Conducting urinary tract

Synonyms in a broader sense

Medical: ureter, vesica urinaria

English: bladder, ureter

  • Renal pelvis
  • Ureter
  • Urethra
  • Urinary tract

The draining urinary tract includes renal pelvis (pelvis renalis) and ureter (ureter), which are lined by specialized tissue called urothelium.


1. renal pelvis It develops from the confluence of 8-12 renal calices (Calices renales), which surround the renal papillae and collect the final urine. Depending on the arrangement of the calices, a distinction can be made between an ampullary (with short tubes and wide renal pelvis) and a dendritic (with long, branched tubes and small renal pelvis) caliceal system. Renal calices and renal pelvis are surrounded by a richly supplied with blood connective tissue, which also contains a network of smooth, i.e. not deliberately controllable, muscle cells, which regulate the width of the cavity system.

2nd ureter The 25-30 cm long ureter represents the connection between the renal pelvis and the bladder. A distinction is made: Both ureters pass through the bladder wall at an angle, which together with the internal pressure of the bladder ensures that the orifice is usually closed to prevent the accumulation of urine. They are opened when a contraction wave of the ureter arrives.

A musculature arranged in three layers ensures the further transport of the urine into the bladder by peristaltic waves. There are three narrow points in the course of the ureter: From time to time a double ureter can also occur, which unites at different heights to form a ureter. Separate junctions in the urinary bladder can also occur.

Nevertheless, such anomalies usually have no disease value and can remain undetected for life. The ureter (ureter), renal pelvis and caliceal system can be depicted in the X-ray image (radiologically) with the aid of special contrast agents, which are either administered through the vein and then excreted through the kidney (intravenous pyelogram) or the contrast agent is administered backwards through the bladder directly into the ureter (retrograde pyelogram). The blood supply is ensured by branches of the renal artery and various other vessels, which form a dense network in the ureteral wall.

The wall of the ureter consists of

  • Pars abdominalis (abdominal segment)
  • Pars pelvica (pelvic segment)
  • Mucus layer (tunica mucosa)
  • Muscular layer (tunica muscularis)
  • Outer covering layer (tunica adventitia)
  • At the exit from the renal pelvis
  • At the crossing by the inguinal vessels (Aa. iliacae)
  • When passing through the bladder wall

Cross section through the bladder and underlying prostate:

  • Bladder
  • Urethra
  • Prostate
  • Seed mound with the two openings of the spray channels
  • Exit ducts of the prostate gland

The urinary bladder (Vesica urinaria) is a muscular hollow organ whose shape varies according to the stage of development or filling. When slightly filled, the bladder is pyramid-shaped with the tip tilted forward.

It can be distinguished: The so-called Trigonum vesicae (bladder triangle) is a triangular area free of mucous membrane wrinkles between the orifices of the ureters and the beginning of the urethra. Here the mucous membrane is immovably connected to the muscles below. In men, the part of the prostate gland close to the bladder lies directly below it.

The wall construction and the fixation of the bladder allow large fluctuations in volume. The wall consists of:

  • Bladder tip (apex vesicae)
  • Bladder body (Corpus vesicae)
  • Bladder floor (fundus vesicae) with the entrance of the ureter and the exit of the urethra
  • The neck of the bladder (cervix vesicae), which merges into the urethra. – Tunica serosa: It consists of the peritoneum in the upper and rear part of the bladder.
  • Tunica muscularis: It consists of three layers of smooth muscles (outer and inner lengthwise and transverse in the middle). The fibre strands merge into one another and form a functional unit (M. detrusor vesicae). The musculature in the area of the trigonum vesicae should be emphasized.

It is only single-layered and lies around the inner opening of the urethra like a kind of ruff. Thus it preserves continence and, in men, the penetration of the ejaculate into the bladder. – Tunica mucosa: It consists of transitional epithelium.

The height of the lining mucosa depends on the filling condition, i.e. the thickness of the wall is approx. 1.5 – 2 mm when filled and approx. 5 – 7 mm after emptying.

Without filling the mucosa lies in folds, with increasing bubble filling the surface becomes smooth. In the area of the cervix and the fundus, the bladder is immovably fixed by connective tissue. Otherwise it is movable in order to adapt to different filling conditions.

This is achieved by a ligamentous apparatus that is different in men and women. When the bladder expands, it emerges from the small pelvis at the front of the abdominal wall and simultaneously pushes the corresponding peritoneum in front of it. If the bladder is filled more strongly, the symphysis line is also crossed, but the bladder usually never rises above navel height.

In general, the bladder has a maximum capacity of 1500 ml, but the urge to urinate already occurs at about 200 – 300 ml. The internal opening of the urethra is normally closed by the muscles of the bladder and by the continuous contraction (tonus) of the M. sphincter urethrae internus. This is controlled by a special nerve plexus.

When the bladder is emptied (micturation), a nervous signal is sent from fibres of the parasympathetic nervous system, which puts pressure on the bladder contents by tensing the M. detrusor vesicae. The bladder neck opens by pulling its front wall forward through the likewise activated pubovesicalis muscle. These processes cannot be controlled intentionally.

However, there is a voluntarily controllable closure, the M. sphincter urethrae (Rhabdosphincter). This allows the urge to urinate to be initiated or interrupted at will. Micturition itself is completely automatic, by means of a spinal cord reflex, which in turn can be inhibited or promoted by centres in the brain (so-called micturition centres in the reticular format).

Emptied, the bladder lies broadly and bowl-shaped on the pelvic floor. During micturition it takes on a spherical shape, with the detrusor vesicae muscle closing concentrically around the contents. In newborns, the bladder protrudes from the pelvis due to the greater spatial narrowness.

Later, as the space in the small pelvis increases, the bladder slips into the pelvic ring (Descensus vesicae). Blood is supplied through branches of the internal inguinal artery (A. iliaca interna) with blood from the venous networks in the mucous membrane and muscles is collected in the plexus venosus vesicalis (venous plexus of the bladder), which surrounds the base of the bladder. From there, the blood is drained either directly or via intermediate stations to the internal inguinal vein (V. iliaca interna).

The nerve supply can be divided into different nerve plexuses with different tasks. – A. vesicalis superior (upper bladder artery) for the lateral bladder wall and the bladder surface

  • A. vesicalis inferior (lower bladder artery) for the bladder floor
  • Intrinsic nerve plexus: It lies in the bladder wall and adjusts the tone of the detrusor muscle to the filling state of the bladder. – Extrinsic nerve plexus: It contains the following fibres sympathetic fibres (motor supply of the detrusor muscle) sympathetic fibres (tone of the vessels, muscles of the bladder neck)
  • Sympathetic fibres (motor supply of the detrusor)
  • Sympathetic fibres (tone of the vessels, muscles of the bladder neck)
  • Somatic fibres: These are the deliberately controlled part and supply the M. sphincter vesicae externus. – sympathetic fibres (motor supply of the detrusor muscle)
  • Sympathetic fibres (tone of the vessels, muscles of the bladder neck)