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• Kidneys


  Excretory organs that separate waste substances from the blood and discharge them
• Ureters


  A pair of thick-walled tubes that carry urine from the kidney to the urinary bladder
• Urinary bladder


  A membranous sac for temporary retention of urine
• Urethra


  A duct through which urine is discharged and which serves as the male genital duct

  
• Organs of the urinary system

  • Kidneys
  • Ureters
  • Urinary bladder
  • Urethra

  
• Kidneys


  • There are 2 kidneys
  • Located behind the peritoneum, retroperitoneal organs
  • Sit between the T12 and L3 vertebrae
  • Right kidney slightly lower than left to accommodate the liver
  • Bean-shaped, about the size of an adult fist

  
• Ureters


  • There are 2 ureters
  • Thick-walled tubes that carry urine from the kidney to the urinary bladder
  • 10-12 inches long, 1/4 inch diameter
  • Superior end continuous with the renal pelvis
  • Mucosal lining continuous with renal pelvis and bladder
  • Enter the posterior aspect of the bladder at a slight angle
  • Run behind the peritoneum
  • Peristalsis aids gravity in urine transport
  • Smooth muscle layers contract to propel urine
  • Valve-like fold of bladder mucosa prevents backflow
• Urinary bladder


  • Smooth, collapsible, muscular sac
  • Temporarily stores urine
  • Located retroperitoneally in the pelvis posterior to the pubic symphysis
  • Trigone - three openings: two from the ureters, one to the urethra
  • In males, prostate gland surrounds the neck of the bladder where it empties into the urethra
  • Urine travels down the ureters into the bladder
  • Bladder expands like an elastic sac to hold more urine
  • Involuntary muscle movements send signals to the nervous system, putting urination under conscious control
  • Internal urethral sphincter is involuntary, external urethral sphincter is voluntary
• Urethra


  • Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis
  • Release of urine is controlled by two sphincters: internal urethral sphincter (involuntary) and external urethral sphincter (voluntary)
  • Females - 3-4 cm long, along the vaginal wall, only carries urine
  • Males - 20 cm long, through the prostate and penis, carries urine and sperm

  
• Kidneys are attached to ureters, renal blood vessels, and nerves at the renal hilus (medial indention)

  
• On the top of each kidney is an adrenal gland
• The kidneys are reddish-brown, bean-shaped, 12 cm long, 6 cm wide, and 3 cm thick

  
• Ptosis is when the kidneys drop to a lower position due to rapid fat loss, creating problems with the ureters
• Ptosis can lead to hydronephrosis, a condition where urine backs up the ureters and exerts pressure on the kidney tissue
• Regions of the kidney

  • Renal cortex
  • Renal columns
  • Renal medulla
  • Medullary pyramids
  • Renal pelvis
  • Calyces

  
• Renal cortex


  • Outer region, forms an outer shell
• Renal columns


  • Extensions of cortex material inward

  
• Renal medulla


  • Inside the cortex, contains medullary (renal) pyramids

  
• Medullary pyramids


  • Triangular regions of tissue in the medulla, appear striated
• Renal pelvis


  • Inner collecting tube, divides into major and minor calyces

  
• Calyces


  • Cup-shaped structures enclosing the tips of the pyramids that collect and funnel urine towards the renal pelvis

  
• Functions of the urinary system

  • Elimination of waste products
  • Filtering fluid from the bloodstream to create filtrate
  • Red blood cell production
  • Blood pressure regulation
  • Blood volume regulation
  • Blood composition regulation
  • Blood pH regulation
• Nephrons


  The structural and functional units of the kidneys, over 1 million in each kidney, responsible for forming urine
• Nephrons


  • Consist of a renal corpuscle (glomerulus and Bowman's capsule) and a renal tubule

  
• Urine produced in the kidneys travels down the ureters into the urinary bladder
• The bladder expands like an elastic sac to hold more urine
• Involuntary muscle movements send signals to the nervous system, putting the decision to urinate under conscious control
• The internal urethral sphincter is involuntary, the external urethral sphincter is voluntary