Wednesday, December 18, 2013
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
Saturday, December 14, 2013
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
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
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
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
Saturday, December 7, 2013
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 -|
VD is not shown because that volume never reaches the lungs.
Thursday, December 5, 2013
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".
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
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).
Monday, December 2, 2013
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 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 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:
- Pneumonia: 6 in 100
- Encephalitis: 1 in 1,000
- Death: 2 in 1,000
- Congenital Rubella Syndrome: 1 in 4 (if woman becomes infected early in pregnancy)
- Death: 1 in 20
- Death: 2 in 10
- 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.
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
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
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.
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.
Monday, November 25, 2013
|Click to embiggen. You want to, trust me.|
Sunday, November 24, 2013
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):
Wednesday, November 20, 2013
Monday, November 18, 2013
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.
Saturday, November 16, 2013
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
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.
Thursday, November 14, 2013
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?
How about now?
-5 cm and in some discomfort
PUSH NOW!!!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
|Normal prion protein on the left, mutant on the right.|
Monday, November 11, 2013
|View the reference here|
Saturday, November 2, 2013
|My official embroidered white coat finally arrived!|
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
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
|Click to embiggen|
Tuesday, October 29, 2013
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!
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
Saturday, October 26, 2013
|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
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
|Click to triangulate|
Tuesday, October 22, 2013
Saturday, October 19, 2013
Friday, October 18, 2013
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.
Thursday, October 17, 2013
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
|My study-skull and my roommate with his|
|The sella turcica of the sphenoid bone|