Everybody and their mother know that cigarette smoke is harmful. In fact, it's the leading cause of preventable death in the United States. There are 480,000 deaths a year that occurs from cancer, respiratory disease, vascular disease and various other types of aliments as a result of cigarette smoke (Tobacco-Related Mortality). The killers in cigarette smoke come from the variety of perilous chemicals – from tar to carbon monoxide – that are all rolled into a single cigarette (What's in a Cigarette?). It's this concoction of chemicals that when lit, makes cigarette smoke so substantially harmful to our bodies.

These unsettling facts about cigarette smoke are well-known by everyone, but what the majority of people do not know is the direct impact that cigarette smoke has on the cells of the respiratory system. That is, it literally changes the shape and structure of the cell. It's not the positive type of change like when an exercise muscle undergoes hypertrophy and increases mass, but more like turning a square cell into a flat egg-shaped cell.

When cigarette smoke is inhaled it cruises along the respiratory tract until it reaches the lungs, and then gets exhaled out. Inside your respiratory tract is a variety of cells which when hit with cigarette smoke repeatedly over time, can undergo – in this case – a nasty process called metaplasia.

Metaplasia is a process in the body that replicates a certain type of cell into another more useful type. This absolutely changes the structure and function of the cell. It can occur naturally and as a positive process, such as in cartilage turning into bone through ossification, or it can occur abnormally with negative impacts through stress or toxic repeated stimuli.

The metaplasia of the respiratory tract cells as you may guess, is negative. The repeated intake of cigarette smoke on the respiratory tract can change the cells from a square-shaped cell – called columnar- with cilia (little hairs that help trap dust) to squamous shaped (which resembles a fried egg) without any cilia. To get a better picture of what the cells in the respiratory tract can turn into, squamous shaped cells are what make up the outer part of the epidermis. To picture the process of squamous metaplasia, imagine a row of sturdy strong cinderblocks protecting the floor benefit it. Now imagine over time with repeated intake of harmful substances those cinderblocks turn into a pile of dough. Well, with the repeated exposure to cigarette smoke, that's what can happen inside the respiratory system.

Squamous metaplasia from tobacco smoke affects multiple parts of the respiratory system including the cells in the pharynx and the bronchus. The damage does not just stop there either: squamous metaplasia is directly associated with chronic obstructive pulmonary disease – COPD – which is a very concern topic these days.

Aside from the well-known consequences from smoking, like cancer, vascular diseases, association with miscarriages, impotence, macular degeneration, etc., one of cigarettes most deadly side effects is chronic obstructive pulmonary disease (COPD). COPD is a progressive disease that makes breathing difficult and can cause what's commonly known as 'smokers cough'. It is the third leading cause of death in the United States and is directly associated with smoking tobacco products (“Chronic Obstructive Pulmonary Disease (COPD) Fact Sheet”).

Oddly enough, squamous metaplasia is actually one of the human body's many defense mechanisms when it comes to damage from cigarette smoke. The human body is always trying to restore balance within itself and when it comes to damage from tobacco smoke, changing the shape and function of its cells is a necessity to keep the barrier in the respiratory tract still useful (Bolton). Sadly though, the complications do not end with just changing the shape of the cells. Up to a certain point, this process is reversible, but if the harmful stimulus is not removed this can reversibility can change (ELSEVIER) – and worse – become cancerous.

It is accepted everywhere that cigarettes have a damaging effect on the human body. Although that fact is known, not everyone knows some of the exact effects cigarette smoke has. Squamous metaplasia is one of those effects. Through changing the shape and function of the cell, squamous metaplasia silently affects the cells of the respiratory tract. So closely associated with COPD, squamous metaplasia is not only a nasty result of cigarette smoke but a deadly one as well.

Bolton, S., Pinnion, K., Oreffo, V., Foster, M., & Pinkerton, K. (2009, November 9). Characterization of the proximal airway squamous metaplasia induced by chronic tobacco smoke exposure in spontaneously hypertensive rats. Retrieved September 4, 2014.

“Chronic Obstructive Pulmonary Disease (COPD) Fact Sheet.” American Lung Association. American Lung Association, nd Web. 30 Sept. 2014.

ELSEVIER. “Cell Injury, Cell Death, and Adaptations.” http://Www.us.elsevierhealth.com . POF ELSEVIER. Web. 30 Sept. 2014.

Tobacco-Related Mortality. (2014, February 6). Retrieved September 4, 2014.

What's in a Cigarette? – American Lung Association. (nd). Retrieved September 4, 2014.