Medical Fact of the Day – The Widowmaker
The heart pumps blood throughout the body through vessels, but it also has its own circulation system. The blood from these coronary arteries supplies the heart with the energy it needs to contract.
One of these vessels is called the left anterior descending branch of the left coronary artery, or the Widowmaker. This artery supplies a large portion of the heart, particularly the section responsible for pumping oxygenated blood to the rest of the body (left ventricle). The reason it's earned its name is that blockage of this vessel is a serious emergency that requires acting within minutes and happens more often in males. Blockage usually causes the heart to pump irregularly or not at all, placing the entire body at risk. The most sensitive organ is the brain, which, if not oxygenated properly, begins dying within five minutes.
This was, unfortunately, the cause of death of Tim Russert earlier this year.
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Medical Fact of the Day – How You Make Antibodies
Over your lifetime you will encounter countless types of pathogens, including bacteria, viruses, and parasites. Additionally, aberrant cells within your body like tumor cells need to be recognized to be killed. Your immune system recognizes all these potential dangers by creating receptors for them - that is, proteins that have a specific shape to recognize other proteins and molecules.
Yet for each type of pathogen, there are countless variants that you might encounter. Over 200 types of viruses can cause the common cold, each expressing different types of proteins that need to be recognized. Furthermore, each individual cell only recognizes one specific shape. How is your immune system able to recognize so many different things?
The answer is an elegant solution to generate diversity called VDJ recombination. Each antibody you make consists of multiple gene segments that are combined together from a much bigger pool. The process is like shuffling three decks of cards and choosing a single card from each deck to create a unique combination for each cell.
One gene from each collection is chosen to form the final product.
For instance, part of the antibody is called the heavy chain. This region contains 65 Variable (V) genes, 27 Diversity (D) genes, and 6 Joining (J) genes. This means there are 65 x 27 x 6 = 10530 combinations. Furthermore, there can be minor modifications in the sequences between genes. Overall, this means that your immune system can recognize billions of different shapes from just a limited set of genes.
The human body really is amazing.
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More About HST
As I've mentioned before, I am in the Health Sciences and Technology curriculum at Harvard Medical School. This is a joint venture between Harvard and MIT, and I thought I'd explain more about it here.
The primary goal of the program is to train physician-scientists. Ideally, the graduates will both manage their own laboratories while seeing patients, although some graduates tend to go entirely into medical practice or research. A large component of what we learn is therefore cutting-edge research in the field. Each week in all our classes we will probably have at least four scientists in the field explaining their work and the state of the field.
This means that what we learn is not directly relevant for medical practice or for our medical licensing exam, but the point is instead to train a system of thinking about medical science.
Within the rest of the medical school, the HST student is stereotyped as being nerdy, less attractive, and bookish. But this is OK, as we have fun stereotypes for the other programs as well.
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First Semester with HST
The HST program began its classes today. This term lasting until December, we will be taking four:
- Anatomy - The human body - nerves, muscles, circulation - through dissection of a cadaver.
- Pathology - What tissues look like and what can go wrong.
- Immunology - The development and maintenance of the immune system to fight disease.
- Genetics - Survey of genetic disorders - that is, caused by mutations in specific genes.
The HST curriculum always has concurrent classes, while New Pathway tends to study one block at a time. For instance, they will study anatomy for several weeks everyday.
While we have more variety day to day, we have a larger time commitment - we spend between 9AM-6PM each day in class. This doesn't include the work we have to do at night after class.
It should be fun, but it's also daunting. A number of students here are worried about balancing personal life, classwork, and sleep. We'll see.
Me in a month?
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