URINARY BLADDER

Urinary Bladder

The Urinary Bladder is a hollow, distensible, and muscular sac-like organ that stores urine. It is located in the pelvis, inferior to the abdominal cavity.

Development

• The Bladder develops from the urogenital sinus during embryonic development.
• The urogenital sinus forms from the cloaca, which is a shared cavity for the reproductive, urinary, and digestive systems.

Gross Anatomy

• The Bladder is a pear-shaped organ with a capacity of approximately 400-500 ml in adults.
• It is located in the pelvis, anterior to the rectum and posterior to the pubic symphysis.
• The Bladder is surrounded by peritoneum, except for the part that is in contact with the pelvic floor muscles.

Blood Supply

• The Bladder is supplied by the superior and inferior vesical arteries.
• The superior vesical artery arises from the common iliac artery, while the inferior vesical artery arises from the internal iliac artery.

Nerve Supply

• The Bladder is innervated by the autonomic nervous system, consisting of both sympathetic and parasympathetic fibers.
• The sympathetic fibers originate from the lower thoracic and upper lumbar spinal cord, while the parasympathetic fibers originate from the sacral spinal cord.

Lymph Drainage

• The lymph vessels of the Bladder drain into the lumbar and iliac lymph nodes.

Urine Storage and Voiding

• Urine is stored in the Bladder by the detrusor muscle, which relaxes during storage.
• During urination, the detrusor muscle contracts, and the internal sphincter relaxes, allowing urine to flow out of the Bladder.

Urine Storage Mechanism

1. The detrusor muscle relaxes → Urine enters the Bladder → The internal sphincter remains closed → Urine is stored in the Bladder.

2. The internal sphincter relaxes → The external sphincter relaxes → The detrusor muscle contracts → Urine flows out of the Bladder.

Function

• The Bladder stores urine from the kidneys until it is expelled through the urethra.
• It plays a crucial role in maintaining the balance of fluids in the body.

Clinical Significance

• Urinary incontinence and urinary retention are common problems related to the Bladder.

• Bladder stones and tumors can cause pain and discomfort.

• Describe the morphology of urinary bladder:

  • The urinary bladder is a hollow, muscular, and distensible organ.
  • It has a triangular base and a rounded apex.
  • The base is fixed to the pelvic floor.
  • The apex is free and projects into the pelvic cavity.
  • The bladder has three layers: the mucous membrane, the muscularis, and the adventitia.

  • Diagram:

    +---------------+ | Mucous | | membrane | +---------------+ | Muscularis | | (trabecular) | +---------------+ | Adventitia | | (peritoneum) | +---------------+

• Describe the relations of urinary bladder:

  • The bladder is situated in the pelvis, anterior to the rectum and the uterus in females.
  • It is connected to the urethra by the internal urethral orifice.
  • The ureters enter the bladder at an angle and open into the trigone area.
  • The bladder is surrounded by the detrusor muscle.

  • Diagram:

          +---------------+
          |  Rectum      |
          +---------------+
          |  Uterus      |
          |  (females)    |
          +---------------+
          |  Detrusor    |
          |  muscle      |
          +---------------+
          |  Bladder     |
          |  (with ureters)|
          +---------------+
          |  Urethra     |
          +---------------+
    

• Describe the ligaments of urinary bladder:

  • The bladder is supported by the following ligaments:
    • The bladder is attached to the pubic bone by the pubovesical ligament.
    • The bladder is attached to the cervix by the cardinal ligament.
    • The bladder is attached to the rectum by the rectovesical pouch in males.

  • Diagram:

          +---------------+
          |  Pubic bone  |
          +---------------+
          |  Pubovesical  |
          |  ligament     |
          +---------------+
          |  Bladder     |
          +---------------+
          |  Cardinal    |
          |  ligament    |
          +---------------+
          |  Uterus      |
          |  (females)    |
          +---------------+
          |  Rectum      |
          |  (males)     |
          +---------------+
    

• Describe the applied anatomy:

  • The bladder functions as a reservoir for urine.
  • The detrusor muscle contracts to expel urine through the urethra.
  • The internal urethral sphincter relaxes to allow urine to flow through the urethra.

  • Diagram:

          +---------------+
          |  Bladder     |
          +---------------+
          |  Detrusor    |
          |  muscle      |
          +---------------+
          |  Internal   |
          |  urethral   |
          |  sphincter  |
          +---------------+
          |  Urethra     |
          +---------------+
    

• Describe the pathways:

  • Urine flows from the kidneys to the bladder through the ureters.
  • Urine flows from the bladder to the urethra through the internal urethral orifice.
  • Urine flows from the urethra to the outside of the body.