Smoking is bad for you. We all know that, and yet according to the Centers for Disease Control, approximately 15 percent of all Americans over the age of 18 smoke cigarettes.

The CDC also notes that cigarette smoking is directly or indirectly responsible for one in every five deaths each year. Contrary to popular belief, not all those deaths are related to lung disease. As it turns out, this habit directly (and negatively) impacts your entire body:

1. Circulation and heart disease

Your circulatory system is responsible for carrying blood to and from your heart. When we talk about keeping our circulatory systems healthy, we tend to focus on diet and exercise. However, the National Heart, Lung, and Blood Institute points out that smoking is a major risk factor for heart disease.

The chemicals found in cigarettes can cause plaque to build up in your arteries. This can lead to a condition known as atherosclerosis, more commonly called "hardening of the arteries."

If enough plaque builds up on the walls of your arteries, you may experience a blockage. Depending on where it's located and how big the blockage is, it may lead to chest pain, a heart attack or a stroke.

2. Reproduction and fertility

If you want to have children, you should pay special attention to this side effect of smoking. Did you know that smoking cigarettes can negatively impact the fertility of both men and women?

Human fertility is dependent upon good circulation. Smoking a cigarette means letting 7,000 chemicals spread through your entire body, inhibiting that circulation. In men, smoking (or even second-hand smoke) can damage blood vessels, leading to a reduced sperm count, hormonal issues and even lead to complete infertility.

For women, the risks are just as great. The chemicals found in cigarettes can affect your cycle, disrupt ovulation and even damage your reproductive organs. If you do manage to get pregnant while smoking, you'll have an increased risk of experiencing a miscarriage - and your baby will have a higher risk of serious health problems, too.

3. Stomach

The chemicals found in cigarettes are not good for your digestive system and can lead to deadly health problems.

For example, your chances of developing cancer of the stomach or esophagus are more than doubled if you smoke cigarettes.

Likewise, smokers are far more likely to develop gastroesophageal reflux disease, or GERD, than non-smokers. Smoking relaxes the esophagus, increases the acidity of your stomach and reduces salivation, all of which can cause GERD.

4. Bones

As women and men age, their bones become increasingly brittle and porous. We all experience it, but smoking cigarettes can speed up the process and cause osteoporosis.

Smoking impacts your bones' strength in two ways. First, it reduces your body's ability to absorb calcium, a mineral that's essential for bone building. Second, it reduces estrogen, something that both men and women need to help their bones hold onto calcium and other minerals.

The longer you smoke, the more likely it is that you'll end up with brittle, breakable bones as you age.

5. Brain

Smoking can damage your brain, making it dependent upon nicotine and increasing the chances that you'll experience a stroke or aneurysm.

We already talked about arterial blockages and smoking, so you know that having a stroke is a real possibility for smokers. However, it's also true that smoking is the single biggest risk factor for developing aneurysms - a bulging of the blood vessel - in the brain. If this aneurysm bursts, it can be deadly.

Smoking is particularly dangerous if you already carry one of several gene variations; having one of these genes can make it five times as likely you'll develop an aneurysm. However, "even if you have the gene, you can dramatically affect your risk by not smoking. If you smoke, you are multiplying the effect of the gene," says Joseph P. Broderick, M.D.

6. Skin

Skin is the human body's largest organ. It can be easy to forget that, but the truth is that smoking can cause damage to your skin and cause you to look years older than your age.

Here are just a few of the ways that smoking can affect your skin:

It can cause bags underneath your eyes
It can cause premature wrinkles
It can greatly increase your chance of developing psoriasis
It can make it harder for wounds to heal and easier for scars to form
It can make you susceptible to human papillomavirus, which causes warts
One of the best ways to protect your skin and keep its healthy glow is to quit smoking.

Ready to Quit?

As you can see, smoking is not just bad for your lungs. The chemicals in cigarettes and the process of smoking them can damage your whole body from your head to your toes.

The good news is that if you quit, you can expect to see rapid improvements in your health. So, what are you waiting for? Put down that pack and get ready to reclaim your healthy today!