hello anatomy colleagues this is dr alsup and i am super excited to talk about one of my favorite
things muscle attachments and there are quite a few terms associated with muscle attachments and
we want to differentiate these in order to be successful throughout the year and understand
what we even mean by proximal attachment or distal attachment throughout the year we will be asking
you in lab and through dissection supplementary videos to identify bony landmarks and some
of these bumps and lumps are associated with certain structures attaching to the bone so you
may have heard the term ligaments ligaments are connective tissues that will attach bone to bone
also importantly tendons which is where we'll spend some more of our time in this session
tendons are going to attach to bone as well so in essence tendons will connect muscle bellies
to bone so if a muscle belly contracts often and forcefully this will pull on that bony attachment
more and more and it will create larger projections or processes one bony attachment
site we are learning today is the coracoid process was which i have outlined here in red and this is
on the anterior scapula or your shoulder blade and this will be the distal attachment site
of the pectoralis minor muscle the m right here means muscle so this is one of the reasons we have
you learn these bony landmarks so you can kind of put the distal attachment side and match it with
the proximal attachment site and understand a lot of important things about the muscle
so let's get into those muscle attachment sides understanding these sites even the very basics as
as in which muscle or excuse me which bone a muscle attaches to will give you information on
two major things first it will help you understand which joint or joints that muscle crosses
and a muscle and this is an important concept so make sure to put a little star next to it a
muscle must cross a joint or pass over a joint to be directly involved with the action of that joint
so understanding say for this biceps brachii which is here that the biceps brachii is crossing over
the shoulder joint due to the tendons here as well as the elbow joint and even
the proximal radial ulnar joint but mainly this elbow joint is kind of where it's at
so the fact that the tendon or the muscle belly cross over those joints means that
that muscle can play a role there additionally based on the location and attachment points
of the the muscle this can give you some important clues regarding the action or the actions of that
muscle without really having to memorize it so one example in the upper limb is most muscles
that are anteriorly placed are going to be flexor muscles whereas most muscles posteriorly placed
are extensor muscles so that's just kind of an intro into that we'll get more details into
movements in other videos but that just kind of knowing basically where the muscle
is if you learn some overall rules will help you understand what those muscles do
now one point regarding what when we describe what actions a muscle can perform you als often
see a list of actions and say for this session we're going to be learning about pectoralis major
which is kind of located here-ish going this away and so um you'll hear you'll see a list of actions
that that muscle can do and the pectoralis major at the shoulder joint can abduct immediately
rotate and some other actions the shoulder joint don't worry we'll talk about that in more detail
in a mini video but what i wanted to note is that the actions that are described in such lists
are concentric contractions and um these are what occurs when a muscle
shortens when contracting so if you think the muscle shortens it will pull on a bone
in order to create an action so it's typically what we think of with muscle contractions now i
do want to note here that muscles are certainly capable of lengthening or stretching as well
and these types of contractions are very important part of fluid movements but the actions of a
muscle that you will be seeing throughout the year will be these concentric contractions
okay let's now discuss the pertinent terminology for these attachments
proximal sometimes you'll see superior but more often you'll see proximal
attachments are exactly what they sound like they will be the proximal most attachment of the muscle
or the attachment that is closer to the trunk and you will see in this case here of the biceps
brachii that there are actually two proximal attachments that are on the scapula so these are
closer to the trunk than say the distal attachment that's way down here on the radius so these would
be the proximal attachments traditionally proximal attachments were called the origin sites and you
will definitely hear or see the term origin and other resources and sometime in our own resources
they're kind of used interchangeably but i'll talk about why there's been a transition away from that
these particular attachments are the ones that are typically fixed during major concentric
contractions meaning that during those movements this bone is not moving all right these will be
the immovable bone or the fixed bone so in one of them for biceps brachii one of the
major movements will be flexion of the forearms i think the the forearm bones are moving this way
moving up that way and so the distal attachment or the insertion site will be the movable bone
toward the other attachment side so the distal attachment or the insertion or typically
the when that muscle contracts and shortens will pull this bone up towards the proximal attachments
in this case that'd be the radius so the radius is moving more towards those proximal bones
you always need one immovable bone to allow more precise and safe movement on the other end
now these rolls may reverse with certain um certain muscles and the proximal attachment
would be the bone that moves and the distal attachment is the bone that stabilizes
and that's why we've moved more to the descriptive proximal and distal attachments
because that's just descriptive of where the the muscles attaching rather than origin and insertion
because these more traditional terms kind of pitch and hold the proximal end as always being
immovable or the distillate is always being movable which we know is not always the case
so this is play more descriptive if you hear the term proximal attachment
you know that that's the attachment site that's most proximal whereas origin not so much
so you will be seeing these terms quite a bit as we talk about each individual muscle
sometimes we'll get quite specific in terms of an exact bony structure sometimes it'll
be more general as it just attaches to the radius or to the scapula it's dependent on
the the specific muscle but you will certainly be hearing those so we wanted to introduce them here
all right so for this session we will begin our first few muscle attachment sites
for a few select muscles like pectoralis major and minor serratus anterior but in this video
we are more describing what that terminology associated with muscle attachment sites mean
so this slide is a nice summary of some of those key terms those kind of high-yield
terms that will keep coming back and i recommend coming back to this for both
studying but also as a reference as you're getting used to navigating anatomy which
may take a little while but eventually you will become a bit more comfortable with these terms
thank you for your time and attention and have a great rest of your day