hi let's talk about the cervical muscles of the posterior neck so when we look at the posterior
or lateral neck the first landmark that we want to identify is this muscle here that I'm outlining
this is the sternocleidomastoid muscle sterno from the sternum, cleido from the clavicle and
mastoid to the mastoid process of the temporal bone the sternocleidomastoid muscle is what is
sitting between the anterior neck which we can see here and the posterior neck or the lateral neck
which we can see there now the sternocleidomastoid muscle has two inferior attachments there's the
manubrium of the sternum which is just a little out of frame there and then there's the the medial
third of the clavicle which we can see there so there are two distinct attachments there
and then the the SEM runs superiorly and has one major superior attachment which is the mastoid
process of the temporal bone and also posteriorly it inserts a little bit on the superior nuchal
line as well the sternocleidomastoid muscle is innervated apparently by the accessory nerve
that's cranial nerve 11 and apparently by branches of the ventral primary ram i of c2 and c3 when
bilaterally flexed the SEM flexes the c-spine when unilaterally flexed there's some lateral
flexion of the c-spine or and it rotates the face in the contralateral or opposite direction so the
the next muscle that that we'd like to talk about here is the trapezius muscle the trapezius muscle
I'm outlining there and there is trapezoidal in shape hence that's where it gets its name it has
several attachments superiorly so the superior nuchal line much like the SCM the external
occipital protuberance of the occipital bone the ligamentum new key or the ligament of the neck
as well as spinous processes of c7 through t12 these are all coming together and then there's
an inferior attachment to both the clavicle and the spine of the scapula for the trapezius so the
trapezius muscle like SCM is also innervated apparently by the accessory nerve and it's
innervated apparently by branches of the ventral primary ram i of cervical nerves c3 and c4 when
bilaterally flexed the trapezius muscle is either going to extend the c-spine that would be if the
scapula or shoulder blades are fixed if the if the head and neck are fixed it's going to elevate or
depress or retract the scapula and unilaterally it's capable of severely rotating the glenoid
cavity or the the tip of the shoulder to act with the upper limb now when we when we look between
the trapezius muscle and the lateral border of the SEM we catch a glimpse of the posterior triangle
here and so it has those two borders along with the clavicle as its inferior border so SCM
trapezius clavicle make up that that posterior or lateral triangle we can see here that the inferior
belly of omohyoid we'll just put in dashes there is going to divide that posterior triangle of
the neck into two triangles there's the occipital triangle superior to that and then the subclavian
also known as the Omo clavicular triangle below that and we can see that the external jugular
vein here crosses over into the posterior triangle and then it's going to dive deep in the subclavian
triangle to meet up with the subclavian vein we can see also in the occipital triangle there are
cutaneous afferents so these are the the branches that are coming from the the nerve point of the
neck that originate from there and we can't really get a good view of it but the accessory nerve is
going to traverse this space as well moving right along we can examine some of the muscles that are
important in the root of the neck these are the scalene muscles there are three what we're seeing
here as I'm outlining is the anterior scalene muscle the anterior scalene muscle is going to
be situated between the subclavian vein which has been removed here would be running across there
and then the subclavian artery which we can see here so the anterior scalene muscle separates the
the subclavian vasculature like so that anterior scalene muscle has superior attachments on the
transverse processes of cervical vertebra c3 to 6 and it's inferior attachment is on the scalene
tubercle of rib 1 so we can see here there's a there's a slight fossa for what would be the
subclavian vein and posterior that on rip 1 there would be a fossa as well for the subclavian artery
and between the two we have that tubercle which we'll see when we discuss osteology the
anterior scalene is innervated by branches of the ventral primary rami of cervical nerves see 4
through 6 and when flexed it can provide some forward or lateral flexion of the c-spine and
it's major action is to elevate the the first rib so it's going to pull up that first rib
and when it does so it's going to increase the volume of the thoracic space and by increasing
the volume of the thoracic space it's going to contribute to inhalation because by increasing
the volume it decreases the pressure now we have two other scalene muscles so we've removed the
first of the of the three or the anterior scalene we can see here are some elements of the brachial
plexus moving through here to serve the up and we get a view of the middle scalene muscle here and
then the posterior scalene muscle there the middle and the posterior scalene muscles are oftentimes
closely adjacent and sometimes intertwined with their fibers these are found posterior to the
brachial plexus elements here so there are the brachial plexus elements that middle scalene is
the largest of the three scalene muscles it has superior attachments on the transverse processes
of cervical vertebra three through seven and it's going to inferiorly attached on rib one there's
a tubercle of rib one that's posterior to the fossa four the subclavian artery sometimes the
the middle scalene muscle can even have a superior attachment on the transverse process of the Atlas
vertebra as well and it's innervated by ventral primary rami branches from c3 all the way down
through c8 it elevates rib one it can also flex the c-spine and what's interesting about the the
middle scalene muscle is that it's typically active even during diaphragmatic breathing so
even without engaging the intercostal muscles which are those muscles that we use to expand
our ribcage for very deep breaths like the one that I just took the middle scalene muscle tends
to activate even during diaphragmatic breathing which is interesting then the posterior scalene
muscle which we can see there so I'll just indicate the middle scalene muscle has superior
attachments from the transverse processes of c-4 through c6 vertebrae and it inserts down on
rib two so it's its tubercle is on the second rib which makes it somewhat unique among all
of the scalene muscles it's the only one to do that it's innervated by branches of the ventral
primary rami of c6 through c8 and it can like its friends the anterior and middle flex the
c-spine but it can also elevate the second road which is something that the other two scalene
muscles cannot do so we've we've discussed the sternocleidomastoid the trapezius muscle as
well as the anterior middle and posterior scalene muscles I thank you for your time