Lecture 6- Anatomy of Urinary Bladder and Urethra

1. Urinary Bladder- Sac containing fluid which collects and stores urine until it is ready to be excreted- The body know when to urinate when it’s time to urinate- LOCATION:

Muscular, hollow pelvic organ varies in size, shape, position & relations according to content and state of neigbouring organs

Empty adult urinary bladder located in lesser pelvic, superior & posterior to pubic bones.

Separated by retropubic space Lies mostly under cover of peritoneum Resting on pubic bones

Located above the urogenital diaphragm

Male sagittal section

Female sagittal section

2. External structure of urinary bladder : 4 surfaces ( superior, 2 inferolateral, inferoposterior)

4 ducts: 2 ureters, urachus(median umbilical fold), urethra

Apex: points toward superior edge of pubic symphysis Fundus(base) : opposite to apex (formed by convex posterior wall) Body : major portion between apex and fundus Neck: where fundus and inferolateral surfaces meet Wall has 3 layers

o Mucosa : forms ruga which in contact with urine ( also line ureters and urethra)

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o Submucosa (layer that lines the mucosa layer) : blood and lymphatic vessels

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o Muscularis: 3 layers of smooth muscles – 1 circular between longitudinal layers

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o Internal sphincter- involuntary because it is a type of smooth muscleo External sphincter- voluntary because it is a skeletal muscle

o Trigone : ureters attach via superior/posterolateral angles [right and left ureterovesical orifices] and open through internal urethral meatus

o Urethra drains urine via neck of bladdero Trigone: when all three orifices are connected, it is a smooth, relatively

indistensible area within the base

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o Bladder relatively free within extraperitoneal subcutaneous fattu tissue but it is firmly held by

Local fascia Median umbilical ligament Lateral umbilical ligament Retropubic fat Tendinous arch of pelvic fascia ( for male called puboprostatic

ligaments and for female is called pubovesical ligamnets) Urogenital diaphragm

3. Blood supply for urinary bladder

- It is supplied by superior, middle and inferior vesical arteries that form anastomoses with internal iliac ( hypogastric) artery

- All the blood is drain back into internal iliac vein that and then prostatic venous plexus in men

- External and internal iliac nodes

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4. Innervation of urinary bladder- Autonomic nervous system

SNS= from T11-T12PSNS= from S2-S4

- Somatic nerves, from S2,S3,S4(pudendal nerve)

5. Urethra- Passage of urine out of neck of bladder to exterior- Male: 18cm, Female: 4 cm- Human males do not have stronger urethral sphincter muscles than females- Females pee more frequently because bladder shares space with uterus and vagina

- Urethral sphincters(US)

Internal US is located at bladder’s inferior end as a continuation of detrusor

muscle (therefore autonomic control as they are smooth muscle). It’s primary muscle for prohibiting release of urine. Ureteric orifices tighten when bladder contracts to help prevent urine reflux into ureter

External US is a secondary sphincter at bladder distal end ( somatic)- Regulation of urination

Bladder fills Stretch receptors sense the filling Internal sphincter relaxes SPONTANEOUSLY External sphincter can be relaxed VOLUNTARILY

- Male Internal urethral sphincter Contracts involuntarily during ejaculation to prevent retrograde ejaculation of

semen into bladder

- Male Urethra : 2 FUNCTIONS-

Prostatic urethrao Travels through prostate and here it meets with ejaculatory ducts which

carry sperm from vas deferens and seminal fluid from seminal vesicles Membranous urethra

o Travels through UG diaphragm then forms voluntary external urethral sphincter

Spongy penile urethrao From urogenital diaphragm to outside

- Female External US : 3 PARTS

- Female urethra passes through UG diaphragm Sphincter urethrae : wraps solely around urethra ( as in males) Urethrovaginal muscle : wrap along vagina and urethra. Contraction leads to

constriction of both Compressor urethrae- wraps anteriorly around urethra. Contraction squeeze

urethra against vagina The shorter urethra the female have cause them to be more susceptible to

Urinary tract infections6. Nerve supply of Urethra

- Release of urine is controlled by autonomic NS (via the hypogastric plexus) PSNS-The Preganglionic Parasympathetic nerves from S2, S3 and S4 travel in

the pelvic nerve and synapse in the cholinergic ganglia in the pelvic plexus. They also provide the major motor innervation to the Detrusor muscle (wall of the bladder). Detrusor muscle is made of smooth muscle. When detrusor muscle relaxed, the internal urethral sphincter is close. When detrusor muscle is contracted, it force the internal sphincter to open

SNS- lumbar. Internal sphincter receives sympathetic innervation which causes contraction of the sphincter

The external sphincter is innervated by somatic motor neurons that cause contaction.

7. Clinical aspects- Extravasation of urine in males

Escape of fluid (blood, urine) into surrounding tissue Urethra typically in males is the most common site. Interruption of urethra leads to collection of urine in other activities : perineal

spaces, scrotum, penis, thigh

The membranous or spongy urethra get damaged usually due to trauma,

periurethral abscess [pus around ureter] or incorrectly placed devide [bougienage : an insertion of bougie to increase a structure’s calibre]

Fractures of pelvic girdle often cause rupture of membranous urethra. This will result in extravasation of urine and blood from ruptured blood vessels into deep perineal space; may distribute extraperitoneally around prostate and bladder

Rupture in spongy urethra will cause extravastion into penis[forceful blow toperineum, incorrect passage of transurethral catheter or device that fails to negotiate angle of urethra in bulb of penis or superficial perineal space with rupture of bucks fascia/ corpus spongiosum [Attachments of perineal fascia determine direction of flow: loose connective tissue in scrotum, around penis, superiorly deep to membranous layer of connective tissue of lower anterior abdominal wall

Extravasation from bladder- due to superior position of distended bladder, injuries to inferior anterior abdominal wall or pelvic fractures may rupture the bladder. This will cause urine to escape either extra or intra peritoneally

Superior rupture often tears the peritoneum and lead to extravasation of urine into peritoneal cavity. Posterior rupture cause passage of urine extraperitoneally into perineum

- The combination of urine and infection produces severe oedema of a patient's scrotum and abdominal wall. If this is not treated, the skin over his scrotum, penis, and anterior abdominal wall may slough. He may be very ill, toxic, febrile, dehydrated, anaemic, or uraemic, or all of these things. If his renal function is impaired, as it often is after a long standing stricture, extravasation may kill him.

- Treatments include : Intravenous fluid replacement Catherization

Divert urine flow

Drain urine out of tissue Antibiotics