Why can't humans breathe underwater?

So today, the diversion appears, the interesting question that was posed by my biology teacher nearly two weeks ago, I confess, it did excite me, the large depth and breadth that I could go to with this really did open up many different trails to follow. So here what I have come up with so far, but I am still trying to get more information about the Silurian period in the Archeozoic time, which is nigh on the Precambrian period. I am really interested in finding out where fish and humans actually seperated through the journey of evolution. 

 

The principle of respiration for humans is breathing, without the lungs and diaphragm this would not be possible. The theory of inhalation and exhalation is that the pressure outside the lungs is less than within, so therefore the air rushes out. In water, if a human filled their lungs with water, they would be unable to exhale, firstly because of the lack of difference in density inside and outside the lungs, but also for many other reasons. Kinetic theory, Fick’s Law and many other aspects contribute to the fact that homo sapiens cannot breathe underwater.

The act of breathing begins at the mouth and nose – the two entry points for the air surrounding the face; it travels down your throat and into your trachea where it is divided down the two bronchial tubes. The air is then divided into smaller passages – the bronchioles, from there it goes into the alveoli. The alveoli are each surrounded by a mesh of capillaries and the oxygen diffuses through the alveoli and then capillary wall to bind with haemoglobin in a red blood cell. This oxygenated blood travels to the heart and is then pumped to the extremities of the body to allow respiration to take place. The deoxygenated blood returns to the lungs and the carbon dioxide that was released during respiration diffuses across the two membranes and is then exhaled. The diaphragm plays a huge part in respiration, it increases the pressure in the lungs, forcing exhalation.

Humans inhale a high concentration of oxygen which enables fast diffusion and is increased due to the low density, whereas water, due to being a liquid is denser, so therefore would be more difficult to inhale. Furthermore, exhaling would be nearly impossible due to the weight of water that would press down on the diaphragm, preventing it from contracting and therefore it would be impossible to expel the water that has a low concentration of oxygen to allow the lungs to fill with fresh water. Additionally, water contains a lower percentage of Oxygen compared to the blood that has just been freshly oxygenated so realistically the oxygen in the blood surrounding the alveoli could theoretically diffuse into the water, due to the concentration gradient being reversed. Moreover, the concentration of oxygen in air is higher than in water so therefore diffusion will require less energy because of the high contrast in concentration gradient.

Aquatic respiration is very different to human respiration. Fish respiration takes place through gills, the water flows to their mouth and is then forced out of their gills on either side of their body, this means that the water is filtered through their gills which consist of large amounts of gill filaments that are all in close proximity of each other. The gill filaments are all attached to the gill bar, stacked up to be specific and each filament has lamellae which increase the surface area of the gills. The water flows in the opposite direction than the blood over the gill filaments; this is known as countercurrent flow. The principle for aquatic respiration is that the water flows over the oxygenated blood, allowing oxygen to diffuse into the blood and then the water flows over the deoxygenated blood, allowing for the oxygen and carbon dioxide to diffuse out of the blood and into the water. This means that when the water flows over the oxygenated blood there is a small difference in the concentration of oxygen in the blood compared to the water, but diffusion can still take place so the concentration of oxygen dissolved in the water decreases, so when it proceeds and flows over the deoxygenated blood there is a concerntration gradient that allows for diffusion out of the blood and into water.

The evidence in contrast between human and aquatic respiration helps to explain why humans cannot respire under water.  The different organs and mechanisms used by each animal for respiration also demonstrates where each creature evolved, and how they have adapted to allow from respiration in the optimum ppO₂.  

I found this image online, but it didn't provide as much answers as I would like, as this picture shows, fish and humans seperated many years ago, even before the renowned Jurassic Period. So, the possibility of humans being able to breathe underwater is so far off possible it is almost bordering on ridiculous. Not only the amount of time since seperation, but the distance, as you can see the different branches show how many species have arisen in between fish and humans. 

I have been spreading the word around my school, my viewer numbers have increased considerably, and I am very grateful to the new readers, along with the increasing numbers of those 'across the pond' (Hi american readers!) - I would just like to say thanks to all my readers for reading. 

See you all soon, hopefully, School is crazy but I really enjoy writing this.

The History of Medicine continued...

Well Hello, I am back again, a few days late, so I apologise, however I intend to amaze you with my newly acquired knowledge and pictures. Schoolwork has been piling high around me so I have been dedicating most of my time to that. But I am happy to return, because this is where I can truly return to my own thoughts.

Andreas Vesalius came from a long line of Doctors, at the age of 17 he began medical studies at the University of Paris, he became bored of his teacher Sylvius, a firm believer in all of Galen's teachings and theories, because of his own knowledge acquired by previous experimentation.

I am aware that some context is needed here, it was in 1536 this all happened. Therefore there was reformation going on at every boundary and war was breaking out, Vesalius left Paris to study at the University of Louvain, near Brussels, Belgium.

He got a chance to study a human body in detail - he stole a skeleton of a robber whose corpse had been pecked clean by the birds that was hanging in the gallows. Bit by bit he took it back to his room and wired together the full human skeleton, which he then learnt it in extreme detail.

Noticing the flaws between the skeleton he had and the teachings of Galen he was enraged to realise that Galen had based all of his teachings on animals, there was no evidence to indicate that Galen had ever actually seen the inside of a human. The sternum, I learnt, consists three parts; the manubrium, the body and the xiphoid process.

Vesalius then came to the shocking conclusion that doctors treated humans based on the knowledge of apes. 

In 1537 he traveled to Padua to study further, the university there was Europe's most famous school, students ran the university and hired professors by vote. Vesalius got his medical degree on December the 5th 1537, the next day he was made professor of anatomy, because he was so popular his lectures became overcrowded and the students were unable to see the dissections properly, so Vesalius made illustrations, allowing the students to see at a glance what would take hours to explain.





I had a look at some the drawings by consulting a famous book created by Vesalius called 'De Humani Corporis Fabrica' (The Fabric of the Human Body), here are a few images from the book that contains detailed images of the human body, the muscles and the nervous system.

I thank you, once again for returning here, and welcome any newcomers, my page views have increased by a lot recently, I do believe I have some people from the USA reading this, I would really appreciate some comments and if there is anything you would like me to research a particular area of medicine or just science in general I would be willing to create a spin off blog. 

Additionally, as sad as it is to confess, I have been given an essay to write for biology, specifically 'Why can't humans breathe underwater?' and I am extremely excited to finish researching it, because as simple as it sounds it is not such an easy answer, there is an extremely complex answer concerning many different aspects of science as a whole.

Thank you for reading, I will return soon, I am on my half term from school but have a very busy schedule, maybe one day I will be able to do nothing during a holiday, so goodnight my friends, I hope to see you soon.

The History of Medicine

Why good day my chums, thank you for returning here (if you did) and I welcome any new readers.
Today is focused on the History of Medicine - from the original thought that evils spirits caused disease right up to the discovery of Penicillin.

So, Yesterday I got a book out of my school library, 'The History of Medicine' by John Hudson Tiner and I must say it has enlightened me to the past misconceptions of cause and effect when it comes to illness. The first page is dedicated to Hippocrates - yes, the man behind the oath. 

Hippocrates is known as the 'Father of Medicine'.

He was one of the first to believe in a fault in the body, compared to the previous beliefs that evil spirits, hateful demons and vengeful gods struck people with diseases, the Greek god Apollo shot invisible arrows that caused pain. Before Hippocrates treatments for illnesses mainly consisted of travelling to a pagan temple, the sick person would then make a sacrifice and spend a night in the temple 'dreaming away the sickness'.

Hippocrates was the first to ask his students to ask the patient if anything had changed in his diet and how he felt when the illness began. Diet was a large focus of Hippocrates, he believed 'one man's is another man's poison.'

"Desperate diseases require desperate remedies" 

"Illness is sometimes stronger when a mind is troubled"

These are two more of Hippocrates beliefs, which connects to now, 2013. This week in psychology I have been studying stress and its effect on the immune system. Many studies have been done that prove that when stressed, the immune system response is dulled and the count of B and T lymphocytes decrease.

Now back to the famous oath. The Hippocratic Oath is a tradition for most physicians, swearing to practice honestly and ethically. Hippocrates, in 460 B.C. changed how physicians looked upon their own profession - it was as corrupt as any other at that point. People would pay physicians to ensure that a patient died, or to prolong their illness or even to concoct poisons. 

A guide to the Hippocratic Oath, via a website I frequently visit

'I will use treatment to help the sick according to my ability and judgment, but never with the view to injury and wrong doing... Into whatsoever houses I enter, I will enter to help the sick'

Galen, another famous man in the history of medicine. He was the first person to believe that nerves came from your spine, someone came to him with numbness in their hand and recovered, thanks to the advice of Galen  He believed that illness was a result of the imbalance of the humors of the body. 

'The body has in itself blood, phlegm, yellow bile, and black bile... We enjoy the most perfect health when these elements are in the right proportion'

This caused a problem, the serious misconception of imbalance led to the bleeding out of George Washington, a rather well known occasions, but if you are in the dark I will indulge you...

He went riding and contracted a cold, his physicians, with the belief of imbalanced humors, opened his veins and drained some of his blood, his illness continued so they repeated this until they literally bled him to death. 

Realistically this contrasts completely what we now know - blood is what combats infections. White blood cells.

Any way, thank you for reading today, I hope to continue this tomorrow, but I am not sure, A levels are not a walk in the park, they are more like a run through a thick forest that has booby traps, mud and large tree trunks crossing the path. 

Good day