Hello my dear students of anatomy, welcome to a new video from this
easy anatomy channel by Juan José Sánchez, today I bring you a video about the generalities of the
muscular system, today we are going to learn what the muscle is, what is its structure and what its
disposition is, this is a video that you should know in a basic way to be able to understand the
subsequent anatomical study very well, we are going to start by first talking or conceptualizing
what a muscle is, which is a good muscle classically you look for the concept of muscle,
it will tell you that the muscle is nothing more than a structure that has the ability to contract
and with that contraction generate a movement, however when you delve into the study
of muscles you will see that generally this The concept applies to most muscles, but
not all muscles have a function of moving some structure. Muscles may have
other functions, such as fixing or preventing structures from moving, but they are not always
going to be generators of movement. However, the vast majority do fall within this concept,
in fact you see the image how these muscles are contracting in this case in order to achieve
chewing now etymologically where does the word muscle come from, it is a word of
Latin origin. made up of two roots, a first root which is mus which literally means mouse
as well as the mouse, while culus means something that is small as well as when it says that it is
tiny like a diminutive then literally the word muscle means small mouse,
it is believed that It is because when you contract a muscle, for example when you flex your arm
to demonstrate your strength, it flexes the biceps, you see how the muscle bulges and adopts more or
less the shape of a mouse, so it is believed that that is why those Latins They gave the
word muscles and even today we still continue to call it that, now
we know the muscle is the most important unit of the muscular system but every muscle will have four
capacities or four properties to make it easier for you, the first property is the properties
better known, which is the property of excitability, a fine muscle can be a structure that can
contract and generate movements but it has to have someone to tell it that it should contract
that it should generate that movement and this is when we are going to see the concept of excitability that does not It is
more than the ability of the muscles to be able to receive information from the nervous system
and to be able to respond to this information or to this warning that is in the nervous system. It responds
and can respond with movement. So, it is its first capacity, its first property, the
property of excitability, then we have the property of contractility, the capacity of
contractility is the capacity that a muscle has to shorten its fibers and be able to contract that is the
capacity of contractility, one of the most important that we find within
the muscles, especially within the We are going to study today, what is the skeletal muscle? Then,
the next capacity that the muscular system or certain parts of the muscular system
has is the capacity of extensibility, this is the capacity that the muscle has to extend,
the name itself says it or to distend without suffering any damage but it happens that you
may have the concept of muscle as the muscle that you see here and the one you see
in the limbs, the one you see in the thorax, in the abdomen but, it turns out that the entire system
gastrointestinal for example, it is made of smooth muscle, this this gastrointestinal system
is made up of the stomach, esophagus, an intestine, it can extend it can distend it can stretch
and then return to its original size this is the capacity for muscular extensibility then,
we would have the capacity of elasticity, this elasticity capacity would be the fourth and final
property of muscles and the ability of the muscle to return to its original shape once
contractility ceased and once extensibility ceased in the way of being able to return to its
shape . original without undergoing any change, this is the elasticity capacity, we are going to continue talking
then about the classification of muscles but first do not go away from this video
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make for you as long as it is a video within the anatomical canons, muscles are classified
into two large groups, we talk about muscle striated and we talk about smooth muscle, each
with particular morphological and histological characteristics, but since this is anatomy, this
is not histology, we are not going to touch on those histological characteristics much. What you do have to
know is that the striate is a reddish color, which is what you It characteristically looks like a muscle
when you study the limbs, when you study the thorax, the abdomen, the neck muscles,
this muscle is like that because when you read the microscope and without seeing them under the microscope
you see it in the form of striae, which in the Under the microscope these stretch marks are even more noticeable,
however the smooth muscle is the characteristic muscle of the gastrointestinal system, a muscle that the
arteries have in their walls, that the lymphatic system has, that the
sweat glands have, the ducts that you find in the body and the fibers are whiter to see
that this muscle is whiter and also lacks the foothills that the striated muscle has,
now the striated muscle is going to be subdivided into skeletal muscle and
cardiac muscle, the skeletal muscle is going to be our Let's say king of today's class is the muscle that
we study in anatomy why, because the cardiac muscle is not studied that much because
simply when you study the heart you study it at that moment, the parts of the heart
you know that the myocardium exists and everything else but up to that point, you totally forget when
you study the skeletal muscle system that is what we find the extremities we find
in the chest wall, in the abdominal wall, in the neck, the face, in the skull,
you know what predominates In the body each one has a name, a different function and therefore that is
what we study at this moment and it is where we are going to emphasize in today's video,
the cardiac muscle is unique to the heart, what differentiates a skeletal muscle from a
muscle cardiac, who innervates it, the skeletal muscle is a muscle that we can
move at will and how we can move it at will is said to be innervated by
the peripheral nervous system, it is the muscle with which we walk, with which we move our
arms of the muscle that we can contract at will and even that of facial expressions
in moving the neck, that of breathing, all those muscles are skeletal striated muscle, you
can move them at will, the cardiac striated muscle even though it is a muscle Striated is
an involuntary muscle with an involuntary muscle because I cannot contract the heart at will
but rather it is innervated and moved and contracted by the autonomic nervous system, for its part the
smooth muscle, for example that we find in the digestive tract, is a muscle that is Also under
involuntary control we cannot tell the stomach to contract, the intestine to contract,
a tubular system of some gland that helps move secretions we cannot do it,
we cannot tell the uterus to contract or not because the smooth muscle is also innervated. by
the autonomic nervous system, now we do not study the smooth muscle much in anatomy, we
simply know that the walls are the viscera, but when I am saying the stomach,
I study its portions, I study its innervation and irrigation, but he did not name the muscular walls
because that is more study of histology so basically what we study in anatomy
is the skeletal striated muscle and speaking of the skeletal muscle we are going to see what its ultra
structure is we are going to go from the simplest to the smallest to the largest until we see that
the muscle It is composed, notice here that everything begins with the muscle fiber,
that is, with the muscle cell that is also called myosite, it is muscle in the prefix mine is
muscle and when you see the word cyto it is cell then the muscle cell the myocyte the
muscle fiber or muscle cell these myocytes each one each each cell is surrounded by a let's
say a membrane of connective tissue called endomysium that here I am putting it a
little light pink you see each muscle cell is surrounded by an endomysium, now you grab a
group of several muscle cells each with its endomysium and pass another membrane over it again
and it forms what is the muscle fascicle or also called by some authors bundle muscle,
do like this with z, so what is a muscle bundle? It is nothing more than the union of several muscle cells,
each with its endomysium, but it turns out that each muscle fascicle, each of them
is wrapped by a membrane, see, this would be all of this, this would be a fascicle, so
each fascicle is wrapped in its own way. time by a connective tissue membrane called perimitiium,
which would be all this that is wrapping like the cable so that you can understand it more easily later,
the set of several muscle fascicles or several muscle bundles as you want to call it is
wrapped by another membrane further outside and It is what makes up the muscle, so the muscle is nothing
more than the union of several muscle fascicles and the muscle fascicles are nothing more than the union
of several muscle cells, but notice that the muscle on the outside is surrounded by another
membrane and that membrane It is the famous epimysium, then the one that surrounds the muscle cells
is the endomysium, the one that surrounds the fascicle is the perimysium and the one that surrounds the entire muscle
is the beginning, which would be the outermost layer of the muscle. Outside of this perimysium, we can
find the aponeurosis so that they are not going to confuse the epimysium with the aponeurosis that
has a fibrous structure that is outside the muscle and that sometimes uses the muscle to
achieve its insertions, very well we continue with the skeletal muscle, this is a classic skeletal muscle
is to say more from bone to bone but we are going to see that the skeletal muscle goes from
bone to bone, what are the parts of the skeletal muscle we are going to generally have an origin,
the origin is what we generally call muscle head is what what some authors call
fixed insertion what does this mean, it means that the origin of the muscle is what generally
the muscle does not contract in the fixed portion it is like where it grabs where the muscle grabs
to move but that part has very little contractile capacity, however there are origins that
can move indistinctly but I tell you that it is not always going to be the fixed part of the world,
then we have what is insertion, insertion is also called mobile insertion, this
mobile insertion is going to be the opposite of the origin because this mobile insertion is the part of the
muscle that can generally contract or that manages to contract and is the one that generates
movement, this insertion is generally made through tendon that the tendon is the fibrous part
it is the part let's say very little contractility of the muscle that manages to insert itself now the part
that has the greatest contractility capacity is the part that is between the origin and the insertion,
which is the belly, so the closer the belly gets to the origin the less contractile capacity
it has, The closer the belly is, the closer the tendon is, the greater the contractile capacity it has and that is why
this insertion zone in the area that, having the greatest contractile capacity, is the one that will
generate movement, for example, if this muscle contracts, this is the humerus. So that you understand, this
is the ulna and this is the radius. If this muscle contracts, it will not move the humerus,
because the humerus is the origin. In this case, it will move the ulna because that is its insertion
and we see the tendon. of insertion this membrane that we see out here that is wrapping the muscle
that would be the aponeurosis, now this is not always true sometimes a muscle can have two tendons
sometimes the two tendons can be found at the same moment so in that case
Its function is not to move, its function may be to fix a bone joint, or sometimes the origin can
also be moved according to what you ask the body to do somewhere.
of the body is fixed, you can find the origin more than the insertion or if that part is mobile,
you can contract the insertion more than the origin and there are muscles that can achieve the mixed part
, however, they are exceptions, the majority is how it is done. I am showing here a fixed origin and
an insertion that is much more mobile than the origin. Now that insertion is not always going to be in bone, that is,
do not believe that the striated muscle, because it is called skeletal, is always going to be bone to bone,
most of the Sometimes yes and in fact that is why it is called skeletal but there are muscles that, for
example, those of facial expression are inserted in the skin. They originate in bones but are inserted in
the skin of the face. There are some that are inserted in the mouth. in the mucosa of the mouth, or in the pharynx
that reach the mucosa of the pharynx, there is also muscle that reaches the aponeurosis and even reaches
the synovial capsule, it is from the joints, so it is not common although that is not
what It is not the only thing, I mean that it reaches the bone, but if it is the most common, it is the most common.
Very well, what do we study the skeletal muscle? You always look in my videos and
look for any anatomy book and four things are studied about a muscle. We study what its
origin is, we study what its insertion is to be able to know where you go from, where it comes from, we study the
innervation, which in this case, like the skeletal muscle system, has to be some
nerve fiber from the peripheral nervous system that moves it, which leads them to the information to move it
and this is through the nerves, for example you see the nerves of the cervical plexus,
of course, these are nerves that are sensitive but it is more or less so that they understand
the concept that the nerves are the that are responsible for moving the fourth characteristic that
we study about muscles, the function and the function is going to be what is the final movement that that
muscle achieves. Obviously we are not going to know the function or we are not going to understand it if we do not know the
origin and the insertion, because with you knowing the origin and the insertion you already know that the place
where it is inserted is what is going to move and you can more or less elucidate the function of that
muscle in relation to the movement it performs here we put the example of the biceps brachii,
the origin is here at the level of the shoulder, its insertion is the forearm, see well its insertion in the
forearm means that when it contracts it will not move the shoulder in this case it moves the
forearm so its function you are looking for and it is flexion of the forearm, the opposite is the muscle
that is working as it grips the forearm and from behind this is the triceps brachii,
it originates in the shoulder and is also inserted in the forearm but as it grips the forearm from
behind when it contracts it It is about pulling the forearm backwards and this is the
extension movement of the forearm. The biceps is a flexor and the triceps is an extensor of the forearm. It is the
fourth characteristic that we have to study of every skeletal muscle, origin, insertion,
innervation, and function. What shape we can find in the muscles are varied, they can be fusiform,
so a characteristic shape is mouse, such as the anterior brachialis muscle,
there are two-headed fusiform, such as the biceps brachii, there are muscles that can have two
bellies joined with a intermediate tendon, as in the case of the digastric that we find in the
jaw, there are some that are quite flat fibers and have multiple heads, such as the
major oblique muscle, which is the same external oblique muscle, one that has many bellies would be the
polygastric muscle, such as the rectus femoris. In the abdomen there are semi-peniform muscles, also called
unipeniform, in which there is a central tendon and from there muscle fibers
such as the tibialis posterior muscle are detached. Others are bipeniform where the same central tendon is
and there are muscle fibers on both sides such as the muscle. rectus femoris or rectus femoris,
now, what nomenclature will the skeletal system have, the nomenclature is easy today
thanks to the current anatomical terminology since the muscles that have to say more
or less some characteristics that help you identify it, The nomenclature is very varied,
Sometimes they classify it according to its morphology and I had that there are muscles that, for example, the trapezius,
the rhomboid, you see, it has a rhombus shape and that is why they call it rhomboid-shaped rhomboids,
sometimes simply the name of the muscle tells you a physical morphological characteristic,
sometimes the name of the muscle tells you the origin and insertion, for example, you
see the sternocleidomastoid and look, it says sternocleido and tells you that it is the sternum and the
clavicle, and mastoid because it reaches the mastoid position of the mastoid process of the temporal,
so sometimes he simply helps you, the study becomes easier for you, the anatomy of
each time the study becomes easier because the names cannot be strange or
crazy names, they are simply names that indicate or that tell you make it easier to learn the muscle,
sometimes the muscles have a location name, for example the
anterior ulnar muscle, you remember the ulna bone, if you say well, a muscle that
is anterior to the ulna, the same name tells you the location, some tell you the location. According to the
number of bellies, for example, you see the biceps brachii and you already know that it is a
muscle that already tells you the location, which is the arm, that is, brachialis, and that it is also
a muscle that has two heads. There are names that are mixed. or that they have two bellies,
others tell you the action, for example, you look for the levator muscle of the scapulae and you already know
that this is a muscle that brings the scapula upward towards its function that will elevate the scapula, another one
is the common extensor of the fingers. It is telling you that its function is to extend the fingers,
it also tells you the location that it is in the fingers. If sometimes different classifications are mixed, let's say
classifications within the names of the muscles, but they are names that have been in place for
many years and we cannot any longer. change them, this was then the entire video of the muscular system,
do not forget to subscribe to the channel, like the video if you liked it and you can find me on my
social networks like instagram at arroba juan floor sánchez 13 15 see you in the following videos
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