Re: How do our cells protect our body?

Hi Amanda,

Cells protect our bodies in many ways. The most 'visible' form of protection is your skin. The outer layer of skin, called the epidermis, represents dead skin cells that will soon be lost from the body through contact with other surfaces, clothes, etc.. This dead layer provides a tight, waterproof barrier to microbes, and other elements in the world around us. Beneath the epidermis lies the dermis an actively dividing layer of skin cells. As the 'new' skin cells age, they die and become part of the epidermis. This constant renewal of cells serves to keep your skin healthy and intact. A similar process happens in the mucous membranes that line the nose, mouth, digestive, and genitourinary tracts. In many cases this 'internal skin' is only one cell layer thick!, yet it provides a primary barrier to things you have eaten, and the many species of bacteria that live in the small and large intestine. Like your 'external skin' cells from this barrier (or epithelium) are constantly turning over. Dead cells are lost from the epithelium and replaced by younger, healthier cells that maintain the functions of the epithelial barrier. In the gut they also play a significant role in absorbing nutrients from the foods you eat.

Many other cell types help 'protect' the body. Liver cells remove harmful wastes from the blood, as do cell types in the kidney.

Of course, most people think about the immune system when it comes to protection. White blood cells fight invaders that make it through the skin and epithelial barriers of your body. These cells develop in the marrow, or inner areas of your bones, circulate in your blood stream, and reside in tissues throughout your body, so no matter where you get an infection, there are immune cells to fight it. Humans have three primary kinds of immune cells:

1. Granulocytes: These include neutrophils and eosinophils. These cells make proteins and other factors that help destroy bacteria or parasites when you get an infection.
2. Phagocytes: Phagocytosis represents a process whereby a large cell engulfs another cell. Macrophages are the body's primary phagocyte. These cells will 'eat' bacteria and kill them, rather like a cellular garbage collector cleaning up an infection.
3. Lymphocytes: Lymphocytes are commonly divided into two groups: B cells which produce antibodies, and T cells which have a variety of functions. Some T cells can kill other cells directly, particularly if they have been infected with a virus. Others have important functions regulating other immune cells like B cells and macrophages.

I hope this answers your question.

-Lynn Bry, MadSci Admin