How bones make blood - Melody Smith
-
0:07 - 0:11At any given moment, trillions of cells
are traveling through your blood vessels, -
0:11 - 0:15sometimes circling the body
in just one minute. -
0:15 - 0:19Each of these cells
has its origins deep in your bones. -
0:19 - 0:23Bones might seem rock-solid,
but they’re actually quite porous inside. -
0:23 - 0:26Large and small blood vessels
enter through these holes. -
0:26 - 0:30And inside most of the large bones
of your skeleton is a hollow core -
0:30 - 0:32filled with soft bone marrow.
-
0:32 - 0:35Marrow contains fat
and other supportive tissue, -
0:35 - 0:38but its most essential elements
are blood stem cells. -
0:38 - 0:41These stem cells are constantly dividing.
-
0:41 - 0:43They can differentiate
into red blood cells, -
0:43 - 0:46white blood cells, and platelets,
-
0:46 - 0:48and send about hundreds of billions
of new blood cells -
0:48 - 0:51into circulation every day.
-
0:51 - 0:53These new cells enter the bloodstream
-
0:53 - 0:56through holes
in small capillaries in the marrow. -
0:56 - 0:57Through the capillaries,
-
0:57 - 1:01they reach larger blood vessels
and exit the bone. -
1:01 - 1:03If there’s a problem with your blood,
-
1:03 - 1:06there’s a good chance
it can be traced back to the bone marrow. -
1:06 - 1:10Blood cancers often begin
with genetic mutations in the stem cells. -
1:10 - 1:12The stem cells themselves
are not cancerous, -
1:12 - 1:16but these mutations can interfere
with the process of differentiation -
1:16 - 1:19and result in malignant blood cells.
-
1:19 - 1:23So for patients with advanced
blood cancers like leukemia and lymphoma, -
1:23 - 1:27the best chance for a cure is often
an allogeneic bone marrow transplant, -
1:27 - 1:30which replaces the patient’s bone marrow
with a donor’s. -
1:30 - 1:32Here’s how it works.
-
1:32 - 1:36First, blood stem cells
are extracted from the donor. -
1:36 - 1:37Most commonly,
-
1:37 - 1:40blood stem cells are filtered out
of the donor’s bloodstream -
1:40 - 1:42by circulating the blood
through a machine -
1:42 - 1:45that separates it
into different components. -
1:45 - 1:47In other cases,
the marrow is extracted directly -
1:47 - 1:52from a bone in the hip, the iliac crest,
with a needle. -
1:52 - 1:55Meanwhile, the recipient
prepares for the transplant. -
1:55 - 1:59High doses of chemotherapy or radiation
kill the patient’s existing marrow, -
1:59 - 2:03destroying both malignant cells
and blood stem cells. -
2:03 - 2:05This also weakens the immune system,
-
2:05 - 2:09making it less likely
to attack the transplanted cells. -
2:09 - 2:14Then the donor cells are infused into
the patient’s body through a central line. -
2:14 - 2:17They initially circulate
in the recipient’s peripheral bloodstream, -
2:17 - 2:22but molecules on the stem cells,
called chemokines, act as homing devices -
2:22 - 2:25and quickly traffic them
back to the marrow. -
2:25 - 2:26Over the course of a few weeks,
-
2:26 - 2:31they begin to multiply and start producing
new, healthy blood cells. -
2:31 - 2:33Just a small population
of blood stem cells -
2:33 - 2:37can regenerate a whole body’s
worth of healthy marrow. -
2:37 - 2:39A bone marrow transplant
can also lead to something -
2:39 - 2:42called graft-versus-tumor activity,
-
2:42 - 2:45when new immune cells
generated by the donated marrow -
2:45 - 2:50can wipe out cancer cells the recipient’s
original immune system couldn’t. -
2:50 - 2:53This phenomenon can help eradicate
stubborn blood cancers. -
2:53 - 2:56But bone marrow transplants
also come with risks, -
2:56 - 2:59including graft-versus-host disease.
-
2:59 - 3:02It happens when the immune system
generated by the donor cells -
3:02 - 3:05attacks the patient’s organs.
-
3:05 - 3:09This life-threatening condition
occurs in about 30–50% of patients -
3:09 - 3:13who receive donor cells
from anyone other than an identical twin, -
3:13 - 3:16particularly when the stem cells
are collected -
3:16 - 3:18from the blood
as opposed to the bone marrow. -
3:18 - 3:21Patients may take
immunosuppressant medications -
3:21 - 3:24or certain immune cells may be removed
from the donated sample -
3:24 - 3:27in order to reduce the risk
of graft-versus-host disease. -
3:27 - 3:31But even if a patient
avoids graft-versus-host disease, -
3:31 - 3:34their immune system
may reject the donor cells. -
3:34 - 3:38So it’s crucial to find the best match
possible in the first place. -
3:38 - 3:41Key regions of the genetic code
determine how the immune system -
3:41 - 3:43identifies foreign cells.
-
3:43 - 3:46If these regions are similar
in the donor and the recipient, -
3:46 - 3:50the recipient’s immune system
is more likely to accept the donor cells. -
3:50 - 3:55Because these genes are inherited,
the best matches are often siblings. -
3:55 - 3:58But many patients
who need a bone marrow transplant -
3:58 - 4:00don’t have a matched family member.
-
4:00 - 4:03Those patients
turn to donor registries of volunteers -
4:03 - 4:06willing to offer their bone marrow.
-
4:06 - 4:10All it takes to be on the registry is
a cheek swab to test for a genetic match. -
4:10 - 4:12And in many cases,
the donation itself -
4:12 - 4:15isn’t much more complicated
than giving blood. -
4:15 - 4:17It’s a way to save someone’s life
-
4:17 - 4:20with a resource
that’s completely renewable.
- Title:
- How bones make blood - Melody Smith
- Speaker:
- Melody Smith
- Description:
-
View full lesson: https://ed.ted.com/lessons/how-bones-make-blood-melody-smith
Bones might seem rock-solid, but they're actually quite porous inside. Most of the large bones of your skeleton have a hollow core filled with soft bone marrow. Marrow's most essential elements are blood stem cells and for patients with advanced blood cancers like leukemia and lymphoma, the best chance for a cure is often a bone marrow transplant. How does this procedure work? Melody Smith explains.
Lesson by Melody Smith, directed by Artrake Studio.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:21
lauren mcalpine edited English subtitles for How bones make blood | ||
lauren mcalpine edited English subtitles for How bones make blood | ||
Alexandra Panzer approved English subtitles for How bones make blood | ||
Alexandra Panzer accepted English subtitles for How bones make blood | ||
lauren mcalpine edited English subtitles for How bones make blood |