Wednesday, December 18, 2013

WILTIMS #86: Must...sleep...

Sorry for the brief post, but I need all the study/sleep time I can get tonight.

TIL: Babies don't like getting shots, or having their nose wiped, or being looked at funny, or anything depending on the moment. Also, there seems to be at least three levels of crying: I'm not sure if I'm upset, I'm really upset, and I think I'm dying so I might as well take out your eardrums on my way out.

Even medical students don't like doing spirometry tests (myself excluded).

Tuesday, December 17, 2013

WILTIMS #85: Before the plunge

More exams are upon us, but the next couple days are blessedly light on new content. Sorry for saturating you with respiration stuff (pardon the pun), but it's all we're doing right now.

TIL: When a person exhales to their fullest extent, there is always some air left over in the lungs. This volume is important for certain clinical calculations, but cannot be determined through spirometry (measuring the volume of air going in and out of the lungs). To measure this last bit of air, known as the Residual Volume (RV), we have to use one of several other techniques. One such method is helium dilution, where the patient breaths from a known volume of an air/helium mixture. When the external mixture and the air remaining in the lungs has had time to equilibriate, the RV can be found using simple algebra.

In a normal person, the pressure in the chest is always negative. Put another way, the lungs are elastic and always trying to collapse. They continually pull on the fluid between the lungs and the chest wall, creating a suction-like effect. When a patient is on a ventilator, however, the machine is forcing air into the lungs without the chest cavity expanding, as it would with normal breath. The thoracic pressure is accordingly higher than normal. This affects fluid return to the heart, often resulting in peripheral edema (swelling of the limbs) amongst other problems. These side-effects are acceptable to keep the person breathing, but must be kept in check.

Saturday, December 14, 2013

Study Aid #7

WILTIMS #84: Mito-what?

...two freshmen high schoolers in a junior year biology class did a genetic disease report on a strange and very rare set of diseases called mitochondrial disorders. They did research using resources to which few had access because one of the kids' families was affected by this disease. Whereas his friend had always wanted to be a doctor, the kid wouldn't decide to go into medicine for several years. Little did he know that one day he would be writing in third person at medical school.

Mitochondrial diseases didn't get me interested in medicine per se, but they did turn me on to biology and set me down this path. In the years since I first investigated their peculiarities, my understanding has grown alongside that of the biomedical community. It turns out mitochondrial diseases aren't as rare as we once thought, and may still be greatly underestimated due to the difficulty that comes with diagnosing them. That's why it was so exciting that our school invited a guest lecturer to give an hour and a half long talk on mitochondrial genetics and diseases. Now 200 soon to be doctors will think of mitochondrial diseases a bit sooner in their differential diagnoses.

TIL: Azidothymidine (AZT) was the first approved HIV medication and along with other drugs that work by the same mechanism, it has the side effect of causing transient mitochondrial diseases. AZT targets the DNA reverse transcriptase of the HIV, disrupting viral replication.

Though it does not affect the nuclear replication machinery, AZT has an extremely high affinity to the DNA polymerase utilized my mitochondria. Patients thus develop all the symptoms of mitochondrial dysfunction (such as myopathy and lactic acidosis) while having this life-saving drug administered. If the side effects are severe enough, the patient may be taken off the drug, resulting in rapid recovery of mitochondrial DNA expression.

Friday, December 13, 2013

WILTIMS #83: Leeches

Sorry, not much interesting to report today. We were going over more respiration (which I've written oodles about over the last week) and the math behind genetics (which is no fun to write about). Tomorrow seems promising though!

TIL: Hemochromatosis is an autosomal recessive genetic disease caused by high levels of iron in the blood. It is one of the few diseases that can actually be treated effectively with leeches.

Autosomal dominant diseases typically are only expressed by heterozygotes (individuals with only one of the two copies of the disease gene are mutated) because the homozygous diseased genotype is almost always fatal. An example of this is achondroplastic dwarfism, the most common form of dwarfism. An exception to this rule is Huntington disease, which presents with the same disease phenotype for both heterozygotes and homozygotes.

Thursday, December 12, 2013

WILTIMS #82: Don't Panic

TIL: Giving supplemental oxygen (O2) may increase the arterial oxygen saturation but it does nothing to decrease the partial pressure of carbon dioxide in the arterial blood (PaCO2). Instead you must change the respirator settings to increase the alveolar ventilation (the amount of air that comes in and out of the lungs).

If hyperventilating get the CO2 out of your body faster, why is it so bad? Your body does not monitor its blood oxygen level directly, but instead looks at the carbon dioxide level which, theoretically, should be just as effective. If the CO2 level is high, O2 should be low and vice versa. The problem is that hyperventilation causes the CO2 level to go down without affecting the O2 level. The body responds by constricting blood vessels in the brain and other tissues, thinking that O2 must be abundant, effectively suffocating itself. This is why breathing into a bag when hyperventilating can help; it traps more CO2 in the lungs - normally a bad thing - to alert your brain to the real O2 level.

Why doesn't hyperventilating increase your blood oxygen levels? O2 is transported via the hemoglobin protein in red blood vessels and, at normal respiration rates, the hemoglobin are already saturated with O2. They can't hold any more O2, even if you are breathing more in per minute.

X-linked agammaglobulinemia (yes, I occasionally pick things to share just because they have sufficiently multisyllabic names) is a genetic immune deficiency resulting from a mutation to the X chromosome that prevents B cells from maturing. B cells are responsible for producing antibodies which are the primary weapon the immune system has to fight off pathogens. The disease is expressed far more often in males due to the X-linked recessive inheritance. As women have two X chromosomes, a woman with one diseased allele will not show symptoms but will instead be a carrier of the disease. Men (who have one X and one Y chromosome) can never be carriers and will always fully express the diseased phenotype.

Wednesday, December 11, 2013

WILTIMS #81: Do palm it pull his phat is hoc go line

TIL: Beta-thalassemia is a genetic disorder that affects the beta sub-units of the hemoglobin proteins in red blood cells. Hemoglobin are responsible for transporting carbon dioxide and oxygen to and from the lungs, so patients with beta-thalassemia often have symptoms of anemia. The disease is caused by an error in transcription from the DNA to the mRNA of the gene for the beta strand of the protein. The spliceosome, which normally cuts out the useless bits of the genetic transcript and splices back together the useful parts, for one reason or another cannot correctly remove all the fluff, which results in an altered hemoglobin protein. It can take as little as one errant nucleotide out of the over 3 billion that make up the human genome to cause this disease.

Atelectasis is the collapse of part or all of a lung. This has several causes, one being a deficiency of the surfactant secreted by the type II pneumocytes (lung cells) which reduces the surface tension of the fluid coating of the lungs, preventing the alveoli from collapsing. The chief surfactant is dipalmitoylphosphatidylcholine (which, by the way, my phone initially autocorrected as "do palm it pull his phat is hoc go line").

Atelectasis can be a problem in infants following a premature birth because, though the type II cells start producing surfactant during the 25th week, they don't begin to secrete until the 30th. The treatment is to give the mother glucocorticoids to stimulate surfactant release. Maternal diabetes can be another cause of this condition because high fetal insulin levels inhibit surfactant production. You can treat this by administering a surfactant into the infant's lungs through an intubation setup. The only problem is that the surfactant has a consistency of honey, so in order to coat the whole lung surface, you must pick up the baby and rotate them around, just as if you
were coating a ceramic pot with resin.

Tuesday, December 10, 2013

WILTIMS #80: To be or not to be

 Yesterday, my school's Ethics Club screened the documentary "How to Die in Oregon" on campus. The film follows various individuals and families, in and out of the state of Oregon, as they struggle with the incredibly difficult task of planning for an imminent and often painful death. Oregon is one of the three states that has legalized doctor assisted suicide - marketed better as "death with dignity" - which allows a doctor to write a prescription for patients with terminal illnesses to peacefully end their life at a time of their own choosing. The process is not simple and requires substantial hoop-jumping to complete.

Physician assisted suicide is distinct from euthanasia because the physician does not administer the drug them-self. The patient must be able to take the drug (usually in the form of a powder dissolved in water) unaided by anyone and they are free to change their mind at any time.

I highly recommend that, regardless of your views on the issue, you watch this documentary (it's even on Netflix streaming), though I warn you to stock up on Kleenex first. It's not terribly preachy and pretty much leaves it to the audience to sort out their own feelings based on the stories presented. Nearly everyone in the audience yesterday agreed with the law, but there was at least one person that was unconvinced, predominately on religious grounds. I would love to hear your opinion on the matter (feel free to email me if comments would be too public).

TIL: Patients with emphysema adopt a tripod position when sitting and struggling to breathe. This allows them to stabilize their shoulders with their arms, freeing the muscles of the neck to aid in respiration instead.

Heliox is a gas mixture composed of 79% helium and 21% oxygen (the same as air) that can be administered to a patient to breathe instead of air. The mixture lowers the density of air, which reduces turbulent flow and is used to treat conditions of large airway narrowing.

Saturday, December 7, 2013

WILTIMS #79: Deep breath!

Today started out rather embarrassingly. I decided to attend the weekly neurosurgery conference up at the hospital. I had never been before, so I figured I'd play it safe and wear a shirt with a collar. I had to go to class right after, so I opted for my nicest pair of jeans. Turns out that dress shirts and ties are the norm. Oops! It didn't help that today was also apparently an interview day for prospective residents, meaning that half the room was wearing suits. Joy.

Anyways, after biting the bullet and finding a hiding spot in the corner, the presentation started. The five neurosurgical residents sat in the front row and alternately led the discussion of current interesting cases and were grilled by the attendings asking what they would have done in each case (and telling them why they were wrong). Both the cases and the gauntlet were terrifying and fascinating at the same time.

I think the most disconcerting part was watching the insensitive reactions of the residents to the grim prognoses of the patients. They've seen crazy cases like this every day for years and the only way to cope is apparently to laugh. I'll definitely be going back next week (with more appropriate attire), but I'll endeavor not to be desensitized too quickly.

TIL: Dead space volume (VD) is the volume of air involved in respiration that is stuck in the trachea, bronchi and other rigid non-respiratory spaces. When you inhale, the fresh air in this space never makes it to the lungs; similarly, during exhalation some used air never makes it out of the body and gets sucked back in during the next inhalation. This is normally not an issue because the total volume inhaled is far more than the VD.

However, if you hyperventilate, taking lots of super-shallow breaths, you start increasing the proportion of each breath taken up by that used air, which eventually can lead to hypoxia and unconsciousness. Snorkels, when used improperly, can result in a similar effect. The tube of the snorkel effectively doubles your VD, meaning more stale air re-enters the lungs.

Diagram showing the various lung volumes -
Vis not shown because that volume never reaches the lungs. 
Obstructive sleep apnea is a condition that is caused by the collapse of the airway due to weak muscles that can't resist the negative pressure of inspiration during sleep. Essentially, instead of sucking in air, the lungs suck the walls of the pharynx closed, causing the patient to choke. This is treated by the administration of CPAP (or BiPAP) which involves the wearing of a mask while sleeping that helps push air into the lungs, preventing the collapse of the airway.

Thursday, December 5, 2013

WILTIMS #78: Children of the Night

TIL: Half of what we digest, we produce in the form of secretions and dead cells.

Xeroderma pigmentosa is a fascinating if awful disease. Sufferers are born without the proper cellular machinery to repair UV damage. The upshot of which is that they cannot be in the sun. Ever. Even the tiniest bit of UV light causes severe sunburn and blisters, then freckles and dark growths, and finally countless skin cancers. If caught early and followed by life-altering concessions by the child's family, children can live into their 20s (the oldest can reach their 40s).

These kids live very different lives from their unaffected peers. They must be home-schooled in their windowless home or teleconferenced into a classroom. They can only go outside at night and often convert to a mostly nocturnal lifestyle. To go anywhere, such as a doctor's office, they must be cocooned in a sleeping bag and carried around. None of these precautions are really possible in developing countries and the prognosis is far worse for affected children (see image on the left).

This disease make us remember that we take for granted how marvelously skilled our bodies are at fighting off mutations. By just walking in the sun we expose each of our skin cells to hundreds of mutations every minute. Our cells work tirelessly every moment to let us navigate the unsafe environment we live in, called Earth.

WILTIMS #77: Anarchy in the classroom!

Today we had our first Medical Ethics classes and, amusingly, our first ethical dilemma was with the class itself. We were meeting in our small groups and our instructor didn't show. At first we thought that she was just running late or going off an old schedule. 10 minutes after the latest possible start time we sent out a few students to see if the other classrooms all had their instructors and we found one other that had been similarly abandoned.

Collectively, we tried to decide what to do. Who do we contact? Do college no-show rules apply? Could they trace it back to us if we left? Is it somehow more ethically wrong to ditch an ethics class than a normal class? Eventually we decided to take our own attendance and then some people left while others interrupted another room to ask what to do. Those of us who stayed joined the neighboring room for the second half of the class.

TIL: "Up the butt" may not be the most eloquent way to explain "suppository". It is recommended we use "inserted in one's bottom or rear".

A doctor can refuse to take any patient. A doctor cannot, however, refuse to see a patient with whom they have already established a doctor-patient relationship. The doctor must give the patient a reasonable amount of time (a few months) to find another doctor before the doctor can refuse care.

Telomerase carries its own RNA primer. Let me back up a bit... DNA polymerase, the enzyme that helps make new copies of DNA from old copies, requires an RNA primer to help it initiate replication. Think of it like the little metal guide at the end of a zipper* that helps the slider attach to the teeth. The problem is that the RNA primer isn't stable and will be degraded, leaving the DNA strand a little bit shorter. To make sure that the important information coded by the DNA isn't lost after multiple cycles of replication, the cell adds a whole bunch of non-coding repeat sequences. These chromosomal end caps are called telomeres. Eventually, these do run short and need to be built back up.

That's where telomerase comes in. This is an enzyme very similar to DNA polymerase that's sole job is to add telomeric repeats to the end of chromosomes. It gets around DNA polymerase's primer problem by providing it's own primer. It then extends one strand of the DNA until it is long enough that another primer can be added and DNA polymerase can take over.

*Apparently this is called an "insertion pin" by zipper aficionados

Tuesday, December 3, 2013

WILTIMS #76: [Gasp!] What. did. you. say‽

I'm aiming for a little more sleep tonight, so this will be short and sw- uh... soapy. Yesterday's post was a doozy though, so feel free to take a gander, if you haven't already.

TIL: Washing a kid's mouth out with soap is actually quite dangerous because the soap disrupts the mucosal lining of the stomach which normally stops the stomach from digesting itself. Soap can quickly cause gastric ulcers and damage the stomach.

WILTIMS #75: Open wide?

Phew! That's the way to return from a break! I attended four hours of lecture, sat on a student panel for interviewees, participated in a pap smear workshop, and listened to a neurosurgical resident for an hour and a half as he described the crazy things he does every day.

TIL: how to give a pap smear. Also, the pap smear is named after Dr. George Papanicolaou, who invented the procedure in the 1930s.

Any given cell in the body has tens of thousands of mutations to its DNA that it is trying to repair at any given moment. That seems like a lot until you remember that any given cell has six billion base pairs of DNA. Evolution likes a nice balance between an accurate transcription mechanism (so as not to cause disease/death) and a certain degree of purposeful variation (to allow populations to differentiate and diverge).

O6-methylguanine-DNA methyltransferase is an enzyme that directly repairs a specific kind or replication mutation by transferring the aberrant modification to itself and becoming deactivated.

Borborygmi are the noises made by air and fluids moving in the intestines. Relatedly, surgeons listen to the abdomen after surgery because the stress of the procedure causes a reflex whereby the intestines stop moving. When they hear borborygmi again, it shows that the body is recovering.

Proline-rich proteins are responsible for binding tannins in red wine, making one's mouth feel dry.

If someone has a problem that causes them to drool extensively, they will not only be losing fluid volume, but also be developing a potassium deficiency. This is because saliva contains a higher concentration of potassium than blood plasma.

Cystic fibrosis is caused by a defective chloride channel.

The original test for the Mumps was to have the child suck on a lemon. The acid in the juice stimulates the salivary glands to produce and release saliva, but since they are already swollen this just causes acute pain.

Monday, December 2, 2013


Last week at my preceptor visit, a boy came in the office for his yearly check-up. The doctor assumed the child would be receiving his flu shot until the mother broke in, "No. Not the flu vaccine! We go through this every year." The doctor tried to quickly give the spiel as to why it's good, why it's safe, etc. but the mother would have none of it. The doctor conceded this fight - she had more people to see, this kid was fairly healthy and this mom was very stubborn.

While the doc went to answer a phone call, I sat in the waiting room. The mom from earlier came into the room with her son and found another woman that she knew, who was taking her daughter to a similar appointment. Somehow the topic of vaccines came up and Mom #1 told Mom #2 that she had refused to let her son get it. Mom #2 exclaimed, "Oh! I didn't know you could do that. I've never really liked the idea." Sure enough, ten minutes later the doctor came back to the office complaining that yet another person has refused the flu shot. The patient herself had refused, but the mother hadn't insisted either.

This little bout of contagious denial is incredibly frustrating for anyone with a background in public health. It is so easy to convince someone to opt out of vaccinations and so hard to fight back. No one likes vaccines themselves. You get stabbed with a needle, your arm usually hurts, some people don't feel 100% in the following days and, with a disease like the flu, you sometimes get sick anyways. I can't prove to you that you personally avoided getting the disease, or that you avoided passing it to your family. I can't prove to you that if you did get the flu, it was less severe.

All of the benefits of vaccines are statistical. If a large percentage of the public gets a vaccine, disease rates go down, death rates go down, and the duration and severity of illness is decreased. These benefits are proven in enormous, comprehensive studies which are repeated every few years. The same studies look at side effects. Yes, there are side effects. Some, like soreness around the injection site and a mild fever are fairly common; others, like deadly allergic reactions are so rare they can barely be shown as anything more than a statistical fluke. But on average, these reactions pale in comparison to effect of the diseases being targeted.

Take the flu, the mildest disease vaccinated against. The flu kills between 3,000 and 49,000 people in the US a year[1] varying greatly depending on the active strains. The majority of these deaths are in the elderly population, but even children, who are typically robustly healthy by comparison are susceptible. Between 50 and 200 children die each year of the flu[2] in the US alone. Over 40% are totally healthy at the time of infection. Over a third die within 3 days. 84% were unvaccinated.

Furthermore, a vaccine-defender can find him or herself battling a Gish Gallop. This is a type of argument where an attacker rapidly spouts over-simplified falsehoods so quickly that a defender cannot keep up because each reply requires a nuanced explanation of a complicated issue. Here are a few common claims and (relatively) quick rebuttals:
  • The risk from the vaccine is greater than that of the disease. Here are some data from the CDC comparing the risks for common diseases/vaccines:
      • Measles
        • Pneumonia: 6 in 100
        • Encephalitis: 1 in 1,000
        • Death: 2 in 1,000
      • Rubella
        • Congenital Rubella Syndrome: 1 in 4 (if woman becomes infected early in pregnancy)
      • Diphtheria
        • Death: 1 in 20
      • Tetanus
        • Death: 2 in 10
      • Pertussis
        • Pneumonia: 1 in 8
        • Encephalitis: 1 in 20
        • Death: 1 in 1,500
      • MMR (Measles, Mumps, Rubella)
        • Encephalitis or severe allergic reaction: 1 in 1,000,000
      • DTaP (Diphtheria, Tetanus, Pertussis)
        • Continuous crying, then full recovery: 1 in 1000
        • Convulsions or shock, then full recovery: 1 in 14,000
        • Acute encephalopathy: 0-10.5 in 1,000,000
        • Death: None proven
  • Natural immunity is better than vaccinated immunity. This one's tricky. Yes, natural immunity often lasts longer, but the added risks of a wild infection far outweigh any added risk of having to get a vaccine booster on occasion (see above statistics).
  • Giving someone more than one vaccine at a time can overload the immune system. Compared to the amount of antigens that a person is exposed to daily, vaccine introduced antigen levels are very small. Also, an activated immune system is more capable of resisting additional infection, not less.
  • Something something something... Sudden Infant Death Syndrome (SIDS). This myth shows the pitfall of our human tendency to confuse causation with correlation. Children receive their DTaP vaccinations at around the same time that SIDS deaths spike. The exact same proportion of kids who have and have not received their vaccinations die of SIDS. After extensive studying, no causal correlation has been found.
  • Something something something... autism. No vaccine has ever EVER been shown to cause autism. The one guy who published the one paper was shown to have purposefully altered the data. The paper was redacted and the guy fired and disgraced.
  • Big Pharma/doctors/etc are making tons of money off all these vaccines. Nope. If the medical industrial complex wanted to make more money, they'd hold off on the vaccines and treat patients for the conditions they'd develop. Vaccines are so unprofitable, only a handful of companies even manufacture them anymore. The big money for pharmaceutical companies is in chronic conditions like heart disease and arthritis.
Back in my preceptor's office, I tell the two doctors what I had seen in the waiting room and my preceptor's partner, being so fed up with this dangerous trend asks for the girl who refused her flu shot to come in and talk to her. The doctor starts by saying that she doesn't need to get the flu shot today, but then explains how dangerous the flu can really be, citing the same studies I linked to above. It's the best we could do at the moment. Hopefully next time she comes in, she will choose the shot, even if her stubborn mother doesn't understand the risks she is taking with her child.

If anyone has any unanswered questions regarding any vaccine, leave a comment or send me an email. I will happily research an answer and respond.

Wednesday, November 27, 2013

WILTIMS #74: Not that kind of acid test

'Twas a short pre-Thanksgiving day, but it still provided entertainment.

Quote of the day from my physiology professor: "And then if you have an acid meal... I presume they're talking about lemonade not LSD here..."

TIL: The upper portion of the stomach (the orad, made up of the fundus and top of the body) is functionally different from the bottom (the caudad, including the antrum and lower body). The top is mainly used as a storage space and accommodates large quantities of food. The bottom starts the digestive work by mixing, breaking up and pushing the food towards the pyloric sphincter and the small intestine.

WILTIMS #73: Rosettes of inspiration

12 years ago, in my freshman year of high school (wow, I'm old!), I took my first true biology class. And in our text book was one image that enamored me to this squishy science. It showed the entire structure of DNA, from individual nucleic acids to an entire chromosome. In a single diagram it connected the theoretical world of atoms and molecules to the observable world of cells and chromosomes. I think it showed me that, with enough study and a good enough microscope, I could someday explain everything around me. In that class I learned the genetic causes of my family's genetic disease and that through understanding the molecular mechanisms I could learn how to heal them. Though I wouldn't realize it for years, I had started down the road to a career in medicine.

TIL: That image from all those years ago has become clearer in the intervening time. We knew that the DNA double helix was wrapped around histone proteins and that these bundles formed helices of their own. Further we knew that proteins called cohesins and condensins seemed important in the higher-order folding of chromatin into a structured chromosome, but we didn't understand exactly how. Now we know (mostly)!

Both condensin and cohesin are ringed proteins composed of SMC subunits. These rings circle the DNA/histone coils and then link together forming rosettes (seen on the right). The rosettes loosely coil to form the superstructure of chromosomes.

Can't wait to see what the next dozen years brings!

Tuesday, November 26, 2013

WILTIMS #72: Sleep now?

Round 1 of block 2 is over and done with. Little victories!

Today was a marathon day. This morning I had a 2½ hour long biochemistry test that was brutal. I then had to don my white coat for my 2nd preceptor visit. After returning to campus 4 hours later, I switched back into street clothes for an hour and a half suture clinic run by emergency medicine doctors from our Manhattan teaching hospital.

But it was all worth it, because awaiting me when I got back to my apartment was a potluck Thanksgiving feast (to which I brought nothing thanks to my schedule and car-lessness). I'm now enjoying a festive libation with my turkey and fixin's. Ah..... Cheers!

Discerning readers may have noticed that I never actually wrote about my first preceptor visit, which took place about a month ago. This was mostly because I've been trying to figure out how to navigate patient privacy concerns in regard to this blog. After talking to a few administration officials, it seems that I'm golden when using appropriate judgement if I dissociate myself from the school/hospital. As long as everything I write is as an individual, not as a representative of either institution, then it's simply my responsibility to follow HIPAA rules for my own sake.

I precept at a local pediatrics office with one other student from my year. We shadow a doctor about once a month throughout the year. This provides us with a mentor as well as an opportunity to practice our history taking and physical exam.

TIL: Fifth disease is a viral skin condition common in children that presents as red inflamed cheeks with additional rashes found on the rest of the body, particularly on the extremities. Though it also goes by the more scientific name "erythema infectiosum" it is commonly known as fifth disease because there were 6 traditional rash-like diseases in children (measles, rubella, scarlet fever, Duke's disease, fifth, and roseola) of which fifth was... the fifth.

Anyways, fifth disease is caused by a virus that a child's body can easily fight off. The rash actually only shows up after the child is no longer contagious. Usually, no treatment is needed. The rash clears up after a few days and the child is now immune to the virus. The only danger is that someone else with whom the child had contact has developed the virus and hasn't presented with symptoms yet. Again, not a problem for that person in all likelihood, but there can be serious complications for pregnant women and immuno-compromised patients. So you can write a note letting the kid go back to school, but you should ask the school nurse to warn any pregnant teachers or staff of the danger.

Pigs' feet are very thick skinned.

Size 2-0 sutures are enormous. In a lovely counter-intuitive way, suture sizes (as well as needles sizes) are inverse to their thickness. The higher the number (4-0, 5-0, 6-0) the thinner the needle/thread; the lower (3-0, 2-0), the thicker. Using 2-0 was a challenge. I can't imagine what 0-0 must be like. [EDIT: Sorry everyone! I should do more research before I post, because the sizing is even more interesting than I described here. See the comments for a better description. Done that? Good! Now imagine what a 6 is like; I'm imagining a surgeon on a ship using bits of rope...{Actually, it's only a millimeter wide!}]

Monday, November 25, 2013

Study Aid #6

Not sure if this was studying or procrastination, but it turned out pretty nice! There are a couple not entirely accurate things, but it's good enough for my purposes. I will hopefully get a chance to fix it up before the final or Step 1.

Click to embiggen. You want to, trust me.

Sunday, November 24, 2013

Study Aid #5

Apologies for the dearth of posts over the last few days. Thursday was a study day for our first physiology test on Friday and first biochemistry test on Monday. I'll try to post any concept maps I make over the weekend to prepare for biochem.

You may remember my purposefully jargony description of blood coagulation factors the other day. Here is a fully fleshed out version that I made for studying (click for higher resolution):

Looking back at that previous post, I think I like the version I stole from wikipedia better... but making a new one helped me study! So there.

Wednesday, November 20, 2013

WILTIMS #71: Pronouns are confusing

Today, in between our biochem/physio lectures and our "how to be a doctor" classes, we had an optional guest discussion by a transgender woman on her experience with the medical field during her journey from Bill to Sally*. I (and apparently whoever ordered food for the event) thought only a few people would likely show, but over 150 students attended (even after the promised lunch was quickly consumed). Doctors, as well as all other health care providers, have to be ready to treat anyone who walks through the door and since the transgender community is very small, this was a rare opportunity to hear from someone with this perspective.

TIL: A person in the midst of a gender reassignment can change their outward appearance, such as through plastic surgery to the face and neck, electively without any other restrictions. They cannot however have sex reassignment surgery without years of paperwork, hormone injections, and mandated psychological evaluations. The speaker today brought up the very interesting point that it is odd that you are allowed to change the parts of you that the world can see, but not the parts that are, well... private.

SMADs are proteins used in the transforming growth factor beta signal pathway. The acronym stands for "small mother's against decapentaplegic" which is a reference to MADD by drosophila fly researchers who spent too much time in the lab. SMADs are often mutated in patients with pancreatic cancer which is one of the reasons pancreatic cancer is so hard to treat. The SMAD cascade is in most cells of the body, so modifying parts of it would have huge negative effects on the body - worse effects than even the cancer you're trying to treat.

*Names changed for anonymity, though her actual name change was just as striking

WILTIMS #70: New look, same great taste!

So today there was a error in word-wrapping across all of Blogger for the dynamic template that I had been using. To fix the problem, I've switched back to a more traditional template and I think I like it better! Let me know what you think in the comments.

TIL: The diseases cholera and pertussis are both caused by bacteria that release toxins that disrupt intracellular signal transduction (the receipt and amplification of a signal from outside the cell to the interior of the cell). The specific enzyme affected by both toxins is adenyl cyclase which converts AMP to cAMP. Even though both conditions have the same effect, the main difference between them is the location of the bacterial infection. The vibrio cholera bacteria colonize the gut, meanwhile bordetella pertussis settles in the lungs.

The other big difference in these diseases is that unlike cholera, pertussis can be vaccinated against. This is why whooping cough (the other name for pertussis) has been so rare in developed countries. It it making the news again as certain populations have stopped vaccinating their kids, disrupting our herd immunity and resulting in outbreaks. Vaccines save lives and are incredibly, reliably safe. Make sure everyone you know is vaccinating their kids!

Monday, November 18, 2013

WILTIMS #69: Gobble gobble

There is an issue with the text justification right now. I'm working on finding a solution.

Let me... um... "enhance" your Thanksgiving by giving you the exact physiological difference between the dark and white meat in a turkey. There are two basic types of skeletal muscle: slow-twitch and fast-twitch. Slow-twitch are used for slower, more enduring movements, as in the legs of a marathon runner. Fast-twitch (as you may have guessed) are those of the sprinter - fast but fleeting.

The slow-twitch muscles need a constant supply of oxygen in order to continue to contract for hours, so they are loaded with myoglobin, a similar molecule to hemoglobin, that store and transport oxygen. Much as hemoglobin is what gives your blood its red color, myoglobin is what tints muscle red. Slow-twitch is redder and thus browner after cooking. So this Thanksgiving, "Can you pass me some of the slow twitch muscle fibers?"

TIL: A prothrombin time (PT) is a lab test used to measure the extrinsic pathway of blood coagulation, a delay in which indicates disruption of factors XII, XI, IX and/or XIII. Partial thromboplastin time, or PTT, measures the intrinsic pathway and defects in coagulation factor VII. If both values are delayed it indicates a defect in factors common to both pathways: factor I (fibrinogen), II (prothrombin), V and X.

Relatedly, today I learned that coagulation factors are named in order of their discovery not their function, which is absolutely useless to all but a biochemistry historian...

Saturday, November 16, 2013

WILTIMS #68: Myasthenia gravis

Apologies for the brief post this evening; the SO is in town and takes precedent. I will give you this sunset picture I took yesterday as some little recompense.

TIL: Myasthenia gravis is a rare autoimmune disease whereby the body attacks a specific postsynaptic receptor at neuromuscular junctions. This means that the nerves send neurotransmitters to the muscles telling them to contract, but the muscles gradually lose their ability to recognize this signal. The result of this is the very slow cumulative debilitation of muscle strength. It is often first noticed as an eye condition, because the muscles of the eye are very fine tuned and are easily affected. Untreated, it can progress to near paralysis.

The most amazing thing about the disease is the treatment. An acetylcholinesterase inhibitor is administered which causes the neurotransmitters released by the nerve to stick around longer, amplifying the signal to the muscle and reversing the condition (at least for a while). This was seen as a miracle drug when it was first used for this disease because it is able to turn a bedridden patient into a normal healthy person within seconds.

Friday, November 15, 2013

WILTIMS #67: Ickle Sickle Pickle

In a refreshing reminder that we are adults (and occasionally treated accordingly), we had homework due today that we were simply trusted to have completed. We then had an intelligent student led discussion of the answers, with the people who researched the most complete responses to questions supplementing the answers of others. A smidge of my faith in my fellow classmates has been restored.

TIL: Sickle cell anemia is caused by the substitution of one amino acid (the building blocks of proteins) for another in the beta globin subunit of hemoglobin (the protein in red blood cells that carries oxygen from your lungs to your tissues). The mutant hemoglobin can bind with other hemoglobin proteins, resulting in polymerization. These aggregations of hemoglobin cause the red blood cells (RBCs) to become deformed (hence the sickle cell name) and get stuck in the narrow capillary blood vessels of the body. The tissues become deoxygenated due to the RBCs piling up causing damage and pain.

The body also quickly attacks these sickle cells in the spleen, the body's quality control center for blood cells resulting in anemia and the bone marrow can't replenish RBCs fast enough. The spleen often gets infected due to damage and overwork from this process.

The only cure is a bone marrow transplant, which replaces the stem cells that create the mutant RBCs. Other treatment options include blood transfusions (to swap out bad cells for good), antibiotics (to fight infection in the spleen), erythropoietin (to spur RBC production to combat the anemia), and the administration of the anti-tumor drug hydroxyurea which promotes the production of fetal hemoglobin (which cannot aggregate like the mutant adult hemoglobin).

Thursday, November 14, 2013

WILTIMS #66: I'm ready. I'm ready. I'm ready. I'm ready.

The grades are in and I officially passed my first block! Huzzah!

We covered mostly review topics today with a heavy emphasis on thermodynamics (yuck!), so instead I'll share some insights from Sunday when I shadowed an OB/GYN resident at the medical center for the day.

When I arrived on the unit at 7 am, the resident that I was following had already been there since 10pm the previous night. By the time I left, exhausted even after doing very little, she was still writing up reports over 19 hours into her 16 hour shift. Oh yeah, and she was 7 months pregnant herself. Fun!

To borrow a saying, OB seems like hours of boredom punctuated by minutes of sheer terror.
How's room 3 coming along? 
-2 cm

How about now?
-3 cm 
Room 3?
-5 cm and in some discomfort

My exciting experiences for the day included helping with a delivery (I held the mother's right leg) and watching a cervical cerclage procedure. I was complimented by the nurses for not passing out watching my first vaginal delivery. Woot!

A cerclage is the surgical suturing closed of the cervix. This procedure is done when an expecting woman has cervical incompetence, which can result in midterm miscarriages unless corrected. The suture is then taken out at about 8½ months, after the most dangerous period has passed.

Wednesday, November 13, 2013

WILTIMS #65: Grr. Argh.

Don't be a zombie! Eating brains is bad. We got to watch NOVA in class and it was as engaging as ever (albeit a bit dated in this case). The episode was on transmissible spongiform encephalopathies, such as scrapie (in sheep), mad cow disease (in... cattle) and Creutzfeldt–Jakob disease (in humans).

Normal prion protein on the left, mutant on the right.
These diseases are terrifying, as is their cause. Each disease is transmitted in one way: through the cannibalistic consumption of the brains of members of one's own species. The only exception is that certain forms of the disease can cross into other species, again, when brains are consumed. This was a major concern in Britain where the seemingly harmless sheep scrapie, which cannot transfer to humans, was introduced to cows, which were routinely fed protein supplement made from the ground remains of other cows and sheep. Once cows became infected, the toxin spread wildly through the same feed due to the cow component.

Creutzfeldt–Jakob disease (CJD) in humans was known to spontaneously arise very infrequently, causing the same symptoms seen in all other mammals. The patient rapidly loses motor coordination and then becomes progressively more demented, before dying within months. These spongiform encephalopathies are so named because the brain (encephalon) takes on a spongy appearance during autopsy do to the formation of many holes in the brain tissue. The disease progresses as more and more of the brain is consumed. There is no treatment. In the early nineties, people began coming down with a slightly different form of CJD, widely believed to have come from the the bovine disease that was transmitted through contaminated meat.

The biochemical cause of spongiform encephalopathy is very zombie-like. There is a normal version of a certain protein that is found in all healthy individuals. The disease is caused when a bad version of the protein is introduced that is able to bind with its healthy form in such a way so as to convert the normal form into the diseased form. It doesn't actually change the transcript of the protein. The order of the amino acids remains the same; the protein is merely folded differently. This causes a chain reaction that forms plaques of the aggregated diseased protein that build up and damage the surrounding tissue.

The protein can't be killed, because it's not alive and it is incredibly resistant to degradation, even when irradiated, burned and buried. Sleep well tonight!

TIL: There are protein motifs called "zinc fingers" formed by a zinc-stabilized hairpin turn. 

Epidermolysis bullosa is a disease resulting from the malformation of the keratin protein that results in incredibly fragile skin that blisters at even the softest touch.

Ehlers–Danlos syndrome is a collection of disorders caused by the mutation of genes involved in the organization of collagen. Collagen is the most abundant protein in the body and is generally found in connective tissue, providing a measure of flexible stability. Persons with this disease show many diverse symptoms, but a couple classic signs are of hyperflexible joints and stretchy skin that can be easily pulled away from the body.

Monday, November 11, 2013

WILTIMS #64: Curse your sudden but inevitable betrayal

View the reference here
Me: This block is going to get pretty interesting...
Mal: Define interesting.
Wash: [Deadpan] Oh god, oh god, we're all gonna die?

I'll start this new block of medical school with a quote from our professor and course director for physiology: “Weekends are a concept, not a reality."

Having moved away from anatomy, we are no longer taught by MDs but rather PhDs. I sometimes wonder if these folks are gluttons for pain. During undergrad, I always felt bad for scientific researchers teaching premed classes because, not only are premeds inherently incredibly annoying students, but the professors always seemed disappointed that we weren't choosing to go into their field. But the professors that we met today, both in physiology and biochemistry, have truly embraced the medical field and found ways of finding clinical correlations for even the most basic (or acidic) material.(Thank you, thank you, I'm here every night)

TIL: There are 20 standard amino acids that make up nearly every piece of every protein in all of life. There are only two exceptions which take the form of "non-canonical" amino acids. One, pyrrolysine, is only found in certain single-celled organisms. The other, selenocysteine (pictured on the left), is used in only 25 of the 105-107 proteins that the human genome encodes.

Homeostatic variables are physiological features that our body is trying to keep within a narrow range, like temperature, pH and blood pressure. Heart rate is not a  homeostatic variable because the body wants the HR to change depending on the circumstances, usually to manage one of the other true homeostatic variables.

Whereas feedback regulation is the body's response to a perceived change, feedforward regulation is the preemptive response to a predicted stimulus. Metaphorically, feedforward regulation is looking up the weather forecast and deciding to bring an umbrella; feedback regulation is walking outside, noticing it's raining, and then going back to get the umbrella.

Saturday, November 2, 2013

WILTIMS #63: End of Block 1

My official embroidered white coat finally arrived!
It's been a long blur, but the first block of medical school is over! I feel like I've learned so much; yet, it's amazing how much is left to tackle. But the most important thing that I've learned so far is that I really do belong here. It hasn't been easy (and according to the 2nd, 3rd and 4th years it will only get progressively worse), but I'm going to make it through. On to the next course!

TIL: The posterior cricoarytenoid muscles are the sole abductors of the vocal cords. These are the only muscles that open the vocal folds within the trachea, allowing for unimpeded airflow. All of the other intrinsic muscles of the larynx either bring the vocal cords together, allowing them to make sound, or change the length and thickness of the cords to change the pitch.

All but one of these muscles (the cricothyroid muscle) is innervated by the recurrent laryngeal nerve. If you've been following this blog closely from the get go, you may remember the recurrent laryngeal nerve as the branch of the vagus nerve that loops around the arch of the aorta for no apparent reason and then heads back up into the neck. Amazing how long it took for us to connect that nerve with its muscles!

Friday, November 1, 2013

WILTIMS #62: The ciliary muscle abides

Last histo lab today! Only one anatomy lab left tomorrow and I'll be officially 1/15th* done with med school!

TIL: [This may sound like medical babble, but I'll have a go at translating it in a sec.] The ciliary muscle of the eye is innervated by parasympathetic fibers of the oculomotor nerve (cranial nerve III). It is well known that the contraction of this muscle results in the accommodation of the eye through the counteraction of zonular fibers, whereby the lens becomes more spherical and decreases the focal length.

Put more simply: When you are relaxed, you brain contracts a muscle that changes the shape of the lens of the eye, causing your eyes to focus closer to your face.

The mechanism for this is not 100% understood, but the best guess is that it works like this: imagine you have a rubber dodgeball held in the center of a pillowcase. Normally, you have 4 super strong people pull on each of the corners of the pillowcase, flattening the pieces of cloth against each other and squishing the ball inside so that it's no longer round. All this tension makes you uneasy, so you send in a strong but relaxing guy (think The Dude from The Big Lebowski) and have him pull on one of the flat surfaces of the pillow case. This counteracts some of the tension from the folks pulling from the corners and allows the ball to get a little rounder again.

That's it! The ball is the lens of the eye, the pillowcase is zonular fibers, and The Dude is the ciliary muscle.

*This block is 3 months of the 4 years of medical school, or 1/4th of 1/4th of medical school. However, since we don't have class for the summer between 1st and 2nd year, we lose a block and are left with 15 3-month segments, of which we have completed one - thus 1/15th.

Thursday, October 31, 2013

WILTIMS #61: It's not procrastination if it's pretty!

Following histology yesterday, today was our last anatomy lecture. Makes me kinda sad. Also, do I actually know anatomy now?! Enough to pass this class? Sure. Enough to pass the boards? Maybe. Enough to go into surgery? Not even close.

But I have learned an awful lot! And hopefully you have learned a bit too by reading along with me. I only hope that I can find fun, interesting facts during the biochemistry and physiology courses during the next block, so we can keep this going. I'll have a couple more posts this week as we wrap up the remaining lab sections, but next week is all tests and studying, so pardon the upcoming radio silence.

Click to embiggen
Apropo to nothing, here is a diagram I made for our histology pre-lab assignment due tomorrow, showing a simplified menstrual cycle in relation to the maturation of an ovarian follicle and uterine endometrium:

TIL: Ears begin development below the jaw of the growing embryo. The ears don't actually move as development continues, rather the jaw and rest of the face grows out and down between them.

You can hear (with magnification) a fetus' tongue move in and out of the mouth in utero. They do this in part to get the tongue out of the way of the two halves of the developing palate (roof of the month) as it extends from the sides of the proto-face to separate the nasal and oral cavities.

Tuesday, October 29, 2013

WILTIMS #60: Sing "Ahhhh"

TIL: ...the super complicated way that we manipulate our vocal cords. Explaining it would take too long for a blog post, so instead I give you a video of a quartet singing from the inside. Enjoy!
Make fullscreen for better viewing!

There are spillways on either side of the epiglottis (the flap at the bottom of the tongue that blocks off the trachea when you swallow) that allow you to constantly swallow excess mucus while breathing.

Whales sing underwater by moving air back and forth between their mouths and their stomachs through the vocal cords. You can try this at home by taking a modest breath, plugging your mouth and nose, and trying to make noise. Sounds pretty whale-like, doesn't it?

Topical anesthetics can be used to numb/paralyse the muscles of the larynx (say for a bronchoscopy), however they don't reach the superior and recurrent laryngeal nerves. These nerves innervate the muscles of the larynx but also sense distension of the aorta. A problem can arise when the brain, unaware of the scope in the throat, interprets an increase in pressure on the laryngeal muscles as sudden high blood pressure in the aorta. This can set off a dangerous reflex where the brain tries to lower the blood pressure leading to a heart arrhythmia and even cardiac arrest.

Prescribe lemon candy for salivary stones. The lemony acidity will cause the patient to increase salivary production and reduce stagnation and crystallization of the salivary fluid.

Monday, October 28, 2013

WILTIMS #59: Splitting headache

Today I sawed a human head in half with a handsaw. So there's that...

TIL: The Eustachian tube (aka the pharyngotympanic tube or auditory tube) connects the middle ear to the pharynx (top of the throat). This canal is what allows you to pop your ears after a change in air pressure that you might experience at the bottom of a pool or flying in an airplane.

There is a muscle in the ear called the tensor tympani that is like a dampening pedal for your eardrum. It tenses when you hear an extremely loud noise, restricting the movement of the tympanic membrane (eardrum) and dulling the sound.

If you plug your ears in a quiet room, you can actually hear your own internal carotid artery which runs through the skull very near the structures of the internal ear.

Tilting your head back when you have a bloody nose does nothing (besides make you swallow blood). Pinching the nose, however, may be helpful depending on the location of the bleed.

If a kid (or really clumsy adult) trips while drinking out of a straw, they can puncture the back of their throat. This is not primarily dangerous and should heal just fine. The problem is that the retropharyngeal space that was punctured by the straw is continuous all the way to the posterior mediastinum (space immediately behind the heart). If an infection develops, it will quickly progress from a simple deep throat infection to pericarditis (an infection of the sac surrounding the heart), which can be deadly.

Saturday, October 26, 2013

WILTIMS #58: Why so serous?

We only had one 2-hour anatomy lab on the schedule today, so I don't have much to report. We were dissecting the parotid and temporal regions of the head (above, in front of and below the ear). It was not the most elegant dissection thanks to the slapdash layouts of the nerves, blood vessels and glands in relation to the bones and muscles, but we made do and managed to see most of what we were supposed to see.
The salivary glands: #1 parotid,
#2 submandibular, #3 sublingual

TIL: The parotid gland and pancreas are the only two glands that produce amylase, the enzyme that breaks down starches into sugar. The parotid gland secretes serous fluid, including the amylase enzyme, into the mouth via a duct that can, on rare occasions, become occluded causing the sides of the face to swell. This condition is easily confused with the mumps, which also results in the swelling of the parotid gland, but from the inflammatory action of the mumps virus rather than the obstruction of the parotid duct.

Seizures originating in the temporal lobe are associated with the perception of an strange smell. These seizures can be caused by radiation from the treatment of salivary gland cancers located in the parotid gland.

Friday, October 25, 2013

WILTIMS #57: Gone fishin'

Today was a long but good day filled with fun, mostly extracurricular goodies.

On the brief curricular side of things, we had yet another histology lab (only 2 more!). This time we were investigating the skin... and a monkey fingertip.

This afternoon I got to step back over to the patient side of medicine at my first appointment with my new oncologist. I was first seen by an oncology fellow* working under the main doctor. It was fun chatting with (and silently judging) someone who is, though already 10 years ahead of me, still completing his training. When my actual doctor came in, it was entertaining watching him simultaneously tend to me and teach his student.

After my appointment (everything looks good btw), I ran back to campus to play in our final flag football match of the season. We were crushed by a team of second-years, but they were such good sports that we still had a blast.

After the game, I quickly changed and headed back out to a neurosurgery interest group meeting. We met in the radiology conference room in the hospital and, unlike other interest group meetings I've attended, were greeted by not one, but easily half a dozen doctors, fellows and residents. The head of neurosurgery welcomed us and then a pediatric neurosurgeon presented on current interventional techniques for common maladies.

TIL: The skin contains three types of glands: two sweat glands and one that secretes an oily substance called sebum. This third secretion is released by a holocrine gland which emits its cargo by literally filling up until it bursts. Accordingly, your skin perspires sweat, oil and cellular debris.

A bone marrow biopsy is not indicated for a stage 2 Hodgkin's lymphoma patient (hopefully the fellow learned this too!).

When a cranial suture (the border between bones of dome of the head) fuses earlier than normal in a child, the head will elongate in the direction parallel to the suture. This is called craniosynostosis and doesn't usually cause and neurological deficits directly. But because children aren't generally as nice to a kid with a noticeably oblong head, if the defect was not corrected the child is almost certain to suffer socially and subsequently educationally.

Young children recover extremely well from cranial surgery thanks to their still-developing skeleton. A 6-month old could have the entire surface of the skull removed and grow it back within weeks.

Neurosurgery before good imaging techniques were invented used to be described thusly: For a hobby you can either do fishing, hunting or neurosurgery. Your prey never survives, but at least you can have some fun.

*For those unfamiliar with the ridiculously complicated nomenclature for students of medical education:

  • 1st-2nd year of medical school → medical student
  • 3rd-4th year of medical school → medical student/sub-intern
  • 1st year of residency → intern and/or doctor
  • 2nd-6th year of residency (usually 3-4 years) → resident and/or doctor
  • 1st-4th year of fellowship (usually 2-4 years)→ fellow and/or doctor

Wednesday, October 23, 2013

WILTIMS #56: Teeth and triangles

Click to triangulate
Today we had a surprisingly enjoyable anatomy lab dissecting the anterior neck and paralingual space (area under the jaw). Some combination of our cadaver and our dissecting skill resulted in a beautiful display of muscles, blood vessels, glands and nerves (except that damn accessory nerve [shakes fist angrily at the anatomy gods]). We received many a compliment and actually learned quite a bit... mostly about triangles.

TIL: Teeth provide proprioception for the mandible (i.e. send the brain information about the location and movement of the jaw). When dentists numb your teeth while performing their acts of torture, they tell you not to eat for a few hours after. This is not because the dental work needs time to set, but rather because your numbed teeth are temporarily unable to let you know their location, so you risk biting your cheek or chomping down extra hard on your newly fixed smile. This also explains why people with complete dentures have a hard time biting and chewing smoothly; they no longer have accurate information about the movement and location of their jaws! Interestingly, keeping just one tooth would be enough to maintain this sense.

WILTIMS #55: BIC pen to the rescue!

Today was a day of battling the urge to nap ...and losing. The heat has been on noticeably high in our primary lecture hall and as a result, you can see so many heads drooping and then jerking awake you might think you watching a metal concert in slow motion.

TIL: Like in the digestive system, the ureter is covered with both a longitudinal and circular layer of smooth muscle. In the ureter, however, the longitudinal layer is the innermost layer covered by a circular layer - the opposite of the layering of the digestive tract.

In the event of a potentially lethal ventricular tachycardia, you can attempt to calm the heart by stimulating the vagus nerve. This can be done by massaging the carotid bulb (the lowest section of the internal carotid artery in the neck). However, you have to be careful not to put too much pressure on the artery or you can risk the patient passing out.

When performing a tracheotomy, you stab between the first cartilaginous rings of the trachea below the thyroid cartilage. Usually the thyroid gland (which looks like a butterfly from the front) is low enough not to be in the way but occasionally it reaches up and blocks your path. What do you do? Cut it in half! The thyroid gland doesn't have a duct; it secrets directly into the bloodstream which it accesses bilaterally. This means you can cut the thyroid right down the middle with no noticeable effect. Push the two halves apart and insert the tracheal tube.

Tuesday, October 22, 2013

WILTIMS #54: Eye spy

Today we explored the orbit (socket) of the eye, both in lecture and in lab. The eye is incredible both as a complex sensory organ and as a clinical tool. The movement of the eye is controlled by six muscles which are innervated by three distinct cranial nerves. This apparent inefficiency is a great diagnostic tool for classifying nerve or brain damage and the reason for those seemingly bizarre "follow my finger" eye tests.

In lab, we skinned the eyelids and explored the tear glands and ducts. We then turned to the space behind the eye, which was only accessible by breaking through the roof of the orbit with a chisel. The complexity of the eye was finally exposed after nearly an hour of meticulously clearing out all of the fat that cushions the eye and associated muscles, nerves and blood vessels.

TIL: The superior rectus muscle of the eye is innervated by the same nerve as the superior levator palpebrae, the upshot of which is that you can't look up without pulling the upper eyelids up as well.

The superior oblique muscle (the topmost muscle in the accompanying diagram) actually uses a naturally formed pulley system. In order to exert more force on the eye, the muscle passes from its attachment on the eye through a tendinous loop called a trochlea (literally: pulley wheel), before finally travelly to the back of the eye socket.

Tarsal glands are located on the edges of the eyelids and secrete an oil that both keeps the eyelids from sticking together as you blink and acts as a hydrophobic barrier, keeping the tears within the eye.

The lacrimal caruncle (literally: teary meaty lump) on the nasal side of the eye surrounds a duct which siphons excess tear fluid into the nasal cavity. Ever notice that when a person gets misty eyed, they start sniffling? Turns out the bulk of  fluid that ends up in their tissue is tears, not snot. The tears are secreted from the outer upper part of the eye socket, flow over the surface of the eye, are held within the socket by the oil on the eyelids, collect near the meaty lumps and drain into the inferior nasal meatus of the nose.

During embryonic development we form remnants of gill slits that we inherited from our common ancestor with the jawless lamprey eel. The tissue between these slits eventual develop into the jaw, hyoid bone, and the cartilaginous structures of the pharynx and trachea. Bony fish evolved a covering over their gill slits and, sure enough, embryologically you can see the analogous human structure that forms from this covering: the external structures of the ear.

Saturday, October 19, 2013

WILTIMS #53: Brains and lightsabers

Yesterday was a dramatic day that concluded months of waiting on a couple fronts.

First up was learning how to perform an HEENT (head, eye, ear, nose, throat) exam, which meant finally getting to use the most expensive single item we've had to buy for medical school: our ophthalmoscope/otoscope (eye/ear scope). The cost was particularly annoying because it's not obvious why we need to buy one of these devices in the first place, as they are provided in every exam room and hospital unit in the country. Now, we didn't need to buy the fanciest model, but it was part of a bundle with our blood pressure cuff, reflex hammer, tuning forks, etc, so I splurged. Anyways, it was nice to finally get to use some of this doctor-y stuff!

To examine the eye with an ophthalmoscope, you start out about a foot away from the patient and place your thumb above their eye (to reassure them that you won't smack them in the head with the scope as you move in). You then align the beam of light with the pupil by looking for the “red reflex” which is weirdly named as it is merely the light reflecting off the retina on the back of the eye. This same phenomenon causes red eye in photographs. After finding the red reflex you move closer to the eye, being sure to keep the light centered on the pupil. Once you get close enough, you can see the blood vessels in the back of the eye. In order to see the vessels clearly, you have to counteract the lens of the eye by focusing the lens in the scope. Interestingly, people with different glasses prescriptions will need a different focus setting on the ophthalmoscope.

In anatomy lab yesterday, we finally reached the apex of the class: cutting open the skull and removing the brain. The day before, we had removed the scalp, so we started by placing a rubber band around widest circumference of the skull to mark out our planned cut. We then took an electric oscillating circular saw and cut through the bulk of the skull, trying to leave a small part of the inner surface intact to protect the brain. Oscillating saws, rather than rotary saws are used to cut through bone and casts because they have a much harder time ripping through soft tissue. Next we used a rubber mallet and chisel to break the remainder of the bone and finally expose the brain.

One cool thing about the interior of the skull is that it has indentations in the bone from the blood vessels of the dura mater (outermost meninx). These meningeal layers are the last thing we had to remove to see the brain, which looked... exactly like you'd expect a brain to look. It felt rather rubbery and stiff as a result of the preservation process.

Literally 5 minutes after I was touching the brain of a dead person amidst the smell of burning bone and flesh, I was waiting at a bus stop to leave town for the weekend. More than anything I wanted to turn to the other bus-riders and shake my smelly hands at them yelling, “Brains!” I managed to hold back my impulse, but let this be a lesson to you - you never know if the guy next to you on the bus was touching brains five minutes prior.

Friday, October 18, 2013

WILTIMS Preview - Brains and lightsabers

It's been an amazing, fun-filled day. I learned how to do an HEENT exam, how to use my $600 glorified flashlight, how to cut open a skull with an electric bone saw, and what the consistency of a human brain is. But I also travelled to see my significant other, so I'm deferring writing about my super awesome day until tomorrow. See you then.

WILTIMS #52: Pursuit of hoppiness

Our surprisingly deep simile for the day: Cranial nerves are like country club members; they think that because they spend time in an exclusive place that they are somehow different from the rest, but in reality they are not. ~Awesome Anatomy Professor

TIL: The eardrum is innervated by the same nerve as the muscles for chewing. This is a vestige of the evolution of the ear, whereby the ossicles (little bones) of the ear originally developed from outgrowths of the jawbone.

The vagus nerve innervates (among many many other things) the taste receptors of the epiglottis. Unlike the taste buds in the tongue, which can detect a cornucopia of flavors, these specialized receptors are responsible for detecting the taste best described as the hoppiness of beer. This is why professional beer tasters will often try to splash the beer to the back of the mouth, skipping the tongue, to get better feel for the hoppy flavor.

Thursday, October 17, 2013

WILTIMS #51: Eye to eye

Today we came face to face with our cadavers for the first time. Up until now, we had kept the cadavers' heads covered, in part to keep them from drying out prematurely, but mostly because it's the most disturbing part of working with human bodies. After over two months of skinning, slicing, tearing, and prodding, nothing can phase us. I will say that the half open eyes were a bit disconcerting.

TIL: While motor innervation of the muscles for facial expression are supplied by the facial nerve (Cranial Nerve VII), the sensory input from the skin on the face is communicated via the three branches of the trigeminal nerve (CN V).

You haven't gotten all the way to the bone of the skull until the metal probe makes a "ping" noise when you tap it.

In the surprisingly lyrical words of my anatomy professor, the superior sagittal sinus is one of the main veins that drains the brain.

Tuesday, October 15, 2013

WILTIMS #50: Alas, poor Yorick!

My study-skull and my roommate with his
A new day a new anatomy block! Once again, mere hours after finishing our exam on the previous unmanageable load of material, we are buried in even more. This block is on the head and neck and to aid us in studying the complex 3D structure of the skull, we have each been given an actual human skull to share with a partner. Since there's an odd number of people in our lab section (and I'm masterfully skilled at Rock-Paper-Scissors), I get my own! He keeps me company on my desk and listens to my soliloquies. 

TIL: Because the bones of the skull of a newborn have yet to fuse, there are soft spaces between them. The larger spaces, such as at the junctures of more than two bones, are called fontanelles. Fontainelle translates to "small fountain or spring" in old French, and these soft spots were given this name because in just-born babies you can actually see the blood pulse and gurgle within the meninges.

The mastoid process of the temporal bone (the big bony lump behind and below your ear) is not present in newborns; it develops due to the sternocleidomastoid muscle pulling on it as you grow.

The mental nerve innervates the skin on the jawbone on either side of the chin. It was named this because of how people massage their chin while thinking, and originally, it was thought that this manual stimulation could somehow pass through the nerve and affect the brain.
The sella turcica of the sphenoid bone

One of the features of the sphenoid bone is called the "sella turcica" or "Turkish saddle" which it apparently resembles because it has 4 horns (see animation on the left).

And finally, my favorite cocktail trivia piece from today: do you know where the temple on the side of the head gets its name? There are quite a few well-reasoned urban myths regarding prayer and whatnot, but these are totally off-base. As a clue, the temple shares it's name with the temporal bone over which it located.

Do you have your guess?

Both features are named for the passage of time, specifically because the hair around the temple is usually the first to turn gray as we age.