Notes

Gross Anatomy of the Bladder and Urethra:
Bladder is a muscular sac that stores urine until it is ready to be excreted. Empty adult bladder typically rests superoposterior to the pubic bones, separated by retropubic space, rests anteriorly on pubic bones and posteriorly on the pelvic floor muscles.
The urinary bladder lies above the urogenital diaphragm, which is a triangular musculofascia diaphragm that occupies the area between the pubic symphisis and ischial tuberosities. The UG triangle is formed by the external urethral sphincter muscle and transverse perineal muscle.
Bladder Relations in Males and Females for non-distended bladders
- In females, the bladder is superoanterior to the wall of the vagina and separated from the uterus by vesicouterine pouch and from the rectum by the rectouterine pouch of Douglas
- In males, the bladder is separated from the rectum by the rectovescial pouch. It is related to the seminal glands and ampulla of ductus deferens posterolaterally and prostate inferior.
Empty Urinary Bladder Structure:
Tetrahedron shape, 4 sides, 4 angles 4 ducts. There are 4 surfaces; superior, two inferolateral, and inferoposterior. For ducts, there is the two ureters, the uretrha, and urachas.
External Structure of Urinary Bladder: an apex that points anteriorly to the pubic symphisis, a fundus that is inferoposterior, a body between the apex and fundus, and a neck where fundus and inferolateral surfaces meet.
UB Wall Layers: detrusor muscle, submucosa (lamina) containing vessels, mucosa (rugae) made up of urothelium.
UB Trigone: Where the ureters and internal urethral meatus meet to form a triangular structure. Ureters meet bladder at uterovesical orfices.
Bladder neck: muscle fibers are continous with urethral wall muscles. In females it is continous with the pelvic fascia and in males it is continous with with the fibromuscular tissue of the prostate
Urinary bladder is relatively free except for the firmly fixed neck which is held in place by pubovesical ligaments
Urinary Bladder Supply: The bladder is supplied by the superior, middle, and inferior vesical arteries from the the internal iliac artery. It is drained by the internal iliac vein.
Urethra: Muscular duct for passage of urine out of the bladder from internal urethral sphincter to external urethral meatus. It is shorter in females, but their sphincter muscles are stronger.
Urethral Sphincters:
- control the flow of urine by enveloping urethra. When contracting the internal and external urethral muscles close the urethra. The internal urethral sphincter is continous with the detrusor muscle of the bladder neck. Internal is autonomic while external is somatic.
- Ureteric orifices prevent reflux due to tightening of detrusor muscle during contraction
-External urethra sphincter is primary mechanism for preventing urine release in females, IUS in males
Innervation of urinary bladder and urethral sphincters is by the autonomic nervous system via the hypogastirc plexus. T12 to L2 for sympathetic and S2 to S4 for parasympathetic
How to Pee: Storage and voiding are due to the coordinated effort of smooth and skeletal muscle. Bladder fills, stretch receptors in the muscle detect filling. Voiding begins with the voluntary relaxation of the external urethral sphincter. Internal urethral sphincter relaxes. Parasympathetic impulses induce contractions of the bladder. EUS is under voluntary control from pudenal nerve. IUS is under autonomic control by the hypogastric plexus.
Male Internal Sphincter: prohibits release of urine and contracts involuntarily during ejaculation to prevent retrograde ejaculation. Ejaculatory ducts create semen, vas deferens and seminal vesicles flow into duct.
Female EUS: prohibits release of urine, made up of sphincter urethrae, compressor urethrae, and urethrovaginal muscle.
Clinical Considerations:
- Urethra can rupture during sex and birth for females. Since urethra is shorter and wider, women are more susceptible to STIs.
- Extravasation: leak of fluid (urine, blood) to surrounding tissues. Typically occurs in the urethra in men. Caused by pelvic fracture, periurethral abscess, incorrectly placed device.