remove waste products

2 KIDNEYS (10-12cms)

• Consists of 3 parts 
  • The Cortex – outer 
  • The Medulla – inner contains pyramids 
  • The Pelvis – opens into the ureters 
  • Cortex and Medulla contain Nephrons - the functional units of the kidneys 

NEPHRONS 

• Filter from blood: 
  • Protein, Chloride, Sodium, Bicarbonate, Glucose, Urea, Potassium, Uric acid, Water 
•  Water, Glucose and Proteins are re-absorbed into the capillaries 
• 1.5 litres leaves body as urine 
• Process occurs in nephrons 

COMPONENTS OF THE URINARY SYSTEM

2 URETERS

Urine passes from kidney to bladder through ureters by peristalsis (wave like muscular contraction) 

BLADDER 

• Hollow, muscular organ – reservoir for urine 
• Capacity 700-800ml of urine 
• When 200-400ml of urine is in bladder, stretch receptors send 
• messages via spinal cord to the brain, causing urge to urinate 
• 2 sphincters at the base of the bladder – internal (involuntary) and external (voluntary) control emptying of the bladder 

URETHRA 

• 95% water plus 
  • Urea – waste product of protein metabolism
  • Uric acid – waste product of nucleic acid metabolism derived from food
  • Sodium Chloride 

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