now the organs of the body are all
located within their cavities and the
body cavities are really important
because they protect compartmentalize
surround the organs of the body so the
organs of the body can be in a nice
logical place in the right situation in
the right position so they can perform
their appropriate physiological
functions and if we start at the top we
see that the top cavity here is the
cranial cavity so this is the cranial
cavity at the top and the cranial cavity
is going to contain the brain and it's
also going to contain the meningeal
layers that surround the brain and it's
surrounded by the cranial bones so the
cranial bones surround define
compartmentalize the cranial cavity now
you probably know that the spinal cord
is continuous with the brain so the
cavity is also continuous so what we
notice is there's a spinal or vertebral
cavity that's projecting down so the
spinal cord can go down this cavity and
this cavity is surrounded by the the
vertebrae the vertebrae
these are back bones and the spinal cord
which is in the vertebral cavity can go
through these bones and that means it's
protected and this is why it's so
important if we have any injuries to the
vertebrae because if there's any
injuries to the vertebrae then what can
happen is imagine that's the imagine
that's the spinal cord this piece of
paper is the spinal cord and that's
going through the vertebrae like that
now that's all absolutely fine as long
as the vertebrae are intact
but if the vertebrae is damaged and then
we move the patient's neck or we move
the patients back in the wrong way then
it can translate the spinal cord which
is now useless now this turns an injury
from the vertebra
this is a serious injury into a
catastrophic injury this is terribly
serious I was joking a bit then but he's
really serious we must be so careful
with this because that means that
whatever level the spinal cord is
transected out the patient will not feel
or move anything below that level ever
again so we can see already that's
important clinical implications here and
the spinal cord actually stops about
there stops about there but the spinal
cavity or the vertebral cavity goes on
further down because we have large
nerves going down there as well to
supply the pelvic organs and and the
bottom part of the body so we have this
cranial cavity in the vertebral cavity
now these are sometimes described as the
the dorsal body cavities now when we're
talking about the body this is the
dorsal surface here at the back and this
is the ventral surface here well another
way to put it is this is the posterior
and this is the anterior but these are
sometimes described as dorsal body
cavities and these are the these are the
neurologic cavities neurological because
the brain and the spinal cord of course
are they the neurological tissues so
they're the dorsal body cavities now
going down of course we have the the
thoracic cavity which is here which
we've drawn in blue now the thoracic
cavity is going to contain the lungs
it's going to contain the heart the
major blood vessels that are associated
with the heart so you might know that
leaving the heart we have the aorta and
the pulmonary arteries well one
pulmonary artery leaves the heart it
quickly divides into two one going to
each lung we've also got the inferior
and superior vena cava taking blood back
to the right side of the heart and the
pulmonary veins taking blood back to the
left side of the heart so we've got the
heart and the lungs there and the major
vessels and also the esophagus the food
pipe because you swallow food up there
but it's actually used to have air in
your stomach so it has to go through the
thoracic cavity so the esophagus and
also the trachea
in the thoracic cavity which is taking
air to the right and left main bronchus
to go into the right and left lung
there's also a rather interesting gland
in the thoracic cavity called the thymus
gland which has a fascinating
immunological functions so there within
the thoracic cavity which we've drawn
here in blue so that's the thorax or the
thoracic cavity comes from the Greek
word for chest now going lower down we
have the abdominal pelvic cavity the
abdominal pelvic cavity now I'm just
going to trace the outline of this now
so it goes here this is the diaphragm
the diaphragm is dividing the thoracic
cavity from the abdominal cavity so it's
the diaphragm then that's the anterior
surface of the abdominal pelvic cavity
going down here all the way down here
and back up to back back up there so
that's the abdominal pelvic cavity it's
covering the abdomen and the pelvis the
abdominal pelvic cavity and the reason
we call it one cavity really
anatomically is it is one cavity so for
example if you were pregnant then the
the uterus will expand up into the
abdominal cavity as you will clearly
remember if you have been in a state of
gestation that the baby will rise up
that the fetus will rise up here as the
uterus rises up or even indeed if you've
got a very full bladder that can also
rise up into thee into the abdominal
cavity as well and but medically is very
often useful to think about the
abdominal cavity as being separate so
the abdominal cavity is actually this
part here the top part of the abdominal
cavity is the inferior surface of the
diaphragm and that's it there we've
drawn in orange and then the pelvic
cavity is the bit below that so this is
the pelvic cavity here in yellow now
the abdominal cavity is going to contain
the stomach the
liver spleen the gallbladder the small
intestine most of the colon and the
large intestine as well and further down
the pelvis is going to contain the it's
going to contain the bladder as we've
said part of the large intestine and the
anus but also mostly the the
reproductive organs are going to be in
the in the pelvis and the pelvis
actually is the area of anatomy which is
surrounded by the pelvic bone so you
have the pelvic girdle here that
surrounds the surrounds that the pelvic
cavity so the pelvic cavity actually
goes from about l4 the fourth lumbar
vertebrae there to to the anterior rim
so the the volume of the pelvis really
is described by the bone round about it
rather than an individual cavity because
it's continuous with thee the abdominal
cavity so we see that the cavities
aren't cavities at all in life they're
actually filth will filled with the
organs so if you were saw the top of my
skull pull out my brain pull out the
vessels in my brain in the meninges what
you'll be left with is is the the cavity
the the hole where those things were so
the cavities are the holes where the
organs are actually located now let's
look at this from the from an anterior
view and I've started to hatch this one
in already I think just before we do
that we'll mention the we mentioned that
these were the the back we have the the
dorsal cavities which were the cranial
cavity in the spinal cavity all these at
the front are sometimes also referred to
as the the ventral body cavities or the
anterior body cavities at the front so
the ventral cavities are going to be the
thoracic cavity and the abdominal pelvic
cavity
now the ventral or the anterior cavities
now as we're looking at the looking at
this from the front the anterior view so
here we can see the cranial cavity as we
know that contains the brain and there
we see the top of the vertebral or
spinal cavity now what we have around
here is the thoracic cavity which is
going round about here like this and
this is the diaphragm and the thoracic
karat is protected by the ribs and the
intercostal muscles to protect these
delicate organs and it's
compartmentalized from the abdominal
cavity by the diaphragm which runs
across there this dome shaped muscle
that compartmentalizes the thoracic
cavity above the superior eventual
cavity and the inferior ventral cavity
which is the abdominal pelvic carbon
cavities but we notice I've drawn two
colors here so we have the in blue we
have these are the lung fields the these
are the the pleural cavities the pleural
cavities and these are surrounded by the
pleural membranes and we noticed that
each lung really is in its own little
cavity well not that little the lungs
are quite big so we have the right
pleural cavity and the left pleural
cavity there and this is so important
that the lungs are in their own cavity
because if someone comes along with a
with a knife and they stab you in the
chest with it then what's going to
happen is air from the outside world is
going to get into this cavity and that
one was going to collapse and that's
really serious but if both lungs
collapsed that would be even more
serious so only one longer will collapse
with a penetrating chest injury because
the other lung is in its own individual
pleural cavity that's just very very
important but what I've covered in red
here in red we have this area here this
is the mediastinum now the mediastinum
you
the bits in the middle medias in the
middle so it's in the middle of the
chest so it's going down the middle of
the chest then it goes from the sternum
all the way to the vertebra at the back
and it's in two parts the the top part
we're going to call the top part or the
top parts always called superior isn't
it so that's the superior mediastinum
with drawn here and this is going to be
the inferior mediastinum here now the
inferior medius mediastinum in a sense
has got its own cavity this is the this
is the pericardial cavity parry around
about cardiac heart so the pericardial
cavity is surrounding the heart and
that's in a tough pericardial membrane
and the heart is inside here and the
superior part of the mediastinum
now the superior starts where the if you
feel your chest there there's a there's
a sternal notch in the sternum that is
the sternal notch and if you go back
from there you come to the junction
between the fourth and the fifth
thoracic vertebra anything above that is
the superior mediastinum anything below
that is the inferior mediastinum
now the superior mediastinum contains
largely the large blood vessels like the
the aorta and the superior vena cava
this is why injuries to the center of
the chest are so significant so if
someone has injuries to the center of
the chest that can damage the large
blood vessels or the heart as we see so
the heart does go slightly towards the
left
so lateral chest injuries are sometimes
still serious of course but they can be
less serious where the central chest
injuries can be immediately
life-threatening because of the heart
and the major blood vessels and
penetrating injuries there can resort in
exsanguinating hemorrhage and clearly a
fatal potentially fatal condition in in
in pretty short order now going down to
the abdominal cavity
so the the top right of the abdominal
cavity in this area here here we have
the liver so the liver is top right and
the livers just underneath your right
costal margin which is just there so
that's your liver there and underneath
your left costal margin just there on
this side we have the spleen
so it's liver and spleen kidneys of
course at the back and the colon goes
from here but pier in the the ascending
colon transverse colon descending colon
then he goes back through the sigmoid
colon to the to the rectum so this is
the abdominal cavity here and then
further down here as we see we have the
pelvic cavity now in in females of
course this contains the ovaries and the
the fallopian tubes what we now call the
uterine tubes it's going to contain the
uterus and the vagina the bladder as
well of course in men of the sperm comes
from the testes but it comes up into the
pelvic cavity to mix with the secretions
from the air the prostate gland so we
have the pelvic cavity there as we said
defined by the bones of the of the
pelvic rim so there the main body
cavities the cranial vertebral the back
the dorsal body cavities the thorax
thorax being divided into the pulmonary
pericardial cavity all of the
pericardial cavity as part of the
mediastinum the abdominal cavity with
these major organs and digestive organs
in and the pelvic cavity with the
bladder and reproductive organs in very
important for protection so obviously we
have the bones of the skull and the
vertebra protecting and your logical
structures but then we've got the ribs
and the intercostal muscles and actually
the ribs in the intercostal muscles
actually protect the top part of the
liver and the kidneys to some extent as
well also the spleen here
we have the vertebrae at the back and we
have firm muscles over the top of the
abdominal cavity is about protecting the
the organs of the abdominal cavity so
they're the main structures that's the
first part of this video now in the next
part what I want to do is look at the
membranes which are associated with the
organs in these cavities so just to whet
your appetite we're going to have the
meninges surrounding the brain and the
spinal cord very important for
meningitis but you have the pleura
membrane surrounding the lungs we've
already noted the pericardial membrane
surrounding the heart and in the
abdominal cavity we're going to hand and
indeed in the pelvic cavity to ER to
some extent we're going to have the
peritoneal membranes which of course
become inflamed in peritonitis for
example so tune in for the next video
for that interesting next episode