Everyone knows that we need oxygen to survive. The way we get oxygen from the atmosphere is through our lungs – the organ where gas exchange takes place. The pair of lungs take up a large proportion of the chest cavity and they link up with each other to form the trachea (windpipe). The left lung is slightly smaller to accommodate for the heart.
The lung is extremely soft and light, so much that it floats on water. It is essentially made up of an intricate tree-like system of airways, which become narrower and narrower as it divides out from the trachea. Since every airway divides up, the number of airways increases exponentially. Every bronchiole (small airways) ends in a bubble-like sac called an alveolus. Because of the sheer number of alveoli, the lungs actually have a total surface area the size of a tennis court. To picture this, scrunch up a piece of newspaper into a ball to pack a large surface area into a small space. The massive surface area allows for enough gas exchange to occur to give us the oxygen we need and excrete all the carbon dioxide we produce.
When we take a breath in, the chest cavity expands and stretches the lungs in all directions because of the negative pressure (like a vacuum). Air fills the airways all the way to the alveoli. The alveoli are extremely thin; so thin that the oxygen in the air effortlessly seeps through into the blood vessels that surround the alveoli. On the other hand, carbon dioxide seeps out of the blood into the alveoli, which is then breathed out as the muscles of your ribcage contract to force the air out. This process is called gas exchange and is driven by diffusion – the movement of particles from an area of high concentration to an area of low concentration (like how dye spreads throughout water).
It is well-known that smoking is bad for your lungs. This is because of two major reasons: COPD and lung cancer. COPD (chronic obstructive pulmonary disorder) is when your lungs become so damaged by smoking that they cannot function, leading to hypoxia(lack of oxygen) and hypercapnia(excess of carbon dioxide). Smoking causes inflammation in the lungs, which causes airways to shut down from swelling and mucus, while destroying the fine walls of the alveoli. This causes the alveoli to thicken from scarring and less elastic due to the destruction of elastic tissue. Ultimately, the lungs become hyperinflated as the patient cannot breathe out air properly and the lungs are not elastic enough to return to their original shape and size. Ergo, the patient becomes progressively breathless, gasping for breath as they suffer a sensation of impending death as the carbon dioxide level builds and the oxygen level falls.
In the New Testament of the Bible, there is a scene where Jesus resurrects a man by the name of Lazarus back four days after his death. This “miracle” is of course a fictitious event, but nonetheless, the name Lazarus has come to symbolise resurrection after death. For example, there are two actual medical conditions named after Lazarus, both related to death.
The first is called Lazarus phenomenon, where a person who is declared to be clinically dead spontaneously returns to life. This is an extremely rare event that has only been recorded in about 30 cases. In most of these cases, the patients had suffered a cardiac arrest, with all attempts at resuscitation (e.g. CPR, adrenaline) had failed. Sometime after the person was declared clinically dead (usually around 5~10 minutes), the person’s circulatory system would suddenly start on its own and the person would be “resurrected” (quite literally). In one case, a 61 year-old woman was declared officially dead after her heart stopped and her vitals did not return after continuous resuscitation. At the morgue, however, she was found to have a pulse and breathing on her own. She later sued the hospital for the neurological and physical injury caused by oxygen deprivation during her death. There is even a case report of a patient who returned to life two and a half hours after dying (although he died again 3 weeks later).
Of course, the Lazarus phenomenon is not a miracle. In most cases, it is hypothesised that when resuscitation is attempted then stopped, there is a rare chance of the relieving of pressure causing blood to fill the heart, causing a sudden expansion and kickstarting the electrical circuit. Other factors that may influence this is hyperkalaemia resulting from ischaemia and high doses of adrenaline given to the patient during resuscitation having a delayed effect.
Because of this rare “complication” of death, doctors are advised to observe the patient for about 10 minutes after declaring them dead. Just in case.
The second is called Lazarus sign and it occurs not in dead patients, but brain-dead patients. Brain-dead patients are immobile as their higher functions such as cognition and motor functions are destroyed. However, there are rare cases where the brainstem is somehow stimulated, triggering a reflex arc from the spinal cord. This reflex is seen as the patient suddenly raising their arms and dropping them on their chest in a crossed position, much like Egyptian mummies. As the spinal cord is not usually damaged in brain-dead patients, this reflex arc is possible, similar to a knee jerk reflex. The Lazarus sign should not be misinterpreted as a sign that a brain-dead patient is conscious, as it is an involuntary movement. However, it has been mistaken for the resuscitation of a patient, or in some cases, as a miracle.
It is a common chemical fact that water is flavourless and odourless. However, most people will know that water “tastes” subtly different each time. Taste is composed of information from taste buds on the tongue, combined with the sense of smell from your nose. Although water itself has no flavour or smell, it has many things dissolved in it such as gases and minerals that can be tasted. This is why tap water can taste bad due to the chlorine used to treat it, or metals such as copper that have come off the pipes.
It is also well known that temperature affects the taste of water. The ideal temperature is between 10~17°C, where oxygen saturation is sufficient, giving the water a “refreshing” taste. Any hotter and the oxygen escapes, giving the water a flat taste, just like distilled water. Warm water also causes the brain to think it is saliva or mucus, sometimes producing an uncomfortable sensation. Any colder, the tongue is numbed and it loses its ability to taste.
When making tea, the ideal temperature is 70~80°C. A simple way to achieve this is by leaving a cup of boiled water for a minute or two before putting the teabag in. This is the temperature when the dissolving of the various chemicals in tea leaves is optimal. If it is too hot, bitter-tasting tannins and catechins are released in excess, whereas if it is too cool, not enough dissolving occurs.