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Immune and infectious diseases

Contain yourself: The language of your body's linings

By , Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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A professor in a white lab coat teaches anatomy to a class using a life-size model of a human body that is open in front to show the skeleton and digestive system.

I once heard a comedian asked to name his favorite part of a woman's body. "The skin," he said. "If she doesn't have skin, I'm not going to be seen with her." Fair enough!

In fact, our skin has many purposes. It has an obvious role in appearance: Healthy-looking skin can affect how good you look. It also serves as a cooling system (think sweat glands) and contributes to bone health (as UV light helps your skin to make vitamin D). And that's just the beginning.

Your skin is also a container. It protects your internal organs and structures from the outside world. And keeps everything where it belongs - inside.

The body has several other "containment systems." Think of them as "liners" that protect vital organs. Most people don't hear about these until they need to - when something goes wrong. In case that happens, you'll understand what your doctor is saying.

For example:

  • Pericarditis: inflammation of the lining of the heart; common causes include viral infections, kidney failure and lupus.
  • Pleurisy (or pleuritis): inflammation of the lining of the lung; again, infection is the most common cause.
  • Meningitis: inflammation of the lining of the brain; infection is the most common cause.
  • Peritonitis: inflammation of the lining of the abdominal cavity; common causes include appendicitis or perforation of a part of the digestive tract (as with an ulcer or diverticulitis).

Other diseases that involve the body's linings include:

  • Gingivitis: inflammation of the gingiva, the lining of the gums, due to infection. It can cause pain, swelling, and tooth loss.
  • Conjunctivitis: inflammation of the conjunctiva, the lining that covers the surface of the inner eyelids and eye.
  • Endometritis: inflammation of the endometrium, the lining of the uterus (womb). This is usually due to infection and can be a serious condition, especially during pregnancy or childbirth.
  • Mucositis: inflammation of the mucosa (or mucous membrane), the lining of many inner portions of the body. Areas with mucosa that are prone to inflammation or infection include the digestive tract (from mouth to anus), nose, and vagina.

Our body's liners do more than just separate one part of the body from another. In the digestive tract, for example, the mucosa

  • prevents toxins from entering the bloodstream
  • discourages foreign proteins (as in certain foods) to which we may be allergic from getting into the bloodstream
  • provides a barrier and an immune defense that prevents infectious organisms from getting into the body
  • produces substances the body needs, such as antibodies, digestive enzymes, and acid
  • absorbs nutrients such as water, vitamins, and electrolytes.

In my view, the body's containment systems and liners are parts of the body that are underappreciated. They are also a part of your doctor's lingo that may be hard to understand... until now. The next time your doctor mentions pleurisy or meningitis, you'll be ready.

Image: © Chih Chieh Hsiao/Getty Images

About the Author

photo of Robert H. Shmerling, MD

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio
View all posts by Robert H. Shmerling, MD
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