Urinary Bladder

Describe the location, shape and gross features of urinary bladder.

Urinary bladder is a hollow muscular viscus that acts as a reservoir of urine.

Location

• In adults: Empty bladder lies in the pelvic cavity and the distended bladder rises above the pubic symphysis and reaches the  hypogastric region  of abdominal cavity.

• In infants:  Urinary bladder is located in the abdominal cavity.

Shape:  It is  tetrahedral  in shape when empty and ovoid when distended .

Gross features and relations

Empty urinary bladder presents the following parts:

• An apex: Lies at the level of upper border of pubic symphysis. It is connected to the umbilicus by median umbilical ligament ( remnant of urachus).

• Base/Fundus/Posterior surface: Is triangular in shape.  In males it is related to ampulla of vas deferens and seminal vesicle. In females it is related to anterior  vag vaginal wall.

• Neck: Is the lowest and most fixed part.  It lies 3-4 cm. behind the lower part of pubic symphysis. In males it is related to prostate gland & in females to pelvic fascia. It is pierced by internal urethral meatus.

Borders: There are four borders – Anterior, Posterior, and two lateral.

Surfaces:

• Superior : Is triangular in shape and is related to coils of ileum and pelvic colon.
• Two inferolateral surfaces: Are related to pubic bone, retropubic fat and levator ani.
• Posterior surface: also called base of urinary bladder.

 Describe in brief the supports of urinary bladder.

Following are the Supports of urinary bladder :

True ligaments: Are condensations of pelvic fascia.

• Lateral and medial pubovesical/puboprostatic ligaments:  From  posterior surface of body of pubis to the neck of the urinary bladder.
• Lateral true ligaments: From tendinous arch of levator ani muscle to inferolateral surface of the urinary bladder.
• Posterior true ligaments: base of bladder to pelvic wall along the internal iliac vessels. *
  *Median umbilical ligament – from the apex of bladder to the umbilicus ( contains urachus – remnant of allantois).

False ligaments: Are formed by peritoneal folds.

• Median umbilical fold –  fold of peritoneum over the median umbilical ligament.
• Lateral umbilical ligaments: from bladder to the lateral pelvic walls.
• Posterior false ligaments/sacrogenital folds: from base of bladder to sacrum.

Describe briefly the trigone of bladder.

Trigone of urinary bladder: It is an equilateral triangular area on the inner surface of base of urinary bladder.

• Boundaries:

• Base – is formed by interuretric ridge (bar of Mercier) which extends between the two openings of the ureters.
• Apex – is formed by the internal urethral orifice.
• Sides – formed by uretro- uretric ridges(Bell’s bars) from the ureteric orifice to the urethral orifice

• Characteristic features:

• Mucous membrane is firmly adherent to the musculature.
• Absence of rugae (temporary folds of mucosa)
• Submucosa is absent

What is uvula vesicae?

Uvula vesicae : Is a rounded elevation just behind the urethral orifice which is formed by the median lobe of the prostate. In old aged man, the uvula vesicae may be enlarged due to enlargement of prostate and obstruct the outflow of urine through the internal urethral orifice.

Name the arteries supplying and the lymph nodes into which lymph drains from the urinary bladder.

Arteries supplying urinary bladder: It is supplied by branches of internal iliac artery. Superior vesical artery  is the main arteryo. Other arteries that supply uninary bladder are obturator,  inferior vesical , inferior gluteal and in females uterine artery

 Lymph nodes draining urinary bladder: Internal and external  iliac lymph nodes.

Describe briefly the nerve supply of urinary bladder.

Urinary bladder is supplied by autonomic nervous system.

Parasympathetic innervation: Efferent fibers arise from from S2 – S4 spinal segments  and supply urinary bladder via  pelvic splanchnic nerves /nervi ergentes. They are concerned with emptying of the bladder.. The fibers are  motor to the detrusor muscle and  inhibitory to the sphincter urethrae. The  afferent fibres convey the sensation of bladder distension.

Sympathetic innervation:  The  efferent fibers arise  from T11–L2 spinal segments and reach the urinary bladder via hypogastric plexus. The fibers are motor to sphincter urethrae muscle and  inhibitory to detrusor muscle. The afferent fibers carry pain sensation. Sympathetic  fibers are concerned with filling of the urinary bladder..

Applied Aspects