hello anatomy colleagues this is dr kathleen alsup and welcome to the first video mini
lecture for the skeletal system basics i am very lucky that i get to start my discussions with all
of you with one of my all-time favorite subjects in anatomy which is the skeletal system it is just
really on up there in terms of my favorites within this entire session of the skeletal system basics
we will discuss a multitude of things related to the skeletal system which includes things
like bone growth bone cells and composition but we are going to start with the basic of basics
and start with a discussion of the multitude of functions that the skeletal system has
but before we can really get into that and to make sense of some of these functions we're
going to start with a discussion of what the skeletal system is actually composed
of so what makes up the skeletal system and spoiler alert it is more than just bone
now for each mini lecture i will have a list of questions like you see here
that you should be able to answer from the information we discussed throughout
i highly recommend writing down or maybe saying out loud the answers to these in your own words
after you viewed the video the act of really doing this is quite powerful and will get you so much
further than trying to memorize or just straight memorize everything i say so kind of watch the
video take notes and then try to answer these on your own afterwards so we will begin breaking down
each function of the skeletal system we'll take these one by one and i expect you to know all of
these but pay close attention to these details and these particular questions here as we discuss the
functions and and you'll have a good time working through these and answering these questions
all right so when you think of the skeletal system i am sure your first thought is bone and that
is great that means you're on the right track bone makes up the majority of the skeletal system and
it is extremely important to note that this is a dynamic organ meaning it is not static
this means that bone changes throughout your life we always or when we're you know thinking about
this more colloquially we kind of think of you reach adulthood and your bones just stop growing
which is true when we're talking about in terms of bone length but it certainly can and does change
throughout childhood and adulthood and width as well as composition so bone density can increase
or decrease based on certain things like aging or disease or even a lot of weight-bearing exercise
so it is a dynamic organ and as mentioned it is the major component of the skeletal system
but there are other tissues included or involved with the skeletal system
osseous tissue is the major component of bone
and we will spend a considerable amount of time discussing those specifics in an upcoming video
cartilage can be found on the ends of long bones you can see it here and here and
it's going to be found in other areas where bones form joints most long and also most long
bones will form within a cartilaginous model so we will talk in considerable detail regarding
endochondral ossification ossification which is important in terms of um bone development
so cartilage is super high up there in terms of importance of the skeletal system as well
bone will be lined by a layer of dents irregular connective tissue called the periosteum
and in addition connective tissue will compose ligaments which will serve to connect bone to bone
so ligaments are very important in terms of the skeletal system as well so we'll
spend a bit more time in terms of talking about these different parts of the long bone so don't
fret if we're not quite down with some of this terminology we'll talk about that but i did want
you to note that this dense connective tissue is going to play a role in terms of the periosteum
epithelial tissue will line some of the hollow areas in bone
particularly in certain areas like your paranasal sinuses of the skull so if you think of
your sinuses acting up those are your paranasal sinuses
so epithelial tissue will play a role with some of the some of the bone but certainly not all
marrow both yellow which you're looking at right here as well as red can be found in bone with
differing percentages dependent on many factors particularly age adipose tissue is going to be the
major component of the yellow bone marrow so over here you're going to have adipose really composing
the majority of the yellow bone marrow and that's going to be housed in this hollow medullary cavity
in the middle of these long bones and lastly but certainly not least the skeletal system will
have a very robust neurovascular supply and when i say neurovasculature i mean a collection
of arteries veins and nerves and this is not the last time or even close to the last time we'll
be talking about these different structures here bone is richly supplied with blood from
arteries and it's especially abundant in these areas of bone containing this red bone marrow
veins and nerves will typically accompany or travel close to these arteries
and the periosteum on the outer portion of bone is especially rich in sensory nerves
okay so let's begin working our way through these functions and this first one is probably
something you have known for a good amount of your life already the skeletal system is very
important in terms of support it serves as the major structural framework for the body providing
attachment for tendons of most skeletal muscle so all these bumps that you see on bones are
these bumps and lumps on bones are mostly areas where muscle tendons attach during life
so very important in terms of providing that supportive framework
the skeleton also serves an important role in protection
and this is a another fairly intuitive function of the skeletal system it protects some of our
most important internal organs including the brain which you can see here being protected by this the
skull but also the heart and lungs are going to be housed within this thoracic cage region
you would have a lung here and along here and then a heart here obviously not drawn to scale
additionally the spinal cord will be protected within the vertebral column which is running down
the midline and there are many other in important internal organs that are supported or protected
by the skeletal system we'll talk a bit more about that as we discuss each bone
okay so those are some of the more intuitive ones bones while not capable of contracting themselves
will play a big role in movement because most skeletal muscles are going to attach to bone
so very important in terms of that so it is a skeletal muscle that will actually be what's
contracting but since it is attached to bone it will pull on the bone to produce the movement that
we see say when you are flexing your elbow so your biceps brachii in this situation that muscle will
contract or shorten and it will pull the bones in your forearm in order to create this action
now moving into some slightly more complex functions let's talk mineral storage and release
that's associated with bone and the main mineral stored in bone is of course
calcium and we've all heard that catchy ad campaign for milk calcium is good for your bones
mainly because bone is the major reservoir for calcium up to 99 of the total blood calcium
and calcium will be released from bone to maintain mineral balances homeostasis
it will help to distribute calcium throughout the body to help important bodily functions one
example of that is calcium plays an important role in terms of allowing muscle contractions to happen
and we will uh additionally talk in some more detail and subsequent sessions about
how certain hormones will actually play a role in initiating increased or decreased
calcium storage in bone so hormones that are secreted by the thyroid gland
can actually play a big role in terms of what's going on with bone and calcium storage
within certain bones there will be variable amounts of a connective tissue
lovingly referred to as a red bone marrow and red bone marrow is going to produce
red blood cells white blood cells and platelets and a process called
metapoesis sorry that was hard for me to say hematopoiesis and this is basically blood cell
production now you are going to have a whole session later on in the course about blood so
i don't want to spoil too much of the fun here but it is directly related to bone because red
bone marrow is present in developing bones of the fetus and in the early juvenile and will persist
even in some adult bones such as the coxal bones or your which more colloquially we refer to as
your hip bones the ribs will also still have red bone marrow persisting the sternum um your vertex
some of your vertebrae so just to name a few but with age much of the red bone marrow will convert
to yellow bone marrow which leads us to our last function and this is going to be
triglyceride storage yellow bone marrow consists mostly of adipose tissue or adipose cells
which are very important in terms of triglyceride storage this is a potential
chemical energy reserve sorry if you heard my uh email pop up i meant to turn that off you
can see in this image why the different marrows get their name so red bone marrow is really red
and yellow bone marrow is uh relatively yellow so please make sure um that you kind of get an idea
of some of the basics of these structures and how they're playing a role in terms of
the functions like i said we will refer and come back to this particular image to talk about these
specific structures in a bit more detail but at least we're starting to think through some of
the reasons why we're learning about the skeletal system and what their functions are so this wraps
up the content for this mini lecture please make sure you go back to the learning objective slide
and you know really take what you have learned here and answer those questions and like i said
previously answer those questions in your own words that will make it so much more meaningful
additionally i like to end each one of my sessions with a question that we can work through and many
of these questions are just a quick gauge for you to assess your knowledge here some will make
you think a bit more many will be similar to what you see on the exam so let's get to this question
all right so i wanted us to ease into this so i've started with a true or false question
just so you know i typically don't ask many or any true or false questions on the exam even though i
could but i do like them in the lecture format to serve as a jumping off point for you to be able to
assess your knowledge or your basic understanding of the concepts so see if you can answer this
true or false all bone marrow in adults is yellow bone marrow is this true or false and
if it is false then why write out why it's false or say out loud why you think it's false so take
a moment to think through this and i recommend pausing the video if you need a bit more time
but if you are ready let's review the answer and hopefully you have landed on the fact that this
question is false this true or false question is false recall that i noted that red bone marrow can
persist in some adult bones let's head back to this slide here so uh red bone americans
persist in some adult bones like we mentioned the hip bones uh the vertebrae the ribs the sternum
or that breast bone if we are talking about what we colloquially refer to that as
so if there is some red bone marrow in adult bones it can't all be yellow bone marrow correct
so again the answer to this question is going to be false
alright so that was so much fun the skeletal system i think is just so deliciously complex and
i just can't wait to keep exploring this area with you in subsequent videos please always feel free
to reach out to me with any questions you may have regarding this content after you've reviewed and
kind of tried to answer the questions if you've tried to answer it and you just can't then that's
the time to come come reach out to me and and do it early and often and i think we'll be in good
shape as we move through the course alright so thanks again and please have a great day