The Meninges and the Deadly “Itis”

Your Meninges and You

"Whoah, play that back..whose heart is gonna stop?"

“Whoa, play that back…whose heart is gonna stop?”

It doesn’t seem fair about the brain does it…all the E-Hollywood, red carpet attention it gets? I mean there isn’t a single one of us out there in this crazy world that can survive if our heart stops beating and that’s just as true for snow leopards, crickets, Glen Beck, and 3-toed sloths as it is for foxy human-beings like you and me. However, the brain is treated like the commander and chief of the body (which it pretty much is). By that I mean consider the level of security and protection the body invests in its head of state. Not only is some of the densest sections of bone in the body (contained in the skull) there to protect it from impact like a souped up, Seattle Seahawks NFL helmet but there is layer upon layer of security measures in place to maintain this safe, warm, cozy, zen-like environment surrounding the brain and spinal chord as well. One of those layers of security is a super fancy barrier of connective tissue between the brain and skull referred to as the “meninges.”

Your meninges has 3 layers of its own, the dura mater, arachnoid mater, and subarachnoid space, which all kind of sound to me like strange galaxies of the Star Trek universe in old episodes of the Next Generation. (just saying, I’m a nerd like that)

Oh yeah, that's what I'm talking about.

Oh yeah, that’s what I’m talking about.

No, I’m not going to compare them to layers of a cake. We all know that’s really gross, but it is a fairly dynamic, intricate space. The Dura mater is the outermost layer. It’s thick, tough stuff just like you would imagine the outer layer of a barrier to be. Just beneath the dura is a single layer called the arachnoid mater that has thousands of spindly little projections that connect to the layer below, like scaffolding to a building under construction. The third layer is really more of a space, the subarachnoid space, that contains blood vessels, arachnoid spindles, and cerebrospinal fluid that basically coats the brain and spinal chord.

MeningesBlum

the subarachnoid space is a mesh of branching vasculature within a matrix of CSF fluid

Meningitis

Just like other tissues of the body the meninges is susceptible to infection and can become infiltrated by pathogens like bacteria, viral particles, or any other bad boy microbe within our circulation that makes it past our immune system or the blood brain barrier. When this happens the meninges becomes inflamed (e.g. Meningitis) and it’s about as bad news as bad news gets. Picture the meninges as a continuous inflatable mattress wrapped around the brain and spinal cord that suddenly gets blown up, squeezing and pressing on the delicate wiring of your central nervous system. Not exactly the best summer ever.

Hey, don't get distracted. I'm talking about meningitis here

Hey, don’t get distracted. I’m talking about meningitis here

Meningitis sufferers typically complain of a biggie-sized headache coupled with neck stiffness along with a fever. Other symptoms mimic that of a migraine…light sensitivity, confusion, disorientation, and a general sense of “something just ain’t right!” Now meningitis is an inflammatory process and you know that there are about a bazillion microbes out there that can trigger an inflammatory response upon infection. So when a patient, or even worse, when multiple patients display clinical features of meningitis the clock is ticking for medical detectives to seek out the “infectious agent.”

The Usual Suspects

N. meningitidis, pain in the butt, gram negative staining diplococci that looks like tiny coffee beans under the scope

N. meningitidis, pain in the butt, gram negative staining diplococci that looks like tiny coffee beans under the scope

When we want to point the finger at bacterial causes of Meningitis three misfits come to my mind almost immediately; Neisseria meningitidis aka meningococcus, Streptococcus pneumoniae aka pneumococcus, and Hemophilus influenzae. All three of these shady characters like to hang out in the nasopharynx of our upper respiratory tract. So they typically spread from infected individuals by means of “respiratory secretions” as in kissing, coughing, and sneezing. Of course, if the infected is an infant the mode of transmission can include just about anything they can put in their mouths and pass on. S. pneumoniae and H. influenzae are opportunistic little bastards. That means don’t go spraying everything and everyone down with lysol just yet, because these guys typically only spring into action when we are already immunocompromised in some way. Meningococcus, on the other hand, is the only known bacteria to cause meningitis on an epidemic level.

You may have noticed that I didn’t dive into viral causes of meningitis. Are you kidding..that list is like 3 pages long! Viruses pose an even greater threat in that they are much much smaller, mutate at the drop of a hat, and have more modes of transmission than…Lil Jon has bling.

Lil+Jon

Exactly, more than that.

A lumbar puncture is typically the diagnostic procedure of choice when meningitis is suspected. This undeniably scary, long needle is inserted into the patient’s back to extract Cerebrospinal fluid from the spinal canal, usually through access to the lumbar vertebrae. Remember that your brain and spinal chord are suspended in fluid 24/7 that should be vacant of things like, viruses, bacteria, and even your own blood cells. So those few precious drops of CSF are like diagnostic gold to the folks working the clinical lab. They will make microscope slides to look for white cells and microbe hitchhikers and perhaps most importantly culture that CSF sample on clean, nutrient rich agar plates to see what pathogens grow. Many times they can positively ID the culprit like a closed case file in an episode of “The First 48.”

Stay curious, stay classy, and never stop learning my friends 🙂

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Kidney Confidential

Just couldn't help myself..you know how it is. Magically Yours, Forgotten Physiology :)

Just couldn’t help myself..you know how it is. Magically Yours, Forgotten Physiology 🙂

Surprising isn’t it, that we’ve never talked about the kidneys until now. Well sure there were a few times that I might have mentioned them in other articles, but kidneys should never play supporting roles. We’re not talking Mary Kate and Ashley. No sir, the kidneys are Siegfried and Roy, center stage in Vegas with white tigers jumping through rings of fire.They deserve the full, Maxim magazine centerfold treatment.

The Low Down

CRAZY SIMPLIFIED - aorta branches to feed kidneys blood which do their filter thing, make the pee which drains through ureters and empties into bladder. Nothin but net!

CRAZY SIMPLIFIED – aorta branches to feed kidneys blood which do their filter thing, make the pee which drains through ureters and empties into bladder. Nothin but net!

Let me level with you for a minute. Urine…it’s nothing to be afraid of. It is the ultra filtrate of blood plasma. “Pee” is the result of a highly specialized filtration system, the kidneys, receiving a rich blood supply from the abdominal aorta. They selflessly separate the good stuff from the bad and send the filtered blood, squeaky clean to the vital organs. What waste products are left over leave the body as urine. A large component of urine is urea which is a substance representing the end of nitrogen metabolism. It’s actually odorless but when the stuff comes into contact with water or water vapor we get ammonia from the reaction which definitely has its own pungent, sweaty gym sock charm. So If I were ever tempted to give you the cliff notes summary of what the kidneys do I would say that they remove soluble waste or excess metabolic byproducts from the blood by concentrating them into urine.

No Dude, Seriously….

Friends don't let friends forget about renal blood flow.

Friends don’t let friends forget about renal blood flow.

When serious people talk seriously about kidney function they DARN well better know that they need to mention filtration, reabsorption, and secretion. Otherwise they’re just wasting time, air, and parking space. So let’s do this thing right.

Filtration

The show kicks off with the renal artery which, branching off of the abdominal aorta, supplies blood to the whole operation (the kidneys). Like all fashionable arteries it branches into smaller vessels. STOP

[This is where we enter the microscopic neighborhood of the nephrons, the thousands of tiny functional units that make up the plumbing and wiring of the kidneys. Surprisingly, what does the work of each kidney is the collaborative effort of thousands of tiny nephrons. Your key words are: Tiny and Thousands. Please, please keep this in mind because these itty bitty nephrons perform some major league physiology. Ok back to the show.]

Those arteries having branched until they can’t branch any more now make up the afferent and efferent arterioles. These form a kind of yarn ball of capillaries called the glomerulus. The glomerulus forms such a fine mesh of blood vessels that not only are blood cells separated out of the blood but just about any substance exceeding a particular molecular weight to include most plasma proteins. Only things like water, sodium, the occasional glucose, and something called urea are all that slip through the gate and slide down the drain. Now that’s IF everything is working properly. This mesh of capillaries sits in a receptacle formed of cells called the Bowman’s capsule, which is kind of like the bowl basin of the sink.

The afferent arteriole sends blood to the glomerulus while the efferent arteriole carries blood away from the glomerulus and articulates into the peritubular capillaries that are going to surround the tubular portion of the nephron where they will play a super fun role in tubular reabsorption.

nice diagram right...took some serious google image surfing for this baby. Oh how the muscles burned!

nice diagram right…took some serious google image surfing for this baby. Oh how the muscles burned!

Tubular Reabsorption

Ok so blood has passed, Brita filter like, through the gates of the glomerulus, but that was a nonspecific filter. Now we’ve entered the world of reabsorption which is way selective. To put this into perspective we’ve gone from the freckled, learners permit sporting, ticket stub tearer at the movie theater to the veteran TSA agent with white gloves, only 4hours of sleep, and an itchy trigger finger. When it comes to letting substances back into the blood post filtration, the body takes ONLY what the body needs (sodium, potassium, chloride, bicarbonate, glucose) any access gets the royal flush (secretion). When it comes to things like sodium there’s a combined effort between crazy natural forces like passive diffusion via osmosis and whatever mood our adrenal cortex is in. Let’s say it’s Monday afternoon and the body says “man, I sure could go for some more sodium.” So your adrenal cortex will secrete aldosterone which is like a chemical text message that directs the cells of the proximal convoluted tubule to absorb more sodium.

[Substances reabsorbed by PCT(proximal convoluted tubule) – sodium, potassium, water, urea, glucose, chloride]

The reabsorption of water is completely dependent on sodium reabsorption. This is where the whole osmosis thing comes into play because water is naturally going follow the flow of sodium ions, moving in the direction of higher concentrations, Tai Chi like to restore osmotic balance. Now of course, increasing water in the vessels (fluid volume) increases blood pressure. So if A+B=C then increasing sodium reabsorption increases blood pressure.

A change in blood pressure is sensed by the cells of the juxtaglomerular apparatus (another portion of the nephron) which secretes renin. Renin converts the protein angiotensinogen into…wait for it…angiotensin. This is the substance that signals the adrenal cortex to do its aldo thing in the first place. Sounds like one of them crazy feedback loops to me (another article I promise).

Thirst

Yes, your mind does play tricks on you. There is this clever thing that your hypothalamus does in response to high sodium concentrations in the blood. It tells you to drink more water. Meanwhile, it signals your pituitary to secrete ADH (antidiuretic hormone) which tells your distal convoluted tubule to reabsorb mas agua as well (my hypothalamus is bilingual BTW) rather than just dump it down the drain (excrete in urine).

the juxtaglomerular-whatchamacallit is a collection of cells in the neighborhood of the glomerulus

the juxtaglomerular-whatchamacallit is a collection of cells in the neighborhood of the glomerulus

Loop of Henle

Best summer ever!

Best summer ever!

No, it’s not a 700ft water slide where they take your picture as you plummet half naked on a large rubber inner tube. It is the section of the nephron leading from the proximal convoluted tubule to the distal convoluted tubule and it represents some pretty badass architecture so show some respect! It is the sinking, looping construction of the Loop of Henle that allows urine to concentrate sodium, potassium, and chloride ions via a concentration gradient which allows water and valuable ions to be reabsorbed. This however, should be an article all to itself so..you may want to give this the Wiki treatment.

Secretion – Last Call

Ok so we came, we partied, we danced all night, and now the kidneys are saying “everybody out!” This is where the body rids itself of all those high and low molecular weight substances that got the reabsorption shaft (excess H2O, sodium, and urea/nitrogenous wastes).

Now you are probably saying “whoa now, there are way more substances that end up in urine after reabsorption.” Ok, there is a threshold that the kidneys reach. For example they reach a maximum capacity for how much glucose they can filter at one time and yep, the stuff slips through the glomerulus and if that concentration is high enough then the loop of Henle just doesn’t have the molecular horse power (energy) to pump glucose back into the blood.

And the moral of the story is….

Blood enters the kidneys to be maticulously filtered by thousands of microscopic, fancy pants structures called nephrons which filter soluble and insoluble substances from the blood, reabsorb vital substances like sodium, water, and glucose depending on the body’s need for it, and secrete excess waste by concentrating it into urine which flows through the ureters and empties into the bladder for the royal flush.

What’s that…you say there’s more to it than that? You bet your efferent arterioles there’s more, but for now stay classy, stay curious, and never stop learning my friends 🙂

The Liver Files

Ok, so I thought she had pretty eyes. Don't judge.

Ok, so I thought she had pretty eyes. Don’t judge.

I mean frankly, the liver performs so many necessary functions that it’s almost boring. The liver is like that movie in the Oscars that wins every award…best screen play, best performance, best soundtrack…and you’re like “come on, give someone else a little credit.” Well when it comes to the body the liver deserves all the credit. For starters the people who write textbooks can’t even decide what organ system to put the liver in. It produces enzymes that are necessary for the emulsion of fat, and the metabolism of proteins and carbohydrates so obviously it’s part of the digestive system…well kinda. It has a hefty blood supply, produces lymph, and harbors antibodies for the destruction and removal of old and ineffective red cells so maybe it’s part of the immune system…well kinda. It produces an [EXPLETIVE] load of useful proteins that aid in everything from helping your blood to clot to detoxifying drugs, and toxins that enter the blood stream so….don’t look at me, your guess is as good as mine. If you want a meeting with the Liver you’ve got to ride the elevator to the top floor, follow the arrows to the door labelled “The Man” and wait in line. Well ok, this stays between me and you, but I can tell you what I know. Keep your voice down and close the door behind you…

Is it just me or does the invisible man have great biceps?

Is it just me or does the invisible man have great biceps?

The Liver is the original Renaissance man. I mean forget the Dos Equis commercials. Just take a look at this organ’s resume..

Metabolism

glycogen synthesis and degradation, gluconeogenesis from protein, amino acid, and lipid / non-carbohydrate sources

Toxicology

drug metabolism and detoxification

Digestion

synthesis of bile salts…nasty but necessary

Synthesis

plasma proteins, cholesterol and its carrier lipoproteins

And I wouldn’t be suprised if it knows magic tricks

Digestion and Metabolism

The liver produces bile which looks a lot like it sounds, nasty, but it gets stored in the gallbladder to aid in the breakdown of lipids (fats basically) in the small intestine.

About that whole bile thing…

bile facilitates the action of pancreatic amylase which actually degrades triglycerides. The bile’s salts have two sides, molecularly speaking, hydrophobic and hydrophyllic. The main reason why fats don’t dissolve in water is because their molecular surface repells water. So bile salts can surround fats with their water loving (hydrophillic) sides out which gives enzymes like pancreatic amylase the back stage pass.

Synthesis

So not only does the Liver make cholesterol but it produces the carrier molecules, lipoproteins like HDL and LDL that transport the stuff. Cholesterols are insoluble in water so the lipoproteins facilitate their deep sea journey through the bloodstream.

Some light anatomy

so the main cellular component of the liver is the hepatocyte. They make up roughly 70-80% of the total mass so naturally, because I do choose favorites, that’s what I’m focusing on in this article. They are the working parts of the organ that together make the magic happen. An organ is the sum of it’s parts…microscopic processes equating to bigtime changes. Ah yes, and it get’s it’s hefty blood supply from the hepatic arteries and portal vein. Now you know in case Jay Leno asks you in the street. You’re welcome.

Da Sugar

When I say metabolism I want you to think “what happens to the glucose?” Let’s say it’s half priced Tuesday at The Gringo Burger Bodega (I made that name up. Can you tell?) and you’ve treated yourself to the #6 diablo fries with a dulce shake made extra dulce. While being transported to takeout heaven you wonder “What is my body doing with that access glucose?” You’re always thinking. I love that!

Here’s what happens…

Blood from your portal vein supplies your hepatocytes with fresh glucose. Those cells will form long chains of the glucose molecules linked by a-1,4 glycosidic bonds to form this nice biggie sized storage form of energy called glycogen which happens when your blood glucose levels are high hence there is a raise in blood sugar so having all those hepatocytes uptake glucose lowers blood sugar. So in classic, clever physiology fashion when blood sugar is low the glycogen can be broken down/degraded into glucose which is then available to adjust for blood glucose level.

Gluconeogenesis

Another neat trick…

another innocent victim clearly possessed by 10k demons

another innocent victim clearly possessed by 10k demons

The other thing you have to know about the liver is that it doesn’t like to let anything go to waste. If it’s an organic molecule and your body can make use of it, chances are your liver is breaking it down and recycling it as we speak…no seriously, like just now. oh you missed it.

Sometimes carbohydrates just aren’t enough. Sorry blue box mac n cheese, I know we go way back but it’s true. The body needs a way to derive glucose, that oh so sexy cellular currency, from non-carbohydrate sources. The process by which the liver pulls this off is of course referred to by the cool kids (scientists) as gluconeogenesis. Your kidneys can also pull this off, but don’t get too excited about this clever trick. It’s just another way the body compensates for potentially “bad news” drops in blood glucose apart from the breakdown of glycogen. It’s the kinda thing that is supposed to kick in when you’ve been fasting, starving, or exercising like you’ve been possessed by demons.

Detox Rocks! (see what I did there)

So one more thing…

hell yeah

hell yeah

The liver is probably the best defense our body has to protect us from ourselves. If it’s toxic or in a form the body can’t use…the liver will convert, breakdown, and package it like there’s no tomorrow..because if it didn’t there really would be no tomorrow. This is typically referred to as xenobiotic metabolism and it’s made possible by the bountiful community of enzymes and their biochemical pathways that call the liver home. The liver typically accomplishes this by modifying the fat loving (lipophilic) nature of many pharmaceuticals into a more user friendly and excretion friendly, water loving (hydrophilic) form. However, it’s not always about solubility. Some nasty little substances require a little versatility (I’m looking at you Alcohol..you know what you did last weekend). Thankfully our livers come equipped with a nifty alcohol dehydrogenase that allows for the reduction reactions that keep this party animal in its cage reasonably well.

I should mention however that the liver’s gift can also be its curse. The liver has such mad skillz for the bio-conversion of compounds that every now and then it can convert foreign compounds into substances that are actually more toxic than what you started with. We call these metabolites and they are no fun.

Well my friends it’s time for me to go make a difference (eat dinner). Stay curious, stay classy, and as always never stop learning 🙂

Spleen for All Seasons

"Yup, I'm old and mysterious and I could tell you stories that'll make you sleep with the lights on."

“Yup, I’m old and mysterious and I could tell you stories that’ll make you sleep with the lights on.”

Oh yes, this is one sketchy organ. The spleen is the epitome of the mysterious old man the townsfolk all whisper about. No one really knows his story accept that he’s always lived in this town (our bodies). As far as organs go, the spleen hardly ever shows up on the 6 o’clock news. Most of us don’t know what it looks like, where it’s located, if it votes republican, democrat, or green party.

The spleen is one of those organs that helped us survive in the womb. When we are born and just fresh out of the wrapper like a snappy, hard pretzel our bodies were still adjusting to an oxygen rich environment. While we were still hitching a ride in Mommy Dearest our bones were still developing and not quite ready for the full time responsibility of being the primary producers of our blood cells (whites and reds). In the early stages of development our liver and spleen jump start us with all the oxygen supplying cells we need. As you develop, your organs pass the baton of blood cell production, or hematopoeisis, until this process is effectively carried out by the bone marrow. What a lot of folks don’t realize is that the spleen never stops looking after those red cells, in fact the spleen receives it’s own blood supply to act as blood filter extraordinaire. The spleen is an incredibly attentive, highly adapted filter to be more exact. Just calling it a filter is like saying the Iron Chef makes a mean peanut butter & jelly sandwich or that Yanni plays a mean chop sticks (which I’m sure he does). The liver receives a much larger blood supply and carries out more of the blood cleanup but the spleen is considerably more meticulous.

Ah, now why can't anatomy be this cut and dry all the time?

Ah, now why can’t anatomy be this cut and dry all the time?

The spleen can selectively remove the misshaped or malformed cells from circulation. To a red cell, shape and form is everything. They have to be firm and flexible to squeeze through vessels without leaking their precious hemoglobin payload. The spleen acts as a final physical exam for new reds entering the bloodstream. It squeezes them through tight fitting vessels and has it’s very own elite team of white cells to pick off trash along the red cell membranes(precipitated proteins or remnants of DNA), changing their shape, roughing them up. Cells that make it to the other side have essentially proven themselves worthy to deliver oxygen another day.

The spleen also acts as a kind of lymph node whereby a population of B and T cells reside to take part in the immune response. It has so many macrophages scouting the blood for trash that we typically classify the spleen as a lymphoid organ. It also houses a backup supply of blood for the body to compensate for blood loss.

So ok… yes, when someone has to have an enlarged or infected spleen removed (splenectomy) they can live a perfectly normal, healthy life without it. They are susceptible to a few more infections (especially the very young), but considering that they are an organ light they do pretty well in most cases.

This is my problem..I really don’t like referring to the spleen as an accessory organ or dispensable based only on the fact that we don’t die when we get them removed. I mean if science only considered something important based on whether or not something bad happened to us if it was gone then we would get nowhere as a civilization. So let me just say that perhaps the full functionality of the spleen is yet to be realized. Once upon a time someone said “there must be something in the air too tiny to see that can cause disease.” Science has always been wide open baby. Stay classy my friends and never stop learning.

Adrenal Gland Greatest Hits

I think it’s safe to say that the average American knows way more about the dating habits of Snookie than the basic functions of their own adrenal glands. My fellow Americans let’s beat the statistics shall we.

6198582_f260

Jessica Biel – personal favorite tight leather sporting supporting actress

You know all this talk about adrenaline bores me to tears. Anytime anyone talks about the adrenal glands all you hear about is the “fight or flight” response. It’s like the preview to a summer blockbuster where all they show are the explosions and 15 seconds of car chases with tight leather wearing supporting actresses in the passenger seat (which I don’t mind so much). If anyone asked you what the movie is actually about, good luck. There is however, way more to this E-hollywood bad boy than running from a fight. He does the work. So right here and now we’re going to attempt to answer the question “Adrenal Cortex, what have you done for me lately?”

Anatomy 101

Your adrenal glands rest atop the kidneys like really ugly shoulder pads, secreting hormones into the bloodstream in response to stress. Anatomically speaking we’ve designated the adrenal gland into two distinct regions, the cortex and the medulla. The cortex (forming the exterior portion of the gland) is largely known for producing cortisol and aldosterone. The medulla (forming the center or guts of the gland) specializes in producing epinephrine and norepinephrine (one of the most notoriosly misleading names in physiology).

Fun fact – both epinephrine and norepinephrine contribute to the fight or flight response with a few subtle differences. So if you’ve been thinking this whole time that they were highschool rivals or that norepinephrine was Latin for “not friends with epinephrine” I promise that I won’t tell anyone…fingers crossed.

Also, why is it that the term cortex, which sounds a lot like “core” actually refers to the outside of the organ? Sorry, that just irritates me to no end.

Pop Culture

it happens all the time….one day a band makes it big, working their way to the top of the charts, but the next week it’s the lead guitarist who’s on the cover of Rolling Stone’s magazine. Whenever people talk about the human stress response to danger or exhiliration we tend to focus on the adrenal medulla, the site of epinephrine production A.K.A adrenaline. However, this is merely responsible for a short term response to stress…the increased heart rate, breathing rate, and rapid conversion of nutrients for the sudden burst of muscle action. We’ve forgotten all about the long term response to stress largely coordinated by the adrenal cortex, the electric bass player who never stopped setting the tempo.

Adrenal Cortex, boy you so crazy…

We like to talk about the big picture but the truth is that so many of our physiological responses begin with baby steps, minutia, small subtle changes that lead up to bigger, longer lasting events. If you want to affect an organ there is no secret doorbell with a note that says “push ringer to call the kidney.” Hormones like aldosterone act on the cellular level, and “talk” to the tiny functional units of the kidney.
One such hormone, aldosterone, produced by the zona glomerulosa of the adrenal cortex works on the distal convoluted tubule and collecting duct of the nephrons (tiny fuctional units of the kidneys) to increase the reabsorption of sodium from the plasma which in turn affects the water balance. Why do we care? This ultimately effects blood pressure. Your blood is more than 50% water (i.e. plasma) so since water makes up such a significant volume of the blood, influencing the salt/water concentration effects overall blood pressure. This again helps us to maintain metabolic balance.
Aldosterone production is triggered both by ACTH (adrenocorticortropic hormone) from our good friend the pituitary and angiotensin triggered by the juxtaglomerular cells (in the kidneys) when renal blood pressure drops (blood filtered through the kidneys).
Another fun trick the adrenal cortex has up its sleave is the production of cortisol. In response to prolonged stress. Cortisol is chiefly responsible for increasing blood glucose over time through glyconeogenesis, which is basically a means of utilizing non-carbohydrate sources such as lipids and amino acids to form glucose. This is just another way our bodies maintain homeostasis, that amazing zen-like balance of our metabolic needs. Cortisol also suppresses the immune system. This makes it quite useful in medicine as an effective anti-inflammatory agent.

It’s human nature…we like to compare things. That’s just how we roll and every now and then it helps us learn so….

Adrenal Medulla V.s. Adrenal Cortex

medulla – the production of epinephrine & norepinephrine – “Fight or flight” car chases, explosions, tight leather pants

cortex – the production of aldosterone & cortisol – homeostasis, zen-like balance, long term response to stress

Forgotten Physiology – The Endocrine System Part 1

If someone asked you to describe the endocrine system in three words and the words “What is that?” are all that come to mind then…yeah, you should check out these articles.

5899276_f260Ah yes, the endocrine system is one of my favorite misunderstood topics in biology (did you just get chills…me too). I’ll bet that if we gathered up all of the skeletons from America’s academic closet they would all be huddled around the endocrine system for warmth. Beneath his rough exterior of ten syllable physiological names the endocrine system is just a big ole softy. However, once you learn half of what this system is capable of you’ll be happy that you never leave home without it (which would be impossible and gross).

It will be difficult. There is an [EXPLETIVE] load of hormones and chemicals involved that you’ll need to commit to memory and unfortunately, your professors will want you to “apply your knowledge” on an exam, requiring you to magically posses an intimate understanding of the facts you’ll probably stay up all night on Coke and Doritos, force feeding your brain. So let us dive into the nuts and bolts of how this system works.

It’s all about the Glands

The endocrine system is a network of ductless glands (chemical secreting glands without the fancy side channels) that secrete chemical signals called hormones directly into the bloodstream. These hormone signals communicate with organs in our bodies on a cell to cell basis, like wickedly efficient chemical text messages.

“Hey liver cells, let’s lower the blood sugar later.” – Your BFF the Pancreas.

They will tell you that this change occurs gradually but when you consider just how many trillion cells there are in the body this is really an extraordinarily rapid process.

Some Basic Anatomy

There are about 6 glands that have been granted endocrine VIP status:

Pituitary AkA the Hypophysis(anterior & posterior) – which hangs out on the lower fore brain, riding shot gun with the hypothalamus just a few centimeters away from the spinal chord.

Thyroid – forms a mass over the trachea like a really ugly, trippie butterfly

Parathyroids – four tiny masses with each pair hitching a ride with either side of the thyroid

Adrenal glands (cortex & medulla) – you have two that ride piggie back on top of each kidney

Pancreas – parked along the lower curvature of the stomach just before it forms into the duodenum, essentially hanging along the sagging waistline of the digestive system

Gonads – general name that describes the testes in men and the ovaries in women which are located within the pelvic cavity, A.K.A the nether region, the land down under, cave of secrets, magic kingdom….yeah, well you get the idea.

The Pituitary Gland A.K.A Hypophysis

Whatever you do don’t confuse the hypophysis with the word hypothesis…seriously try not to think about how similar those two words sound.
As endocine glands go, the pituitary is like a sleek, sophisticated hybrid model. Your pituitary and hypothalamus form a neuroendocrine network of neurons and endocrine cells, granting the pituitary global access to other endocrine glands in the system. If the body were highschool the pituitary would be that trendy, oh so popular chick with everyone’s number programmed into her phone.
In many ways it is the brains of the endocrine system, sensing subtle changes in the body and signaling endocrine organs such as the thyroid or adrenal gland to produce hormones that allow the body to compensate for those changes. For example, if a decrease in blood sugar is detected by the hypothalamus the pituitary will produce a trophic hormone ACTH (adrenocorticotrophic hormone) which triggers the adrenal gland to secrete cortisol, which gradually increases the blood sugar. Trophic hormones signal the secretion of hormones by other endocrine organs. Since the pituitary is souped up with nifty neural connections it can pass notes fairly easily to all the cool kids in the class (endocrine target organs within the system) with an assortment of trophic hormones.

Pituitary Gland Top 5 Greatest Hits (Trophic hormones)

here’s a fun list of trophic hormones produced by the anterior pituitary and their functions

TSH (thyroid stimulating hormone) – stimulates the thyroid gland to secrete thyroid hormone which actively regulates metabolism….more on this later

ACTH (adrenocorticotrophic hormone) – stimulates adrenal cortex to release glucocorticoids, steroid hormones that regulate glucose

FSH (folicle stimulating hormone) – stimulates the maturation of eggs in females and the production of sperm cells in males

GH (growth hormone) – stimulates bone and muscle growth as well as the production of IGF (insulin like growth factor) produced primarily in the liver which triggers growth in many tissues. Plays a crucial role in growth and development in early childhood.

LH (Leutinizing hrmone) – induces ovulation in women and the secretion of testosterone in men…more on this later.

THe EnD..well for now…

Hey don’t worry, I’ve got way more to say about the endocrine system. It’s kind of a big topic so I’ve broken it down into a few articles for your convenience. Please keep reading and if I’ve made some incorrect or misleading points along the way let me know..but be nice. I’m sensitive 🙂 Stay classy and never stop learning.