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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!


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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 & 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).


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Related Posts:

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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.


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Related Posts

The Anatomy of Vision
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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!


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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.

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Related posts

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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?


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Year in Review: 7 Coolest Medical Stories of 2013

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

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

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


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

Robotic assist coronary bypass stents

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

Let the SkyNet jokes commence.


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

3D printing heart

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

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

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

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

Blood arteries veins hand ankle surgically attached

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

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

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

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

Systemic circulation arteries veins artificial blood

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

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

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

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

Brain neuro coma vegetative listening

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

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

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

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

Mitochondria aging process reversed NAD

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

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

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


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

Antibacterial soap sanitizer FDA

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

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

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

Thanks for an amazing year! See you in 2014! 

Topics: anatomy and physiology, 2013

Five Cool Facts about the Middle and Inner Ear

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

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

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

Stapes middle ear auditory ossicles inner ear cochlea

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


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

Stapedius muscle middle ear stapes inner ear cochlea

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


3. The ear is not just for detecting sound.

vestibule semicircular canals ear inner ear bony labyrinth

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


4. The ear drum actually looks like a drum.

Tympanic membrane ear drum external auditory 

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

It's very easy to perforate the ear drum, which is why you shouldn't stick cotton swabs in your ears.


5. You have a pressure equalizer in your head.

Eustachian tube auditory canal inner ear

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

Want to learn more?

Additional References:

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

Topics: anatomy and physiology

Anatomy and Physiology: Anatomical Planes and Cavities

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

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

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

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

Here is a list of commonly used planes:

Frontal (Coronal) plane

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

Transverse plane

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

Sagittal plane

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

Midsagittal plane

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

Oblique plane

Divides the body at an angle.

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

Frontal Plane Coronal Sagittal midline

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

Transverse plane coronal frontal sagittal oblique

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


Cavities: Because things need to be kept somewhere.

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

Here are the body’s cavities:

Cranial cavity

Formed by the cranial bones and holds the brain

Vertebral canal

Formed by the vertebrae and contains the spinal cord

Thoracic cavity

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

-          Pleural cavity

Fluid-filled spaces that surround both lungs

-          Pericardial cavity

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

-          Mediastinum

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

Abdominal cavity

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

Pelvic cavity

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


Cranial cavity body anatomy physiology

Thoracic cavity body anatomy physiology

Abdominal cavity body anatomy physiology

Pelvic cavity body anatomy physiology


Want to learn more?


anatomy and physiology science learning education


Related posts

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

Topics: anatomy and physiology