This brief video tutorial discusses the anatomy of the kidney:
Ureter
Kidney stones (referred pain)
Bladder and Internal urethral sphincter
Urethra
Intravenous pyelogram (IVP)
In-a-Nutshell
Acknowledgements
#kidney
#Ureter
#Bladder
Ureter
Kidney stones (referred pain)
Bladder and Internal urethral sphincter
Urethra
Intravenous pyelogram (IVP)
In-a-Nutshell
Acknowledgements
#kidney
#Ureter
#Bladder
Category
📚
LearningTranscript
00:00okay we're going to talk about the ureter bladder and urethra and answer the
00:04questions what are the functions topography and innervation of the
00:07ureters the bladder and the urethra hello everyone my name is dr. Morton and
00:11I'm the noted anatomist so let's begin with the ureter the ureter transports
00:17urine from the kidney to the bladder so in this coronal section we have the
00:22ureter identified and the kidneys going to filter blood plasma into filtrate
00:26which is excreted as urine and the ureter transports that urine from the
00:30kidney down to the urinary bladder the ureters are also retroperitoneal which
00:36means the behind the peritoneum in this coronal section with the GI tract
00:40removed we can see the parietal peritoneum where it's been cut where it
00:46becomes mesentery and you'll notice the behind the parietal peritoneum is the
00:50kidney and then the ureter travels down all the way into the pelvis where the
00:55bladder is and the bladder is below the peritoneum so in this cross section or
01:01axial section of the abdomen that's taken below the kidneys there is the
01:06ureters the ureters are located and they are retroperitoneal behind the
01:11peritoneum as well as the IVC in blue the aorta in red in the psoas major
01:16muscles the ureter is about 25 centimeters long and it's three millimeters in
01:23diameter which is about the thickness of a grain of rice and that lumen of the
01:28ureter is has common constriction locations three of them and so one is
01:35where the renal pelvis is going to become the ureter another is where the
01:40ureter crosses over the pelvic brim and this occurs at the bifurcation of the
01:46common iliac arteries into the external and internal iliac arteries and the final or
01:52third places where the ureter obliquely traverses the bladder wall these are
01:57the three locations where kidney stones can be occluded because of these
02:01constrictions some this is a superior view of the pelvic cavity in a female and
02:09there is another topography of the ureter that's important where the ureter
02:13crosses under the uterine artery and the ureter transports urine and the uterine
02:19artery is blood so we we call this water under the bridge and why because what
02:24happens is if we look and focus on that that ureter crosses underneath the
02:31uterine artery so water courses under the bridge and this is important because the
02:37ureter is at risk of injury during ligation of the uterine vessels in a
02:42hysterectomy so this relationship is known as water under the bridge the
02:48innervation of the ureter is through sympathetics and the sympathetics arise in
02:55the lateral horn spinal cord level usually between T10 and L1 L2 but then
03:02those sympathetics go to the sympathetic ganglia to the ureter plexus so here we
03:07have that sympathetic chain from T10 to L1 which then the sympathetics travel
03:12through the lumbar and sacral splanchnics to the pre aortic ganglia and plexus
03:19those different ones shown here and then the sympathetics are going to transport
03:24sympathetics to the ureter through the ureter plexus or uteric plexus now the
03:33innervation of the ureter it can also be shown in this cross section where
03:38sympathetics arise in the lateral horn of the gray matter of T10 through L1
03:42spinal cord levels and follow that axon through the sympathetic ganglia and
03:47through the splanchnic nerves to synapse in the pre aortic ganglia and then
03:52through the ureter plexus those post ganglionic sympathetics are brought to the
03:56ureter causing contraction of the smooth muscle resulting in peristalsis and it
04:01squeezes the urine from the kidney down to the bladder at each level there are
04:07also visceral sensory neurons that go from the ureter back along the same
04:12pathways except through the dorsal root to the spinal cord and this is bringing
04:16information of such a stretch and damage that may occur but these are visceral
04:21sensory which means they are not pain and that's what makes kidney stones so
04:26interesting because as kidney stones scrape down the ureter they present with a
04:30migrating pain but it's a type of referred pain what do we mean by that well
04:35there's a cross-section of T10 and there you can see the sympathetic pathway that
04:39goes to the ureter squeezing the ureter and the urine goes down and so as the
04:44as we progressively go down the ureter we see the sympathetic innervation from
04:50T10 to L1 squeezing urine down if a kidney stone is now scraping the inside of
04:57the ureter think fingernails on a chalkboard then visceral sensory neurons
05:03take that information to the spinal cord but the central nervous system has a
05:07difficulty distinguishing visceral sensation from the ureter where the
05:12kidney stones scraping versus somatic sensation from the associated dermatome and
05:18so as a result because the ureter rarely has any type of sensation that is sent the
05:25CNS refers pain to the dermatome and then as the kidney stone is moved down the next
05:33inferior segmental level visceral sensations brought in and the spinal cord says hey
05:37this is messed up but it cannot distinguish if the pain is coming from the or the damage is
05:43coming from the ureter or there's so much sensation come from the dermatome we
05:48refer pain to the associated dermatome and this happens at every segmental
05:54level as that kidney stone goes down so you'll notice those red dots are
05:59representing of referred pain even though you could put novocaine in the skin
06:05there and knock out all sensation you'd still have this referred pain there
06:10because it's the brain's perception of pain coming from those dermatomes and as
06:15you get down to the t12 and l1 that often refers down into the inguinal or
06:20groin area so this migrating pain is known as loin to groin for kidney stones as it
06:26moves down let's talk about the bladder and I'm going to add the internal
06:30urethral sphincter to this part I'll show you why so the bladder's function is
06:35storage of urine and here's a coronal section of the kidney with the
06:39ureters paired going into the bladder and the wall of the bladder is made up of
06:43the detrusor muscle which is smooth muscle meaning it's involuntary and the
06:48sympathetics relax the detrusor and the parasympathetics contract the detrusor
06:54so para makes you pee that was fun wasn't it let's do it again so oh yeah I'll do
07:01it again in a second so right now let's talk about topography the male bladder is
07:04between the pubic symphysis and the rectum so in this mid sagittal section there's
07:08the pubic symphysis and there's the rectum and the bladder is in between the
07:12two which is also infra peritoneal below the peritoneum in the same fascial plane
07:18as the retroperitoneal space so there's the peritoneum in the bladders below it
07:23and that little fold we call the vesico for bladder rectal pouch the topography
07:30for the female bladders between the pubic symphysis and the uterus so in this
07:34mid sagittal section there's a pubic symphysis there's the uterus and then
07:38there's the rectum and the bladders between the pubic symphysis and the
07:42uterus and it's also infra peritoneal below the peritoneum in the same fascial
07:48plane as the retroperitoneum you'll notice the vesico uterine pouch vesico
07:54meaning bladder and then the recto uterine pouch of Douglas which is the
07:59lowest part in the pelvic cavity where the peritoneum goes so blood and pus would
08:05accumulate there or endometrial tissue on this mid sagittal hemisection there's a
08:11pubic symphysis in the right side of the hemipelvis and the two ureters dumping
08:16into the bladder and and then at the neck goes down to the urethra and these three
08:22openings form this this structure called the trigone which is has high or
08:29increased sensitivity to stretching of the bladder as urine is filled giving the
08:35sensation like yeah i gotta go to the bathroom also notice the apex of the
08:39bladder becomes the obliterated urecus and so here we zoom in and there is the
08:46bladder and the the apex goes up to this obliterated urecus which drains up into the
08:51umbilicus and then when this was this individual's a fetus that was what helped
08:56form the amniotic fluid but an adult it's obliterated the urecus is
09:00obliterated and covered in peritoneum so we call it the median umbilical
09:04ligament now the innervation of the bladder through sympathetics is through the
09:09sympathetic trunk and the splanchnic nerves bring
09:12sympathetics to the superior hypogastric plexus part of the preaortic
09:17plexuses and then the vesicular plexus remember vesicle means bladder
09:22brings the sympathetics to the bladder and the internal urethral sphincter both of
09:27which are smooth muscle okay and so sympathetic innervation of the
09:32bladder enables the bladder to fill with urine and the detrusor muscle then
09:38relaxes through sympathetic innervation and the internal urethral sphincter
09:42contracts that's what allows to urine to fill so here we have the detrusor and
09:47internal urethral sphincter with these two different adrenergic receptors beta 2 and alpha
09:521 sympathetics are going to release norepinephrine in which binds to the
09:58detrusor internal urethral sphincter causes relaxation of the detrusor
10:03contraction of the internal urethral sphincter this is what enables the
10:07bladder to fill with urine the constriction or contraction of the
10:10internal urethral sphincter is also what ensures that during an
10:14ejaculation in the male urethra you do not get retrograde ejaculation of
10:20semen into the bladder it just continues out through the urethra
10:26now parasympathetic innervation let me say that one again
10:29parasympathetic innervation of the bladder and internal urethral sphincter
10:34arises from the s2 to s4 ventral rami because those parasympathetics are going to
10:40come from the lateral horn gray matter of s234 spinal cord levels the
10:45parasympathetics then come out those ventral rami
10:48and then each of those ventral rami have these pelvic splanchnic nerves that form
10:53this pelvic splanchnic nerve combined a note about splanchnics
11:01you hear about cardiopulmonary splanchnics greater lesser least lumbar sacral
11:06splanchnics all of those are sympathetics the only
11:11splanchnic nerve in anatomy that transports
11:14parasympathetics is the pelvic splanchnic nerve
11:19pelvic p for p parasympathetic that's the way i remember it
11:23you're welcome so then the vesicular plexus
11:27also transports not only sympathetics but parasympathetic
11:30neurons to the bladder and the internal urethral sphincter
11:35so parasympathetics enable the bladder to empty the urine
11:39parasympathetic to make you pee so the detrusor muscle contracts
11:44squeezing urine out of a now relaxed internal urethral sphincter
11:48here we have the detrusin internal urethral sphincter there are these
11:51muscarinic cholinergic receptors on both
11:55so when acetylcholine is released by those pelvic splanchnic nerves
11:59what you see is contraction of the detrusor relaxation of the internal
12:04urethral sphincter emptying the bladder now how do we have so
12:08many things happening with just sympathetic and parasympathetic
12:11innervation it's the location of the receptors
12:14on the detrusor and internal urethral sphincter
12:17it's the receptor is it a cholinergic or adrenergic receptor
12:21and is it the neurotransmitter is it acetylcholine or norepinephrine
12:24so here we have parasympathetic on the left and sympathetic on the right
12:28you have muscarinic cholinergic receptors or
12:33and then acetylcholine or you then have
12:36beta and alpha adrenergic receptors with norepinephrine and that's what makes
12:43the detrusor and internal urethral sphincter have so many different
12:47functions with only these two structures
12:49let's now talk about the urethra the urethra
12:55the urethra transports urine from the bladder to the outside world
13:00in males it also serves as the passageway not only for urination
13:04but also ejaculation the length varies between male and female so in the
13:10sagittal section of the male you see the bladder
13:13the urethra is about 20 centimeters in length
13:16it has three parts the prosthetic urethra
13:19the part of the urethra surrounded by the prostate
13:22it receives not only urine from the bladder but also the two ejaculatory ducts
13:27enter into the urethra bringing sperm
13:32then you have the membranous urethra the part of the urethra
13:36surrounded by that external urethral sphincter
13:40and then the spongy urethra the part of the urethra that is within
13:44the uh corpora cavernosum pardon me corpora spongiosum
13:50erectile tissue within the penis now the female bladder it's about four
13:54centimeters in length is much shorter one of the reasons why urinary tract
14:00infections are more common shorter distance for bacteria to travel
14:04now the external urethral sphincter that is shown i just did the external
14:11urethral sphincter right there which is in the urogenital diaphragm is a
14:16skeletal muscle voluntarily contracting to allow you to
14:21urinate or not to urinate so in this location is that they call it we call it
14:26the deep perineal space or the urogenital diaphragm that's the location of this
14:31external urethral sphincter its innervation is through the pudendal
14:36nerve and so their pudendal nerve arises from the s234
14:41ventral rami which then gives rise to the pudendal nerve a different branch
14:46than the pelvic splanchnics and that pudendal nerve brings
14:50uh somatic motor and somatic sensory neurons to the external urethral sphincter
14:56for motor and general sensation to the distal urethra the
15:00part that's uh closer to the external environment pudendal nerve
15:09it enables the bladder the external urethral sphincter enables the bladder to
15:13voluntarily void urine so there is our internal urethral sphincter there's the
15:18which is smooth muscle the external urethral sphincter which is skeletal muscle
15:23so when the internal urethral sphincter relaxes
15:27then what happens is urine starts compressing against the external urethral sphincter that's
15:32the part of the time near the end of a movie when you've been drinking a lot of soda you're like
15:36i think my bladder is going to burst because urine is compressing so you finally run to the loo
15:42and you voluntarily relax the external release urethral sphincter which allows you to void your
15:48bladder now how can we view the urinary system in x-ray we do this through an intravenous in the veins
15:56pylogram it's an iodine containing contrast that's injected into a vein and the contrast collects
16:04after the kidney filters it the contrast collects in the kidneys the ureters the bladder making them
16:09appear bright it's a contrast on an x-ray so here we have an example of an ivp where outline there's
16:17the kidney on the one side and on the other side we can see renal calyces the large renal pelvis
16:24a ureter draining down to the urinary bladder and that my friends is the ureter bladder and urethra in a
16:33nutshell
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