Introduction to Anatomy & Physiology: Crash Course Anatomy & Physiology #1

Summary

This script invites viewers to marvel at the complexity of the human body, highlighting its intricate systems and functions. It introduces the disciplines of anatomy and physiology, explaining their roles in understanding the body's structure and function. The script delves into the history of anatomy, the concept of homeostasis, and the importance of precise anatomical language for medical communication. It concludes with a vivid example of how anatomical terms can be crucial in a medical scenario.

Takeaways

• 😃 The human body is a complex and magnificent system, with every movement and function being the result of various systems working together.
• 🌟 The body is a 'convoluted and prolific' organism, with fascinating facts such as the length of the intestines and the amount of saliva produced over a lifetime.
• 🧬 Anatomy and physiology are twin disciplines that study the structure and function of the body, respectively, and are essential for understanding how the body works.
• 🔍 The study of anatomy has a rich history, from the taboo of human dissection to the public events of the 17th and 18th centuries, and the Anatomy Act of 1832.
• 💡 The principle of 'complementarity of structure and function' is a central theme in anatomy and physiology, showing how the form of cells, organs, and organisms dictates their function.
• ⚗️ The body is made up of atoms, and understanding the chemistry at the atomic level is fundamental to grasping how the body functions.
• 🔬 Cells are the basic units of life, varying greatly in size and shape to serve different functions within the body.
• 🤝 Tissues are groups of similar cells that work together, and when combined with different types of tissues, they form organs that perform specific functions.
• 🔄 Organs collaborate to form organ systems, which work in concert to maintain the body's processes, such as digestion in the digestive system.
• 🌡 Homeostasis is the body's ability to maintain stable internal conditions, which is crucial for survival as imbalances can lead to life-threatening situations.
• 🗺️ Anatomical terms provide a precise language for describing the body's parts and their relationships, which is vital for medical communication and understanding.

Q & A

What is the main focus of the script provided?

The script focuses on the study of human anatomy and physiology, emphasizing the complexity and wonder of the human body, its systems, and the historical context of how we've come to understand it.

What are the two disciplines the script mentions for understanding the human body?

The two disciplines mentioned are anatomy, which is the study of the structure and relationships between body parts, and physiology, which is the science of how those parts function and work together to keep the body alive.

Why is the study of anatomy and physiology important?

The study of anatomy and physiology is important because it helps us understand why we are alive, how we came to be alive, how diseases harm us, and how our bodies recover from illness and injury. It provides insights into the big-picture processes of life such as death, sex, eating, sleeping, and thinking.

What is the historical significance of the Anatomy Act of 1832 in Britain?

The Anatomy Act of 1832 in Britain was significant because it provided a legal source of cadavers for medical students to dissect, ending the need for grave-robbing and making the study of anatomy more accessible and regulated.

What is the concept of 'complementarity of structure and function'?

The concept of 'complementarity of structure and function' refers to the idea that the function of a cell, organ, or organism is always a reflection of its form. In other words, the specific shape and structure of a biological component determine what it can do.

How does the script describe the process of learning anatomy and physiology?

The script describes the process as one that involves learning a lot of new terms from Latin and Greek, studying the relationships between body parts, and understanding how these parts work together. It also involves learning from the dissection of cadavers, which is a hands-on approach to understanding the human body's internal structure.

What is the term 'homeostasis' and why is it important for survival?

Homeostasis is the ability of living systems to maintain stable internal conditions regardless of changes occurring in the external environment. It is important for survival because it involves maintaining a balance of materials and energy, such as blood, water, nutrients, oxygen, body temperature, blood pressure, and waste removal, which are all critical for life.

How does the script illustrate the concept of 'anatomical position'?

The script illustrates the concept of 'anatomical position' by describing a person standing erect and facing straight ahead with arms at the sides and palms forward. This position is used as a reference for the standardized set of directional terms in anatomy.

What are the different types of body planes mentioned in the script?

The different types of body planes mentioned are the sagittal plane, which divides the body into left and right parts; the coronal or frontal plane, which divides the body into front and back parts; and the transverse or horizontal plane, which divides the body into top and bottom parts.

How does the script use the example of a toothpick to explain the importance of anatomical terms?

The script uses the example of a toothpick lodged in the esophagus to demonstrate how anatomical terms can provide precise locations within the body. By describing the toothpick's position relative to other body parts using anatomical language, it helps the surgeon know exactly where to look and operate.

What is the significance of the 'twin disciplines' of anatomy and physiology in understanding the living body?

The significance of the 'twin disciplines' is that they provide a comprehensive understanding of the human body. Anatomy provides the 'what' - the structure and relationships of body parts, while physiology provides the 'how' - the functions and processes that keep the body alive and operating.

Outlines

00:00

😃 The Wonders of Human Anatomy and Physiology

This paragraph introduces the viewer to the complexity and beauty of the human body, emphasizing the intricate systems that allow us to perform simple tasks without a second thought. It highlights the importance of understanding both anatomy, the study of body structures, and physiology, the study of how these structures function. The paragraph uses vivid examples, such as the length of the intestines and the amount of saliva produced in a lifetime, to illustrate the body's complexity. It also touches on the historical aspects of anatomy, including the taboo nature of human dissection and the evolution of the field from secretive practices to a regulated science.

05:05

🔍 The Hierarchical Organization of Life

This paragraph delves into the hierarchical organization of biological systems, starting from cells and moving up to tissues, organs, organ systems, and finally the complete organism. It explains the concept of homeostasis, the body's ability to maintain stable internal conditions despite external changes, and how this balance is crucial for survival. The paragraph also introduces the standardized language of anatomy, including various directional terms that help in precise communication about the body's parts, using the example of a swallowed toothpick to illustrate how these terms can guide medical procedures.

10:07

📚 Anatomy and Physiology: The Language of Life

The final paragraph wraps up the introductory lesson by summarizing the key points discussed in the video. It reiterates the roles of anatomy and physiology in understanding the body's structure and function, the principles of structure-function complementarity, the hierarchical organization of biological systems, and the concept of homeostasis. It also highlights the importance of the anatomical language introduced, using the toothpick example as a practical application of these terms. The paragraph concludes with credits and acknowledgments for the team behind the video, encouraging viewers to support the educational series.

Keywords

💡Anatomy

Anatomy is the study of the structure and relationships between body parts. It is a fundamental aspect of understanding the human body, as it deals with what the body is made of. In the video, anatomy is presented as the counterpart to physiology, focusing on the physical components of the body, such as organs and tissues, and their spatial relationships.

💡Physiology

Physiology is the science of how body parts come together to function and maintain life. It complements anatomy by explaining what the body does, such as the processes of digestion, respiration, and circulation. The video emphasizes the interplay between anatomy and physiology, highlighting how the structure of the body dictates its functions.

💡Homeostasis

Homeostasis refers to the ability of living systems to maintain stable internal conditions despite external changes. It is a central theme in the video, illustrating the body's constant efforts to balance materials and energy, such as body temperature, blood pressure, and nutrient levels. The video explains that the ultimate cause of death is often the loss of homeostasis, as seen in cases of organ failure or extreme environmental conditions.

💡Complementarity of Structure and Function

This concept states that the function of a biological entity, such as a cell or organ, is a direct reflection of its form or structure. The video uses this principle to explain how the specific shapes and arrangements of body parts enable them to perform their designated roles, such as the one-way flow of blood in the heart due to its valve structure.

💡Organ Systems

Organ systems are groups of organs that work together to perform complex functions. The video mentions the digestive system as an example, where the liver, stomach, and intestines collaborate to process food. Understanding organ systems is crucial for grasping how the body coordinates various functions to sustain life.

💡Cadaver

A cadaver is a dead body that has been preserved for study, typically used in anatomy to provide a hands-on learning experience. The video discusses the historical and modern use of cadavers in medical education, emphasizing the ethical practice of using donated bodies to advance scientific understanding of human anatomy.

💡Directional Terms

Directional terms are standardized anatomical terms used to describe the location and orientation of body parts in relation to one another. The video provides an overview of terms such as anterior, posterior, superior, inferior, medial, and lateral, which are essential for precise medical communication and understanding body orientation.

💡Tissues

Tissues are the result of similar cells grouping together to form functional units, such as muscle tissue, nervous tissue, or epithelial tissue. The video explains that tissues represent a level of organization between cells and organs, contributing to the complex hierarchy of the human body.

💡Cells

Cells are the smallest units of life and the basic building blocks of all living organisms. The video mentions that all cells share some common functions but can vary widely in size and shape depending on their specific roles, such as the small red blood cells compared to the large motor neurons.

💡Organs

Organs are structures formed by the combination of different tissue types, each with a specific function. The video uses the heart, liver, and lungs as examples of organs, which are essential components of organ systems that work together to sustain life.

💡Homeostasis Disturbance

Homeostasis disturbance refers to a situation where the body's internal balance is disrupted, leading to potential health risks or life-threatening conditions. The video uses the example of an untreated arterial wound causing a drop in blood pressure, which can lead to death due to the loss of oxygen delivery to cells.

Highlights

The human body's complexity and the interconnectedness of its systems are emphasized, highlighting the marvel of everyday movements and functions.

An introduction to the study of anatomy and physiology, explaining their focus on the structure and function of the body, respectively.

The historical evolution of anatomy, from taboo practices to regulated dissections and the Anatomy Act of 1832.

The importance of understanding the complementarity of structure and function in biological systems.

The hierarchical organization of the body, from atoms to cells, tissues, organs, organ systems, and the complete organism.

The concept of homeostasis and its critical role in maintaining life through the balance of materials and energy.

The ultimate cause of death being the extreme and irreversible loss of homeostasis, illustrated through various scenarios.

The necessity of precise anatomical language for accurate medical communication and diagnosis.

An explanation of standardized anatomical directional terms and their significance in medical descriptions.

The anatomical position and its relevance to understanding directional terms in the study of anatomy.

A detailed description of the planes used to section the body for study, including sagittal, parasagittal, coronal, and transverse planes.

The distinction between axial and appendicular parts of the body and their respective functions.

Directional terms such as anterior, posterior, superior, inferior, medial, and lateral, and their usage in anatomical descriptions.

A practical example of how anatomical language can be used to describe the location of a foreign object in the body for medical purposes.

The interdisciplinary nature of anatomy and physiology, incorporating knowledge from chemistry and physics.

The historical significance of figures like Galen and Da Vinci in the development of anatomical knowledge.

The ethical and legal evolution of using cadavers for educational purposes in anatomy and physiology.

Transcripts

I’d like you to take a second and really look at yourself.

I don’t mean take stock of your life, which really isn't any of my business, but I mean just

look at your body.

Hold up a hand and wiggle it around. Take a sip of water. Hold your breath. Sniff the air.

These things are so simple for most of us that we don’t give them a moment’s thought.

But each one of those things is, oh, SO much more complex than it feels.

Every movement you make, every new day that you live to see, is the result of a

collection of systems working together to function properly.

In short, you, my friend, are a magnificent beast.

You are more convoluted and prolific and polymorphously awesome than you probably even

dare to think.

For instance, did you know that, if they were all stretched out, your intestines would be about as long

as a three story building is tall?

Or that by the time you reach old age, you’ll have produced enough saliva to fill more than

one swimming pool?

Or that you lose about two-thirds of a kilogram every year in dead skin cells? And you will

lose more than 50 kilograms of them in your lifetime? Just tiny, dried-up pieces of you, drifting

around your house, and settling on your bookshelves, feeding entire colonies of dust mites.

You’re your own little world.

And I’m here to help you get to know the body that you call a home, through the twin

disciplines of anatomy - the study of the structure and relationships between body parts,

and physiology - the science of how those parts come together to function, and keep

that body alive.

Anatomy is all about what your body is, physiology is about what it does. And together, they

comprise the science of us.

It’s a complicated science - I’m not gonna lie to you - and it draws on a lot of other

disciplines, like chemistry and even physics. And you’ll have to absorb a lot of new terms

- lots of Latin, gobs of Greek.

But this course isn't just gonna be an inventory of your

individual parts, or a diagram of how a slice of pizza gives you energy.

Because these disciplines are really about why you’re alive right now, how you came

to be alive, how disease harms you, and how your body recovers from illness and injury.

It's about the big-picture things that we either spend most of our time thinking about,

or trying not to think about: death, and sex, and eating, and sleeping, and even the act

of thinking itself.

They’re all processes that we can understand through anatomy and physiology.

If you pay attention, and if I do my job well enough, you’ll come out of this course with

a richer, more complete understanding not only of how your body works, to produce everything

from a handshake to a heart attacks, but I think you’ll also start to see that you

really are more than just the sum of your parts.

We have come to understand the living body by studying a lot of dead ones.

And for a long time, we did this mostly in secret.

For centuries, the dissection of human bodies was very taboo in many societies. And as a

result, the study of anatomy has followed a long, slow, and often creepy road.

The 2nd century Greek physician Galen gleaned what he could about the human form by performing

vivisections on pigs.

Da Vinci poked around dead bodies while sketching his beautifully detailed anatomical drawings,

until the pope made him stop.

It wasn’t until the 17th and 18th centuries that certified anatomists were allowed to

perform tightly regulated human dissections -- and they were so popular that they were

often public events, with admission fees, attended by the likes of Michelangelo and Rembrandt

The study of human anatomy became such a craze in Europe that grave-robbing became a lucrative,

if not legal, occupation … until 1832, when Britain passed the Anatomy Act, which provided

students with plentiful corpses, in the form of executed murderers.

Today, students of anatomy and physiology still use educational cadavers to learn, in

person and hands-on, what’s inside a human body by dissecting them.

And it’s totally legal. The cadavers are volunteers -- which is what people mean when

they say they’re “donating their body to science.”

So what have all of these dead bodies shown us?

Well, one big idea we see over and over is that the function of a cell or an organ or

a whole organism always reflects its form.

Blood flows in one direction through your heart simply because its valves prevent it

from flowing backward

In the same way, your your bones are strong and hard and this allows them to protect and

support all your soft parts.

The basic idea -- that what a structure can do depends on its specific form -- is called

the complementarity of structure and function.

And it holds true through every level of your body’s organization, from cell to tissue

to system.

And it begins with the smallest of the small: atoms.

Just like the chair you’re sitting on, you are just a conglomeration of atoms -- about 7

octillion of them, to be precise.

Fortunately for both of us here, we've covered the basics of chemistry that every incoming

physiology student needs to know, in Crash Course Chemistry. So I’ll be referring

you there throughout the course, when it comes to how things work at the atomic level.

But the next level up from the chemistry of atoms and molecules includes the smallest

units of living things -- cells.

All cells have some basic functions in common, but they also vary widely in size and shape,

depending on their purpose.

For example! One of the smallest cells in your body is the red blood cell, which measures

about 5 micrometers across. Now contrast that with the single motor neuron that runs the

length of your entire leg, from your big toe to the bottom of your spine, about a meter

from end to end. Typically, cells group with similar cells

to form the next level of organization: tissues, like muscles, membranes and cavity linings,

nervous, and connective tissues. When two or more tissue types combine, they

form organs -- the heart, liver, lungs, skin and etcetera that perform specific functions

to keep the body running.

Organs work together and combine to get things done, forming organ systems. It’s how, like,

the liver, stomach, and intestines of your digestive system all unite to take that burrito

from plate to pooper.

And finally, all those previous levels combine to form the highest level of organization

-- the body itself.

Me and you and your dog -- we’re all glorious complete organisms, made from the precise

organization of trillions of cells in nearly constant activity.

This ability of all living systems to maintain stable, internal conditions no matter what

changes are occurring outside the body is called homeostasis, and it’s another major

unifying theme in anatomy and physiology.

Your survival is all about maintaining balance -- of both materials and energy.

For example, you need the right amount of blood, water, nutrients, and oxygen to create

and disperse energy, as well as the perfect body temperature, the right blood pressure,

and efficient movement of waste through your body, all that needs to stay balanced.

And by your survival depending on it? I mean that everyone’s ultimate cause of death

is the extreme and irreversible loss of homeostasis.

Organ failure, hypothermia, suffocation, starvation, dehydration -- they all lead to the same end,

by throwing off your internal balances that allow your body to keep processing energy.

Take an extreme and sudden case -- your arm pops off. If nothing is done quickly to treat

such a severe wound, you would bleed to death, right?

But … what does that really mean? What's gonna happen? How do I die?

Well, that arterial wound, if left untreated, will cause a drastic drop in blood pressure

that, in turn, will prevent the delivery of oxygen throughout the body.

So the real result of such an injury -- the actual cause of death -- is the loss of homeostasis.

I mean, you can live a full and healthy life without an arm. But you can’t live without

blood pressure, because without blood, your cells don’t get oxygen, and without oxygen,

they can’t process energy, and you die.

With so many connected parts needed to make your life possible, you can see how we need

a hyper-precise language to identify the parts of your body and communicate what’s happening to them

A doctor isn't gonna recommend a patient for surgery by telling the surgeon that the patient

has an “achey belly.”

They’re going to need to give a detailed description -- essentially, it's like a verbal map

So, over time, anatomy has developed its own standardized set of directional terms that

described where one body part is in relation to another.

Imagine a person standing in front of you -- this is what’s called the classic anatomical

position -- where the body is erect and facing straight ahead, with arms at the sides and

palms forward.

Now imagine slicing that person into different sections, or planes. Don't imagine it too

graphically though.

The sagittal plane comes down vertically and divides a body or organ in left and right

parts.

If you imagine a plane parallel to the sagittal plane, but off to one side, that plane is

the parasagittal.

The coronal, or frontal plane splits everything vertically into front and back.

And the transverse, or horizontal plane divides the body top and bottom.

Look at that body again and you’ll notice more divisions, like the difference between

the axial and appendicular parts.

Everything in line with the center of the body -- the head, neck, and trunk -- are considered

axial parts, while the arms and legs -- or appendages-- are the appendicular parts that

attach to the body’s axis.

Everything at the front of your body is considered anterior, or ventral, and everything in the back

is posterior, or dorsal.

So your eyes are anterior, and your butt is posterior, but you’d also say that your breastbone

is anterior to, or in front of, the spine, and that the heart is posterior to, or behind

the breastbone.

Features toward the top of your body, like your head, are considered superior, or cranial,

while structures that are lower down are inferior, or caudal.

So the jaw is superior to the lungs because it’s above them, while the pelvis is inferior

to the stomach because it’s below it.

And, there's more: if you imagine that center line running down the axis of a body, structures

toward that midline are called medial, while those farther away from the midline are lateral.

So the arms are lateral to the heart, and the heart is medial to the arms.

Looking at the limbs -- your appendicular parts of your body -- you’d call the areas

closer to the center of the trunk proximal, and those farther away distal.

In anatomy-talk, your knee is proximal to your ankle because it’s closer to the axial

line, while a wrist is distal to the elbow because it’s farther from the center.

Okay, so pop quiz!

I’m eating a club sandwich -- I'm not, I wish I was, but imagine I am. I’m so ravenous

and distracted that I forget to take out that little frilly toothpick at the top, and I

end up swallowing it with a raft of turkey, bacon, and toast.

A fragment of the toothpick gets lodged somewhere in here, and my doctor takes an x-ray, and

says I need surgery.

Using anatomical language, how would she direct the surgeon to that tiny wooden stake inside of me?

She might describe it as being “along the medial line, posterior to the heart, but anterior

to the vertebrae, inferior to the collarbone, but superior to the stomach.”

That would give the surgeon a pretty good idea of where to look -- in the esophagus,

just above to the stomach! I warned you at the beginning: Lots of terms!

But all those terms might have just saved my life. And it’s the end of your first

lesson, and you’ve already started to talk the talk.

Today you learned that anatomy studies the structure of body parts, while physiology

describes how those parts come together to function. We also talked about some of these

disciplines’ central principles, including the complementarity of structure and function,

the hierarchy of organization, and how the balance of materials and energy known as homeostasis

is really what keeps you alive. And then we wrapped it all up with a primer on directional

terms, all held together with a toothpick.

Thank you for watching, especially to our Subbable subscribers, who make Crash Course available

not just to themselves, but also everyone else in the world. To find out how you can

become a supporter, just go to subbable.com.

This episode was written by Kathleen Yale, edited by Blake de Pastino, and our consultant,

is Dr. Brandon Jackson. Our director and editor is Nicholas Jenkins, the script supervisor

is Valerie Barr, the sound designer is Michael Aranda, and the graphics team is Thought Café.