All Episodes

September 30, 2013 2 mins

As hair cells form in follicles, they push other cells out of the follicle. Check out this HowStuffWorks podcast to learn more about your hair's growth and rest phases.

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Mark as Played
Transcript

Episode Transcript

Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
Streaming TV shows and movies directly to your home is
a breeze with Netflix. As a Netflix member, you can
instantly watch TV and movies on your PC, Mac, mobile device,
or television. Get a free thirty day trial membership. Go
to Netflix dot com slash stuff and sign up today.
Welcome to brain Stuff from how Stuff works dot com
where smart happens. Hi. I'm Marshall Brain with today's question.

(00:30):
Why does the hair on your arms stay short while
the hair on your head can grow very long? Each
hair on your body grows from its own individual hair follicle.
Inside the follicle, new hair cells form at the root
of the hair shaft. As the cells form, they push
older cells out of the follicle. As they're pushed out,

(00:52):
the cells die and they become the hair that we see.
A follicle will produce new cells for a certain period
of time, depending on where it's located on your body.
This period is called the growth phase for the hair.
Then it will stop growing for a period of time
This is called the rest phase, and then start the
growth phase again. When a hair follicle enters the rest phase,

(01:14):
the hair shaft breaks off, so the existing hair falls
out and a new hair takes its place. Therefore, the
length of time that a hair is able to spend
growing during the growth phase controls the maximum length of
that hair. The cells that make the hairs on your
arms are programmed to stop growing every couple of months,
so the hair on your arms stays short. The hair

(01:36):
follicles on your head, on the other hand, are programmed
to let the hair grow for years at a time,
so the hair can grow very long. Animals that shed
have hair follicles that synchronize their rest phase, so all
the follicles enter the rest phase at once. This way,
all the hair falls out at the same time. A
dog that sheds will lose its hair in large clumps.

(01:59):
Some animals can also switch the coloring agent in the
hair follicle audit off, so in the summer of the
hair is pigmented brown with melanin, but in the winter
it's not pigmented, leaving the hair white. For more on
this and thousands of other topics, because it how staff
works dot com. Audible dot com is the leading provider

(02:21):
of downloadable digital audio books and spoken word entertainment. Audible
has over one hundred thousand titles to choose from to
be downloaded to your iPod or MP three player. Go
to audible podcast dot com slash brain stuff to get
a free audio book download of your choice when you
sign up today

BrainStuff News

Advertise With Us

Follow Us On

Host

Lauren Vogelbaum

Lauren Vogelbaum

Show Links

AboutStore

Popular Podcasts

CrimeLess: Hillbilly Heist

CrimeLess: Hillbilly Heist

It’s 1996 in rural North Carolina, and an oddball crew makes history when they pull off America’s third largest cash heist. But it’s all downhill from there. Join host Johnny Knoxville as he unspools a wild and woolly tale about a group of regular ‘ol folks who risked it all for a chance at a better life. CrimeLess: Hillbilly Heist answers the question: what would you do with 17.3 million dollars? The answer includes diamond rings, mansions, velvet Elvis paintings, plus a run for the border, murder-for-hire-plots, and FBI busts.

Crime Junkie

Crime Junkie

Does hearing about a true crime case always leave you scouring the internet for the truth behind the story? Dive into your next mystery with Crime Junkie. Every Monday, join your host Ashley Flowers as she unravels all the details of infamous and underreported true crime cases with her best friend Brit Prawat. From cold cases to missing persons and heroes in our community who seek justice, Crime Junkie is your destination for theories and stories you won’t hear anywhere else. Whether you're a seasoned true crime enthusiast or new to the genre, you'll find yourself on the edge of your seat awaiting a new episode every Monday. If you can never get enough true crime... Congratulations, you’ve found your people. Follow to join a community of Crime Junkies! Crime Junkie is presented by audiochuck Media Company.

Stuff You Should Know

Stuff You Should Know

If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.

Music, radio and podcasts, all free. Listen online or download the iHeart App.

Connect

© 2025 iHeartMedia, Inc.