At this point, you’d have to be living under a rock to not know that smoking is bad for you. 

The dangers tobacco poses to the heart and lungs have been well established by medical science, and anti-smoking campaigns are now decades-old. To protect nonsmokers from secondhand smoke, dozens of cities and states have banned smoking in public spaces.

And it’s all for a very good reason: Cigarette smoke contains more than 7,000 chemicals, at least 69 of which are known to cause cancer. When you think of the health hazards of smoking, you may imagine lung and heart diseases, or the visible effects of smoking on teeth and skin. But the particles inhaled from tobacco smoke make their way to nearly every organ in the body. Here’s what happens when you smoke, and how it affects your entire body.

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When you smoke …

When you inhale smoke from a cigarette, particles of tar and soot remain on the inside of your mouth and esophagus; you swallow them, and they enter the stomach. The rest of the tar particles in the smoke get filtered out by the lungs— where the tar stays and builds over time. Nicotine reaches the brain to produce a mild high and an addictive effect, while many toxins become concentrated in the kidneys and liver.

Whether through the lungs or the stomach, the majority of the chemicals in smoke end up in the bloodstream. Your blood carries them to your organs, where they can cause damage, says Michael Gordon, a specialist with Hoag Orthopedic Institute in Irvine, Calif.

“This leads to chronic inflammation and cellular damage— and, by the way, secondhand smoke is generally worse” than what actually enters the smoker’s mouth, Gordon says. That’s because the smoker is typically breathing it in through a filter that removes some of the byproducts of the burning tobacco. Secondhand smoke is completely unfiltered.

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It’s a cellular thing

That cellular damage is widespread, especially for longtime smokers. “At the cellular level, nicotine and other chemicals damage DNA and alter the cell’s metabolism,” Gordon says. “Some tissues are more susceptible than others,” he adds. The lungs and the respiratory tract as well as the upper gastrointestinal tract are the most susceptible, which is why those tissues are more likely to develop cancer.

But other cells are also at risk, notably those in the bones. “Cigarette smoking is associated with reduced bone mineral density and increased fracture risk,” says Gordon, who specializes in osteoporosis. In your bone cells, calcium receptors are damaged by cigarette use, so less calcium is absorbed. Without calcium, bone cells cannot rebuild, and they eventually weaken.

“This is how cigarette use complicates bone healing in fractures, and decreases fusion rates in spine surgery patients, and increases osteoporosis and fracture rates in smokers versus nonsmokers,” Gordon says. There is evidence, he says, that quitting smoking reverses this process.

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The bones are not alone

If you didn’t know that cigarette smoking makes your bones more brittle, you probably didn’t know it can also affect your blood sugar. Tobacco use increases the risk for Type 2 diabetes, and diabetics who smoke need more insulin, on average, than those who don’t, according to the Centers for Disease Control and Prevention (CDC).

Smoking also prevents adequate nutrients from reaching your skin, which causes uneven coloration or paleness. Additionally, the chemicals in cigarettes break down collagen and elastin, which are two key fibers in healthy skin. Without them, skin sags and wrinkles.

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A cumulative effect

Though smoking is destructive even in small amounts, the negative effects build up over time. “The earlier an individual is exposed to smoke, the longer the smoke has time to create an adverse effect,” Gordon says. But the caveat is that younger tissues are more susceptible to damage.

“Infants, toddlers and young children have lung tissue that is many times more sensitive to the deleterious effect of the particulates in cigarette smoke,” he says. That means children of smokers tend to have higher incidences of pulmonary disease, asthma and colds than children of nonsmokers.

So what does Gordon tell his patients who smoke? “The only message that is appropriate for smokers is that this is the leading cause of preventable death,” he says, adding that all organ systems are affected negatively. The only effective treatment for cigarette-induced illness, he says, is to stop smoking— or, better yet, to never start.