Posted in Psychology & Medicine

Viscera: Spleen

(Learn more about the organs of the human bodies in other posts in the Viscera series here:

The spleen is one of the lesser known organs of the human body. If you asked the lay person, they would not know what the spleen does, let alone where it is. The spleen is a solid organ that lies in the left upper corner of the abdomen, tucked under the left diaphragm (opposite to the liver which lies under the right diaphragm). Its functions are mainly related to blood, such as removing old red blood cells (sequestration), storing platelets in case there is an emergency bleeding, making antibodies and releasing lymphocytes (type of white blood cell) to help fight infection and in times of need, creating red blood cells. Red blood cells are usually made in bone marrow in adults, but if the bone marrow fails (e.g. leukaemia), the spleen and liver can step in to create vital blood components (extramedullary haematopoiesis).

As most of the functions of the spleen are not technically necessary to sustain life, it can be removed without significant consequences. The spleen is sometimes removed when a patient has severe thrombocytopaenia (lack of platelets) or when the spleen is damaged by trauma. Because it is a solid organ, trauma to it such as a kick to the stomach can cause it to rupture (i.e. break in to pieces). Splenic rupture can cause life-threatening haemorrhage (bleeding) and may not be evident in trauma cases. A person without a spleen needs regular check-ups and immunisations to help fight infections as they have a weakened immune system.

The role of the spleen was a mystery for thousands of years and thus various cultures tried to explain various medical phenomena using the spleen. The ancient Greeks thought the spleen produced black bile, which was associated with melancholy. The spleen was also associated to anger by the English and laughter by the Talmud.

Posted in Psychology & Medicine

Viscera: Liver

(Learn more about the organs of the human bodies in other posts in the Viscera series here:

The liver is the second largest organ (next to the skin) in the human body, weighing about 1.4~1.6kg. It is found tucked under the right side of the ribcage, underneath the 5th to 10th rib in height and almost spanning the entire width of the trunk. When enlarged, the liver grows downward and can be felt in an abdominal exam (sometimes it is so large that it covers most of the abdomen).

It is a vital organ with many life-sustaining functions (hence “liver”) such as building various proteins, breaking down toxins, storing sugars in the form of glycogen, decomposing red blood cells and producing bile. The liver metabolises (breaks down) a large proportion of medications and drugs as it treats them as “toxins”. For example, the enzyme alcohol dehydrogenase breaks down alcohols into acetaldehyde, which causes hangovers and liver damage. Many Asians have a variant of this enzyme that is extremely efficient, causing a massive build-up of acetaldehyde when they drink alcohol. This is responsible for the so-called “Asian flush”.

Liver disease is associated a myriad of symptoms. The classic sign of jaundice (yellow skin and whites of eyes) is caused by obstruction of bile flow. Because of its location, pain in the right upper quadrant of the abdomen is commonly seen. As the liver is involved in synthesising various proteins, signs such as ascites (fluid in the abdomen) or bleeding may occur when the liver is damaged. A syndrome called portal hypertension is commonly seen in chronic liver disease such as cirrhosis as a major vein to the liver is blocked. This can cause an enlarged spleen, oesophageal varices that can bleed, ascites and prominent veins radiating from the belly button (caput medusae).

An interesting property of the liver is that it can regenerate at an amazing rate. A liver will regenerate to its original size even when a half of it is cut out (this is how live donor liver transplants work). What is more interesting is that the ancient Greeks probably knew of this fact as well. In Greek mythology, the gods punish Prometheus for bringing fire to humans by chaining him to a mountain and commanding an eagle to peck out his liver. The liver would then regenerate overnight and the eagle would return every morning to eviscerate him, causing him eternal anguish.


Posted in Philosophy

Ship Of Theseus

An ancient Greek philosopher named Plutarch pondered this scenario. Imagine that the Greek hero Theseus was to repair his ship after a long journey by replacing broken parts with new timber. If he was to embark on so many journeys and repair his ship so much that all of the original material that made the ship were replaced, is that ship still the same ship of Theseus?

This is an interesting philosophical question where some may argue that the ship is still, by definition, the “ship of Theseus” while some may argue that it is no longer the same ship Theseus once owned, but merely a replacement.

Although it is hard to grasp the significance of this question when using an analogy of ancient Greek heroes and ships, it comes closer to home in the field of biology. It is a known fact that the human body is under constant change; cells divide to produce a new lineage of fresh cells while shedding away old, dead cells. Different cells turnover at different rates; skin is almost completely replaced every 4~6 weeks, the lining of the gut is turned over every 4~6 days, while brain cells are almost never replaced (but contrary to popular belief, they can regenerate). If this is the case, are you the same “you” as you were a year ago when the majority of your skin and gut cells were technically “different” (but genetically identical) cells to what they are now? Or are you simply a replacement shell for your brain?

A simpler way of thinking about this would be to consider the case of clones: are clones the “same” as their originals?

The paradox of the ship of Theseus can be extended into a larger scale. Consider a large city like New York. If we were to assume that all of the inhabitants of a city are replaced over a hundred years, then is that city still “New York”? Not only would it looks different because of its new buildings and whatnot, but the people that make up the culture and substance of the city would be completely changed. However, New York is still called “New York” just as it was in the early 1900’s. So is the modern day New York still New York or New New York?