Brief notes on Ureters

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• Brief notes on Ureters
• by
• Dr. R.G. Cooper
• Senior Lecturer
• Division opf Physiology

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Task

• Please read through these notes carefully and
  bring any questions you may have to the session
  on 11/10/04. Try and read around the topic by
  sourcing journal articles and specialised
  textbooks in the library. Include one example of
  a pathological condition affecting the ureters.

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• Ureter
• Thick-walled tube that conveys urine from the
  kidney to the urinary bladder. It is
  approximately 10 in. (25.4 cm) long, with the
  upper half located in the abdomen and the lower
  half in the pelvic region.
• Urine is transported down this tube under the
  impetus of gravity assisted by contractions of
  the smooth muscles that line the ureteral walls.
• A blocked ureter can result from congenital
  abnormality, a tumour, or the formation of kidney
  stones. Blockage may require surgery to prevent
  loss of urinary function and eventual urea
  poisoning.

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• The ureters are fibromuscular tubes that convey
  the urine from the renal pelvis to the bladder.
• Each ureter is approximately 16 inches long and
  the one leading from the right kidney is slightly
  shorter than the left.
• The ureters consist of mucosal, muscular, and
  fibrous layers.
• The area where the ureters enter the bladder is
  called the trigone.
• Valves in this region prevent the reflux
  (i.e.backing up) of urine into the kidneys.

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• Histology
• The ureter is a muscular tube lined by
  transitional epithelium
• The epithelium
• The epithelium is the same from the minor calyces
  to the exit from the bladder. Transitional
  epithelium appears to be multilayered although
  each cell does have contact with the basement
  membrane. Cell division can occur anywhere. The
  cells tend to be flattened towards the base and
  more rounded towards the epithelial surface. The
  attachments between cells are such that urine
  cannot pass between them. The epithelium sits on
  a connective tissue submucosa. When the ureter is
  constricted the epithelium is folded into
  longitudinal ridges.

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• As a wave of peristalsis passes the bolus of
  urine distends the lumen and stretches the
  epithelium. The epithelium is able to cope with
  distention by the arrangement of cells and by
  recruitment of the folds. Although the epithelium
  is termed a 'mucosa' there are no mucus secreting
  cells or glands.
• The muscle coat
• The smooth muscle fibres in the wall of the
  ureter are arranged in a spiral fashion forming
  two layers that are close to circular and
  longitudinal.

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• Innervation
• Innervation of the ureter supplies the
  vasculature and smooth muscle with motor fibres
  and the wall with sensory fibres. The source of
  innervation is the autonomic nervous system.
• The nerve fibres are derived from the renal,
  aortic and superior and inferior hypogastric
  plexuses. The sources of the fibres are the lower
  three thoracic, first lumbar and second to fourth
  sacral nerves. The innervation is not necessary
  for normal peristaltic action in the ureter.
  Peristalsis is usually initiated in one or more
  of the minor calyces and spreads down the ureter
  to the bladder. The afferent fibres carry
  information concerning distention of the ureter.
  The pain of a blocked ureter is excruciating and
  radiates to the flank, top of the thigh and
  labium majus in females and in males, to the
  scrotum and penis.

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• Stones
• Stones tend to be trapped at three places. Stones
  forming in the minor and major calyces may not be
  able to pass into the ureter from the pelvis
  since the lumen is too narrow. If they do manage
  to pass this first barrier they may become lodged
  at the point where the ureter crosses the
  bifurcation of the common iliac artery and into
  the pelvis. At this point the ureter is changing
  direction, passing backwards. The artery is also
  unyielding in that it is pressurized. The final
  barrier is the valve-like arrangement of the
  bladder wall. The ureter passes obliquely through
  the wall and the muscle of the bladder keeps the
  ureter closed. This normally prevents
  regurgitation of urine when bladder pressure is
  increased in micturition. Obstruction of the
  ureter causes dilation of the renal pelvis and
  calyces.

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