hello all this is Dr. Alsup and we're going to finish up this section of videos by talking about
some of the muscles of the neck and the back and we'll talk about how some of them will
discuss in later parts of the course all right so you can see we're going to start with our
our good friend the sternocleidomastoid and then we're going to talk a little bit about the supra-
and infrahyoid muscles and then finish off with some of the deeper back muscles referred to as the
erector spinae muscles all right so one of my all-time favorite muscles the sternocleidomastoid
it has a long name but the name tells you exactly where the attachments are so the sterno-
is indicative of the attachment to the manibrium of the sternum the cleido- cleido- is indicative of
the clavicle so you can see that attachment here so that both the sterno- and the cleido- are the
inferior attachments and then the mastoid part of the name is telling you that one of the superior
attachments is up on the mastoid process those processes that you can palpate underneath your ear
of the temporal bone additionally portions of the muscle will go back towards the occipital bone as
well so if you're looking at yourself it's going to be this rope-like muscle right here on the neck
very easily palpable can serve as an important landmark for other structures of the neck
and as you can see here this this muscle these muscles cross those cervical vertebral joints
so that's indicative of which joints these muscles will affect when they contract so with bilateral
contractions so contraction of both of the sternocleidomastoid muscles you can have flexion
of the cervical vertebrae with unilateral contraction so contraction of just one of the
sternocleidomastoids you can have lateral flexion of the neck and also rotation of the head in the
opposite direction and that's really where i feel like you can best feel your sternocleidomastoid
because it's contracting at that time you can really palpate the whole length of the muscle
there are other other actions that the sternocleidomastoid will play a
role in but these are the ones we're going to focus in on that you're responsible for
in terms of innervation sternocleidomastoid is unique with its friend the trapezius on
the back in that it is going to have a separate efferent or motor innervation from the afferent
or sensory innervation remember when we're talking about sensory innervation of a muscle
we're mainly focused on proprioception in that region so the efferent innervation or motor
innervation is coming from the accessory nerve or cranial nerve 11. and as you will talk more about
when you get to the neuro section accessory nerve is an example of one of the cranial nerves that
is solely motor or solely efferent so you have to get those afferent or sensory fibers from other
nerves and specifically the sternocleidomastoid gets its afferent innervation from branches of
the cervical spinal nerve 2 and cervical spinal nerve 3. so you can see some of those branches
kind of coming off from that region and going to innervate the deep side of the sternocleidomastoid
there are other muscles in the neck so sternocleidomastoid is kind of the big one you
can see that here but if you're looking anteriorly there's these fairly thin muscles in these these
regions and we kind of separate them as to whether they're superior to the hyoid bone or supra- or
inferior to the hyoid bone or infra- both sets have four pairs of muscles so the suprahyoid muscles
again are going to be superior to the hyoid bone these really form the floor of the mouth
and again they will support both sets will support the hyoid bone kind of keeping it where it should
be but when they contract they can also play a role in terms of elevation of the hyoid bone
whereas the infrahyoid muscles you can think about when they contract they're going to pull
the hyoid with it and depress the hyoid and certain ones can depress the larynx as well
because they'll have an attachment there the infrahyoid muscles are sometimes referred to as
strap muscles because they look like these ribbon like straps and they will cover these
hidden things underneath here so you have the larynx here you have the trachea here you have
the thyroid gland right here so the infrahyoid muscles are covering quite a bit in this region
there are a lot of muscles associated with the back and we'll we'll talk about the
superficial back muscles in with the upper limb because they can affect the movement there
and there are a tremendous amount of extremely deep back muscles the multifidus muscles
multifidus muscles these are literally these little bitty muscles that are going to
attach specific parts of the bone to bone so we're not going to talk about the deepest spinal muscles
or the most superficial we're mainly going to focus in on these kind of intermediate but really
thick and prominent muscles associated with the back and these are referred to as the erector
spinae muscles all these deep back muscles are going to play a role in terms of extension
of the vertebrae so think about kind of standing up and extending and keeping extended also these
can play a role in terms of lateral flexion of the vertebrae so moving from side to side
and these can commonly be strained when we think about strained back muscles it's generally these
erector spinae muscles or maybe these deepest back muscles if you think about lifting from the
legs and not from the back that's kind of the improperly lifting something if you're lifting
a heavy moving box you want to lift from the legs and not from these deep back muscles
the erector spinae muscles can be separated into three kind of columns but their functions
are generally the same in terms of this extension and lateral so we often talk about them together
so the most lateral of these are going to be the iliocostalis muscles you can
see some of these here the intermediate or the middle are going to be the longissimus
and then the spinalis are going to be the most medial think they're closest to the spinal column
so I often remember these as I love spaghetti that helps me in terms of memorize the order here
and you can see here that these these divisions are separated into separate regions based on
are they more superior more inferior so if you're looking at the iliocostalis you see the cervicis
those are going to be the most superior thoracis and then lumborum as the most inferior but I don't
want you to worry too much about these but I do want you to at least
know these three divisions of the erector spinae muscles so if you're looking at
an individual's back generally you see these these fairly distinct columns next
to the spinous processes and these are those erector spinae muscles
there are a lot more there's a lot more going on in the neck and the back than what we're
going to talk about in this specific video but we will talk about them later so the superficial
back muscles that i kept mentioning your traps or your trapezius as well as your lats or your
latissimus dorsi those are going to be the most superficial most prominent muscles of the back
but they're going to affect the upper limb so we're going to talk about them there pharyngeal
muscles that are making up the pharynx that's going to be discussed in the gastrointestinal
section and the laryngeal muscles and cartilages will be discussed with the respiratory section
all right so last but not least our review question here which rope-like muscle is
important in the anterolateral neck as a palpable landmark and hopefully you remember I kept palpating it on my own neck is it the anterior scalene, erector spinae, latissimus dorsi,
sternocleidomastoid, or trapezius hopefully this popped in your mind immediately if not go back
and review how the sternocleidomastoid which is this rope-like muscle right here on either side
is going to be an important anterolateral landmark you can palpate it you can get an idea of what's
going to be more medial what's going to be more lateral anterior scalene we didn't talk about as
much it is in the neck deep neck but not correct erector spinae that's going to be deep back
and then lat and trapezius we didn't talk about either but these are both superficial
back muscles and we'll discuss that a little bit later with the upper limb all right excellent
so we made it through this third portion of the course we're going to move to thorax, abdomen, and
upper limb in our next set of videos i hope you enjoy your time in the lab to be able to review
some of these structures thanks for your time and attention and I'll see you in the next video