Anatomy of the urinary bladder Flashcards
Where is the urinary bladder situated?
Its size and position vary with the amount of urine and age
1) Young children:
- In the abdomen, and the neck of the urinary bladder lies at the upper border of the symphysis pubis
2) In adults:
- A pelvic organ (when empty, when distended it becomes abdomino-pelvic), and the neck lies at the lower border of the symphysis pubis
Describe the shape of the urinary bladder
1) Tetrahedral when empty
2) Ovoid when distended
What are the parts of the urinary bladder?
1) Apex (posterior)
2) 4-surfaces
3) 4-Borders
4) Neck
What are the borders of the urinary bladder?
1) Anterior border
2) 2-Lateral borders
3) Posterior border
What are the surfaces of the urinary bladder?
1) Posterior surface (base)
2) 2 Inferolateral surfaces
3) Superior surface
What are the angles of the urinary bladder?
1) Supero-lateral angle (where the ureters are attached)
2) Inferior angle (where the urethra is attached)
What is the ligament attached to the apex of the urinary bladder?
The median umbilical ligament
What are the relations of the posterior surface (base/fundus) in MALES?
1) Upper part: Covered by the peritoneum (terminated by the seminal vesicles and vas deference), which forms the anterior wall of the rectovesical pouch
2) Lower part (separated from the rectum by):
1- Pair of seminal vesicles (lateral)
2- Pair of vas deference dilatation (medial)
3- Seminal vesicle
What are the relations of the posterior surface (base/fundus) in FEMALES?
- It is separated from the rectum by
1) Upper part of the vagina
What are the relations of the superior surface of the urinary bladder in MALES?
In an empty bladder, it is triangular and covered with peritoneum, and it is related to:
1) Sigmoid colon
2) Coils of S.I
What are the relations of the superior surface of the urinary bladder in FEMALES?
Uterovesical pouch, which separates it from the body of the uterus
- The pouch is empty except when the uterus is retroverted (leaning posteriorly on the ano-rectal canal, instead of the urinary bladder and then the uterovesical pouch will be occupied by the S.I
What are the relations of the infero-lateral surface?
- It is not covered by peritoneum
1) Pody of pubis
2) Pubic symphysis
3) Fascia covering the levator ani muscle
- These structures are separated from the bladder by the space of retzius, which contains a retropubic pad of fat and vesical venous plexus
What is the importance of the infero-lateral surfaces?
In surgical operation, the bladder and prostate are approached through this space
What is the ductus deferens?
- It is a muscular tube in males that conveys sperm from the epididymis
- It is found at the posterior surface of the bladder and hooks over the ureter and runs medially
- Its terminal part is dilated, forming the ampula of the vas deference
- The inferior end of the ampulla of the vas joins the seminal vesicle to form the ejaculatory duct, which passes through the prostate to open into the prostatic urethra
Describe the structure of the seminal vesicle
- Two lobulated sacs
- They lie on the posterior surface of the bladder
- Their upper end are widely separated
- Their lower extremities are close together and narrow; they join the vas deference on the same side (medially) to form the ejaculatory duct
What forms the ejaculatory duct?
The union of the seminal vesicle and the ampulla of vater
What is the seminal colliculus?
- An elevation found in the center of the urethral crest, where the right and left ejaculatory ducts opens
- Above those ejaculatory openings on the seminal colliculus is the prostatic utricle
What is the urethral crest?
It is a median longitudinal mucosal fold
What is the seminal colliculus?
A rounded eminence in the middle of the urethral crest, where the ejaculatory ducts open
What is the prostatic utricle?
A small depression at the centre of the urethral crest
- It represents an embryological reminant (in females they have uterus or vagina)
What is the prostatic sinus?
It is a mucosal gutter on each side of the crest, and it receives the opening of the prostatic glands
What is the internal trigone?
Formed by the two openings of the ureters above and the urethral opening from below
- It does not have a submucosa
- The rest of the urinary bladder has mucosal folds
What is the external trigone?
- Found at the external aspect of the base of the male bladder, lined by:
1) Base: Posterior border of the urinary bladder
2) Apex: lies at the neck of the bladder
3) Both sides: Seminal vesicles and vas deference
What is meant by a suprapubic puncture?
- AKA Cystostomy
- As the bladder fills, the superior surface enlarges and enters the abdomen, peeling off the peritoneum from the anterior abdominal wall (making the bladder in direct contact with the anterior abdominal wall)
- Suprapubic punctures can be performed without entering the peritoneum
- Urinary calculi, small tumors, and foreign bodies might be removed from the bladder using the suprapubic intraperitoneal approach
Describe the anatomy of the neck of the urinary bladder
- The lowest point where the urethra begins
1) In males: The neck of the bladder lodges the prostate
2) In females: It lies at a lower level and comes in contact with the superior fascia of the urogenital diaphragm
Describe the spaces found on the perineal region (area between the thigh)
1) Superficial space
2) Deep space (Inside it, we have the deep transverse perineal muscle, which forms the urogenital diaphragm; on top of this muscle, we have the superficial fascia of the urogenital diaphragm, and underneath it, we have the inferior urogenital diaphragm fascia
What muscle forms the urogenital diaphragm?
The deep transverse perineal muscle only and not the sphincter urethra
Describe the structure of the interior of the urinary bladder
1) The mucous membrane of most of the urinary bladder in an empty bladder forms folds which disappear when the bladder is full
2) Trigone:
- The internal surface of the base of the urinary bladder
- Its mucous membrane is always smooth, even when the bladder is empty, because it is firmly adherent to the underlying muscle coat and it does not have a submucosa
- It is derived from the mesoderm, unlike the rest of the bladder
What are the boundaries of the internal trigone of the urinary bladder?
1) Superior angles: Ureter entry
2) Inferior angle: Internal urethral meatus
3) Superior limit of the trigone: interuteric ridge (muscular ridge which runs between the two opening of the ureters
4) Uvula vesicae: A small elevation behind the urethral orifice in males, it is produced by the underlying median lobe of the prostate
What forms the bed of the bladder?
- It consists of several structures upon which the bladder rests on; these structures are:
1) Anteriorly:
- Symphysis pubis
2) Inferolaterally:
- Fascia of levator ani and the obturator internus
3) Posteriorly:
- Ampulla of vater in males
- Anterior wall of the vagina in females
4) Inferiorly:
- Prostate in males
- Superior fascia of the urogenital diaphragm
What is the internal urethral sphincter?
- The detrusor muscle at the neck surrounds the urethra, forming an involuntary sphincter vesicae
- If it contracts, it will prevent the urine from going into the urethra
- During ejaculation, it contracts to prevent the retrograde movement of semen into the bladder
What is the arterial supply of the urinary bladder?
1) Superior vesical artery: supplies the superior part of the urinary bladder
2) Inferior vesical artery: supplies the postero-inferior part of the bladder, prostate, seminal vesicles, and the artery to the ductus deference (in females it corresponds to the vaginal artery)
What is the venous drainage of the urinary bladder?
- They correspond to the arteries and form a vesical venous plexus along the inferolateral surface of the bladder
- They finally drain into the internal iliac vein
- Tumor cells spread via the venous plexus
What is the lymphatic drainage of the urinary bladder?
1) External LN
2) Internal LN
3) Common iliac LN
4) Sacral LN
What is the nerve supply of the urinary bladder?
It is supplied by the vesical plexus (mix of sympathetic and parasympathetic) of nerves containing both sympathetic and parasympathetic components
What is the sympathetic nerve supply of the urinary bladder?
1) Sacral splanchnic (T11-L2) of the lateral horn cells
- Motor to the internal sphincter and inhibitory to detrusor (nerve filling)
- Motor to the seminal vesicles and ejaculatory ducts
- FYI, is it L1/2 But that not precise and they won’t ask about it in the exam as sometimes they cut L1/2, but the nerve function of the urinary bladder is still functional
Describe the route of the sympathetic nerves reaching the bladder
1) Spinal cord L1/2
- Preganglionic fibers
2) They descend in the sympathetic chain
3) They descend until they reach the Superior hypogastric plexus (a single plexus found near the bifurcation of the common iliac)
4) It then descends as two branches from the superior hypogastric plexus on each side as the inferior hypogastric plexus (found on both sides of the urinary bladder)
- Once it reaches the inferior hypogastric plexus, it is closely related to the bladder, and it relays its information to the (Post-ganglionic fibers) which supply the urinary bladder
- Sympathetic chain (preganglionic) - superior hypogastric plexus (preganglionic) - Inferior hypogastric plexus (preganglionic) - post-ganglionic fibers
What is the parasympathetic nerve supply of the urinary bladder?
- AKA nerve of emptying/voiding
- It arises from the preganglionic fibers of S2, S3, & S4 segments of the spinal cord and from the PELVIC SPLANCHNIC NERVES (nervi erigents)
- It supplies the body and neck of the urinary bladder
- It supplies the detrusor muscle (motor) and the muscles of the proximal urethra, it has an inhibitory effect on the sphincter vesicae
What is meant by the pelvic pain line?
- Areas of the urinary bladder in contact with the peritoneum will refer pain to different nerves compared to areas that are not in contact with the peritoneum, pelvic viscera that are in contact with the peritoneum are superior to the pelvic pain line
1) Areas of bladder touching the peritoneum: Feel pain - pain gets referred through T11-L2 (sympathetic fibers)
2) Areas of the urinary bladder not touching the peritoneum: feel Pain - pain gets referred via S2-S4 (parasympathetic fibers)
What are the branches of the sympathic innervation of the urinary bladder?
1) Motor to:
- Internal sphincter
- Seminal vesicle
- Ejaculatory ducts
2) Inhibitory to:
- Detrusor (nerve of filling)
What is meant by cytocele?
- The herniation of the urinary bladder into the vaginal wall, due to week deep transverse perineal muscle
- The bladder forms a cyst pushing the anterior wall of the vagina
What happens if the urinary bladder gets ruptured?
- The urinary bladder might be injured due to injuries of the inferior part of the anterior abdominal wall or by fractures of the pelvis:
1) Rupture of the superior part, tears the peritoneum and results in intraperitoneal extravasation of urine (peritoneal cavity)
2) Rupture elsewhere will result in extraperitoneal extravasation (perineal region)
What are the factors that prevent the reflux of urine from the bladder to the ureters?
1) Oblique direction of the intra-vesical part ureter (as the posterior wall of the ureter is firmly anchored to the detrusor muscle of the bladder, if the intravesical pressure increases the anterior wall of the ureter is compressed against the posterior wall like a flap valve preventing reflux)
2) Peristalsis of the ureteral muscles (collects urine in jets and not droplets)
What is meant by a golf ureter?
A pathology that happens due to TB of the kidney, where the ureter is no longer oblique and becomes circular (due to shortening of the ureter)
Which part of the urinary bladder is supplied by the parasympathetic innervation?
1) Body
2) Neck
What are the muscles supplied by the parasympathetic innervation?
1) Detrusor muscle
2) Muscle of proximal urethra
What is the function of the parasympathetic innervation of the urinary bladder?
It senses the distension and painful sensations (due to over-distension) from the bladder and the proximal urethra
How is the painful sensation from the urinary bladder transmitted?
1) Sensory parasympathetic innervation
2) Cell bodies
3) Dorsal root ganglia
4) S2/S4 Spinal nerves
What is the nerve of filling, and what is its function?
- It is the sympathetic innervation of the urinary bladder
- It has a motor supply to the internal sphincter and inhibitory to the detrusor
- It prevents voiding
What are the functions of the sympathetic innervation of the urinary bladder?
1) Motor to seminal vesicles and ejaculatory ducts
- Nerve of filling (inhibits voiding)
2) Motor to internal sphincter
3) Inhibitory to detrusor
