Welcome to the Visible Body Blog!

That Boom Boom Pow: Virtual Dissection (sort of) of the Human Heart

Posted by Courtney Smith on Fri, Jan 06, 2017 @ 03:45 PM

The heart is a bit ubiquitous. While it's responsible for keeping your body in perfectly oxygenated condition, it's also commonly used as a metaphor and a gauge of one's mettle, and is the subject of about a bajillion soft rock ballads from the 80s and 90s.

Thanks, Loki.


I never had the good fortune of dissecting a heart in school. Sheep's brain, yes—as well as a slew of other creatures, including the biggest grasshopper I've ever seen. I asked my teacher where they were from so that I'd never go there ever, but she just smiled enigmatically and began the lesson. I'm pretty sure it was a weta.

If you're like me and still feel cheated out of the satisfaction of a heart dissection well done, then you're in luck! I'm going to peel back the heart layer by layer with Human Anatomy Atlas. Because that's just the kind of heartbreaker I am.

… I'll see myself out.

Don't have time to read? Then watch this:

A Silent Guardian, A Watchful Protector:
The Pericardium

I don't know about you, but when I first learned about the heart I was downright shocked that no one had told me that the heart basically lives inside a pillowcase. That was important information that I could have used in the 4th grade to gain extra points on our "LABEL THE HUMAN BODY" quiz (but I used it down the road as a mnemonic device in my 9th grade lab).

Pericardium, in context

Okay, so here we have a beautiful human heart and the roots of the great vessels enclosed in a protective fibroserous sac known as the pericardium. And like Shrek, it has layers. The outer layer consists of fibrous tissue (fibrous pericardium) and an inner serous membrane (serous pericardium). The serous pericardium has layers of its own—the visceral and parietal layers—with a fluid-filled space between them called the pericardial cavity. The role of the fluid in the pericardial cavity is mainly to reduce friction on the heart as it beats.

The pericardium attaches to the central tendon and muscular fibers of the diaphragm, as well as the posterior surface of the sternum, helping it to anchor the heart in place.

The Sternal Coast:
Cardiac Muscle and The Heart Wall

The thing you're probably going to take away from this post is that layers are the lay of the land as far as the heart goes, even when it comes to the most basic component: cardiac muscle.

The heart wall is made of three distinct layers (told you) that help give the heart its shape and size. The outermost layer is epicardium, a visceral layer of serous pericardium; myocardium is the middle layer, made up of muscle fibers attached to fibrous rings; the innermost layer is endocardium, a thin and smooth membrane of connective tissue and elastic fibers that line the inner surface of the heart.

Myocardium is where a good chunk of the magic happens. Blood is distributed in and out of the heart as a result of its signature contractions (ie: your heartbeat), and those muscle contractions—stimulated by the electrical impulses delivered by the conduction system (we'll get there in a little bit)—occur in the myocardium. This is where your heartbeat originates.


Myocardium (highlighted)

But of course your heart isn't just pumping muscle. There are other important structures within the heart, such as the thick muscular wall that separates the ventricles known as the interventricular septum, and the conus arteriosus, a conical pouch that gives rise to the pulmonary trunk.

More Valves and Chambers Than You Can Shake
A Stick At:
The Heart Valves and Chambers

If you're playing the home game, you may not have known that there are four valves that regulate blood flow—one-way blood flow at that!—in, through, and out of the heart. Varying pressures on either side of the heart cause these valves to open and close, contributing to the process of circulation. There are also four chambers, called atria and ventricles, in which blood flows.

Let's start with the chambers!

The two upper chambers, seated on top of the heart like little muscular berets, are known as the atria. These are the blood collection chambers. The right atrium receives deoxygenated blood from the vena cavae, two of the great vessels, and the coronal sinus and then empties it into the right ventricle. The left atrium, smaller and thicker than its counterpart, receives oxygenated blood from the pulmonary veins and empties it into the left ventricle.

There are two ventricles—a right and a left—with the same job: pump blood out of the heart. However, depending on the ventricle, the destination of that blood is different. The right ventricle (Ventriculus dexter, which is now what I'm going to call my friend Dex until the day I die) is responsible for pumping deoxygenated blood into the pulmonary trunk. The left ventricle (Ventriculus sinister, which is probably a villain that didn't make it into the Star Wars prequels) pumps oxygenated blood into the aorta, where it's then distributed throughout the body.

Now onto the valves.

Each valve is made up of a group of membranous folds or cusps that open and close during the cardiac cycle.


The heart valves (highlighted) in context

The atrioventricular valves—the tricuspid and mitral valves—get their name from their location between the atrium and the ventricles. The mitral valve, the only bicuspid valve up in here, consists of two rectangular cusps that regulate blood flow between the left atrium and left ventricle. The tricuspid valve regulates blood flow between the right atrium and right ventricle.

In the ventricles, attached to the heart wall, are papillary muscles that connect to the atrioventricular valves via string-like tendons known as chordae tendinae. With each ventricular contraction, the papillary muscles shorten and pull on the chordae tendinae, which prevents the valves from inverting. There are three papillary muscles in the right ventricle and two in the left.

Blood from the left ventricle is delivered into the aorta via the aortic valve. It's a tricuspid valve, formed by three semilunar-shaped cusps that open and close during the cardiac cycle. The cusps are larger and thicker than its pulmonary counterparts. When the ventricles contract (systole), the aortic valve opens and oxygenated blood moves into the aorta. The very moment ventricular systole ceases, the pressure of blood in the aorta closes the valve, preventing backflow into the left ventricle. It's an immediate action that happens constantly.

On the other side is the pulmonary valve, another tricuspid valve, which controls blood flow from the right ventricle into the pulmonary trunk, conveying deoxygenated blood to be replenished with oxygen in the lungs. When ventricular systole occurs, the pressure in the right ventricle exceeds that of the pulmonary trunk, forcing the pulmonary valve to open and admit blood. The moment systole stops, the pulmonary trunk closes, preventing backflow.

Goodness Greatness:
The Great Vessels of the Heart

All this blood pumping wouldn't work if there weren't a system in place. That's where the great vessels come in: they act as the relay, just the way your water pipes do! The vessels connect to the heart for pulmonary circulation and to the rest of the cardiovascular system to distribute blood throughout the body.

Superior vena cava

Inferior vena cava

Pulmonary trunk/circulation


Carries deoxygenated blood from the upper body into the right atrium.

Carries deoxygenated blood from the lower body into the right atrium.

In a role reversal from the rest of the body's circulation system, the pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs, while the pulmonary veins carry oxygenated blood back to the left ventricle for distribution via the aorta.

Delivers oxygenated blood from the left ventricle to the rest of the body.

Conduct Yourself Properly:
The Ins and Outs of The Conduction System

The fact that your heart beats constantly until the day you cease to be is incredible, and it's all thanks to the conduction system, which is exactly what it sounds like: it delivers electric impulses to muscle fibers within the heart and motivates its rhythmic contractions.


The conduction system (highlighted)

Pathways for these electrical impulses are formed by a series of bundles of specialized muscle fibers: the sinoatrial node, atrioventricular node, atrioventricular bundle of His, left and right bundle branches, and Purkinje fibers.

Like any well-working system, there are steps to how normal operation occurs. Here are the steps that the conduction system takes to kick out an electrical impulse:

  1. Initiation of the impulse at the sinoatrial node
  2. Pause of the impulse at the atrioventricular node
  3. Passage of the impulse into the bundle of His
  4. Branching of the signal into the bundle branches of each ventricle
  5. Culmination of the signal at the Purkinje fibers

Between steps 1 and 2, the atria contract, pumping blood into the ventricles. Between steps 4 and 5, the ventricles contract, pumping blood out of the heart. Each impulse takes approximately 0.22 seconds to complete each cycle.

Put It All Together and Whaddaya Got?

The human heart is an incredible organ. Yes, it's susceptible to the wear and tear of time and can be host to a bevy of ailments and diseases, but with new technologies innovating how we prolong our lives the heart could, theoretically, keep beating forever. Whether or not the rest of the body can match that is another story.

So there you have it! The human heart in a nutshell.

Be sure to subscribe to our blog so you're the first to know when part two of the brain series posts. Next time, we'll be diving inside. Stay tuned! In the meantime, you should definitely join our email list for free anatomy content, guest lectures, secret sales, product updates, and more.

New Call-to-action

Are you a professor (or know someone who is)? We have awesome visuals and resources for your anatomy and physiology course! Learn more here.

Topics: anatomy and physiology

A Lot on Our Minds: A Virtual Human Brain Dissection with Atlas 2017

Posted by Courtney Smith on Fri, Dec 16, 2016 @ 12:26 PM

The brain is an insanely complex organ. It's the reason you're you. And as I type this, it occurs to me that this post is basically an autobiography—my brain is writing about itself. Isn't that weird? Anatomy is weird.

How many of you have had the good fortune to actually dissect a brain? In a lab setting, I mean. If you were dissecting brains on your own in your kitchen or something, that'd be super weird and I'd be wondering if your name was Hannibal Lecter. I once dissected a cat brain, but that was nowhere near as complex as the human brain, and despite our pleas to our teacher to let us dissect an actual human brain, she was smart enough not to let a group of 9th graders anywhere near one.

As Marius Kwint, curator of the Brains exhibition at the Wellcome Collection in London, once said about brain dissection, "It's pretty intense."

I don't have a brain on me, but I've got the next best thing! With Human Anatomy Atlas 2017, I'm going to do a virtual brain dissection. Sort of. But, again, because the brain is so complex and has so many structures, we're only going to look at some of the outer ones for time purposes.

Don't have the time or inclination to read? Then watch!


Otherwise, are you ready for this? Then let's begin!


YES, MOTHER: The Meninges

You wouldn't think that a grayish pink, wrinkly mass that looks like a blobfish would be the key to everything that is you, but that's where the magic happens.

Before we get to the main event, let's take a look at the structures that protect the brain, starting with the skull and spinal column. They're kind of like armor; when you take a hit (while playing a sport or during a car accident), the skull and vertebrae help keep the vulnerable structures of the central nervous system (CNS) from being injured.

But take away the skeleton and there's still another layer of protection, because your body has evolved to do pretty much everything to keep the brain and spinal cord safe.

The meninges are the three layers of connective tissue that surround and protect the brain and spinal cord. Dura mater is the thick outermost layer, lining the interior of the skull and acting as a sheath around the spinal cord. The arachnoid mater, so named for its spider web–like fibers, makes arachnoid villi, or small protrusions through the dura mater into the venous sinuses of the brain. The villi allow cerebrospinal fluid (CSF) to enter the bloodstream. The pia mater, which is the deepest layer of the meninges, is a thin layer that’s impermeable to fluid, and so it cushions the brain and spinal cord by holding CSF.

"Mater" is Latin for "mother," and like any good mother the mater's job is to protect its ward. Isn't she wonderful?

The Meninges (dura, pia, and spinal mater), in context

Ever hear of meningitis? I vaguely remember being inoculated against four types of it before I went to college. Meningitis is a condition in which the meninges become inflamed, typically triggering symptoms such as headache, fever, and a stiff neck. The most common cause of meningitis is either a viral or bacterial infection. Bacterial meningitis is very serious and can even result in death if not treated within a few hours; most people recover, although permanent disabilities can result, like hearing loss and brain damage.


THE SUPERHIGHWAY: The Central and Peripheral Nervous Systems

Have you ever been so busy that you wished there were three of you to tackle everything you need to do? That's kind of like the nervous system. Imagine that the brain is a super overworked person who needs to delegate certain tasks; the different nervous systems are the coworkers who take on those tasks.

The central nervous system (CNS) is made up of the brain and spinal cord, as stated above. The peripheral nervous system (PNS) is made up of all the nerves and ganglia outside the CNS that connect it to all the tissues throughout the body—it's what tells your organs to keep functioning, your muscles to keep moving, etc. Within the PNS is a division known as the autonomic nervous system (ANS), which regulates involuntary function, like smooth muscle contraction and the heart beating.


The ANS is divided into even more divisions. The sympathetic division is responsible for increasing heart rate and other body functions in response to an emergency, while the parasympathetic division is responsible for rest functions, such as digestion.

It's a team effort, as far as the PNS goes.


THE OLD TIMER: The Hindbrain

Okay, so if we hide the PNS and move on up the spinal cord, we'll eventually get to the hindbrain. The hindbrain is super old—it's been suggested that it first evolved from the Urbilaterian, the hypothetical last common ancestor of chordates and arthropods, somewhere between 555 and 570 million years ago. So homeboy's been around for a while.

The hindbrain, or the rhombencephalon, is an inferoposterior area of the brain that consists of the medulla oblongata, the pons, and the cerebellum. Like the PNS, the hindbrain has its own divisions: the metencephalon and the myelencephalon.


Of the metencephalon, there is the cerebellum, which is the largest part of the hindbrain. It fine-tunes body movements and manages balance and posture, as well as some cognitive functions and puzzle solving. There's also the pons, which bridges the two main function areas of the CNS: the brain and the spinal cord, conveying signals between them via white fibers. The pons is also responsible for breathing rhythms.

Most of the myelencephalon is the medulla oblongata (coolest name ever), which is a structure that’s continuous with the spinal cord and acts as the conduction pathway between it and the brain. It controls involuntary functions of the digestive, respiratory, and circulatory systems, as well as contributes to hearing, balance, and gustation (taste).


LOBE IT! A Look at the Four Lobes of the Cerebrum


Okay, now onto the main event: the telencephalon, or the cerebrum. The cerebrum's the largest part of the brain and is categorized into functional areas called lobes. It's divided by the longitudinal fissure into two hemispheres—right and left—and is connected by the corpus callosum, which you can kind of see in the fissure.


The four lobes of the brain are the frontal, parietal, temporal, and occipital—and both hemispheres of the brain have these lobes. The lobes are all named after the bones that cover them.


The frontal lobe is where higher functions occur, like planning, problem-solving, long-term memory, impulse control, and speech and language.


The parietal lobe integrates sensory information and plays a role in spatial perception—mine must be broken, because I can't seem to leave a room without bumping into the doorway.


The temporal lobe contains an auditory cortex that receives input from the cochlear nerve and is responsible for primary auditory perception. It's also associated with processing sensory input into derived meanings—like attaching emotion to visuals or recognizing faces. You know that rush of love you get when you see a family member or friend? That's the temporal lobe's doing.


The occipital lobe is the brain's posteriormost (and smallest!) lobe. It receives input from the eyes and processes visual perceptions—not just in terms of sight, but in terms of assigning meaning to and remembering what you're seeing.



Now the cerebrum isn't just comprised of these four lobes. There are structures called gyri and sulci as well. A gyrus is a ridge, or a fold, between two clefts—the precentral gyrus and the postcentral gyrus, both between the frontal and parietal lobes. The gyri increase the cerebrum's surface area. The precentral gyrus contains the primary motor cortex and controls precise movements of skeletal muscles. The postcentral gyrus contains the primary somatosensory cortex and is responsible for spatial discrimination. There's a third—the cingulate gyrus—but it's part of the limbic system, which is another topic for another blog post.


The sulci are fissures that separate the gyri; the more prominent ones separate the lobes. The central sulcus, or the Fissure of Rolando (I lied—this is the coolest name ever), separates the frontal and parietal lobes. The less-cool named lateral sulcus separates the parietal and frontal lobes from the temporal lobe. The parieto-occipital sulcus separates—you guessed it—the parietal and occipital lobes.


And there we are! The cerebrum and some of the other structures of the outer brain. If you're feeling proud of yourself for getting through all that information, remember: it's your brain doing that. It's making you feel good about reading an article about itself.

Mind. Blown.


Be sure to subscribe to our blog so you're the first to know when part two of the brain series posts. Next time, we'll be diving inside. Stay tuned! In the meantime, you should definitely join our email list for free anatomy content, guest lectures, secret sales, product updates, and more.

New Call-to-action
Are you a professor (or know someone who is)? We have awesome visuals and resources for your anatomy and physiology course! Learn more here.

Topics: anatomy and physiology

In a Pinch: The Anatomy and Pathology of Cervical Radiculopathy

Posted by Madison Oppenheim on Mon, Aug 22, 2016 @ 08:34 AM

No matter how many thousands of dollars you spend on plastic surgery or hours you spend in the gym doing squats, you can't stop the march of time. Everyone is afraid of getting older and the pain that comes with it: arthritis, herniated discs, and pinched nerves, to name a few.

Cervical radiculopathy, commonly known as a pinched nerve, affects 84 out of every 100,000 people per year and occurs when a spinal nerve root in the neck is compressed. 


The Back Bone's Connected to the Neck Bone 

The "back bone" is actually a collection of 24 stacked vertebrae that protect your spinal cord from the daily disasters of life. The first 7 vertebrae comprise the cervical spine, a.k.a. your neck. Between each vertebra are intervertebral discs, which are flexible and composed of two parts: the annulus fibrosusthe flexible, tough outer ringand the nucleus pulposusthe soft, pulpy, and highly elastic center. These discs are essential in absorbing shock in everyday movements, like when your friend calls your name from down the hall behind you and your neck snaps around to see who it is, or when "your song" comes on the radio and you bop your head up and down in the car.

Cervical vertebrae and peripheral nerves                    

The spinal cord is like the body's message highwayrelaying information from the brain to the peripheral nerves throughout your body. When your brain tells you to scratch that bug bite on your foot, the message travels down the spinal cord to your arm, which completes the action. 


What Is Cervical Radiculopathy?

So we covered the cervical part - relating to your cervical spine, but where does the "radiculopathy" part come from? Radiculopathy is the disease of a nerve root, usually stemming from a pinched nerve. The pain caused by cervical radiculopathy is usually descibed as a burning or sharp pain that begins in the neck and travels down the arm. Other symptoms can include tingling or the feeling of "pins and needles" in the fingers or hand; weakness in the muscles of the arm, shoulder, or hand; and loss of sensation. 

Cervical radiculopathy -- a pinched nerve

A pinched nerve can occur from degenerative changes or an injury to a disc. As I mentioned above, no one is safe from the effects of aging, and as we get older our spine shrinks and can lose water content. This combination leads to a collapse of disc space, which creates bone spurs as the body tries to make up for the lost strength. Bone spurs can cause the foramensmall spaces between vertebrae for nerve roots to leave throughto narrow. These degenerative changes are also known as arthritis or spondylosis. 

We've probably all heard the phrase "Grandpa's got a herniated disc" at one time or another, but what does that even mean? A herniated disc occurs when the nucleus pulposus (the soft center) pushes against the annulus fibrosus (the tough outer ring). If the disc bulges out toward the spinal canal, it applies pressure against the nerve root, causing pain.


Relief and Treatment for Cervical Radiculopathy

The majority of patients with cervical radiculopathy get better over time and do not require treatment, although there are options available to relieve discomfort. One such option is a soft cervical collar: a padded ring that wraps around the neck and allows the muscles to relax and limits motion.

Physical therapy is another option that can help relieve pain and improve range of motion while also strengthening neck muscles.

There are also many medications including nonsteroidal anti-inflammatory drugs, oral corticosteroids, steroid injections, and narcotics that can improve symptoms. 

If the nonsurgical teatment is not successful, surgery is also an option your doctor may recommend. 


Although there is nothing we can do to prevent getting old and wrinkly and eating mushy food, you can prevent cervical radiculopathy from recurring by maintaining proper posture, continuing regular exercise, being mindful of unnecessary forces on your spine (stop spending your days scrolling through Facebook), and keeping a healthy weight.

Want to see more?

Never miss a thing!

New Call-to-action

Related posts



Topics: anatomy and physiology

Into The Carpal Tunnel: Anatomy & Pathology of Carpal Tunnel Syndrome

Posted by Courtney Smith on Thu, Feb 18, 2016 @ 11:00 AM

It's what strikes fear into the heart of every frequent typist (like myself): carpal tunnel syndrome. I just shuddered as I typed that. It's usually referred to as "carpal tunnel," but the thing is that everyone has a carpal tunnel. Well, everyone has two: one in each hand.  But not everyone is affected by carpal tunnel syndrome (or CTS). About 3% of women and 2% of men will be diagnosed with CTS during their lifetime, with women at 3x the risk than men. That's over 9 million people in the United States alone.

But what is it exactly? Why is it such a common ailment? Why do more women have CTS than men? Why do some people have issues with their carpal tunnel while others don't? All very good questions. And my beleaguered wrists and fingers will do the answering.


What is the carpal tunnel?

The carpal tunnel is an actual tunnel created by the tendons, tissues, and bones in your wrists and hands. Think of the bones of your arm, wrist, and hand as a road. The flexor retinaculum and the palmar carpal ligament work like an overpass, and the flexor tendons of your hand and the median nerve pass under it like a car.


The flexors -- the flexor digitorum superficialis, the flexor pollicis longus, the flexor carpi radialis, and the flexor digitorum profundus (highlighted in blue) -- are muscles that originate in your forearm, but insert into the finger bones as tendons (which means technically you don't have muscles in your fingers). These tendons are what allow your fingers to flex, hold things, type, and do pretty much any task you can dream of. Also, when you bend your wrist, you are working the flexors in your forearms, as well as the tendons.

Poke the palm of your hand. That you felt anything at all is all thanks to the median nerve. The median nerve is part of the brachial plexus, which is a network of nerves in the shoulder and upper limb. It supplies sensation to the palm, the side of the thumb, and the index, ring, and middle fingers, as well to the flexor tendons. It also gives function to the muscles at the base of the thumb.


Carpal Tunnel Syndrome Symptoms

I can hear you asking, "If the body has this nice little system going with the muscles, tendons, and the median nerve… why in the world does that system break down?"

The thing is, no one is really sure what leads to carpal tunnel syndrome. CTS is caused by the tissues and tendons around the median nerve (with nerve branches, highlighted in blue) swelling and pressing on the nerve. This reduces oxygen flow to the nerve, which means the signals to the nerve slow. In some cases, it's not the tendons that swell but the nerve itself.

The compression of the median nerve results in pain, numbness, parathesia ("pins and needles"), and a feeling of coldness in the wrist and hand -- with the exception of the little finger. The median nerve does not provide sensation to the little finger and therefore it remains unaffected.


Why is CTS so common?

CTS is associated with repetitive actions that directly affect the wrist/hand area, such as frequent typing or computer use, but manual labor is actually the occupation with the highest CTS risk. Musicians, welders, sheet metal workers, cooks/chefs, laborers in the freight and/or moving industry, and office workers are at the highest risk for CTS. Think of how much you use your hands and fingers during the day to complete certain tasks. I, myself, am well on my way.


Can you prevent carpal tunnel syndrome?

So, how do you prevent it? If you catch it in the early stages, CTS is reversible. There are two key strategies to stopping the onset of CTS: rest and ergonomics.

  1. Rest periods are important, especially for you heavy typists out there. Resting your fingers for short periods of time (3 minutes or so) will be enough time for the tissues to relax. Shaking your hands out to loosen things up is always a good idea too.
  2. Ergonomics is also very important. Ergonomics is the efficient interaction between you and your workspace. For example, when you use a computer, do you have a wrist rest for your keyboard or mouse? Wrist rests are not only for comfort but they help keep your wrists and hands parallel to the device you're using, easing the strain on the muscles. How about your chair? Does it have arm rests? Is the back positioned to encourage good posture? The same goes for those who use tools or manual equipment. Make sure what you use does not put unnatural stress on your wrists. If you use, say, a wrench, make sure that when you hold it for use your wrists are in the same, comfortable position they'd be in if your arms were hanging at your side.

CTS is easy enough to prevent, but if you've been experiencing CTS symptoms for a while you may be a bit out of luck as far as reversing it. But adopt some good habits and you'll prevent the symptoms from worsening.

There you have it: carpal tunnel syndrome, demystified. Now it's time to give my fingers a break.


Want to see more?

Never miss a thing!

New Call-to-action

Related Posts


Carpal Tunnel Syndrome: New York Times.

Topics: learn muscle anatomy, anatomy and physiology

Anatomy and Physiology: The Pharynx and Epiglottis

Posted by Courtney Smith on Fri, Feb 12, 2016 @ 08:30 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 27 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

The oral cavity, oropharynx, nasopharynx, and laryngopharynx

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.



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 in context

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 in context

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 in context

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.




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.



Want to see more?

Never miss a thing!

New Call-to-action

Related Posts

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

Topics: anatomy and physiology

Anatomy and Physiology: The Pitfalls of LDL Cholesterol

Posted by Courtney Smith on Fri, Nov 13, 2015 @ 12:10 PM

As I get older, I try to be conscientious of what I eat, but the problem is that I'm always craving mac & cheese and there's nothing I can do about it. Resisting the urge to shove a block of sharp cheddar down my gullet with a macaroni chaser is, as they say in "Star Trek," futile. No matter how much I fight it, I eventually cave. My doctor isn't impressed. "Stop eating things so high in cholesterol," she pleads, and I nod seriously and say, "I hear what you're saying, but let's be realistic."

And so it goes.

More and more, we're warned about foods that are high in "bad" cholesterol and the dangers of having high cholesterol, but what does it all mean? Read on to find out!


Cholesterol: What Is It and Why Do We Have It?

Cholesterol is a waxy substance that helps maintain the structure of all of your cells and performs certain tasks, like producing hormones and vitamin D, as well as helping you to digest your food.

Red blood cells flowing through an artery

On its own, cholesterol isn't inherently "bad." In fact, your body—particularly your liver—produces all the cholesterol it needs!

So, where does it all go wrong? Why do so many people have high cholesterol levels? Well, look no further than the foods you eat. Meat, butter, shellfish, cheese, and pastries all can be very high in cholesterol, which is a bummer because everyone knows that lobster mac & cheese is the best kind of mac & cheese on the planet. Obviously eating these things in moderation is fine, but too much of a good thing can be bad for you (except ice cream*).


The Good, the Bad, and the Ugly:
Two Types of Cholesterol

Like a Hollywood classic for which I'll probably be sued for naming, "good," "bad," and "ugly" characteristics can be applied to cholesterol.

Two types of proteins carry cholesterol through your bloodstream: low-density lipoproteins and high-density lipoproteins, and too much of one or not enough of the other isn't a good thing. It's important to try and maintain a healthy balance between them.

Cholesterol traveling with blood cells and other substances through an artery

HDL cholesterol is the "good" cholesterol, as it carries cholesterol from other parts of your body back to the liver, which then removes the cholesterol from your body.

LDL cholesterol is "bad" because a high level of it can lead to a buildup of it in your arteries.

A buildup of LDL cholesterol is "ugly" because it can lead to a bunch of issues. Actually, why don't we talk about those right now?


The Good, the Bad, and the Ugly 2:
Electric Heart Disease Boogaloo

Ah, coronary heart disease: the one threat that gets me on my feet and forces me to stay somewhat active. As we discussed previously, CHD is no joke.

What does heart disease have to do with cholesterol? A lot, actually. See, when there's a buildup of LDL in your artery walls, it narrows the amount of space through which blood travels. Add a buildup of other things, like calcium and fat, and you get plaque. When plaque accumulates in the arteries, it's known as atherosclerosis. When less blood flows, your organs don't get the amount of oxygen and nutrients they need. This can lead to stroke, heart attack, or even death.

An artery narrowed by plaque buildup, showing atherosclerosis

In CHD, the arterial walls of the heart become hard with plaque buildup and grow narrow, limiting oxygen to the heart. When there's a limited or lack of oxygen flow, tissues will die and heart attack can occur.

According to the Center for Disease Control, a whopping 73.5 million adults in the United States have a high LDL cholesterol level, which puts them at double the risk of heart disease than someone whose levels are normal. A high LDL cholesterol level usually doesn't come with symptoms, so many people have no idea if their blood cholesterol level is too high. Exercising, eating well, and not smoking will lower your risk of heart disease.

While it may be impossible for me to give up mac & cheese completely, I can certainly curb my intake. It won't be easy, but it's important. My very life may depend on it.

* I’ve been told that this is just wishful thinking on my part.


Want to see more?

Never miss a thing!

New Call-to-action

Related posts

- Anatomy and Physiology: Stroke Is No Joke: Always Act FAST
- Learn Muscle Anatomy: Of Dads and Rotator Cuff Injuries
- Anatomy and Physiology: 7 Facts about Cardiovascular Disease

Further Reading:

1. CDC.gov

2. National Heart, Lung, and Blood Institute

3. Heart.org

Topics: anatomy and physiology

Anatomy and Physiology: Five Things About The Integumentary System

Posted by Courtney Smith on Tue, Oct 20, 2015 @ 03:30 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 see more?

Never miss a thing!

New Call-to-action  

Related posts

- Anatomy and Physiology: Stroke Is No Joke: Always Act FAST
- Anatomy and Physiology: The Pharynx and Epiglottis
- Anatomy and Physiology: 7 Facts about Cardiovascular Disease


1. Care for conditions from acne to wrinkles 

2. Advances in treating eczema and dermatitis

3. Dermatology pictures, Hardin Library for the Health Sciences, University of Iowa

4. A video that shows the development of skin cancer



Topics: anatomy and physiology

A Stroke Is No Joke: Always Act FAST

Posted by Courtney Smith on Wed, Jul 08, 2015 @ 03:22 PM

I’m about to get a bit personal here, so hold onto your butts.

When I was 14, my friend took me to her aunt’s house so we could swim in her pool. Her aunt was always so cool—super funny and smart, with elegant streaks of gray in her long hair—and I was happy to go. We swam for a while until her aunt called us in to help make lunch. My friend wanted melon balls to go with our salads and sandwiches, so we spent about 10 minutes mechanically scooping out little pink globules into porcelain dishes.

Then, my friend’s aunt paused. I’ll never forget the sound she made, a little boof of confusion, the noise a dog makes when it’s not committed to growling but musters up the effort. She frowned at the half-filled dish in front of her. From across the counter, I watched—horrified, rapt—as one side of her face kind of … melted. The hand holding the melon scoop twitched, as if she meant to lift it, and she began to mumble things I couldn’t understand. My friend immediately went to her side and helped her to the floor as she began to fall, and I called 9-1-1.

As the EMTs loaded my friend’s aunt into the ambulance, one of them came over and helped my friend call her mom. The EMT spoke to her mother and said calmly, “It was a stroke, ma’am. We’re taking her to Whidden Hospital; your daughter and her friend are going to ride with us. Can you meet us there?”

It was honestly one of the most terrifying experiences of my life up to that point; I can’t imagine what my friend’s aunt was feeling.

Pardon the rhyme, but a stroke is no joke. But what is a stroke, and why is it so important to act FAST when one occurs? Keep reading to find out.



While her aunt recovered, my friend would tell our curious and sympathetic classmates, “My aunt had a stroke.” And immediately that would shut them up. It was as if the stark, one-syllable word were an expletive, a harbinger whose wrath no one wanted to incur.

The thing is, there are different types of stroke, and those different types have different causes. They happen for a variety of reasons and they’re associated with as many risk factors.

Ischemic Stroke

My friend’s aunt had an ischemic stroke, which is the most common kind—in fact, 85% of strokes are ischemic. An ischemic stroke is caused when the blood supply to the brain is reduced (also called “ischemia”). Reduced blood flow to the brain causes cell death, which is as bad as it sounds.


The most common types:

  • Thrombotic ischemic stroke: A blood clot, or thrombus, forms in one of the brain arteries due to a build-up of plaque or other vascular conditions, and blocks the artery. This blockage causes reduced blood flow to the brain.
  • Embolic ischemic stroke: A blood clot forms elsewhere in the body (like the heart) and travels to the arteries of the brain, where it becomes lodged in a narrow vessel. This type of clot is called an embolus.

There is also something called a transient ischemic attack (TIA), which is a bit like a mini stroke. A blood clot forms and blocks an artery like in an ischemic stroke, but the blockage is temporary. Before the clot is able to move, it briefly reduces the blood supply to the brain. The symptoms of a TIA and a full ischemic stroke are similar, but brief, but a TIA greatly increases a person’s risk for a full-blown stroke.

Hemorrhagic Stroke

On the other side of the stroke spectrum are hemorrhagic strokes, in which a blood vessel in the brain ruptures or leaks. This can happen for a bunch of reasons, including hypertension, overmedicating with anticoagulants, and aneurysms.


There are two types:

  • Subarachnoid hemorrhagic stroke: A vessel in the brain bursts, causing blood to leak into the space between the brain and skull. When this occurs, it’s usually followed by an immediate, unbearable headache.
  • Intracerebral hemorrhagic stroke: A vessel in the brain bursts and spills blood into the brain tissue, causing cell damage or death.


I mentioned above that there are many contributing factors to stroke. Well, I wasn’t kidding. Risk factors associated with stroke range from family history, lifestyle, and present medical conditions.

Obesity, smoking, alcohol abuse, and drug use are all treatable risks for stroke. Conditions like hypertension (high blood pressure), diabetes, high cholesterol, and cardiovascular disease all contribute to stroke risk.

Those with a family history of stroke or heart attack are more likely to suffer a stroke than those without. Age and gender also play a part. People over the age of 55 have a higher risk. Men tend to suffer strokes more than women, but women—particularly older women—tend to die from them more than men.

Suffering a stroke can cause long-lasting, even permanent complications. Luckily, my friend’s aunt was able to get away with nothing more than memory loss of the incident, but others don’t come away from it so easily.

As I said, memory loss is one complication, but more severe ones include paralysis, pain or numbness, aphasia (or difficulty with speaking or understanding speech), and changes in behavior.



I remember seeing a poster about “Acting F. A. S. T.” in the hospital room my friend’s aunt recovered in, and since then I’ve never forgotten it. F. A. S. T. is an acronym for the warning signs of a stroke—I highly recommend you learn it.

Face drooping: During a stroke, the face can go numb or even droop. The person may have difficulty smiling or his or her smile may be uneven.

Arm weakness: One arm may go weak or numb. In this case, ask the person to lift both arms. If one arm drifts downward beyond his or her control it could be a sign of stroke.

Speech difficulty: A person suffering a stroke may slur words or be hard to understand. Ask the person to say a simple sentence, like, “The birds are singing.” If he or she can’t, it may be a sign of stroke.

Time to call 9-1-1: If you suspect someone is suffering a stroke, you need to call 9-1-1 right away, even if the symptoms disappear. Remember, a TIA’s symptoms are temporary; if someone suffers a TIA, their risk for a full-blown stroke increases exponentially.


 F.A.S.T. poster, courtesy of the American Stroke Association

For those of you wondering, my friend’s aunt made a full recovery. She still has no memory of the event, but that’s okay: I remember it enough for the both of us.

A stroke is no joke. If you suspect someone is having one, remember to act FAST (emphasis on the T).



Want to see more?

Never miss a thing!

New Call-to-action  

Related posts

- Anatomy and Physiology: 5 Things about the Integumentary System
- Anatomy and Physiology: The Pharynx and Epiglottis
- Anatomy and Physiology: 7 Facts about Cardiovascular Disease





Topics: anatomy and physiology

The Lymphatic System: Innate and Adaptive Immunity

Posted by Professor Blythe Nilson on Mon, May 11, 2015 @ 02:20 PM

Today’s post is coming all the way from Canada’s western-most province. Blythe Nilson, Associate Professor in the Biology Department at the University of British Columbia—Okanagan campus, is about to school y’all in the lymphatic system. So pop some vitamin C, kick back, and read on.

Take it away, Professor!


The Lymphatic System

First, let’s quickly review the lymphatic system. The lymphatic system carries out the body’s immune responses by producing and distributing cells, such as lymphocytes and macrophages, that combat disease.

Lymph vessels, or lymphatics, drain fluid from all parts of the body and return it to the heart. They begin as narrow blind-ended vessels in tissues then merge with others as they travel toward the vena cavae, where they return the lymph into the circulatory system. Unlike the blood vessels, lymphatics are one-way.


The spleen is a soft, delicate organ that filters blood for pathogens, debris, or worn-out cells. The spleen is made up of compartments called follicles that are filled with lymphocytes and macrophages that can mount an immune response quickly if antigens are detected. The spleen destroys and recycles about 200 billion worn-out red blood cells every day.


The thymus is a soft, bilobed organ that lies between the heart and the sternum. It’s larger in young people because developing T-lymphocytes spend time there as they mature. Only competent T-cells are allowed to leave the thymus, which destroys any faulty ones. After puberty, the thymus is no longer needed; it atrophies and the lymphatic tissue is replaced by fatty tissue.

Lymph nodes are small, roundish organs that form along lymph vessels. As lymph passes from a lymph vessel through a node it slows down and percolates through millions of lymphocytes and macrophages. If a pathogen is detected the immune cells will multiply, causing the lymph node to swell.



Innate Immunity

As you may know, the body has several structures that serve as protective barriers against infection. These include the skin, respiratory and digestive tract mucous membranes, and other structures.

The term immunity refers to the many structures and responses the human body has for preventing pathogens from entering the body and for fighting them off if they do get in.

Immunity can be broadly divided into two categories: innate immunity and adaptive immunity. Innate immunity is the body’s general response to invading pathogens—it’s the same in everyone and reacts the same way each time. Essentially, we are born with innate immunity all ready to go.

Innate immunity includes physical barriers, such as the skin, and chemical responses, such as antimicrobials found in tears. It also includes physiological responses, such as fever and inflammation. These processes stimulate immune cells to take action, hinder pathogen growth, and prepare damaged tissues for repair. Specialized cells, like macrophages, can kill and digest bacteria and parasites, as well as secrete cytokines that can induce inflammation and mobilize other parts of the immune system.


An inflammatory response causes blood vessels to dilate, bringing more blood to the site and causing localized heat. The vessels also become leaky, allowing fluid and immune cells to leave the bloodstream and enter the infected tissue. The cardinal signs of inflammation are swelling, redness, and heat, and often there is pain and loss of function.


Adaptive Immunity

Now let’s have a look at the other arm of the immune system: adaptive immunity.

Adaptive immunity is the body’s way of mounting an immune response that is specific for each pathogen. B- and T-lymphocytes, or B- and T-cells are central to adaptive immunity. They are able to recognize each kind of invading pathogen and respond with a large, focused response tailored to that specific invader. What’s more, each time a new pathogen is found, the lymphocytes that recognized it will multiply and remain in your body so that if that pathogen ever returns, your immune response will be swift and massive.


Antibody-mediated immunity is triggered when  your B-cells recognize a pathogen. Of the trillions of B-cells in your body there are some with receptors specialized to recognize every pathogen you are likely to encounter. When a subset of B-cells is activated they produce antibodies, specialized proteins that are released into blood and tissues where they bind to pathogens, marking them for destruction by macrophages and other immune cells.

Cell-mediated immunity is carried out by T-cells when they recognize pathogens living inside your cells. Infected body cells display pieces of the pathogen on their surface that are recognized by T-cells. This activates the T-cells, causing them to recruit other cells of the immune system that will deal with the invaders, often by killing the infected cell!

Want to learn more?

Never miss another thing:

New Call-to-action  

Related Posts:

Anatomy & Physiology: The Anatomy of Vision
Anatomy & Physiology: Parts of a Human Cell
The Endocrine System: Hypothalamus and Pituitary 


Check out Anatomy & Physiology:

New Call-to-action

New Call-to-action   New Call-to-action   New Call-to-action   New Call-to-action



Special thanks to Professor Nilson for contributing to the Visible Body Blog!

Topics: anatomy and physiology

Anatomy and Physiology: The Limbic System's Major Three

Posted by Courtney Smith on Fri, Mar 27, 2015 @ 02:25 PM

What is your earliest memory?

Mine is the sound of my older brother Steve muttering, "I don't know why you're laughing, we're going to get in trouble," and the rush of sand as he helped me pour a bucketful over my head. We were at my Yiayia's house in her sun-soaked backyard, sitting in the little turtle sandbox that was missing an eye (courtesy of my cousin Billy, I would learn years later while going through pictures). The bed of wildflowers nearby kept catching on Steve's shirt and smelled earthy-sweet. While the adults lounged about on the back deck, toasting my mother for keeping her too-curious child alive long enough to see a second birthday, Steve helplessly held the now empty yellow bucket in his hand while I cackled triumphantly to myself.

Sometimes when I'm lounging in my Yiayia's backyard (now hanging with the adults), I'll smell the wildflowers and bam. Suddenly I'm two years old again with sand in my hair and so very proud of the fact.

Long-term memory is still a mystery in a lot of ways, but we do know that the limbic system has a hand in processing and consolidating it. That's not all the limbic system does, however, and we're going to take a look at the role three of its major components play in the brain.


A Functional Classification:
The Limbic System Is, Well, a System

When one speaks aloud about the limbic system, it sounds as though they consider it to be a single structure. That's simply not true. While there’s some debate in the scientific community about which structures are part of the limbic system, there's a unanimous agreement about three of them: the amygdala, hippocampus, and cingulate gyrus. In addition, there’s also the dentate gyrus, parahippocampal gyrus, fornix, and other nuclei and septa.


The limbic system functions to facilitate memory storage and retrieval, establish emotional states, and link the conscious, intellectual functions of the cerebral cortex with the unconscious, autonomic functions of the brain stem.

While the sensory cortex, motor cortex, and association areas of the cerebral cortex allow you to perform certain tasks, the limbic system makes you want to do those tasks. It's your very own internal motivational speaker!


Amygdala: The (Not Actually) Missing Link

Amygdala is a fun thing to say, yes? Ah-meg-dala. It sounds like a city in Game of Thrones.

While small, the amygdala has the big job of acting as the link between a stimulus and how you react to that stimulus. By receiving processed information from the general senses (your eyes, your skin, your tongue, etc.), it’s able to mediate the proper emotional responses. For example, I'm allergic to chocolate, so smelling it invokes a response of disgust in me. For others, it would invoke a kinder response. In my friend's case, it would send her into a euphoria.


Output from the amygdala goes either to the hypothalamus or the prefrontal cortex. Output going to the hypothalamus influences visceral and somatic motor systems. Through these connections, an emotional response to something might make your hair stand on end, make your heart race, or even induce vomiting! Output going to the prefrontal cortex involves conscious responses, such as telling someone you love them or controlling your anger.  


Hippocampus: Memory Consolidator

Hippocampus sounds like something straight out of myth—which it is. In Greek mythology, the hippocamp(us) was a creature with the top half of a horse and the bottom half of a long, scaly eel or fish. Chances are, there was one swimming around the Great Lake at Hogwarts.

The actual anatomical structure is named for its resemblance to the curved tail of the seahorse-like creature. The hippocampus is found in the medial temporal lobe and consists mostly of gray matter. Not very pretty for a memory-forming center, all things considered.


Memories aren’t stored in the hippocampus, but rather cognitive and sensory experiences are organized into a unified, long-term memory. When you experience something, like touching something hot for the very first time, the hippocampus learns the sensory input in relation to the experience and then plays the memory back repeatedly to the cerebral cortex to form a long-term memory in a process called memory consolidation. Think of it as the hippocampus' way of teaching the cerebral cortex. Memory consolidation continues until a long-term memory is formed, which will be held in one of the various areas of the cortex (different memories are housed in different areas).


Cingulate Gyrus: The Limbic Big Boy

I love the cingulate gyri—they look like something Professor X would wear to help him look for new mutants. While it isn't known whether they can enhance one's telepathic ability to locate others with superhuman abilities, the cingulate gyri are known for other things that are just as cool (okay, maybe not).

Ever been so excited about something that your arms flail around, or so angry that your hands clench into fists? The cingulate gyrus, a large arch-shaped structure, plays a role in expressing emotions through gestures.


A gyrus is a convolution, or fold, in the brain that acts to increase surface area, which in turn increases the number of neurons, as well as gray matter. There are many gyri that interact with the limbic system and the brain as a whole. The precentral gyrus (posteriormost gyrus of the frontal lobe) contains the primary motor cortex and controls the precise movements of skeletal muscles. The postcentral gyrus (anteriormost gyrus of the parietal lobe) contains the primary somatosensory cortex and is responsible for spatial discrimination (recognizing the part of your body that’s being stimulated).


Like what you read in this blog? Then go a step further:

Never miss a thing!

New Call-to-action  


Try Human Anatomy Atlas:

New Call-to-action

New Call-to-action New Call-to-action New Call-to-action New Call-to-action

Related Posts:

Anatomy & Physiology: The Anatomy of Vision
Anatomy & Physiology: Parts of a Human Cell
The Endocrine System: Hypothalamus and Pituitary 


Topics: anatomy and physiology