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- [Voiceover] Switching from the idea

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of being a critical thinker
and society roles of science,

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we can move into the body more.

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Now, even though we're
kinda switching gears,

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still, thinking critically
is very important,

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because, really, what makes up the body?

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We'll start with looking at

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the different structural
levels of organization.

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I'm sure if you look at the
base of the pyramid here,

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you can see the organismal level.

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You know, it's what the person is.

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But what makes up a person?

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Well, you're made up of various
different organ systems,

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things like the urine system,

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the cardiovascular system,
the digestive system.

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But each one of those systems

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is made up of several organs.

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So, for example, you take
the digestive system.

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You have your stomach, you
have your small intestines,

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you have your large intestines.

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But then each one of those organs

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are made up of several tissues.

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Now, these tissues are things like

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smooth muscle or epithelial tissue,

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things that'll connect things together.

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But each one of those
tissues is made up of cells,

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cells that are working together.

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And then if you go beyond that,

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each cell is made up of molecules.

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Well, molecules are actually
groupings of different atoms,

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the most simplistic
level, the chemical level.

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So really, there's six
distinct levels of complexity.

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And then you reach the organismal level.

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So you have your chemical level,

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your cellular level, your tissue level,

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your organ level, your organ system level,

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your organismal level.

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Now we have the different systems

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found in the body.

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So, as we went through
that organisation level,

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it's these different systems

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that help to make up the overall organism.

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If you start at the top left,

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you have the integumentary system.

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Skin, hair, nails.

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It's helping to encase
the body, keep things out,

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as well as keep things in.

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Go down to the muscular system.

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That's what moves the
body, creates movement.

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Endocrine system, you're looking at

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things that produce hormones.

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For example, pituitary
gland, thyroid gland.

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The skeletal system, bones and joints,

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what gives some rigidity to the body.

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The nervous system.

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Looking at brain, spinal
cord, your nerves.

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It's what's carrying the actual impulses

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throughout your body.

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The cardiovascular system.

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Hearts, arteries, veins.

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They're carrying blood, transporting blood

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throughout your body.

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The blood is carrying
and transporting gasses,

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like oxygen and carbon dioxide.

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It's transporting nutrients and waste.

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Your lymphatic system.

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Looking at things like your
lymph nodes, your thymus.

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They're gonna pick up
excess fluid, leaked fluid,

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and return it back into
the cardiovascular system.

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Digestive system, you're
looking at things like

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your stomach, your liver,

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your small intestines,
your large intestines.

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That's gonna help
process the food you eat.

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The bottom row, you can see,

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is male and female reproductive.

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On the male side, you're
looking at things like

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testes, epididymis, penis.

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On the female side, looking
at things like ovaries,

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uterus, vaginal canal.

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If you go to the top right,

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you're looking at the respiratory system.

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Lungs, trachea, your nose.

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It's what helps to
bring air into your body

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so you can process and absorb the oxygen,

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get rid of carbon dioxide.

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Urinary system, well, you're
looking at the urinary bladder,

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ureter, the kidneys, filtering your blood,

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and getting rid of waste,

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but also removing excess ions.

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Those different body systems
we were just talking about,

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well, some of them are found
within certain cavities.

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So, for example, you have
up here the anterior cavity.

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Well, anterior means front,
so this is pretty much

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what's all found in
the front of your body.

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You have a couple of different cavities

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inside the anterior cavity.

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You have what's called
the thoracic cavity.

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Now, think about where
your heart and lungs are,

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the upper part of your chest.

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That's your thoracic cavity.

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There's the two pleural cavities,

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which is where each lung is,

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and the pericardial cavity,
which is where the heart is.

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You then have your abdominal cavity.

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This'll be encasing
things like your stomach,

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your small intestines, large intestines,

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your liver, your gallbladder,

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your spleen, your pancreas.

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They're all down right in the main section

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of your abdominal region.

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And the pelvic cavity is right
down in the groin region.

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This usually contains reproductive organs,

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and you're gonna have a little bit of the

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urine bladder in there as well.

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But go to the posterior side, well,

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posterior cavity is the back side.

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It'll be broken up into two things,

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the cranial cavity, which
is where your brain is,

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and the spinal cavity, which is where

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your spinal cord is,
inside those vertebrae,

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the bones you feel along your back.

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So here's what it looks like.

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If you're looking at the figure

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on the right hand side now,

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the one you can see the
front of the person.

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You can see in the top, you
have that thoracic cavity,

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which is broken into
pericardial and pleural cavity.

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The diaphragm is what splits the parts.

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You can see the diaphragm
is labelled right

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in the middle of the figure there.

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Below the diaphragm is
your abdominal cavity.

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And then at the very bottom,
just in the groin region,

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is the pelvic cavity.

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If you look on the left
side of the screen,

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you can see the view from the
lateral, or from the side.

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You have your cranial
and vertebral cavities.

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So both those are found
within the posterior cavity.

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But some of these cavities
are gonna have membranes

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that help to line them.

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We have what's called the serous membrane.

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You're gonna find this
throughout the abdominal cavity,

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and you'll find it in
other cavities as well.

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But what it's meant to do, is
it's a double layer membrane.

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There's actually two parts.

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One will cover the organ like saran wrap,

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one will line the cavity.

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The goal: reduce friction,

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cause as you move, are your organs moving?

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If you bend forward,
think about what happens

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to your stomach, your intestines.

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You're crunching them down.

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So it helps reduce friction.

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You have mucous membranes.

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Think of the things in
your nose, in your throat.

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Helps to capture any debris that you're

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inhaling in, for example.

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Synovial membrane, these
are found in joints,

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joints like your knees, your elbow,

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your shoulder, your hip.

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They're lining the spaces, and
helping to prevent the bone

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from contacting bone on bone.

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And, the cutaneous membrane.

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That's your skin.

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So what you see, your cutaneous membrane

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is everything you see that is your skin.