hello all this is dr alsup and i am super excited to talk about the muscles in the anterior next
session we have quite a bit to go through but i think you will find many are very aptly named
so we better get started will start with the most superficial muscle of the anterior neck
and this is the platysma which you can see here that i am outlining
you can see that it's a rather expansive muscle but it is a very very thin muscle
this muscle is literally located within the subcutaneous tissue like most other muscles
of facial expression but this particular muscle facial expression is specifically
located in the anterior lateral neck so we have platysma on either side here specifically
this muscle typically spans the space between the superior margins of the pectoralis major
and the deltoid muscle over here in terms of its inferior margin and it will extend superiorly
to about the inferior margins of the rest of the muscles of facial expression so right around the
inferior margins of the mandible so if we were to remove the skin up here you may see some extension
into this region if you can see the platysma muscle in the anterior neck you are not seeing
many other structures of the neck because it would be superficial to most other structures so if
you're not seeing the carotid sheath if you're not seeing the thyroid gland or the infrahyoid
muscles you're likely looking at the platysma muscle it's a fairly distinct looking muscle
next let's figure out how we are going to identify the sternocleidomastoid muscle
the sternocleidomastoid muscle is often abbreviated s c m so you will often hear
us refer to it as that in subsequent portions of the course the name of this of sternocleidomastoid
muscle tells you a lot about the attachments of this muscle the sterno so the sterno portion
means its attachment to the sternum specifically the manibrium so you can
see that right about hereish it's going to be down in this region clido means clavicle
meaning it's attachment to the medial third of the clavicle mastoid indicates the superior attachment
of the muscle to the mastoid process so heading up into this region here the mastoid process is
of the temporal bone which is that bump that you can feel right under your ear the superior
attachment will wrap around to the superior nuchal line as well so this large rope-like muscle
is going to be the sternocleidomastoid and you can see both on this particular image
you can also see in these images the external jugular vein which will run
superficial to the muscle as well so that's another important anatomical relationship
this muscle is an important component in the anterior neck and serves as a major player
in the division of the cervical triangles so we'll come back to this one over and over again
moving into the infrahyoid or strap muscles these muscles largely occupy the area inferior
to the hyoid so here's your hyoid here so these strap muscles will be inferior to the hyoid
but superior to the sternum your sternum is going to be here these are your clavicles here
and they will also be medial to the carotid sheath so you can see carotid sheath components here
so this is true for all infrahyoid muscles excepting the inferior belly of omohyoid
there are two groups of infrahyoid muscles the superficial and deep and
we are looking at a dissection of the superficial infrahyoid muscles
the most medial is going to be the sternohyoid which i am tracing here and over here
the sternohyoid is going to be longer than the two deeper infrahyoid muscles as it extends
between the sternum up all the way to the hyoid bone so you would have to reflect or move this
muscle in order to see those deeper infrahyoid muscles the omohyoid is pretty distinct looking
it is going to be lateral to the sternohyoid but it consists of two bellies that are
connected by an intermediate tendon and you can see the intermediate tendon here
the superior belly which i am labeling right here the superior belly is going to connect the body
of the hyoid to that intermediate tendon the inferior belly which i'm labeling eye
that inferior belly is going to connect the intermediate tendon all the way to the upper
border of the scapula so that's the scap scapula of the shoulder that's where the omo comes from
in its name this intermediate tendon is going to be anchored to the clavicle via what we like to
call a fascial sling and you can see that is a fairly pronounced one on this particular donor
the fascial sling now moving to a deeper dissection you know this is a
deeper dissection because you do not have that long sternohyoid that extends from the sternum
all the way to the hyoid instead you have two muscles that are going to span that space so you
know you're looking at a deeper dissection the sternothyroid which i am labeling here
for outlining so the sternothyroid connects the manibrium of the sternum to the oblique line
of the thyroid cartilage and that's a little hard to see here you can see kind of uh right
around this region of the the prominence of the thyroid and that oblique line is going to be
located right about here so that's going to be the sternothyroid the thyrohyoid oops sorry the
thyrohyoid will fill in the rest of the space from the oblique line of the thyroid cartilage
all the way up to the hyoid bone so this will be the thyrohyoid because here is your hyoid bone
so these infra hyoid muscles are super intuitive once you learn their names
because they explicitly describe their attachment points which will help you with identification
let's finish this discussion with one of the suprahyoid muscles the digastric muscle
we have this one here because it is often visible in an anterior neck dissection
as you can see the anterior bellies of the digastric right here
you can see it right here above the hyoid bone so here are some of those strap muscles or the
infrahyoid muscles here specifically the deep dissection and then right above the hyoid you're
getting into the suprahyoid muscles and that anterior belly of digastric is really visible
this muscle like the omohyoid has two bellies but instead they're called anterior and
posterior so here is the anterior belly of digastric this is its intermediate tendon
and this will be the posterior belly of the digastric
we will return to this muscle in session five when we're discussing the submandibular triangle
which is right around this region here here's your submandibular gland right there and we'll
also return to it in the oral cavity session all right thank you for your attention here
and as always please feel free to reach out to me with any questions have a great day