The femoral sheath is a crucial fascial tube in the inguinal region that surrounds the femoral artery and vein, facilitating their passage and function between the torso and the lower limb, and its associated canal is a potential site for hernias.
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the anatomy of the femoral sheath you're
not going to be a lot of use are you
because you haven't got
much else other than bones on you the
anatomy of the femoral sheath so it's
down here in the inguinal region
what is it
what's in it
and why is it useful
and what might i get it confused with
that's what we'll do because there's a
lot of similar words around there
and sam this isn't there isn't a lot you
can say about the femoral sheath so
don't make this a long one [Music]
the femoral
sheath what
is it well it's uh
it's connective tissue one of the unsung
heroes of the body right
is a bit of cling film that might be so
it's it's fascia
so we have facial sheets
around the body
which hold everything together
and help give us our shape and help hold
everything together help everything move
if you didn't have fascia
you'd be quite different
so it's it's fascia
and we need to look down here
taken the gastrointestinal tract out mostly
mostly
so we can see the bladder structures of
the pelvis there and we can see some
muscles of the posterior abdominal wall
major blood vessels
and muscles of the
anterolateral abdominal walls so fascia
fascia
the innermost muscle of the three layers
forming the abdominal wall is um
transversus abdominis and it is lined on
its internal surface by transversalis
fascia a sheet of connective tissue that
is not particularly stretchy and is
quite strong and tough and that sort of thing
thing
this big muscle here this big chunky muscle
muscle
is psoas major so this major is one of
and this muscle here is iliacus
and iliacus and so this major come
together they get called iliopsoas and
those muscles are also covered in fascia
fascia
which you would call the iliopsoas
fascia or the bit over the source the so
you see
the fascia is sensibly named so the
iliopsoas fascia is helping hold all of
those muscle units together
now here
this is the inguinal ligament this is
like the boundary between the abdominal
pelvic cavity the torso
and the lower limb
and some things have to pass into the
lower limb like blood vessels and nerves
and we'll get to those
so the inguinal ligament like acts as a
like as a strap there's a retinaculum
elsewhere in the body if you know about
that sort of thing so the inguinal
ligament ties everything down at the hip
for when we make
hip movements right it stops it all
slipping out
so what happens is is the transversalis
fascia and the iliopsoas fascia
huh it's like it's doing it already come
together to form a tube
the femoral sheath and that tube passes
deep to the inguinal ligament and into
the upper thigh except it's not a tube
it's more of a funnel that is it's
narrower at the bottom and wider at the top
top
and it
in the upper thigh
it ends by blending with the adventitia
the connective tissues of the blood
vessels and that is the femoral sheath
it's a fascial funnel
funnel
or tube
deep to the inguinal ligament
surrounding the blood vessels but not
the nerve it's about three to four
centimeters long
it's deep to the inguinal ligament oh by
the way see this fascia here this is the
fascia latae
the connective tissue the fascia
covering the muscles of the lower limb
and all the deeper vessels and stuff
and um the
the
femoral sheath is essentially deep to
the fasciae latae we'll talk about this
hole in other bits and bobs here in a moment
moment
okay so the femoral sheath
runs deep to the inguinal ligament
and is a connective tissue tube connecting
connecting
the torso with the lower limb
now there's more to it than that inside
the femoral sheath
it is divided up into three compartments
so there are three tubes within the tube
and what are in those tubes
the femoral artery
in the lateral compartment
the femoral vein
in the intermediate compartment in the
middle and then in the medial compartment
compartment
closest to this side
there is nothing
that's not true but it's an important
idea so the the medial compartment is
essentially it's like an empty space actually
actually
we see
we see lymphatics running in there we
can see a lymph node up there
so we get these deep
inguinal lymph nodes
the the lymph node
that deep inguinal lymph node one of
like the first ones the most inferior
ones that we find
in the
medial compartment of the femoral sheath
um gets referred to as uh the lymph node
of cloquet cloquet cloquet or rosen muller
muller
but we also have lymphatic vessels in
there if we're adding detail then in the
the lateral compartment
with the femoral artery we will also
find the femoral branch of the genito
femoral nerve
store that someplace for another day i'm
not going to come back to that all right
that's it then right femoral sheath and
ah there's more though isn't there what
about the femoral nerve okay so the
femoral artery what happens is is the
femoral artery is actually a
continuation of the external iliac
artery and when it passes deep to the
inguinal ligament we change its name and
it becomes the femoral artery likewise
the femoral vein when it passes deep to
the inguinal ligament we change its name
and becomes the
external iliac vein but what we don't
see on here is the nerve and that's kind
of important
i say that it's important because it's
easy to get confused around here but
here we go here's the left side look so
there's the femoral artery
vein and nerve so the nerve is lateral
the vein is medial
femoral nerve femoral artery femoral
vein so the femoral artery and the
femoral vein are within the femoral sheath
sheath
in their own compartments but the
femoral nerve is not
it passes deep to the inguinal ligament
but it is outside the femoral sheath it
is lateral to the femoral sheath
what is the purpose of this connective
tissue well
we have as i said we when we
move this joint we have these major
blood vessels passing from the torso to
the lower limb we do not want them to be kinked
kinked
like a hose pipe or folded or impeded in
any way because they're supplying blood
to all these muscles of the lower limb
and draining it back again so the
femoral sheath
lets these blood vessels slide up and
down as we move the hip joint that's the
first one now
now
add a little bit more detail
you remember i said there were three compartments
compartments
to the femoral sheath and
and
the lateral compartment holds the
femoral artery the intermediate
compartment in the middle holds the
femoral vein and the medial compartment
has some lymph nodes but is otherwise
empty now that empty part that empty tube
tube
that gets called the femoral canal
so don't mix up femoral canal and sheath
which is very easy to do so the
connective tissue is the sheath that
makes sense the connective tissue makes
a sheath right
the space within the sheath is the canal
because the canal is a space
now the reason the femoral canal exists is
is
partly because of that sliding up and
down thing
but also if
if
the blood flow from the lower limb increases
increases
the vein can dilate so veins um
veins don't have muscular walls they can
stretch more easily than arteries right
so if more blood is coming back the
femoral vein can dilate into that empty
space of the femoral canal there's room
to which for it to stretch out into right
right
also remember that while the blood
inside arteries is arterial pressure
obviously it's at high pressure the
blood inside the veins is at low
pressure and this blood is being drawn
back from the upper limb all the way up
the torso to the heart which is a long ways
ways
it's more being sucked up than pushed up right
right
which means that if you were to
increase the pressure inside your torso
through a valsalva maneuver you know
straight or if you're lifting something
and straining or
you're voiding your bowels or whatever
if you increase the pressure inside the
torso then it's going to impede the
venous return into the torso because the
pressure will be too high and that means
that the femoral canal then gives some
all right so that's the relevant anatomy
but there's more
what other terms or phrases around here
might we confuse these terms with okay well
well
um the other thing here is the femoral triangle
so the femoral triangle describes this
region the femoral triangle is made from
the borders of the inguinal ligament the
sartorius muscle and abductor longus so
the femoral sheath
is within the femoral triangle
the femoral sheath is the connective
tissue the femoral triangle is that
triangle that we've defined there
but there are other canals right let's
go back to the
other one
the inguinal ligament
also has an inguinal canal nearby so the
inguinal canal is different to the
femoral canal the inguinal canal is made
from the muscles of the abdominal wall
curving around and making a tube so it's
a muscular tube
it is superior to the inguinal ligament and
and
it carries the spermatic cord and that
sort of thing so it links the contents
of the scrotum with the
abdominal pelvic cavity right so the
femoral canal
is within the femoral sheath
it runs deep to the inguinal ligament so
it connects the torso with the lower limb
limb
the inguinal canal
is superior to the
inguinal ligament it's a muscular tube
and it connects the scrotum or the labia majora
majora
with the abdominal pelvic cavity okay
we can see part of that here
i said this was the fascialata
the connective tissue the fascia
covering of the lower limb
uh the major vein that we can see here
superficial to that is the great
saphenous vein
big superficial vein of the lower limb
there is an opening here this is the
saphenous opening or the saphenous ring
and the great saphenous vein passes
through that opening so that's how it
gets from superficial to the fascialata
to deep to the fascia later and there it
drains into
the femoral vein
if the femoral sheath has continued down
to that point then the great saphenous
vein will also go through the femoral
sheath to get to the femoral vein so
saphenous opening
but those are the things that you might
um well worth knowing about and get
confused in that sort of thing the
femoral canal
also has a femoral ring
which is where we see it opening
hernia
so um bowel
bowel
because of the high pressures in here can
can
find itself find its way out of
of
the abdominal cavity through weaknesses
the femoral
canal within the femoral sheath is a
potential route for a loop of bowel to
pass inferiorly
deep to the inguinal ligament and into
the femoral triangle
right so if you if you palpate a mass in
the femoral triangle
femoral hernia whereas the an inguinal hernia
hernia
will pass through the inguinal canal so
we'll be in a different place right so
the femoral canal and the femoral sheath
are relevant to a femoral hernia the
bowel pushing through that space um also
if you
want to access the heart
you could
put a wire a catheter a cannula whatever
into the femoral artery
that would then pass to the aorta so you
could access the aorta and the left side
of the heart or here you could put a
wire into
the femoral vein that would pass to the
inferior vena cava and you can access
the right side of the heart
these blood vessels are large
very superficial so they're pretty easy
to access
and you can then access
the thorax
also if you are assessing the blood flow
to the lower limb this is where you find
the femoral pulse
so these blood vessels are formed
passing through the femoral sheath the
femoral sheath is part of their function
so the femoral sheath is part of that
relevant and useful anatomy all right
there you go that's the anatomy of the
femoral sheath it's connective tissue
and we talked about the femoral canal
which is a space
and the femoral sheath has three spaces
in it and we looked at the blood vessels
and what have you and
we linked it up to other things nearby
that we might
confused with why have you got cobwebs
on you
um anyway see told you i couldn't talk about
about
it for that long the femoral sheath and
stuff in the femoral triangle femoral canal
canal
stop by see you next week [Music]
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