Skeletal muscle Structure: Fascicles - Locomotion and Movement, Biology, Class 11 Video Lecture

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now that we understood the basic types
of the muscle tissues we will try to
understand the mechanism of muscle
contraction now when we talk about the
concept of muscle contraction we will
basically be talking about the skeletal
muscles because we are more interested
to know about how the skeletal muscles
work that way
that's because the skeletal muscles are
the voluntary muscles that is they move
as per our own will so we want to see
that how this movement take place and
also the skeletal muscles to choose
movement in close coordination with
bones and the joints so we want to
understand the entire process of
movement so in order to know that we
still need to know a detailed knowledge
on the structure of the skeletal muscles
so let us try to understand the
structure of the skeletal muscle now as
you saw now you might be wondering that
when there are three types of muscle
tissue skeletal smooth and cardiac why
are we talking about the skeleton muscle
now stress it again now this division of
the muscular tissue into the three
categories where based on many different
things for example their location where
they are located their appearance how
their structures are their nature of
their regulation of various activities
for example the skeletal muscles are
controlled by our bill whereas the
smooth muscles
be controlled they haven't just on their
own similarly the tiger cousins they are
very unique in that sense because they
have been even without a kind of
regulation or control from the nervous
system so that is because of these
differences the muscle tissues were
divided with these three categories but
now we are going to talk about we're
trying to focus on the muscular
movements or the external muscular
movements which take is in our body
which is largely due to the skeletal
muscles and that is why we want to spend
more time understanding how the skeletal
muscles cause movement so let us look at
the structure of skeletal muscle now the
various parts that together form the
skeletal muscles are the muscle bundles
which are also known as fascicles
so fascicles is just another term for
muscle bundles so each muscle tissue or
each muscle is made up of muscle bundles
so what what are these muscle bundles
now let us think of a scenario let us
suppose this person is doing exercise so
he is what is it doing he is just moving
his hand up and down holding this
dumbbell right now if we try to observe
the what is there inside his arm what do
we see we see that there are muscles
which are present so this is how muscles
look like at these muscles in turn and
connected to the bones
when these muscles cause contraction
they make the bones move and that is how
movement occurs now let us focus on the
muscles so this is how the muscles look
like now if you look at the
cross-section of the muscles inside the
muscle
you have muscle bundles like this each
of these spherical structure is a muscle
Bible so each of these is a muscle Bible
which is also known as fascicle there is
not a structure on fasciae so fast here
is nothing but a kind of a connective
tissue which connects the muscle bundles
together because this is one muscle
Bible this is another person bundle this
is another person Brendan this is yet
another muscle bundle though all these
bundles need to be connected to each
other and they are connected by a
connective tissue which is called
faster next part is the muscle fibers
now interestingly each muscle bundle in
turn is made up of multiple muscle
fibers so if you see inside each bundle
this is one person bundle inside these
bundles to again get to see some other
structures present which are known as
the muscle fibers so now I have
projected one of the muscle bundles this
is how a muscle by me loose is like a
tube like structure we are just seeing
the top view of the muscle bundle so if
you just try to see how it is inside
just it is as if I have extracted out
one muscle bundle just to show you how
it is it is a long cylindrical structure
this was just the talking now each of
these is again made up of so many muscle
fibers so each of these one again is
extracted out to show it clearly so each
of these is a muscle fiber so each of
these which you see is the muscle fiber
and inside this muscle fiber you have
organelles which are very similar to the
organelles inside the cell what a
sarcolemma sarcolemma is nothing but the
membrane which binds each muscle fiber
so this my brain is gonna sarcolemma so
here if you see this
this muscle fiber would have a membrane
around and said this wasn't likely where
they can have a membrane around itself
so this membrane will be known as
sarcolemma so sarcolemma is basically
the plasma membrane surrounding the
muscle fiber
sarcoplasm cytoplasm would be the fluid
length substance which is present inside
each muscle fiber so inside this muscle
fiber also you have a fluid egg
structure which is present that is like
how you have cytoplasm understand
similarly you have sarcoplasm inside the
muscle fiber and then you have the
sarcoplasmic reticulum which is just
like the endoplasmic reticulum which you
have inside the cell so here inside the
muscle fiber the sarcoplasmic reticulum
is that organelle which is rich in
calcium ions and that is why you would
have heard your patter your mom asking
you to drink a lot of milk if you want
your muscles should be strong because
bones muscles all of these are made up
of calcium factions one of the important
constituents of muscles and bones so
this action is truly in the sarcoplasmic
reticulum
so sarcolemma is the boundary or the
plasma membrane of each muscle fiber
inside the muscle fiber you have the
fluid but cytoplasm and you have
sarcoplasmic reticulum it stores - so
these are briefly the different parts
inside the skeletal muscle structure now
let us have a detailed knowledge on each
of these parts so we will start with
fascicles fascicles is just another name
for the muscle bundles
so these fascicles together constitute
the muscle muscle tissue as I said each
of these is a fascicle so all of them
bind together to form the muscular
tissue
next is the faciem which connects the
muscle tissues together so it is a
connective tissue which connects the
fascicles
or the muscle bundles third is the
muscle fibers as I say
long tubular cells forming the muscle
fibers
they can be up to several centimeters in
length though these muscle fibers are
one of the longest cells of the human
body they can be very long they can be
up to several centimeters in length so
that means they are one of the longest
cells of the human body and many muscle
fibers that is here you can see this is
one muscle fiber right so many such
cylindrical structures together form the
muscle bundles like this is one muscle
fiber so here if you see this is one
muscle fiber and many such muscle fibers
together
form this which is the muscle bundle and
many such muscle bundle which are these
together form this muscle tissue next
sarcolemma it is the plasma membrane
lining the muscle fibers so the membrane
lining this person fibrous Starkel emma
next to sarcoplasm
which is the cytoplasm of muscle fibers
inside the muscle fiber the fluid which
is present is called sarcoplasm and
these are multinucleated that means
inside the muscle fiber you have
multiple nucleus so one muscle fiber is
considered like one stem right like a
human body we when you talk about the
human body we say that it is made up of
different organs organs internal rhythm
of issues which in turn are made up of
cells so here also the my muscle fiber
is at the cellular level
so each muscle fiber is just one cell so
that's then we have the sarcoplasm the
cell will have a sarcolemma the cell
they also have multiple nucleus
sarcoplasmic reticulum
it is like the end impedance that into
plasmic reticulum of muscle fibers and
it is also the storehouse of calcium
ions and calcium ions is very much
required for the activity of the muscles
and that is why intake of calcium ions
can strengthen your neck and makes your
muscles strong so this is about the
structure of the skeletal muscle tissue
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