Urethra (anatomy)


you might be able to hear the steady

thrum of the air conditioning units

keeping the computers cool in another

building nearby not keeping the people

cool keep the computers cool it's not

too bad in here actually but we're

having a bit of a heatwave in Britain in

the moment as we seem to be having every

year there might be a bit of a trend

there right you can also hear the

seagulls occasionally bear drilling I'm

not grumpy cousin yeah I'm grump because

it's hot right onto the topic we've

looked at the kidneys we've looked at

the ureters we've looked at the bladder

we look to the bits of the mainland

female reproductive systems now we're

gonna look at the last bit we're gonna

look at the urethra of course we're

gonna have to look at two urethra me I'm

gonna have to look at the male urethra

which was longer more complicated and

maybe more interesting and we're going

to have to look at the female urethra

because they're a bit different about

the functions a little bit but the main

focus here is on the anatomy so on the

part the features where they run an ass

or thing and we'll talk very briefly

about blood supply in innovation because

it is brief functions well there's a

very obvious one right in both male and

female pelvis is the function is to

carry urine from the bladder to the

outside environment so it carries and

she part of it there it carries a urine

externally we can see part of the male

urethra here part the male urethra here

so Mayo urethra is obviously a lot

longer because there's a penis so the

bladder collects the urine stores a year

in and then when you're a child you

learn to store that urine until a

convenient time to get rid of it and the

sphincters open and the urine passes

from the bladder through the urethra to

outside in the male pelvis the urethra

is also the route the spermatozoa will

take to pass from the testes route and

components of semen will be put into the

urethra so all that stuff gets put into

the urethra event

actually and then follows the urethra

right through the tip of the penis

through the external urethral orifice so

those are the functions of the urethra

tell you what if we're talking about the

functions of the male urethra let's talk

about the parts of the male urethra

first then we'll do the female because

it'd be really short for that has an

Anatomy joke there are four pass to the

male urethra it's around 20 centimeters

long you might imagine that it is a

little bit variable in length and can

even change lengths somewhat and the

first part if we start at the bladder is

the pre prostatic part which is a very

sensible name so it's the bit of the

urethra before the prostate but you can

see the prostate gland is pushed up Y up

against the bladder so that's kind of a

difficult thing to visualize but it's

it's kind of that B there there is a

you've got the detrusor muscle of the

bladder so the muscle around where the

urethra leaves the bladder gets called

the internal urethral sphincter in the

male bladder there's a proper swing to

there that can block this off purpose of

that during ejaculation it makes the

semen and the spermatozoa go in the

right direction not up into the bladder

but the prostatic part of the aretha

which also gets called the intramural

Park is that first part there so as the

bladder fills and stretches an

thing it can change in size and length

and shape a little bit a little bit

stretchy but that's it so the the next

part the second part is the part of the

urethra that's running through the

prostate gland and that's the prostatic

pathway we throw all good so far however

if we look at the urethra within the

prostate gland it's got a few strange

parts to it so if we if we look at this

from a slightly different perspective

right this is a coronal section here's

the prostatic part of the urethra there

and this isn't I mean I don't think I've

got any models of the show this

beautifully but there is a little bit of

a widening there there's a bit of an amp

puller and what we're seeing here we're

seeing some embryological remnants

really there's there are prostatic

sinuses in these spaces I

the side we see seeing on the posterior

wall of the prostatic urethra here is

this there's kind of a ridge sticking

out for me and that's the urethral crest

and that urethral crest kind of looks

like it fattens there and becomes a

seminal colliculus and there's a little

bit of space in there which is called

the prostatic utricle none of this

information is is really important to

know about but if you're wondering what

those names mean and what these little

lumpy bumpy structures are that's what

they are and what happens here so when

the male and female embryos start to

form the structures in this region they

start off using essentially the same

tubes and then they start to form

different structures or some tubes

disappear and some tubes hang around

anyway this is a remnant of that and

that prostatic utricle isn't anything

there's kind of like a little blind

ending sac in there which if it was to

develop in the female embryo mind go on

and form other sac like things nearby

only that's your imagination but right

next to that little opening there into

the prostatic utricle which is included

on this model on either side of that are

the two ejaculatory ducts and the two

ejaculatory ducts are where the two

ductus deferens tubes essentially duct

into the urethra so they're docked into

the urethra at the level of the prostate

gland and then if you were to look even

more closely you'd see lots and lots and

lots and lots of lots of tiny little

ducts from the prostate gland itself

opening into the urethra here so this is

where everything mixes as it were so you

have the spermatozoa passing in here

through the ejaculatory ducts you have

the secretions from the seminal vesicles

which are nearby secreting into the

ejaculatory duct into this space and the

prostate gland is also then secreting

into this space here during ejaculation

if we go back to this model the

ejaculatory ducts are coming in from

either sides if you just look in the mid

sagittal section you don't see them but

if you if you cut a little bit off to

the side you can see the ejaculatory

ducts here so there's a seminal vesicle


left the ductus deferens there coming

together there and there would be two of

these ejaculatory ducts ducting into the

urethra at this point in the prostatic

urethra so if you're looking at the

prostatic part of the male urethra in

the posterior war you'll see a ridge

sticking out and that's the urethral

crest now urethral crest where it widens

gets called the seminal colliculus and

inside there there's this kind of

useless blind ended sack with a little

opening here and that's the prostatic

utricle and then the spaces around that

the widening of the urethra there those

are the prostatic sinuses and then we

move on to the third part which is is

how we're going to see the third part oh

so here's the male urethra in its full


so I mean easiest way to but the third

part is is this bit here this is the

membranous part of the urethra

essentially the easiest way to remember

this is the fourth part is the spongy

urethra and if you know the anatomy of

the penis you'll know that this is the

corpus spongiosum this is one of the

ejaculatory or one of the erectile

bodies so the spongy part of the urethra

is running through the corpus spongiosum

hence its name so the bit of the urethra

between the prostate and the spongy part

of the urethra is the membranous urethra

and this is the bit that is passing

through the pelvic floor right it's

passing through

through that this musculature the

supporting the pelvic floor is here that

we find the external urethral sphincter

which is a bit of muscle under somatic

control that's the bit you can hold when

you really need to hold it so it's

passing through there passing through

the perineum membrane and this level

we're seeing bolbo urethral glands but

in fact the Bobble urethral glands they

ducked into this first part of the

spongy part of the male urethra so the

spongy part of the urethra starts at the

perineal membrane and runs within the

corpus spongiosum all the way out to the


and the external urethral orifice here

which is where it opens and there are

two windings to ampulla the little

widening of the star is the intra bulbar

fossa and the widening in the glans

penis is the navicular fossa navicular

boat and as well as the bulb or urethral

glands ducting into the first part of

the spongy urethra there are also lots

of little urethral glands that ducked

into the spongy urethra along its length

that's the male urethra the female

urethra then is much shorter around four

centimeters long which is the reason why

women are much more likely to get

urinary tract infections than men it

runs from the bladder to the vestibule

and it runs anteriorly to the vagina it

runs directly and straight through the

perineal membrane and the pelvic floor

there is no internal urethral sphincter

in the female bladder

unlike the male bladder and there is an

external resource filter just like we

see in the in the male pelvis

controlling closing the urethra

similarly along the female urethra there

are a number of little tiny urethral

glands doc Dean's of urethra and these

arethe will glance seem to be involved

in in lubrication of this tube and some

of these are called para youthful glands

and these seem to be the female

equivalent of the prostate gland in

terms of lots of little paring arre

through glands and blood supply well

you've got to think of nearby arteries

the both urethras male and female are

supplied with blood by arteries of the

pelvis that sounds obvious but remember

the gonads aren't all right so in the


we have inferior vesicle arteries or

branches of so v zakone refers to the

bladder so there are artery supplying

blood to the bladder those inferior

vehicle arteries are supplying blood to

the inferior part of the bladder and

also to the urethra in the male the

rectum is nearly really nearby so middle

rectal arteries also supply blood to

parts of the urethra and then as the

urethra continues the dorsal artery of


penis is also going to supply blood to

the urethra along its length in the

female pelvis it's similar but different

the vagina is right next to the urethra

so the journal arteries also supply

blood to the urethra as do pudendal

arteries and what have you notice how

the rectum is much further away from the

urethra because the vagina is in the way

so the female urethra supplied with

blood by branches of vaginal arteries

and branches of the internal pudendal

artery and those arteries all come from

the anterior trunk of the internal iliac

artery supplying blood generally to the

the viscera of the pelvis the veins are

similar or the same going in the

opposite direction and the lymphatics

likewise which means that the lymphatic

drainage of the urethra is to lymph

nodes of the of the pelvis so generally

iliac lymph nodes or maybe deep inguinal

lymph nodes just think of your direction

of flow all right

lastly innovation well we're talking

about a sympathetic parasympathetic and

visceral afferent sensory stuff related

to the urethra both male and female

urethras receive nerves from the

pudendal nerve remember there's a

pudendal nerve but there are internal

and external pudendal arteries and the

difference is that the there are

plexuses there's a vizac physical plexus

pertaining to the bladder in the female

pelvis that sends branches to the

urethra and in the male there is a

prostatic plexus and that sends branches

to the urethra in the male visceral

afferent sensory nerves follow the

parasympathetic nerves back to the

spinal cord that levels s2 s3 and s4

parasympathetic uber so they're very low

down in the spinal cord they're not

going to the sympathetic visible so we

have looked at the male urethra and the

female urethra we've looked at the

differences in the similarities the male

urethra habit has a number of parts to

it and that internal urethral sphincter

is an interesting idea and the prostatic

part of the male urethra is the

with the most confusing bits aren't

really very important but if you look at

it in the textbook it kind of seems like

they are important so with a bit of

study hopefully that's not too difficult

to remember we've looked at the blood

supply through pelvic venous drainage

lymphatic drainage very pelvic and we've

talked about the the innovation alright


is there anything left in the renal

system that we haven't done I don't know

I have a look see you guys next week

then although in fact it won't actually

be next week because if you're watching

these at the time they go out I will be

in Austria next week but when I put this

out I will be back from Austria it's all

very confusing this temporal stuff

anyway see you sometime in the future