Welcome to the Visible Body Blog!

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?

Check out Anatomy & Physiology:

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 


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:

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

No dry-erase boards: An ER doctor discusses using our anatomy reference with his patients

Posted by Lori Levans on Mon, Mar 09, 2015 @ 11:16 AM

Meet Dr. Brennen Beatty. He’s an ER physician in Austin, TX.

In recent months, he’s changed the way he talks to patients about their diagnosis. The old way was to tell them what was going on and hope they understood what he was talking about. The new way? Show and tell them using Visible Body’s Human Anatomy Atlas, a visual anatomy reference.

When did you start using Human Anatomy Atlas?

I started using Visible Body’s Atlas on my iPhone just recently—and I’ve kicked myself for not using it earlier. I use Atlas to quickly help patients visualize and understand their diagnosis. This technology helps me improve patient experience, compliance with treatment plans, and my overall efficiency.

Do you find that most of your patients understand their own anatomy?

Not exactly. One out of five Americans are seen every year in the ER and the bulk of patients don’t understand their own anatomy and physiology. To help them understand, patients want to see something. We’re visual animals.

How do they react when you use Atlas?

When I show Atlas on my iPhone my patients become wide-eyed with understanding.


What did you do to help illustrate a point before using Atlas?

Previously I found myself constantly using the dry-erase board in the ER to draw crude anatomy. Or if there was a rolling laptop cart in the room, I’d Google an image. If a patient presented with vertigo and dizziness, for example, I’d call up a picture of the inner ear to explain that connection.


Your overall verdict?

With Atlas, I’m using modern, advanced technology to quickly help my patients visualize and understand their diagnosis. Plus, the learning curve is straight up; it’s easy to use.


Want to see how Dr. Beatty explains gallstones to a patient using Human Anatomy Atlas 7?



Topics: anatomy and physiology

The Endocrine System: Hypothalamus and Pituitary

Posted by Courtney Smith on Fri, Jan 02, 2015 @ 03:31 PM

Are you hot right now? Cold? Maybe you're like Goldilocks and are just right. What about your height? Are you tall? Average? Short? Maybe your metabolism is lightning fast and you're always hungry, or maybe it's a bit slow and you stay full longer. All of these—regardless of which one you identify with—are regulated by the endocrine system.

What is the endocrine system? It's a network of glands throughout the body that regulate certain body functions, including body temperature, metabolism, growth, and sexual development. Though there are many glands, today we’ll focus on just two: the hypothalamus and the pituitary gland.

Hypothalamus-pituitary-gland-brain-1(Hypothalamus and pituitary, highlighted in blue)

I'm going to be throwing a lot of information at you, dear reader, so brace yourself!

Hormone Reaction Regulation


It’s no secret your brain is one busy place—neurons move at incredible speeds, synapses are constantly firing, blood is pumping, and glands are producing hormones. These glands, specifically the hypothalamus and pituitary, are working all the time to keep your body running at optimal performance. Every hormone the endocrine system releases follows a basic set-up: a signal is received, hormones are secreted, and the target cell undergoes changes to its basic functions.


The almond-sized hypothalamus is located below the thalamus and sits just above the brainstem. All vertebrate brains have a hypothalamus. Its primary function is to maintain homeostasis (stability of the internal environment) in the body.


The hypothalamus links the nervous and endocrine systems by way of the pituitary gland. Its function is to secrete releasing hormones and inhibiting hormones that stimulate or inhibit (like their names imply) production of hormones in the anterior pituitary. Specialized neuron clusters called neurosecretory cells in the hypothalamus produce the hormones Antidiuretic Hormone (ADH) and Oxytocin (OXT), and transport them to the pituitary, where they're stored for later release.

Think of the hypothalamus as the pituitary's older sibling—it not only controls the actions of the pituitary but it secretes at least nine hormones to the pituitary's seven.

Pituitary Gland

Attached to the hypothalamus, the pituitary gland is a pea-sized, reddish-gray body that stores hormones from the hypothalamus and releases them into the bloodstream. The pituitary consists of an anterior lobe and a posterior lobe, each of which have distinct functions.


Pituitary: Anterior Lobe (Adenohypophysis)

The anterior lobe (or adenophyophosis) secretes hormones that regulate a wide variety of bodily functions. There are five anterior pituitary cells that secrete seven hormones:



Secrete human growth hormone (hGH), aka somatotropin, which stimulates tissues to secrete hormones that stimulate body growth and regulate metabolism.


Secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which both act on the gonads. They stimulate the secretion of estrogen and progesterone, maturation of egg cells in the ovaries, and stimulate sperm production and secretion of testosterone in the testes.


Secrete prolactin (PRL), which initiates milk production in the mammary glands.


Secrete adrenocorticotropic hormone (ACTH), which stimulates the adrenal cortex to secrete glucocorticoids (like cortisol). Also secretes melanocyte-stimulating hormone (MSH).


Secrete thyroid-stimulating hormone (TSH), which controls secretions of the thyroid gland.


This table represents the types of hormones secreted by the cells of the anterior pituitary.


Target Area


Human-growth hormone (hGH)


Stimulates tissue growth in the liver, muscles, bones, as well as protein synthesis, tissue repair, and elevation of blood glucose levels.

Thyroid-stimulating hormone (TSH)

Thyroid gland

Stimulates thyroid gland to secrete thyroid hormones.

Follicle-stimulating hormone (FSH)

Ovaries and testes (gonads)

Stimulates development of oocytes (immature egg cells) and secretion of estrogen in females; stimulates sperm production in the testes in males.

Luteinizing hormone (LH)

Ovaries and testes (gonads)

Stimulates secretion of estrogen and progesterone, including during ovulation, in females; stimulates testes to produce testosterone in males.

Prolactin (PRL)

Mammary glands

Stimulates milk production.

Adrenocorticotropic hormone (ACTH)

Adrenal cortex

Stimulates secretion of glucocorticoids (cortisol) by the adrenal cortex during the body’s response to stress.

Melanocyte-stimulating hormone (MSH)


When in excess, can cause darkening of the skin; may influence brain activity (its exact role unknown—there is very little MSH in humans).


Pituitary: Posterior Lobe (Neurohypophysis)

While the anterior lobe shoulders most of the work in producing hormones, the posterior lobe stores and releases only two: oxytocin and antidiuretic hormone (ADH), or vasopressin.





Oxytocin (OT), aka the "love" drug

Secretes in response to uterine distention and stimulation of the nipples.

Stimulates smooth muscle contractions of the uterus during childbirth, as well as milk ejection in the mammary glands.

Antidiuretic hormone (ADH), or vasopressin

Secretes in response to dehydration, blood loss, pain, stress; inhibitors of ADH secretion include high blood volume and alcohol.

Decreases urine volume to conserve water, decreases water loss through sweating, raises blood pressure by constricting arterioles.


Pituitary Disorders

Even though it's very small, the pituitary gland isn't free from ailment—nothing is completely foolproof, after all.

Most disorders of the pituitary glands are tumors, which are common in adults. These growths are not  considered brain tumors, nor are they always malignant. In fact, they're almost always benign in nature! There are two types of pituitary tumors—secretory and non-secretory. A secretory tumor produces too much of a hormone, while a non-secretory tumor does not. Regardless, if the tumor is big enough, it can hinder normal pituitary function. These tumors can be removed, or monitored and controlled with medication.

Problems caused by tumors fall into certain categories:

  • Hyposecretion: Too little of a hormone is produced, interfering in normal function.

  • Hypersecretion: Too much of a hormone is produced, interfering in normal function.

  • Mass effects: The tumor presses on the pituitary or other areas of the brain, causing pain, vision issues, or other problems.

While the pituitary and hypothalamus can run into the above issues, on the whole they work a balancing act on your body. So the next time you're feeling juuuust right, you can thank the pituitary, hypothalamus, and all the other organs of the endocrine system.


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

Try Human Anatomy Atlas: New Call-to-action

Available for PC, Mac, iPad/iPhone, Android devices, and Windows devices.

Related Posts

The Anatomy of Vision
Parts of a Human Cell
5 Cool Facts about the Middle and Inner Ear

Topics: anatomy and physiology

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



“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.



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.



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 see more?

Never miss a thing!

New Call-to-action

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!













Tumor; mass


To view


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!


New Call-to-Action


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.

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).


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.


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?


Want to learn more?

Check out Anatomy & Physiology:

New Call-to-action

Available for your AndroidiPadPCWindows Tablet, or Mac

Related posts

Topics: anatomy and physiology