hi let's talk about the urinary bladder in the urethra first the urinary bladder is found in
the anterior superior pelvic cavity so right here you can see it's actually attached to
the the remnant of the urachus that forms the median umbilical fold on the anterior abdominal
wall the bladder itself when full of urine is actually capable of expanding out of the pelvic
cavity and into the abdominal cavity as you can see here the bladder is just anterior to
the uterus if the uterus is present and there is a vesicouterine pouch of the peritoneum between
the two if it's present and it's also anterior to the rectum in males there's a rectovesicular
pouch because there's there's no uterus present we say that the uterus is sub peritoneal
because the parietal peritoneum covers over the majority of the uterus in the pelvic cavity so
the internal anatomy of the uterus is relatively straightforward the uterus is comprised of smooth
muscle we refer to this as detrusor muscle and so it's an expandable sack that is muscular eyes so
urine may accumulate within the urinary bladder and that bladder may expand to accommodate that
urine there are your ureteral openings where the ureters are going to feed urine into the bladder
and when you take these two-year-old openings there's a crest between them and then there's
an internal urethral orifice if you can draw a triangle between these three landmarks and
that's known as the Trigon of the bladder this internal urethral orifice is actually very dense
all around it with smooth muscle and that's the internal urethral sphincter the internal urethral
sphincter is under autonomic control and so whenever there are stretch receptors within
the walls of the urinary bladder that are activated when the walls expand that causes
a signal to go to the the spinal cord and then a message is then sent back down to this internal
urethral sphincter and the detrusor muscles to push urine out now after the internal urethral
sphincter or I should say distal along the urethra we have the external urethral sphincter which is
a collection of skeletal muscle that surrounds the urethra the external urethral sphincter is
somatic motor so you have conscious control over the sphincter and so this is what becomes active
when you have that that feeling of needing to urinate you're you're basically clenching this
muscle so as to occlude the the flow of urine through the urethra now not to be so binary
but with respect to differences of sex the the urethra is really quite polymorphic in females
the urethra is is fairly parsimonious it's a very short it's roughly about four centimeters long
it's runs approximately parallel to the vagina and there's an internal urethral orifice and
an external urethral orifice that is typically found between the clitoris and vagina in males
the urethra is a bit more complex and that's because the urethra is doing dual duty as a
common pathway for both urine and semen so urine is coming from the urinary bladder and semen comes
in from the ejaculatory ducts which may be found on the posterior aspect of the urinary bladder
so semen is conducted from the testes up through the ductus deferens you probably know this is the
vas deferens up to these seminal vesicles and the ejaculatory ducts which are going to push semen
into the urethra at the level of the prostatic urethra now because the urethra is so complex
there are three parts to it so the male urethra is tripartite there's the prostatic urethra which
runs through the prostate gland that sits at the base of the urinary bladder of males and then
there is the membranous urethra that membranous urethra is running through the the muscular floor
of the pelvic cavity and then there's the penile or spongy urethra that runs through the the root
of the penis through the body through the corpus spongiosum and so the external urethral orifice in
males is typically at the distal portion of the the glans penis and so whereas in females the
urethra is approximately four centimeters in males on average it's approximately twenty centimeters
and this is going to vary with respect to penis length of course so we've talked about the urinary
bladder and the peculiarities of its anatomy and we've also discussed the urethra and how it might
conduct urine from the urinary bladder to the outside world in both women and men thank you