Urinary Bladder Anatomy

Question 2. Describe the Urinary Bladder under the following headings:

1. Urinary Bladder Introduction
2. Urinary Bladder External features
3. Urinary Bladder Relations
4. Urinary Bladder Supports
5. Urinary Bladder Arterial supply
6. Urinary Bladder Venous drainage
7. Urinary Bladder Lymphatic drainage
8. Urinary Bladder Nerve supply and
9. Urinary Bladder Applied anatomy.

Answer:

1. Urinary Bladder Introduction:

The urinary bladder is a hollow muscular organ, which lies in the anterior part of the pelvic cavity behind the pubic symphysis. It acts as a reservoir of urine. Its capacity is 220 ml but varies from 120 ml to 320 ml.

Note:

• When the bladder is filled up to 120 ml, one gets a sense of the filling of the bladder
• When the bladder is filled beyond 240 ml, one gets the desire to micturate.
• When the capacity of the bladder reaches 480 ml, one starts feeling pain.

2. Urinary bladder External features: An empty bladder is tetrahedral in shape and presents

1. Apex
2. Base
3. Neck
4. 3 surfaces (superior and two inferolateral surfaces), and
5. 4 borders (left lateral, right lateral, posterior, and anteroinferior).

Note: A full bladder is ovoid in shape and presents: apex, base, neck, and 2 surfaces (anterior and posterior).

1. Apex: It lies just below the upper border of the pubic symphysis. It is directed forward and upward and connected to the umbilicus by the median umbilical ligament.
2. Base (fundus/posteroinferior surface): It is directed backward and downward.
3. Neck: It is the lowest and most fixed part. It lies 3–4 cm behind the lower border of the pubic symphysis and is pierced by the internal urethral orifice.
4. Urinary bladder Surfaces:
   • Superior surface: It is covered by the peritoneum.
   • Inferolateral surfaces: They are devoid of the peritoneum.
5. Urinary bladder Borders:
   • Anterior border: It extends from the apex to the neck and separates inferolateral surfaces from each other.
   • Lateral borders (left and right): Each of them separates the superior surface from the inferolateral surface on the corresponding side and extends from the entrance of the ureter to the apex.
   • Posterior border: It separates the superior surface from the base and extends between the entrances of the ureters.

3. Urinary bladder Relations:

• Apex: Connected to the umbilicus by a median umbilical ligament.
• Base/posteroinferior surface:
  • In females: The cervix of the uterus and vagina.
  • In males: Rectovesical pouch containing coils of the intestine (in the upper part); seminal vesicles and vasa deferentia (in lower part).

• Neck:
  • In females: Pelvic fascia.
  • In males: Base of the prostate.
• Superior surface:
  • In female:
    • Covered by peritoneum except for a small area near the posterior border
    • Vesicouterine pouch
    • Sigmoid colon
    • Coils of ileum
  • In male:
    • Completely covered by peritoneum
    • Sigmoid colon
    • Coils of ileum
• Inferolateral surfaces:
  • Pubis
  • Pubovesical ligaments in females and puboprostatic ligaments in male
  • Retropubic fat
  • Levator ani muscle
  • Obturator internus muscle

4. Urinary bladder Supports/ligaments:

• Median umbilical ligament:
  • It is a remnant of urachus (i.e., obliterated urachus).
  • Puboprostatic ligaments/pubovesical ligaments (4 in number)
  • These are fibromuscular bands extending from the bladder neck to the pubic symphysis.
• Lateral ligaments (2 in number): These are fibromuscular bands extending from the inferolateral surface of the bladder to the tendinous arch of pelvic fascia.
• Posterior ligaments (2 in number): These are fibromuscular bands extending from the base of the bladder to the pelvic wall.

5. Urinary bladder Arterial supply:

1. Major Blood Supply By: Branches of the anterior division of the internal iliac artery
   • Superior vesical artery
   • Inferior vesical artery
2. Minor blood supply By: Branches of the anterior division of the internal iliac artery
   • Obturator artery
   •  Inferior gluteal artery
   • Uterine artery
   • Vaginal artery

What is The Drainage system of Urine ?

6. Urinary bladder Venous drainage: By vesicoprostatic venous plexus in males and vesical venous plexus in females, which drain backward into an internal iliac vein.

Why do you drain the Bladder ?

7. Urinary bladder Lymphatic drainage: Lymphatics from the bladder follow the arteries and drain into external (most) and internal iliac nodes.

8. Urinary bladder Nerve supply:

• Sympathetic supply: From T11, T12, L1, and L2 spinal segments. It is inhibitory to the detrusor muscle of the bladder wall and motor to (i.e., constricts) the internal urethral sphincter (sphincter vesicae), thus allowing the filling of the bladder.
• Parasympathetic supply: From S2, S3, and S4 spinal segments. It is motor to (i.e., constricts) the detrusor muscle of the bladder wall and inhibitory to the internal urethral sphincter (i. e., relaxes), thus allowing the evacuation of urine from the bladder.
• Somatic supply: From the pudendal nerve to the external urethral sphincter.
• Sensory supply: From parasympathetic fibers to S2–S4.

9. Urinary bladder Applied anatomy:

• Distended bladder: It occurs due to obstruction of urine outflow by enlarged prostate or stricture. It may be ruptured by injuries to the lower abdominal wall.
• Reflex (automatic) bladder: In this condition, the voluntary inhibition and initiation of micturition is lost. As a result, the bladder empties reflexly every 1 to 4 h. It occurs in the transection of the spinal cord above the S2 spinal segment.
• Atonic bladder: In this condition, the wall of the urinary bladder becomes thin and hypotonic following the interruption of sensory fibers of the reflex arch of micturition. It results in overflow incontinence.