00:01
We come now to the five
primary muscles of the thorax.
00:04
They're innervated by
the intercostal nerves,
because they have attachment points
to the ribs.
00:11
Here we see the
external intercostal muscles
running in this direction.
00:15
Because of this orientation,
the lower portion is more flexible
and therefore can pull
the ribs upward.
00:21
This motion results in inspiration.
00:23
So the external muscles
induce inspiration.
00:26
Deep to the externals,
we see the course of
the internal intercostals.
00:30
And right here, you can see
the innermost intercostal group
splitting off and coursing inwards.
00:36
Between indeed to the
internal and innermost muscles,
the costal groove is seen
along the inferior rib border.
00:43
In this groove runs
the neurovascular bundle.
00:45
From superior to inferior,
you will find
the vein, artery, and nerve.
00:50
So remember, VAN.
00:52
As they contract,
the internal and innermost muscles
pull the upper ribs inferiorly.
00:58
Therefore, inducing exploration.
01:00
The exception is a small portion
of the innermost group
which is cutaway here
that lie between the
hyaline costal cartilages.
01:07
They assist with inspiration
because they pull the ribs upwards.
01:10
So the externals and
the cartilaginous portions
of the innermost group
can provide inspiration.
01:17
These cartilaginous
parts of the innermost muscles
are sometimes called
intercartilaginous muscles
because they lie between
the hyaline cartilages.
01:25
If we look now at
the thorax from inside,
we can see the course
of the innermost intercostal muscles
on the inside again.
01:34
Here you can see them splitting off
the internal intercostals.
01:38
Running between the
internal and innermost muscles
on the lower edge of the rib
in the costal groove,
you can see the
neurovascular bundle here.
01:46
Remember the order from
top to bottom.
01:49
Vein, artery, nerve.
01:51
Here we see the intercostal nerve.
01:53
This nerve can cause
intercostal neuralgia,
a radiating pain that travels
along the rib to the midline.
01:59
If the herpes virus is in
the spinal ganglion,
irritation to the skin,
sun exposure or stress
allows the virus to activate along
the intercostal nerve distribution.
02:09
This results in a vesticular rash
that's very painful
and can become infected.
02:13
This is shingles, a disease caused
by the Zoster virus.
02:18
So here again is the costal group
containing the neurovascular bundle,
Vein, artery, nerve,
between the internal and
innermost intercostal muscles.
02:28
Here we see the course of
the innermost muscles.
02:31
If you look here, now,
back and down at the ribs,
we can see the subcostal muscles.
02:37
These are elongated
internal intercostals,
which only appear on the
inferior posterior rib areas here.
02:43
Because this is the anterior thorax,
they cannot be seen
and are of no great importance.
02:47
They are often too small to even
identify and some specimens.
02:49
Now, we see the fifth muscle
from this group,
the transversus thoracis muscle.
02:53
They course right and left
like the fingers of a hand
and tense the entire thorax
facilitating exploration.
03:01
So let's summarize again.
03:03
The external intercostal muscles
provide inspiration
as do the
intercartilaginous muscles.
03:15
Conversely,
exploration is facilitated by
the internal intercostals
and the innermost intercostals.
03:21
The neurovascular bundle lies
between the
internal and innermost muscles.
03:25
The vein, artery, and nerve
are protected within
the costal groove.
03:29
Therefore, you should always
make an incision or puncture
on the superior edge of the rib
to avoid disturbing
the neurovascular bundle.
03:37
Then, you can actually disregard
the subcostal muscles
running along the
posterior lower ribs.
03:44
And finally, we have the
transversus thoracis muscle again.
03:47
The transversus thoracis,
subcostals,
internal and innermost intercostals
are all expiratory.
03:55
Only the external and
inner cartilaginous muscles
are inspiratory.
04:01
All five primary thoracic muscles
are innervated by
the intercostal nerves
and stabilize the entire thorax.
04:08
So the functions include
inspiration, expiration,
and Valsalva.
04:13
The transversus thoracis muscle on
the right and left course inferiorly
until they meet the
transversus abdominus,
the lateral oblique
abdominal muscles.
04:25
Here we see the
internal thoracic artery
which runs inside the thorax.
04:30
It used to be named the
internal mammary artery
because it courses under
the mammary glands.
04:35
This artery is the first branch
of the subclavian artery
that travels inferiorly.
04:40
And here it is prepared on
the side of the sternal margin.
04:45
If we look inside the thorax,
we see that it's covered by
endothoracic fascia.
04:52
This is the thick lamina propria,
a connective tissue.
04:56
The outer parietal pleura
around the ribs is called
the costal pleura.
05:03
The arteries endothoracic fascia
covering ends distally
but it is then covered by
the transversus thoracis muscle.
05:10
It then passes over the diaphragm
near the trigonum sternocostale.
05:16
And forms a confluence
with the inferior epigastric artery
which travels behind
the rectus abdominus muscle.
05:22
This muscle also gives rise
to the lateral umbilical plica.
05:28
Here we can see the inferior
epigastric artery again
within the rectus
sheath and posterior
to the rectus abdominus muscle.
05:36
The artery continues inferiorly
and becomes the superior
epigastric artery
because it's now
at the epigastric angle.
05:42
EPI is equal to the gas
which means equal to the stomach.
05:47
Below the umbilicus,
it is then called
the inferior epigastric artery.
05:51
And here travels down
to eventually flow
into the external iliac artery.
05:56
This internal thoracic artery
can be used as a
coronary bypass artery.
06:00
And this is why it's the
so called Clinton artery
because he had the bypass surgery
done using this artery as a graft.
06:07
We come now to the
four secondary chest muscles.
06:10
Here we see the
pectoralis major muscle.
06:14
Under the pectoralis major muscle
lies the pectoralis minor.
06:19
Then here we see
the serratus anterior muscle
with its projections.
06:26
It attaches to the
subscapularis muscle eventually
and the posterior medial scapula.
06:33
The fourth smaller muscle,
the subclavius, cannot be seen here.
06:36
We look at it instead on
the other side.
06:39
We see the subclavius muscle
here under the clavicle.
06:42
So that's the subclavius muscle.
06:44
Let's discuss all the
secondary chest muscles in detail.
06:48
The pectoralis major and minor
muscles are innervated
by the medial and lateral
pectoral nerve.
06:53
These nerves arise from the
supraclavicular nerve
which is a brachial plexus nerve.
06:57
The pectoralis major has three heads
each with its own origin.
07:00
First, the pars clavicularis
from the clavicle,
the pars sternocostalis
from the ribs and sternum,
and the pars abdominalis
from the anterior lamina
of the abdominal rectus
muscle.
07:10
A small portion also attaches on
the front leaf of the rectus sheath.
07:13
Its fibers run along this axis
turning 180 degrees
at the insertion.
07:18
It forms the anterior axillary fold
and inserts on the crista
and greater tuberosity of
the humerus.
07:26
Its function can be remembered by
thinking of knotting a belt,
internal rotation of the shoulder,
arm flexion, and adduction.
07:34
The same motions used
when tying a belt knot.
07:43
Now,
if we fix the arm in place,
the origin becomes
the more mobile portion
and can pull on the ribs.
07:50
This allows it to act as a
secondary breathing muscle.
07:54
Below it, we find
the pectoralis minor muscle.
08:01
It is innervated primarily by the
medial pectoral nerve,
but a small portion is done by the
lateral pectoral nerve as well.
08:07
It originates from
the second or third to the fifth rib
and inserts on the coracoid process
of the scapula.
08:16
Its function is to tilt
the scapula forward
and in short remains fixated
to the chest wall
if the other muscles fail.
08:24
If these other muscles fail,
this scenario results in the scapula
being pulled forward or anterior
at the superior border,
and the inferior angle
protruding outward.
08:34
This is the so called
winged scapula phenomenon.
08:39
The serratus anterior muscle
that we see here has its origin
from the first to the ninth rib.
08:54
It courses ventually
to the subscapularis muscle
and inserts onto
the medial scapular margin.
09:00
It has three heads,
a pars superior,
pars media, and pars inferior.
09:05
The pars superior is the smallest.
09:07
It originates from
the first and second rib
above the superior angle
of the scapula.
09:12
The pars media is also called
the pars divergence
because it diverges along
the medial scapular border.
09:18
The pars inferior
is the largest part.
09:21
And it's called the pars convergence
because it converges towards the
inferior angle of the scapula.
09:29
When contraction occurs,
we see that it pulls the medial
scapular border against the trunk.
09:34
We need this for example when
pushing against something
with outstretched arms.
09:41
So it fixes the medial scapula
tightly to the trunk.
09:47
The lower portion on contraction
pulls the inferior scapular
angle laterally.
09:54
We need this
when we lift our arms
above the horizontal
elevation position.
09:58
The upper part is
antagonistic to this
and functions to return
the scapula back to the position
when the arm is lowered.
10:04
The lower part pulls forward again
and the upper part pulls backward.
10:08
When we support our arms,
the origin becomes
the more mobile part.
10:12
Since the origin is from
the first nine ribs,
the ribs can be elevated
allowing inspiration.
10:19
That is why it's very important.
10:20
Actually, the most important,
auxiliary or secondary
respiratory muscle.
10:29
Because it lies here on the thorax,
it's innervated by
the long thoracic nerve,
which arises from the
brachial plexus as well.
10:38
Our fourth muscle, the
small subclavius that we see here,
comes from the first rib
and inserts
on the underside of the clavicle.
10:48
It helps stabilize
the sternoclavicular joint
and keeps the lumen
of the subclavian vein open.
10:55
This is important because this vein
is close to the heart
and exposed to negative pressure.
11:01
When using a subclavian catheter,
remember that air enters the vein
and can cause an air embolism.
11:06
A subclavian catheter is a
commonly used location
for central infusion access.
11:17
The subclavius muscle is innervated
by the subclavian nerve
which arises from
the brachial plexus as well.
11:24
When the clavicle is elevated,
for example,
by raising the arm to 180 degrees,
the clavicle can be elevated
to 60 degrees.
11:32
This stretches this muscle.
11:35
When it contracts,
the clavicle is then depressed.
11:38
So its function includes,
sternoclavicular joint
stabilization, clavicle depression,
and keeping open the lumen
of the subclavian vein.
11:49
Here we see the thorax,
the right and left lungs
and in the middle, the heart
and the mediastinum.
11:57
The lungs are located in
the [hilum] pulmonis
and the heart sits in between
the right and left cavum pulmonis
in the mediastinum.
12:06
In the right lung,
we have three lobes.
12:10
Here you can see the upper lobe,
here, the middle lobe,
and here, the lower lobe.
12:15
When we do this as a learning aid,
this is how the middle lobe sits.
12:18
Above this point is the upper lobe,
then the middle lobe,
then the lower lobe.
12:22
The left lung has only an
upper and lower lobe.
12:26
When we look at the position
of the heart,
here you can see the pericardium.
12:35
If the pericardium is cut open,
we can now see the heart
inside.
12:41
It shifted 45 degrees to the left,
rotated 45 degrees
and angled 45 degrees down
so that 1/3 is to the right
of the sternum
and 2/3 are to the left
of the sternum.
12:54
Here we can see the aortic arch
going off to the right.
12:58
This is the brachiocephalic trunk
which then branches
into the brachial artery,
the subclavian artery, and
the right common carotid artery
seen running towards the head.
13:08
Because of these branches,
it is termed the
brachiocephalic trunk.
13:20
The second branch
from the aortic arch
is the left common carotid artery.
13:25
And the third branch
is the left subclavian artery.
13:29
Here's a red metal wire
in the aorta.
13:35
In this portion
is the ascending aorta
It comes directly from
the left ventricle.
13:39
Then the arch bends itself downward
and becomes the descending aorta.
13:42
At this level,
it's called the thoracic aorta
and it travels down
towards the diaphragm.
13:49
We see the superior vena cava
next to it.
13:54
The superior vena cava is formed
by the confluence
of the left brachiocephalic vein,
which is cut off here and
the right brachiocephalic vein.
14:03
So the brachiocephalic vein,
as the name suggests,
also gives rise
to the subclavian vein
in the internal jugular vein
which converge at the venus angle.
14:13
Again, it's called the
brachiocephalic vein
because the subclavian vein
comes from the brachium
and the jugular vein
comes from the head.
14:21
This is the angle of the veins.
14:23
But the lymphatic duct also joins
on the right side from
the posterior aspect.
14:30
The left vein angle
is the confluence
of the left subclavian vein,
and the left jugular vein,
and the thoracic duct.
14:37
This thoracic duct
allows lymph
back into the circulatory system.
14:46
If we look here,
the superior vena cava
continues to descend
where it eventually empties
into the right atrium.
14:53
This is what we see here.
14:55
From the atrium it goes into the
corresponding right ventricle
to a leaflet valve
on the right side of the heart
called the tricuspid.
15:07
Some use the learning aid,
D for right.
15:10
D like Dexter, D like three or tri.
15:12
So the tricuspid lies on the
Dexter or right side of the heart.
15:17
We have chordae tendineae threads
here
which connects the valves to
the papillary muscles seen here.
15:26
We have three papillary muscles
because we also have three cusps on
the tricuspid valve.
15:31
These three cusps are the leafs
that formed the valve.
15:33
From here on the right ventricle,
we see the blue wire
as it goes up
over the pulmonary trunk,
which then branches into the
pulmonary arteries.
15:43
These arteries run up
behind the aortic arch
and superior vena cava
to the right.
15:51
And we see the other pulmonary
artery here coursing to the left.
15:57
The pulmonary veins
return the blood from the lungs,
but we have not yet seen
that structure.
16:02
The pulmonary veins
then empty into the left atrium.
16:05
Blood then flows from
the left atrium
into the left ventricle.
16:09
And from the left ventricle
it flows out of the heart via aorta.
16:14
So the superior vena cava brings
the blood into the right atrium.
16:17
From the right atrium,
it goes into the right ventricle.
16:19
From the right ventricle,
it exits via the pulmonary trunk,
Then, to the pulmonary arteries,
and into the lungs.
16:25
It returned from the
lungs via the pulmonary veins,
empties into the left atrium,
and from the left atrium,
it goes into the left ventricle.
16:32
Here you can see
where my tweezers are pointing.
16:34
and I can grasp the red thread.
16:36
This is where it enters into
the left ventricle.
16:38
From the left ventricle
it goes out here via the aorta.
16:42
Now, we come to the
abdominal muscles.
16:44
There are three groups.
16:45
An anterior group,
a side oblique group,
and a rear group with a
muscle that we can't see here.
16:54
Let's start with the anterior group.
16:55
This includes
the rectus abdominus muscle.
17:00
That washboard abdominal muscle
which can be trained to show
the intermediate tendons.
17:06
There can be three or four
distinct levels
and it's not always symmetrical.
17:13
The rectus abdominus muscle is
also located within a rectus sheath.
17:17
With a lamina anterior,
and a lamina posterior.
17:25
So front and back leaf
that envelop the rectus
abdominal muscle.
17:29
This is formed in part
from the right and left
three lateral oblique muscles.
17:36
In addition to the
rectus abdominus muscle,
this anterior group also includes
the pyramidalis muscle
which we can't see here.
17:43
It lies in the rectus sheath
in front of the
rectus abdominus muscle.
17:46
It comes from the pubic symphysis
and forms a kind of pyramid shape
that spans the linea alba.
17:51
The linea alba is the middle
interweaving line
between the right and left lateral
oblique muscles.
17:58
The origin of the rectus abdominus
muscle is up here,
along the costal cartilages of
ribs five to seven
along the cycloid process.
18:13
Then it runs distally
as the right and left muscles taper
ultimately terminating at
the pubic symphysis
It functions in ventral flexion
when the pelvis is fixed.
18:28
Or pelvic elevation
when the upper body is fixed.
18:34
In most cases,
it will not be actively involved
in the abdominal crunch.
18:38
But rather just passively bulge
that this may not be true
in highly trained athletes.
18:45
Behind the rectus abdominus muscle
lies a very important artery
that we see here.
18:49
This is the
inferior epigastric artery.
18:53
It plays an important role
in the inguinal canal.
18:56
Besides it, we have the
fossa inguinalis lateralis
and medial to it,
the fossa inguinalis medialis.
19:02
See the inguinal canal?
The inferior epigastric artery
travels in the rectus sheath
behind the
rectus abdominus muscle.
19:09
It is called the
superior epigastric artery
went above the navel
and is not visible here
at the level of the diaphragm
through the sternal costal triangle.
19:23
As it passes through
the Larry Fisher,
it then merges into the
internal thoracic artery
also known as the
internal mammary artery
which lies behind the ribs about
two or three centimeters
lateral to the sternal margin.
19:34
This artery is often
used in bypass grafts
such as coronary bypass
of the heart.
19:41
Let's discuss
the rectus sheath structure.
19:43
It's very simple.
19:45
That's the rectus abdominus muscle.
19:47
That's the middle of the oblique.
19:49
And that would be the
internal oblique muscle.
19:51
It courses forward and backwards
to the rectus sheath.
19:55
The externus comes in superficially
and attaches to the anterior leaf.
19:59
The transversus abdominus lies
completely inside the sheath
and only attaches to the
posterior leaf.
20:04
These relationships,
internal to the front and back,
external only to the front, and
transverse only to the posterior
applied to the region
above the navel
down to the so called arcuate line.
20:19
Below this level,
all three lateral muscles
pass into the anterior leaf
of the rectus sheath.
20:26
We will see this clearly
in the inguinal canal.
20:39
Now, we come to the three oblique or
lateral abdominal muscles.
20:42
Here we have
the external oblique muscle
that follows a line
similar to placing our hands
in trouser pockets.
20:49
It runs from the ribs
to the inguinal ligament
in the anterior
superior iliac spine.
20:55
Underneath, lies the
abdominal oblique muscle.
20:59
It has fibers that run
downwards, transversely,
and some even slightly upwards.
21:05
Finally,
deep to the abdominal oblique.
21:07
We see the transversus abdominus
which only has
transversely oriented fibers.
21:13
During an appendectomy,
an alternating incision is made
to transverse these muscles.
21:18
The externus is cut in
one direction,
then the internus and another,
and then the transversus is cut back
in the original
incision orientation.
21:25
Beneath the transversus,
there's a connective tissue
called the transversalis fascia.
21:29
Under which,
you'll find the peritoneum.
21:31
Now let's go into more detail.
21:33
The external abdominal oblique
originates from the ribs.
21:38
Its fibers are transversely oriented
from seven points,
on the sixth rib to the 12th rib.
21:47
It alternates distally with the
latissimus dorsi,
and proximately, with the
straightest anterior muscle.
21:52
This creates the linea serrata.
21:57
Above the externus
with the serratus anterior,
below externus
with the latissimus dorsi.
22:05
The fibers then traveled down
radiating towards the iliac crest,
lateral to the intestinal crest,
to the anterior superior iliac spine
and into the inguinal ligament.
22:16
It has an aponeurosis
or flat tendon
that splits here into a
medial and lateral crus.
22:23
These are usually not
clearly visible
and abridged by intercrural fibres,
the superficial abdominal fascia.
22:29
This fascia creates
the superficial inguinal ring
which is more pronounced in men.
22:35
Here we have a female specimen
so it's harder to see.
22:40
The function of the
external abdominal oblique,
because it lies in front of the
flex x axis
is ventral flexion.
22:48
It can also do lateral flexion
because it's oriented sideways.
22:52
Finally,
it can function together
with the internus of
the opposite side
to rotate the trunk.
22:57
The internus turns the trunk
to the same side.
22:59
While the externus
is rotates the trunk
to the opposite side.
23:02
This side here would be fixed
and that would be mobile.
23:10
This is why the trunk is rotated
to the opposite side.
23:15
In addition, of course,
it does the stomach press.
23:19
Below the external abdominal oblique
lies the internal abdominal oblique.
23:24
Its original is not on the ribs
as with the externus
but down here, along the
anterior superior iliac spine
on the lateral edge of
the inguinal ligament,
and from the intermediate line
on the iliac crest.
23:37
It has fibers that travel down
and which join the transversus
below here,
below the ASIS.
23:46
It has fibers that run transversely,
and it has fibers that run upwards
to the lower edges of
the three ribs.
23:56
As before,
its function is like externus,
ventral flexion,
lateral flexion
and the lower part
turns the trunk to the same side.
24:09
By working with the externus
to the opposite side,
you can do trunk rotation.
24:12
It also is involved
with the belly press.
24:15
The transversus abdominus now lies
on the internal abdominal oblique
Its fibers originate from
the lower six ribs
and that lies on the inside
of the iliac crest.
24:32
Here, it originates from
the internal inguinal ligament,
and joints here below the ASIS
with the internal abdominal oblique.
24:39
Both of these muscles are
also raised
so that there's a weak point
on the abdominal wall
that an inguinal hernia
can rupture through.
24:48
The transversus runs
in the direction of the linea alba.
24:51
It's the main muscle
of the abdominal press.
24:55
They are the important points
of the three oblique
lateral abdominal muscles.