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  • The human body is amazing, a symphony of bones, muscles, cells, organs, liquids and an incomprehensible

  • number of chemical reactions, all working together simultaneously to keep us moving,

  • breathing and well living. And we think learning about all these details, big and small, is

  • fascinating. So we put together this new series for youWere calling it Human, a learning

  • playlist dedicated to everything that makes us us, covering all the basics of anatomy

  • and physiology that we could fit into one playlistNow, even though we can’t teach

  • you everything about the body in just a few videos, the goal is to teach you enough core

  • concepts so that you can feel more informed when reading news in your social feed, talking

  • to your doctors or even sitting down to take your midtermsBecause the cool thing about

  • studying the human body is that everyone has one, so it’s relevant to literally everyone.

  • Unless youre a ghost. In that case, I guess not. If you are a ghost, let us know in the comments.

  • My name is Patrick and I’m going to be your host for this series. I studied

  • multiple branches of science having to do with the human body before becoming a teacher

  • and science writer, so I’m very excited to nerd out about the body with you. Well

  • talk about blood and the immune system and hormones and stem cells, just to name a few

  • of the topicsPlus, there’s so much cool research happening right now that uses these

  • basic concepts, and well talk about that, too. Before we get too into the weeds of any

  • one topic, were going to need some background info. There are multiple branches of science

  • dedicated to studying something about the bodybut a lot of them focus on what happens

  • when things go wrong. Studying disease is interesting, but weve already got an entire

  • separate series for that called Sick which you can go watch. In this series,

  • well focus on anatomy, or the study of shape and stuff of the body, and physiology,

  • the study of all the processes that happen within it. Anatomy is form, physiology is

  • functionAnd form influences function at very small and very big levelsTo see how,

  • it’s helpful to organize all of biology into a hierarchy in something called biological

  • organizationIt’s a useful way of organizing tiny things like cells into larger groups,

  • but it also lets us picture bigger things like bodies as a collection of organ systems.

  • Over the course of this video, well take a look at the integumentary system because it provides

  • a great example of this hierarchyTo start with, were all made of matter at the most

  • basic level. This includes all the atoms and molecules that combine together to make the

  • membranes of our cells, the salt in our sweat, or the neurotransmitters that travel between

  • neurons. And when we parse all the matter that makes up skin, we find all kinds of lipids,

  • minerals and proteins that assemble into the structures that make your skin tough but flexible.

  • And water. Weve got so much water in our bodies. Those chemicals combine to form the

  • different parts of cells, the smallest living thing on the hierarchy. Literally the smallest

  • unit you can point to and saythis is alive”. Now, there are a few generally agreed upon

  • criteria on what it means to be alive: the thing needs to be able to reproduce, grow,

  • respond to its environment, use energy, have some kind of organization to its body, and

  • maintain an internal balance called homeostasis. It doesn’t matter if were talking about

  • a skin cell or muscle cell or a single celled organism like an amoeba. To be considered

  • alive, you need to meet those qualifications for life. And even at this tiny cellular level,

  • we can see form influence function first hand. Again, take our skin exampleit has multiple

  • types of cells, but they all serve different purposes. Check this out. All those hairs

  • sticking out of your arms, eyebrows, or nose, are made by specialized cells called keratinocytes,

  • cells that crank out the keratin that forms hair. And your skin’s color comes from the

  • pigment melanin, made by other specialized cells called melanocytes. But the real stars

  • of the integumentary system are the layers of epithelial cells, a cell type that comes

  • together to form tough yet dynamic borders between what’s inside or outside of your

  • body. Those keratinocytes in your skin? Theyre a type of epithelial cell. But if you could

  • take a Q-tip and grab some cells from the lining of your stomach, those are also epithelial

  • cells. This is where we see form influence function againEpithelial cells typically

  • make up borders or walls, protecting us from different types of harm like radiation, chemicals,

  • or bacteria. And just like building a physical wall, multiple layers of material tend to

  • be stronger than a single layer. And when any type of cell, epithelial or not, groups

  • together like this to do a common job, they form the next unit on the hierarchy chart:

  • tissues. There are four main types of tissue: epithelial tissue like your skin, muscle tissue

  • in your heart and skeletal muscles, connective tissue like your ligaments, and nervous tissue

  • like, you guessed it, your nerves. Well go into specific types of tissues in later

  • episodes, but for now, start thinking about tissues as groups of cells. Now, clearly with

  • multiple types of cells we can get multiple types of tissuesAnd when different tissues

  • combine to do a common job, you get organs, the next step on the hierarchy. Youre familiar

  • with some of the big internal organs: liver, kidneys, intestines. But the skin, the example

  • weve been using, is itself an organ. Because it’s not just a protective layer.

  • Like those other organs, it has different tissues combining to do one jobThe epidermis

  • is the outermost layer, that physical wall we mentioned before. But underneath that is

  • the dermis, where youll find the tougher connective tissue to make your skin even stronger,

  • but also more specialized tissues like nerves, sweat glands, and hair follicles. Even deeper

  • than that youll find the hypodermis layer which stores a little bit of fat. So, even

  • though it looks pretty similar from your head to your toes, it features multiple tissue

  • types to function as a dynamic organ. And when organs work together with other organs,

  • they form organ systems, which are exactly what they sound like, functionally similar

  • organs that have a common job. Like how your integumentary system is so much more than

  • just skin. It’s also the glands, nerves, fat and muscles under the skin that you don’t

  • see. Working together, this is one of the systems that helps keep your body in a livable

  • temperature, protects your squishier internals from harm, and helps us interact with the

  • world via touch. Now, that means at some point our integumentary system needs to talk to

  • our nervous system to interpret all of those signals. But in reality, every system interacts

  • with every other system in your body to, you know, stay alive. Like our endocrine system,

  • or hormones, works closely with our reproductive systems, and our digestive system works closely

  • with our urinary system to get rid of wasteThat’s like the number one thing it doesEither

  • way, all of your organ systems get wrapped up into one, unique individual body, or organism,

  • the last unit on our hierarchy. At this point, were talking about bodies that can eat

  • tacos, and pet puppies, and binge watch the entire Lord of the Rings trilogy all at the

  • same time. Not that I have. Just saying you could. Thanks so much for watching this episode

  • of Seeker Human. Were going to be talking about a lot of cool stuff this series so make

  • sure to keep coming back to Seeker, well see you next time.

The human body is amazing, a symphony of bones, muscles, cells, organs, liquids and an incomprehensible

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人体は正確にはどのように組織化されているのでしょうか? (How Exactly Is the Human Body Organized?)

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    林宜悉 に公開 2021 年 01 月 14 日
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