This is an I-Heart podcast.

Welcome to Brain Stuff, a production of IHeart Radio.

Hey, Brainstuff, Lauren Vogelbaum here.

You may have heard that your body replaces and replenishes all of its cells every seven years.

This isn't quite true. It's catchy,

but our bodies are complicated, and your rate of cellular renewal depends person to person and organ to organ. Your skeletal cells might change out every 10 to 15 years or so. Some of the cells in

your brain and heart will stay with you

for your entire life. On the flip side, the cells in your liver get replaced every three years,

and the ones in your gut turn over within a few months. But if it were a race, your skin would win.

Under normal conditions, the cells in your epidermis, your skin's outermost layer,

replace themselves in just four weeks. That's because the outer layer of the epidermis is actually

made up of tough dead cells that help protect us from germs and rough surfaces and everything

else in the world around us. We're constantly sloughing

off the old ones as they wear out. We shed some 40,000 dead skin cells every minute. That adds up to

about one and a half pounds of skin, around 700 grams, shed every year. But that's assuming that everything is working properly. Sometimes, for

reasons that we don't entirely understand, your skin can go into overdrive. In a condition called

psoriasis, your skin tries to replace its outermost layer every four days or so. This leads to a build-up of skin

cells that can cause discolored, uncomfortable patches on your skin that are annoying at best.

It's caused by your immune system being way overactive, so it's not contagious, but there's no

cure. Not yet, anyway. But what's going on here? How

could a process that's supposed to be good, the maintenance of our body's first line of defense,

turn against us? Today, let's talk about what we know and don't know about psoriasis.

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