Okay, so that’s your
midline. That brings you the triangle of the
neck. I’m sure you will know the basic thing.
That's your sternocleidomastoid, trapezius,
midline, here, and that's your angle of mandible.
Okay, so these are your two big
triangles. What are the subtriangles in
the neck? So, what are the subtriangles here?
Submandibular. What are the boundaries? You're
Angle of the mandible.
Angle of the mandible.
Anterior border of the sternocleidomastoid.
I forgot this. Okay, someone else?
What are the triangles?
Just name the triangles in the neck?
Submental. A lot of names coming out. Fine.
The easiest way --
The easiest way
is to identify the hyoid bone okay? You have
the posterior belly of the digastric coming
from here, swings around the hyoid and then
you have the anterior belly of the digastric.
So if you take it from both sides, that forms
your submental triangle. Okay? What are the
important structures in the submental triangle
here? Pretty much nothing really. You just have
some lymph nodes, some fat, you can probably
feel the facial artery at the edge of the
triangle, but apart from that nothing significant.
The next triangle you see here is the submandibular
triangle, which is formed by the anterior
belly of the digastric, posterior belly of
the digastric and the ramus
of the mandible. That's one important triangle
because you have the submandibular glands,
submandibular lymph nodes, what else?
If you are asked to do a lymph node
biopsy from that area,
or you do excision of a lipoma, what are the
things you're worried about? What are the
structures that can be affected?
In the submandibular?
Yeah here. We're here.
Submandibular? Is it retromandibular vein?
Retromandibular vein is quite posterior.
Lingual nerve? Lingual nerve, one.
What else? You’re right,
what else can you think of? Hypoglossal nerve
and nerve to mylohyoid. So lingual nerve,
nerve to mylohyoid, hypoglossal, submandibular
gland and submandibular lymph nodes. They
are all in the submandibular triangle. That’s
quite important. Okay, you mentioned the lingual
nerve? Where does the lingual nerve come from?
From the facial nerve?
Not from the facial.
No. I think I’ll just stop there. I made
it confused with all these answers.
I’ll probably come back to lingual nerve when we
discuss a bit more. Fine, we’ll just remember
the lingual nerve for now. What does the lingual
nerve supply? What does it do?
Tongue. Yeah, what in the tongue?
Sensory, motor or taste?
Sensory? Sensory to what?
Anterior 2/3rd of the tongue. Okay, so because
we’re already there, we’ll just cover
the tongue as well. Okay, so tongue, what
you need to know for the exam is the motor
supply, sensory supply and taste. The whole
of the tongue is by hypoglossal nerve. Motor.
So the protrusion of the tongue, movement
of the tongue, etc. is by the hypoglossal
nerve. It is divided into posterior
1/3rd, anterior 2/3rd. The posterior 1/3rd,
both taste and sensation is by glossopharyngeal.
In the anterior 2/3rd, taste is by chorda tympani
and sensory is by lingual. Where does the
chorda tympani nerve come from?
Facial. Facial. Okay. So these are things you
need to remember in your submandibular gland.
Then you mentioned about the carotid triangle,
which is right. The carotid triangle.
This is your carotid triangle. Okay?
What are boundaries of the carotid triangle?
Sternocleidomastoid, um, I can’t remember.
Posterior belly of digastric.
And, is it on the midline?
It’s not on the midline, because you have
a muscular triangle as well.
The anterior? Superior belly. Superior
belly of the omohyoid.
That’s the superior belly of the omohyoid
and this the inferior belly of the omohyoid,
going into scapula. So this is the carotid
triangle and this one is the called your muscular
triangle. That’s where the strap muscles
are. Okay, that’s your muscular triangle
where the strap muscles are. Okay so this
your carotid triangle. Clearly you have
the carotid artery, internal jugular vein,
vagus. Three mega structures, they are
all in the carotid sheath. Anything else you
can think of?
You have the ansa cervicalis. The ansa cervicalis,
what we discussed, that is embedded on the
carotid sheath, mainly
the superior part of the ansa cervicalis going
to the strap muscles. Okay? They are all in
the carotid triangle. In the muscular triangle,
we discussed, there are the strap muscles.
Posterior triangle, if you understand
trapezius, sternocleidomastoid, then your
inferior belly of the omohyoid divides into
an occipital triangle which is here and a supraclavicular
triangle. What are the structures here?
Important structures in the occipital triangle?
Lymph nodes? What else?
Accessory nerve? Very good. Spinal accessory nerve.
Is it superficial
No, spinal accessory nerve is very superficial.
I can’t see in his neck but in some people
you would be able to see the external jugular
vein, particularly in children when they cry,
you can see the external jugular vein, that
you can use for cannulation as well. So the
external jugular vein lies here and the spinal
accessory nerve runs along with the external
jugular vein and it’s a very superficial
In this part of the neck, when we’re looking
here, you don’t have any important structure
at this point. Spinal accessory nerve. As
you come down, as you can see here you have
the triangle of the brachial plexus. Okay?
What about the supraclavicular fossa, or the
supraclavicular triangle? What are the important
structures here? You imagine if somebody is
stabbed or got an injury at this point? What
are the things will injure?
Subclavian artery. Which one? Subclavian artery?
What did you say about the pleura?
The cupolar or the apex of the lung. Is the
apex of the lung here or not? It’s on the
medial side. The apex of the lung is the medial
2.5 cm of the clavicles. So the apex of the
lung is here. If somebody is stabbed there,
then you have a pneumothorax, but if you’re
coming more laterally you have the brachial
plexus, subclavian artery, subclavian vein.
These are the important structures. This is
what will be asked in your exam at this point.
If the same injury happens on the left side,
there’s an additional structure.
Thoracic duct? Thoracic duct, okay very good.
Tell me about
thoracic duct. You’re right. Tell me a little
bit more about thoracic duct, what does it
do? Where does it drain? It starts from the right
hand side and then
crosses over to the left.
What does it drain?
Below the diaphragm? From where? Below the diaphragm.
So all the lymphatic drainage from the lower
limb and the abdomen is collected into the
sac called cisterna chyli, cisterna chyli,
which is located in front of the L2 vertebra
from which you have the thoracic duct. So
thoracic duct is quite lower down, then it
pierces the diaphragm at what vertebral level?
T12. Along with the abdominal aorta,
ascends up the mediastinum, comes up all the
way to the angle of Louis which is lower
border of the T4 vertebra or the second intercostal
space, then crosses over from the right to
the left and empties into the junction of
the subclavian vein versus the internal jugular
vein. That’s where the thoracic duct drains.
So, if somebody sustains a stab wound to this
part here, you have the thoracic duct. Okay?
As well as apex of the lung. It’s very specific
on the left side.
Okay. Now we’ll just move up a little bit from the
neck, to the lymph nodes back to submental area.