coming from C7 on its own. And the lower
trunk is C8, T1. So if you imagine here
at this level, you have the C5, C6, C7, C8,
T1. That’s how it comes out, and they are
forming the trunk. Upper, middle, lower.
The favorite anatomical question is these
trunks lie between two muscles, what are they?
Scalenus medius and scalenus anterior.
Scalenus anterior, okay. So you have the
scalene muscles like this coming from the
neck, from the transverse process of the vertebra.
And these nerve roots are coming out between
the scalene. So when you do an interscalene
block, this is where you’re going.
What’s the function of scalene muscles? What do they
do? Where do they originate? Where do they
insert? And why is it important?
They insert on the clavicle?
Yeah, very good, the scalene tubercle in the
clavicle as well, yup, as well as the first
trip. How many scalene muscles are there?
Three. So you have scalenus anterior, medius
in posterior. Why are they called scalene?
What does scalene mean? What is a scalene
triangle? When you have an isosceles triangle,
equilateral triangle, what does a scalene
Never heard of it before.
Never heard of a scalene triangle!
No. Unequal sides. So you have
two sides, the
third side is longer than the other two. So
that’s why it’s called scalene. So the three
scalene muscles are of different lengths.
They’re all starting from the transverse
process of the cervical vertebra. You don’t
have to know the insertion of the individual
ones, but you need to remember that from the
neck, it is coming to the clavicle at the
top and the first rib, as well as to the second
rib. So that’s why it’s one of the accessory
muscles of respiration. When you inspire,
these ribs are pulled up because of scalene
muscles. That’s action of scalene, and this
is your anatomy relation, the roots of the
plexus come in between the anterior. Scalenus
anterior and scalenus medius.
So we are here now. We are in the upper trunk,
middle trunk, lower trunk. These trunks
lie in the posterior triangle of the neck,
the clavicular region. These are your three
trunks lying in the clavicular region. So,
what happens to them after this?
Becoming cords. Not at this point. Okay.
You have the roots,
trunk, what’s the next? Imagine a tree,
root, trunk, divide. Yeah. So it divides.
It divides into anterior and posterior. That’s
it. Now, just for the ease of understanding,
I’m just going to draw all the posterior
trunks as posterior divisions in a different
color. Where do these divisions lie anatomically?
We come from the neck. We’re coming to the
supraclavicular fossa. So the divisions are?
Where do they lay? Beyond the clavicle.
Sorry? Beyond the clavicle. So if we have
some of the clavicular fractures, then it’s
the divisions that are affected. So these come
then they lay behind the clavicle.
Now, the lot of MCQs which will be related
to this part, now, you have to understand your
axillary artery. Imagine the axilla and the
axillary artery. Those divisions are now going
to form the cords, all the posterior divisions
form the posterior cord. So that’s posterior
to the axillary artery. The anterior divisions
of the upper trunk and the middle trunk form
the lateral cord. And the anterior division
of the lower trunk on its own forms the medial
cord. These cords are in relation to the axillary
artery. They’re all lying in the axilla.
Lateral cord. Tell me the nerves from the
lateral cord or the brachial plexus.
Take your time, think.
It will be ulna.
Lateral cord, whenever you think lateral,
think lateral. Ulnar is medial, isn’t it?
Musculocutaneous, that’s one. What else?
Next person. Okay. No worries. There are three
Long thoracic nerve.
Not long thoracic. You have the musculocutaneous.
The second one is a lateral root of median
nerve, not the whole median nerve, the lateral
root of median nerve, and the lateral pectoral
nerve. LLM, lateral pectoral nerve, lateral
root of median nerve, and musculocutaneous.
They’re all coming from the lateral cord.
So lateral cord, I’ll draw it in a minute,
but that’s lateral through the axillary
artery. What are the nerves from the medial
cord of the brachial plexus? There would
be the median nerve. The radial.
The medial root of median nerve, right, because
I said there is a lateral root of median nerve.
So, you have the lateral root of median nerve
coming from the lateral cord, and the medial
root of median nerve coming from the medial
cord, joins to form the median nerve. That’s one.
What else? You have a lateral pectoral nerve.
So you need to have a medial pectoral
nerve. So that’s the second one. Third one,
median side, ulnar nerve, so third nerve.
And then you have the medial cutaneous nerve
of the arm, medial cutaneous nerve of the
forearm. So, medial cutaneous nerve of the
cutaneous nerve of the forearm, medial root
of median nerve, medial pectoral nerve, and
ulnar nerve. Medial cutaneous nerve of the
arm, medial cutaneous nerve of the forearm,
medial root of median nerve, medial pectoral
nerve, and ulnar nerve. When we go through
the surface anatomy in a minute, we will put
all these into context on how it works, but
this is pretty much hardcore anatomy and you
can memorize this.
Okay, I will stop here for a minute and go back
there so it will be easier for you to understand.
Let’s start from the beginning. The first
one is the lateral pectoral nerve. What does