Welcome to the Visible Body Blog!

Anatomy and Physiology: Parts of a Human Cell

Posted by Courtney Smith on Thu, Sep 04, 2014 @ 09:53 AM

I remember being in Mr. Farnsworth’s 7th grade science class when we first really began learning about cells. His room looked like the typical high school lab—high, hard tables with Bunsen burners and gas jets that no one was allowed to touch, and a cabinet full of dead things suspended in fluid in jars. My favorite thing about the room was the giant poster of the Triangulum Galaxy (I was, am, and always will be irrevocably fascinated by outer space) on the wall behind his desk. 

But my second favorite thing was the poster depicting the inside of a cell. It hung on the far right wall, next to the chalkboard. While the image of Triangulum was exponentially smaller than the actual galaxy so we could see it in its entirety, the image of the cell was exponentially larger for the same reason. The cell was its own world—but instead of stars, gases, and dark matter, there was mitochondria, a nucleus, and cytoplasm. What that said to me was that, when you got right down to it, there wasn’t a whole lot of difference between a cell and a galaxy.

My 7th grade mind = blown.

Cells are amazing, little things, and I do mean little—cells are tiny. Under the right conditions, you might be able to see an amoeba proteus or a paramecium. To get a better sense of cell size, the Genetic Science Learning Center of the University of Utah has a fun, interactive scale. Prepare to be amazed.

There are two types of cells: prokaryotes and eukaryotes. Eukaryotes contain a nucleus and prokaryotes do not. You, dear reader, are a eukaryotic being. You are made up of trillions of eukaryotic cells, of which there are over 200 different types. Each eukaryotic cell type specializes to perform certain functions. Bone cells, for example, form and regenerate bones. Ever fracture a bone? Within days, cells called fibroblasts begin to lay down bone matrix.

Cells can be divided into four groups: somatic, gamete, germ, and stem. Somatic cells are all the cells in the body that aren’t sex cells, like blood cells, neurons, and osteocytes. Gametes are sex cells that join together during sexual reproduction. Germ cells produce gametes. Stem cells (you may be very familiar with this term because it’s always making headlines) are like blank-slate cells that can differentiate into specialized cells and replicate.

The genetic information within each cell acts as a sort of instruction manual, telling a cell how to function and replicate.

Why don’t we take a look at the inside of a typical cell?

 

Typical Eukaryotic Cell

Eukaryotic cell plasma membrane cytoplasm organelles

The plasma membrane is exactly what it sounds like: a membrane made of plasma. Membranes are structures that separate things; in this case, the plasma membrane of a cell separates its interior from the environment around the cell. It’s not impenetrable, however, as it will selectively let certain molecules enter and exit.

Organelles are the structures within the plasma membrane. Each organelle has a specialized function. They’re called organelles because they act as a cell’s organs.

Intracellular fluid, or cytosol, is the liquid found inside a cell. While most of its makeup is water, the rest isn’t very well understood. Once thought to be a simple solution of molecules, it’s organized on a multitude of levels.

Eukaryotic cell nucleus nucleolus plasma membrane cytosol

The nucleus is a large organelle that contains the cell’s genetic information. Most cells have only one nucleus, but some have more than one, and others—like mature red blood cells—don’t have one at all. Within the nucleus is a spherical body known as the nucleolus, which contains clusters of protein, DNA, and RNA. The genetic information of the cell is encoded in the DNA. The nucleus serves to contain the DNA and transcribe RNA, which exits via pores in the nuclear membrane.

 

Presenting: The Organelles

While all the parts of a cell are important, here are some of the most recognizable.

 

Endoplasmic Reticulum

Besides being very fun to say, endoplasmic reticulum (ER) is a network of membrane-enclosed sacs in a cell that package and transport materials for cellular growth and other functions. There are two types of ER: smooth and rough.

Eukaryotic cell rough endoplasmic reticulum smooth golgi complex apparatus

 

Golgi Complex/Apparatus

Like the ER, the Golgi complex (or apparatus) is an organelle that packages proteins and lipids into vesicles to be transported.

Eukaryotic cell golgi complex apparatus endoplasmic

 

Mitochondria

“A human being is a whole world to a mitochondrion, just the way our planet is to us. But we’re much more dependent on our mitochondria than the earth is on us. The earth could get along perfectly well without people, but if anything happened to our mitochondria, we’d die.” —A Wind in the Door by Madeleine L’Engle (1973)

Eukaryotic cell mitochondria atp power plant energy

While Ms. L’Engle’s concept of mitochondria was more fiction than science (as far as I know, mitochondria don’t talk!), it opened my ten-year-old eyes to the wonders of our bodies. Before Mr. Farnsworth’s cell poster, there was the Time Trilogy.

Mitochondria can number anywhere in the hundreds to the thousands, depending on the cell. They are known as the “power plant” of the cell, providing the main source of energy. Through aerobic respiration, mitochondria generate most of the cell’s adenosine triphosphate (ATP). Active cells in the muscles, liver, and kidneys have a large number of mitochondria to support high metabolic demands.

 

Ribosomes

Eukaryotic cell ribosomes lysosomes organelles golgi complex

Either floating freely in the cytosol, bound to the ER, or located at the outer surface of the nuclear membrane, ribosomes are plentiful within a cell. Ribosomes contain more than 50 proteins and a high content of ribosomal RNA. Their primary function is to synthesize proteins, which are then used by organelles within the cell, by the plasma membrane, or even by structures outside the cell.

 

Lysosomes

Eukaryotic cell lysosomes ribosomes organelles nucleus

These little guys are like the garbage disposals of a cell. Lysosomes contain acid hydrolase enzymes, which break down and digest macromolecules, old cell parts, and microorganisms. They originate by budding off of the Golgi complex.

 

There are more structures and functions within a cell (like, a lot more) than are listed here, but that’s a post for another day!

 

Want to learn more?

All the images and most of the content in this post was taken from Anatomy & Physiology, available for iPad, Android tablet, PC, Mac, and Windows Touch.

Want to go further? Download any of our free A&P eBooks, available now at the A&P eBook Library! Click below.

 



Related posts

- Anatomy and Physiology: Medical Suffixes
- Anatomy and Physiology: Anatomical Position and Directional Terms
- Anatomy and Physiology: Five Cool Facts about the Middle and Inner Ear

Topics: anatomy and physiology, cells

Anatomy and Physiology Vocab: Medical Suffixes

Posted by Courtney Smith on Tue, Feb 18, 2014 @ 10:55 AM

While anatomy & physiology courses tend to be all about biology, anatomy, and other body-related science, there's a smidgen of them dedicated to language. The words used in the medical world all have their specific meanings, and even broken down into their most basic components they still have meaning.

Suffixes are pretty amazing. They have the power to change the meaning of one word into something else entirely.

Dermatology suffix medical ap vocab 1

Bam. A whole new word, just by adding a little bit at the end. Like I said: amazing.

There are quite a few suffixes in the medical world and it can be a task to remember them all. To help you, I've got some of the most common ones right here!

 

Suffix

Meaning

-algia

Pain

-cyte

Cell

-ectomy

Removal

-itis

Inflammation

-oma

Tumor; mass

-opsy

To view

-gram

A record

 

Now that you've got the suffixes and their meanings down, let's put them to good use. Here are some common medical terms that use the preceding suffixes, in context:

- Fibromyalgia is a common ailment in which one suffers chronic, widespread pain.

- The most common surgery performed in the United States is appendectomy, or the removal of the appendix.

Appendix appendectomy colon large intestine digestive ap vocab

- Bronchitis is the inflammation of the mucous membranes of the bronchi.

- To determine certain diseases, a biopsy may be performed, in which tissue is removed for analysis.

- A mammogram is the image(s) obtained by mammography, in which breast tissue is scanned for the possible presence of cancer.


Download the A&P Vocab: Suffixes eBook!

Want more suffixes and context examples? Download our free A&P Vocab: Suffixes eBook! You'll get 25 examples and stunning images from our best-selling Anatomy & Physiology app!

 

 


Related posts

- Anatomy and Physiology: Anatomical Position and Directional Terms
- Anatomy and Physiology: Five Cool Facts about the Middle and Inner Ear
- Anatomy and Physiology: Seven Coolest Medical Stories of 2013

Topics: anatomy and physiology

Anatomy and Physiology: Measuring the Human Heart

Posted by Courtney Smith on Mon, Jan 27, 2014 @ 10:46 AM

When your heart pounds, do you think of how hard your ventricles are contracting to push blood in and out of the heart? Do you think of the astonishing pressure your veins and arteries withstand when you are out of breath and your adrenaline is pumping? Probably not. I know I certainly don't. If my body's flooded with adrenaline and my heart is pounding, I'm either exercising or being chased by a lion; in either case, my mind is going to be focused on not dying rather than how hard my heart is working.

But since we have a golden opportunity here, let's focus on the heart. Enough about hypothetical lions and even more hypothetical exercising.

If you have Anatomy & Function, go to Browse Common Topics and choose Cardiac Output. Follow along!

What is a heartbeat?

It goes far beyond “that sound in your chest.” Systole and diastole are the normal, rhythmic contractions of the ventricles as they pump blood in and out of the heart. The actual beating sound is usually described as lub DUB. The lub occurs when the mitral and tricuspid valves close and push blood out of the heart via the semilunar valves (systole), and the DUB occurs when the semilunar valves close and blood fills the ventricles (diastole).
 

Heart Valves Semilunar Mitral tricuspid aortic pulmonary


The average number of heart beats per minute is 72.

 

What is blood pressure?

As blood moves through your body, it puts pressure on the walls of your veins and arteries, much the way soda does when sucked through a straw. Blood pressure is the amount of force put on your blood vessels, caused by the flow generated by the heart as it pumps and any resistance that blood encounters as it moves through the vessels.
 

Artery Capillary Vein Blood Pressure


The heart beats faster during times of stress, exercise, or, in my case, when I see pictures of Richard Armitage, resulting in blood being pumped in and out of the heart and through the vessels at an increased rate. In this state, your blood pressure is high.
 

Blood Pressure Arteries Veins Blood Vessels

Blood pressure in a resting state is usually around 120 (systolic) over 70 (diastolic).

 

So, let's recap: Blood is pumped in and out of the heart and through the arteries and veins, the force exerted by the blood on the vessel walls is called blood pressure, and Richard Armitage makes my ticker go lub DUB, lub DUB, shalamalama ding dong.

Excellent. Moving on.

 

Measuring Cardiac Output

Now, the average amount of blood pumped per heartbeat is 70 mL. This is called stroke volume.

Cardiac output, on the other hand, is the volume of blood that each ventricle pumps out every minute. How much blood is that? Well, let's find out!

To find cardiac output, we'll first need to determine how many times your heart beats per minute. To do this, place your hand over your heart and count the beats for exactly one minute. Ready? Go.
 

Cardiac Output Heart Blood Volume


Okay, at the end of a minute, my heart beat 74 times. I will take that and multiply it by the stroke volume, which is 70 mL.

My cardiac output is 5180 mL/minute, or 5.18 L. How about you? What did you get? For fun, do 30 jumping jacks and then measure your cardiac output. How much of a difference do you see between your resting state result and your jumping jacks result?

 

Learn More

Want to learn more about the various ways to learn and understand human anatomy? Then check out Anatomy & Physiology by Visible Body. It will change the way you learn A&P forever!


 

Related posts

- Anatomy and Physiology: Anatomical Position and Directional Terms
- Anatomy and Physiology: Five Cool Facts about the Middle and Inner Ear
- Anatomy and Physiology: Seven Coolest Medical Stories of 2013

Topics: anatomy and physiology

Year in Review: 7 Coolest Medical Stories of 2013

Posted by Courtney Smith on Tue, Dec 24, 2013 @ 10:44 AM

2013 was a pretty amazing time for the medical world. New technologies emerged, 3D printing became all the rage, a new ligament was “discovered,” the fountain of youth was discovered (not really, but keep reading), and plenty more! 

To cap off this year, we want to take a look at seven of 2013’s most interesting health and medical stories.

 

1. A robot assisted with a coronary stenting procedure for the first time.

Robotic assist coronary bypass stents

Why robots, you ask? Well, think of the control. I don’t know about you, but I can’t draw a straight line let alone stick a catheter in someone’s heart. The cardiology team at University of California at San Diego’s Sulpizio Cardiovascular Center, led by Dr. Ehtisham Mahmud, FACC, obviously felt the same way, and completed not one but two robotically assisted angioplasty and stenting procedures.

Let the SkyNet jokes commence.

 

2. 3D printing entire organs will be all the rage within the decade.

3D printing heart

While 3D printing has been around for about 30 years, a highly successful kick-starter campaign in 2012 made it available to the public for pretty much the first time, and ever since 3D printing has taken the world by storm.

In November, a team of bioengineers announced that within a decade they will be able to 3D print a human heart from not the relatively easy-to-come-by plastic that is used for commercial 3D printing, but from the recipients’ own cells.

Stuart K. Williams, executive and scientific director at Louisiana’s Cardiovascular Innovation Institute, had only this to say: “I said a full decade to provide some wiggle room.”



3. A man’s hand was grafted to his foot.

Blood arteries veins hand ankle surgically attached

I think that’s the greatest thing I’ve written all year.

Without a blood supply, organs, limbs, and muscles die. If you’ve ever stuck your hand into a snow blower to try and clear a blockage and ended up with a few less fingers than with what you started, you know that time is of the essence when it comes to reattaching limbs.

Normally, severed limbs are put on ice to slow down necrosis. To save a man’s hand that had been severed in an automobile accident, some fast-thinking doctors surgically attached its arteries to those in his ankle, which prevented the limb from dying and significantly increased the chance for it to regain normal function once it was reattached to his wrist. 



4. Artificial blood is finally going to become a thing.

Systemic circulation arteries veins artificial blood

How many times have you heard about the incredible demand for blood and thought, “Why aren’t scientists making blood?” If you haven’t thought this about blood, you’ve probably thought it about oil.

A team at Babes-Bolyai University in Romania have concocted an artificial blood recipe that has been having some very encouraging results. The artificial blood’s main ingredient is a protein called hemerythrin that is used for oxygen storage and transfer.

So far, the artificial blood (which really needs a cool name) has only been used in mice trials, but the results are pretty spectacular: no inflammation or rejection. The mice have “remained indifferent,” according to team leader Professor Radu Silaghi-Dumitrescu.



5. Talking to some patients in comas or vegetative states isn’t just a movie cliché.

Brain neuro coma vegetative listening

You’ve seen it in movies before: in a touching and vulnerable scene, the main character talks to a comatose character, who then wakes up two scenes later having heard him or her. As impossible as that may seem, it’s not too far from reality.

Scientists at the Medical Research Council Cognition and Brain Sciences Unit (MRC CBSU) and the University of Cambridge studied 21 patients in vegetative or minimally conscious states. The patients heard a series of words and were told to parse out a particular word; one patient was able to successfully filter out the erroneous words and focus on the prompted word, while others weren’t able to hone in on that word but focused on other novel words. Bottom line: some minimally conscious patients are paying attention.

“Not only did we find the patients had the ability to pay attention, we also found independent evidence of their ability to follow commands,” said Dr. Srivas Chennu at the University of Cambridge.



6. The fountain of youth is less of a fountain and more of a metabolic coenzyme.

Mitochondria aging process reversed NAD

In December, the beauty industry quaked in fear at the announcement that American and Australian scientists reversed the aging process with the application of a compound called NAD+ (nicotinamide adenine dinucleotide).

Applied to aging mice, NAD+ affects the aging process at the mitochondrial level. It had been the hope of the scientists to slow the process of aging, but they were shocked to discover that NAD+ didn’t slow it down—it reversed it. The mice, which had been experiencing a slew of age-related ailments, experienced an increase in muscle tone and energy.

Human trials of NAD+ are slated to begin in 2014.

 

7. The verdict is in: antibacterial soaps and sanitizers aren’t any better than regular soap.

Antibacterial soap sanitizer FDA

I actually didn’t find this one too shocking. All I had to do was watch my YiaYia wash her hands with her gross-smelling glycerin soap to know that one wasn’t any better than the other. She’s been using that stuff for years, while my mother’s been an advocate of antibacterial soap for a while, and neither of them have experienced anything better than the other. At least the dumb glycerin soap isn’t going to contribute to the creation of some giant, antibacterial-resistant superbug.

The FDA announced that antibacterial products, most of which claim to remove 99.9% of germs, need to put their money where their mouth is. As studies have shown that antibacterial products don’t reduce germs any better than regular soap, these companies need to supply evidence to the contrary or change their labels and claims to keep their products on the market.

Maybe we won’t perish at the metaphorical hands of a superbug after all!



Thanks for an amazing year! See you in 2014! 

Topics: anatomy and physiology, 2013

Five Cool Facts about the Middle and Inner Ear

Posted by Courtney Smith on Mon, Nov 04, 2013 @ 03:41 PM

Do you hear what I hear? It’s the sound of some awesome anatomy truthiness coming atcha! The middle and inner ear are kind of overlooked in the cool anatomical structures department, so I decided to honor some of the awesome things inside that head of yours.

1. The smallest bone in the body resides in the middle ear.

Stapes middle ear auditory ossicles inner ear cochlea

The stapes, also known as the stirrup, is one of the auditory ossicles, consisting of a head, neck, two crura, and base. It looks sort of like a wishbone, or, well, a stirrup! Sound waves strike the eardrum and the vibrations travel into the middle ear. When these vibrations reach the stapes, it pushes the membrane of the oval window, building pressure waves in the cochlea, and this begins a process that generates nerve impulses.

 

2. The smallest muscle in the body is also in the middle ear.

Stapedius muscle middle ear stapes inner ear cochlea

The stapedius muscle attaches to the stapes. It stabilizes the bone and dampens large vibrations to protect the oval window from loud noises.

 

3. The ear is not just for detecting sound.

vestibule semicircular canals ear inner ear bony labyrinth

The semicircular canals of the vestibule of the inner ear are responsible for balance. They provide sensory input for equilibrium by detecting acceleration or deceleration. Each canal ends in an ampulla; these ampullae contain fluid that moves when the head does. The movement of the fluid causes hair cells to bend, which generates nerve impulses.

 

4. The ear drum actually looks like a drum.

Tympanic membrane ear drum external auditory 

The ear drum is a thin, oval-shaped membrane that separates the external auditory canal from the middle ear. Sound waves strike the ear drum, creating vibrations that travel to the auditory ossicles.

 

5. You have a pressure equalizer in your head.

Eustachian tube auditory canal inner ear

Do your ears sometimes “pop” when you yawn? This is actually the Eustachian tube opening, stabilizing pressure in the middle ear with outside air pressure. The Eustachian tube is a channel that links the cavity of the middle ear with the nasopharynx
 

Want to learn more?

Additional References:

1. Anatomy & Physiology by Visible Body (iPadPCMacWindows tablet and Android.)
2. Information on diseases and conditions of the middle ear: http://www.nidcd.nih.gov/health/hearing/Pages/Default.aspx
3. Video that overviews the hearing process: http://www.argosymedical.com/Other/samples/animations/Process%20of%20Hearing/index.html

Topics: anatomy and physiology

Anatomy and Physiology: Anatomical Planes and Cavities

Posted by Courtney Smith on Thu, Oct 17, 2013 @ 12:21 PM

And here we are with part two of our rundown on the things you need to learn before you dive into the meaty stuff of A&P, specifically how to talk about the body. In our previous post, we discussed anatomical position and directional terms. In this post, we’re going to take a look at planes and cavities.

Planes: Because who said anatomy didn’t require an imagination?

No, not the kind that fly you over oceans and have helpful people in uniforms that ply you with bags of stale peanuts. The other kind! The art kind, or in more technical terms the area of a two-dimensional surface. When used in conjunction with anatomy, planes are used to divide the body and its parts, which allows you to describe the views from which you study the body. If you look at your A&P textbook, you’ll most likely notice that a good number of the pictures and diagrams make use of planes.

Here is a list of commonly used planes:

Frontal (Coronal) plane

Divides the body into anterior (front) and posterior (back) portions

Transverse plane

Divides the body into superior (upper) and inferior (lower) portions

Sagittal plane

Vertical plane that divides the body into right and left sides.

Midsagittal plane

Divides the body at midline into equal right and left sides.

Oblique plane

Divides the body at an angle.

Of course, in reality, the planes used are completely imaginary, but they are a helpful visual in terms of describing a view.

Frontal Plane Coronal Sagittal midline

Using a frontal plane to bisect the body lengthwise, we’re able to describe certain areas that would not be easily visible or accessible if we used another plane.

Transverse plane coronal frontal sagittal oblique

The transverse plane bisects the brain horizontally, allowing for a superior view.

 

Cavities: Because things need to be kept somewhere.

A concept easier to grasp than planes and directional is body cavities, as they are a physical thing. When you hear the word “cavity,” no doubt you think of the kind in your teeth that are caused by plaque. A cavity, in any capacity, is a hollow place. In your teeth, it’s a hollow bit in the hard body. In the body itself, it is a hollow place usually filled with organs, nerves, vessels, and muscles.

Here are the body’s cavities:

Cranial cavity

Formed by the cranial bones and holds the brain

Vertebral canal

Formed by the vertebrae and contains the spinal cord

Thoracic cavity

Formed by the thoracic cage, muscles of the chest, sternum, and the thoracic vertebrae; contains the pleural, pericardial, and mediastinum cavities

-          Pleural cavity

Fluid-filled spaces that surround both lungs

-          Pericardial cavity

Fluid-filled space that surrounds the heart; the serous membrane of the pericardial cavity is the pericardium

-          Mediastinum

Central portion of the thoracic cavity; contains the heart, thymus, trachea, several major blood vessels, and esophagus

Abdominal cavity

Contains liver, stomach, spleen, small intestine, and most of the large intestine; the serous membrane of the abdominal cavity is the peritoneum

Pelvic cavity

Contains bladder, some of the large intestine, and reproductive organs (internal)

 

Cranial cavity body anatomy physiology

Thoracic cavity body anatomy physiology

Abdominal cavity body anatomy physiology

Pelvic cavity body anatomy physiology

 

Want to learn more?

 

 

Related posts

- Anatomy and Physiology: Anatomical Position and Directional Terms
- Anatomy and Physiology: The Pharynx and Epiglottis
- Anatomy and Physiology: Homologues of Reproductive Anatomy

Topics: anatomy and physiology

Anatomy and Physiology: Anatomical Position and Directional Terms

Posted by Courtney Smith on Fri, Oct 04, 2013 @ 02:23 PM

For those of you who have taken an A&P course (or are taking one right now), you know that before you get to learning about the body you need to learn how to talk about the body.

Most A&P courses begin with positions and directionals. I’m going to give you the rundown. Stay tuned for part two, featuring planes and cavities!
 

Position Is Everything: Anatomical Position

How many of you have used our apps or at least seen the models and thought, “Boy, that body looks awfully stiff in that one position all the time”?

Which, okay, is true. But there’s a reason our 3D body models (I affectionately call them Brenda and Paul) look stiff as a board—it’s the position in which we study the body.

Anatomical position is the description of any region or part of the body in a specific stance. In the anatomical position, the body is upright, directly facing the observer, feet flat and directed forward. The upper limbs are at the body’s sides with the palms facing forward.

Like so:

Anatomical position

You’ve probably seen all sorts of pictures of the body in your A&P textbooks that look like this. In my college A&P text, right there in the first few pages, every body system was shown in anatomical position. This stance should be very familiar to you. If not, it will be by the time you’re through your first two weeks of A&P.

If the anatomical position is placed face-down, it is in the prone position.

Anatomical position direction prone

If the anatomical position is placed face-up, it is in the supine position.

Anatomical position direction supine

 

Up, Down, Side-to-Side: Directional Terms

Imagine that when you’re studying a (correctly anatomically positioned) body you’re looking at a map. Like you use the cardinal directions to explain the location of certain regions (north, northwest, southeast, etc.), you use directional terms to describe the regions of the body.

Here are some commonly used directional terms:

Anterior

At or near the front of the body (front view)

Posterior

At or near the back of the body (back view)

Midline

An imaginary vertical line that divides the body equally (right down the middle)

Lateral

Farther from midline (side view)

Medial

Nearer to midline (side view)

Superior

Toward the head/upper part of a structure (bird’s-eye view, looking down)

Inferior

Away from the head/lower part of a structure (bottom view, looking up)

Superficial

Close to the surface of the body

Deep

Away from the surface of the body

Proximal

Nearer to the origination of a structure

Distal

Farther from the origination of a structure

In many instances, these terms can be paired. For example, a posterosuperior view combines the posterior and superior, giving us a view in which we are looking down at the back of the body, like so:

Anatomical position direction posterosuperior anatomy physiology

With me so far? No? Okay, let’s do a practice one. Don’t be afraid to refer to the chart before you answer.

Anterosuperior view anatomical position

If you answered B) anterosuperior, you’re right! Remember, the anterior is the front view and the superior is the top view—combine the two and you’ve got yourself a bird’s-eye view of the front of the body.

 

And there you have it: a crash course in anatomical position and directional terms. Stay tuned for part two on planes and cavities!

 

WANT TO LEARN MORE?

 

 

 

Related posts

- Anatomy and Physiology: 5 Things about the Integumentary System
- Anatomy and Physiology: The Pharynx and Epiglottis
- Anatomy and Physiology: Homologues of Reproductive Anatomy

Topics: anatomy and physiology

Anatomy and Physiology: Five Things About The Integumentary System

Posted by Courtney Smith on Wed, Sep 04, 2013 @ 03:18 PM

For all we talk about taking care of our organs, we always seem to leave out one of the most important and obvious. The integumentary system—which is comprised of your hair, nails, and skin—protects everything inside you, acting as a barrier to keep your bones, organs, and muscles safe and sound. It’s one of the many things about our anatomy we take for granted.

The integumentary system is a pretty amazing structure. So amazing, in fact, that it deserves its own post. Let’s take a look at it.


Integumentary skin

 

1. The integumentary system is one big, busy organ

That’s right! The integumentary system is the body’s largest organ, absorbing nutrients (from the sun and other sources), regulating internal body temperature (which is why you’re miserable on hot days, but not as miserable as you could be), and eliminating waste (sweat, anyone?).

It also has a very high cell turnover rate—in one year, you’ll shed over 8 pounds of dead skin! In fact, what you see on your body is dead skin waiting to be sloughed off while everything else is beneath the surface.

 

 

2. The skin is made up of several different types of cells

Each type of cell contributes to the skin in different ways. The epidermis, the outermost layer of skin, is made up of melanocytes, keratinocytes, Merkel cells, and Langerhans cells. At least two of those should look vaguely familiar to you.

Melanin is pigment, which absorbs ultraviolet rays and determines skin color. The more melanin you have, the darker your skin is.

Keratin is a fibrous protein that protects skin and tissue, and it also is the key structural material in hair and nails.

 

 

3. Your skin is divided into layers

Integumentary epidermis dermis hypodermis skin keratinocytes melanocytes

You know this one, though. But did you know that the skin is categorized by three layers, which are then broken down into sublayers?

The three main layers of the integumentary system are the epidermis (outermost layer), dermis (middle layer), and hypodermis (innermost layer).

We’ve gone over the epidermis already, but what about the other two layers? The dermis is a thick layer composed mainly of connective tissue rich in collagen and elastin. The dermis stores water, regulates body temperature and the production of vitamin D, cushions the body, and supplies blood to the epidermis.

The hypodermis is the subcutaneous layer and is composed of mainly adipose (fatty) tissue and collagen-rich connective tissue. It separates muscle from skin, stores fat, and conserves body heat.

 

 

4. Your fingers are primed to detect touch

epidermal cells meissners corpuscles touch skin integumentary

 

There’s a reason you use your hands to feel around in the dark, and it’s not just for balance! Special receptors (free nerve endings) called Meissner’s corpuscles are divvied up around your skin, but are concentrated in places more sensitive to touch, such as your fingers.

 

5. A special muscle causes goosebumps

Integumentary arrector pili dermis hypodermis skin keratinocytes melanocytes

We’ve all experienced goosebumps before—usually when you’re cold or afraid (or, in my case, when you watch the last 20 minutes of Close Encounters of the Third Kind). But have you ever given thought as to what causes goosebumps? What is in your skin that makes it pucker in such a way? The answer is small muscles known as arrector pili.

The arrector pili muscles (one for each hair) extend from the dermis and attach to each hair follicle, just above the bulb. Hair is sensitive to touch, changes in temperature and air, as well as in reaction to an emotion (e.g., hearing beautiful music, seeing something amazing, the last 20 minutes of Close Encounters, etc.), and the arrector pili muscles contract in response to these physical and emotional changes. When the muscles contract, the hairs stand on end.

 

The integumentary system has a low rate of permeability (a.k.a., it’s hard for things in the environment to penetrate it), which makes it the perfect protector for the rest of the body systems.

 

Want to learn more?



Information related to the integumentary system:
1. Care for conditions from acne to wrinkles: http://www.nlm.nih.gov/medlineplus/magazine/issues/fall08/articles/fall08pg22-25.html

2. Advances in treating eczema and dermatitis: http://www.sciencedaily.com/releases/2014/07/140709182238.htm

3. Dermatology pictures, Hardin Library for the Health Sciences, University of Iowa: http://hardinmd.lib.uiowa.edu/derm.html

4. A video that shows the development of skin cancer: http://youtu.be/fYEOEwotRH0

 

 

Topics: anatomy and physiology

Anatomy and Physiology: The 5 Unsung Heroes of the Abdominal Cavity

Posted by Courtney Smith on Fri, Aug 23, 2013 @ 03:48 PM

Sometimes I feel like the organs within the abdominal cavity don’t get enough love. Everything north of the diaphragm seems to hog all the attention (heart, lungs, brain, etc.)—I never hear anyone waxing poetic about the pancreas.

So I want to dedicate this blog post to five of the unsung heroes below the diaphragm. Without them, we’d be nothing.

 

1. Gallbladder: The Bile Keeper

A&P anatomy physiology gallbladder digestive

Bile is a bitter-tasting, dark-green/yellow fluid that is produced by the liver, and it’s super important! It helps the digestion of lipids in the small intestine. This fluid contains cholesterol (the good kind), bile salts, bilirubin (a breakdown product of red blood cells), water, and other things.

Bile is stored and concentrated in the gallbladder, and is then passed into the duodenum.

Relatively hidden (it sits under the liver), the gallbladder works hard to make the process of digestion run smoothly. The next time you’re eating a bag of Doritos, think about the little guy working behind the scenes to help you digest all those Cool Ranch–covered chips. 

 

2. Renal Pyramids: Cleansing Masters

A&P anatomy physiology kidneys renal pyramids urinary system

When people are serious about staying hydrated, they always seem to use the color of their urine as a gauge. What they don’t think about are the urinary system structures that create urine. No, seriously, they don’t. The next time someone proudly exclaims, “MY PEE HAS NO COLOR!”, you should tell them to thank their kidneys.

The renal pyramids are conical masses within the medulla of the kidneys. Most of the pyramids’ mass is nephrons, which filter blood and create urine. The urine created by the pyramids is funneled into the renal pelvis and then the ureters to be collected in the bladder. The normal range of urine creation is 800–2000 milliliters per day (with a normal fluid intake of about 2 liters per day).

That’s about 3–8 cups.

Your renal pyramids are practically superheroes.

 

3. Pancreas: Digestion Wunderkind

A&P anatomy physiology pancreas islet of langerhans

When you think about digestion, you tend to think only about the stomach (another glory hog). But without the pancreas, you wouldn’t be able to process the foods you eat, and your body would—well, what your body would do wouldn’t be pretty.

The pancreas is an exocrine gland that secretes pancreatic juice, another important digestive fluid. This fluid, made up of digestive enzymes, water, and electrolytes, is drained into the pancreatic duct. The duct converges with the common bile duct.

In addition to its digestive functions, the pancreas also has an important role in the endocrine system. The islets of Langerhans in the pancreas are responsible for some endocrine secretions, including insulin.

 

4. Adrenal Glands: Endocrine Celebrity

A&P anatomy physiology kidneys adrenal glands epinephrine

The adrenal glands are associated with the “fight or flight” reaction, but they have a much bigger role than you might think!

They are ductless glands, pyramidal in shape, that sit above the kidneys, making and releasing hormones directly into the bloodstream. There are different zones in the adrenal glands and each zone produces different hormones, including mineralcorticoids (mineral and water balance), glucocorticoids (glucose levels), and gonadcorticoids (adrenal sex hormones).

The medulla of the adrenal glands produce epinephrine (adrenaline) and norepinephrine , which also function as neurotransmitters in the nervous system. Epinephrine, when released during times of stress and excitement, floods the bloodstream, affecting heart rate, breathing rate, arousal, and pupil dilation (among others).

 

5. Cecum: Miss Congeniality (of the Abdomen)

A&P anatomy physiology cecum intestine colon digestive system

Many people aren’t aware of the cecum or its role in the digestive tract, which is a shame. I mean, the cecum is awesome—it makes your large intestine look like a giant caterpillar (with the cecum as the head).

The cecum is a large pouch that marks the first part of the large intestine. It’s responsible for the final absorption of nutrients and the compaction of liquid waste into solid waste. The ileocecal sphincter of the small intestine connects to the cecum and acts to prevent backflow of the contents in the cecum.

At the end of the cecum is the appendix. Yup, the same little structure that has landed at least one of your friends in the hospital to have it removed.


There you have it! And while you may still value the heart, brain, or lungs the most, hopefully you'll look on these five heroes and thank them every once in a while for all their hard work.


Want to venture beyond the abdominal cavity?

 

 

Related A&P posts:

- Anatomy and Physiology: Uterine Anatomy
- Anatomy and Physiology: 5 Facts about the Anatomy of the Pelvic Cavity
- Anatomy and Physiology: Homologues of Reproductive Anatomy


Topics: anatomy and physiology

Anatomy and Physiology: The Pharynx and Epiglottis

Posted by Courtney Smith on Wed, Aug 07, 2013 @ 08:39 AM

Once upon a time, I almost died.

I was two years old and at my grandmother’s house, where my cousins were having a blast trying to find the plastic Easter eggs my grandmother had hid. You see, inside the eggs were quarters, dimes, and nickels. And, if you were lucky, you would stumble upon big plastic eggs, which had dollar bills inside them. But, being two, I wasn't really able to participate. That didn't stop me, though. I stumbled around on my stubby legs and happened upon a plastic egg, inside which were a quarter and a nickel.

Naturally, I scooped out the change and shoved them in my mouth.

The next few minutes were kind of chaotic, what with me choking and turning blue, slipping slowly into unconsciousness, while my grandmother screamed at the 9-1-1 operator to make the ambulance drive faster and my mother tried to perform the Heimlich on my little body to no avail. They realized with horror that the ambulance wasn’t going to make it in time. My dad—thinking fast, or not at all—pried my mouth open and stuck his fingers down my throat. Pretty far, according to my mother. He managed to drag the coins up out of my throat and out of my mouth, which was incredibly lucky, as he had a much better chance of pushing them down even further and sealing my fate. The paramedics arrived some minutes later and declared me A-OK. That day left me with a cool story to tell 24 years later and my parents with a healthy fear of coin currency.

Why did I tell you this story? Because this is a great example of the pharyngeal reflex, or gag reflex, which your body employs to prevent unwanted things (such as coins) from entering the lungs. The digestive system and upper respiratory system share many of the same structures, so to make sure everything goes where it’s supposed to, the body has certain vanguards in place. Let’s take a look at them!

 

Oral Cavity

Oral cavity oropharynx nasopharynx mouth tongue

We’re all pretty familiar with this structure. The oral cavity is the inside of the mouth, an oval-shaped cavity located anteriorly to the pharynx at the start of the alimentary canal. The front of the cavity is bound by the inner surface of the lips and cheeks to the gingiva (gums) and teeth. The cavity floor is defined mostly by the tongue and the roof is formed by the hard and soft palates.

Food is masticated (chewed) in this cavity by the teeth and tongue, mixed with saliva containing enzymes to help break down carbohydrates. The mass created by this process is called a bolus, which is then swallowed.

The oral cavity is also an airway for the respiratory system.

 

Pharynx

The pharynx is a large musculomembranous tube that functions in both the respiratory system and the digestive system. It is made up of three sections:
 

1. Nasopharynx

Nasopharynx pharynx nasal cavity

This portion of the pharynx begins at the back of the nasal cavity, situated behind the nose and above the soft palate. Unlike the other two portions of the pharynx, the nasopharynx remains open all the time. On each lateral wall is the pharyngeal opening of the Eustachian (auditory) tube. The nasopharynx functions as an airway in the respiratory system. Also contained within the nasopharynx are the adenoids, or pharyngeal tonsils.

 

2. Oropharynx

Oropharynx pharynx oral cavity

The oropharynx is the middle portion of the pharynx, working with both the respiratory and digestive systems. It opens anteriorly in the mouth and extends from the soft palate to the hyoid. In each lateral wall is a palatine tonsil; also in this region are the sublingual tonsils, which are under the tongue. The oropharynx functions as an airway and as part of the alimentary canal.

 

3. Laryngopharynx

Laryngopharynx larynx oral cavity pharynx

This is where my near-death experience could have gone either way. The laryngopharynx is the posteriormost inferior region of the pharynx, reaching from the hyoid to the lower border of the cricoid cartilage; it’s the place where the respiratory and digestive systems diverge.

The rear of the laryngopharynx becomes the esophagus and continues into the digestive tract, while the front of the laryngopharynx merges with the entrance of the larynx. The epiglottis, a structure in the laryngeal skeleton, helps direct food toward the esophagus, preventing food and liquids (and coins) from entering the trachea.

 

Epiglottis

Larynx superior larynx laryngeal

I have a love/hate relationship with the epiglottis. On the one hand, I think its function in the respiratory system is fascinating, and I have it to thank for trying to keep the coins from entering my lungs; on the other, I loathe it for all the extra work it made me do in my college linguistics course. If I hear the words “glottal stop” ever again, I will not be responsible for my actions.

The epiglottis is a leaf-shaped cartilaginous structure that is part of the laryngeal skeleton. It’s usually directed upward toward the pharynx, like an open door through which air passes to the trachea. During swallowing, muscles pull it down to close the entry to the larynx—closing the door, so to speak—to prevent food, liquid, and saliva (and coins) from entering the trachea.

Now apply that principle to the stoppage of air. The epiglottis is pulled down to stop air from entering the trachea. For example, you tend to create glottal stops in words that end in t+vowel+n. The word “button” sounds like “butt-n” when spoken—you don’t tend to vocalize the vowel. The vocal cords close sharply, the epiglottis comes down, and no air is passed.

Also, if you’ve ever swallowed the wrong way, you’ve experienced that quick panic and awful seizing in your chest. This is the pharyngeal reflex, or gag reflex, acting to expel whatever you swallowed before it can enter the lungs. Sometimes the reflex is very sensitive, and even accidentally pushing your toothbrush too far can set it off! Your body very much doesn’t want you to asphyxiate; I wish two-year-old me had received that memo.

 

Quiz Time!

Now, other than why it’s a nominally bad idea to eat coins, what have you learned?

Epiglottis quiz A&P

Epiglottis quiz A&P 2

Want to see more?

All the images and most of the content of the blog post came from Anatomy & Physiology by Visible Body.

If you've got a PC, Mac, or iPad you can try an entire unit of this app for free! 


Related Posts

- Anatomy and Physiology: The Process of Olfaction
- Anatomy and Physiology: Homologues of Reproductive Anatomy

Topics: anatomy and physiology