How blood pressure works - Wilfred Manzano
-
0:07 - 0:11If you lined up all
the blood vessels in your body, -
0:11 - 0:15they'd be 95,000 kilometers long
-
0:15 - 0:22and everyday, they carry the equivalent
of over 7,500 liters of blood, -
0:22 - 0:28though that's actually the same four
or five liters recycled over and over, -
0:28 - 0:30delivering oxygen, and precious nutrients
-
0:30 - 0:35like glucose and amino acids
to the body's tissues. -
0:35 - 0:40All that blood exerts a force on
the muscular walls of the blood vessels. -
0:40 - 0:43That force is called blood pressure,
-
0:43 - 0:47and it rises and falls
with the phases of the heartbeat. -
0:47 - 0:49It's highest during systole,
-
0:49 - 0:53when the heart contracts to force
blood through the arteries. -
0:53 - 0:55This is your systolic blood pressure.
-
0:55 - 0:58When the heart is at rest between beats,
-
0:58 - 1:02blood pressure falls to its lowest value,
the diastolic pressure. -
1:02 - 1:06A typical healthy individual produces
a systolic pressure -
1:06 - 1:10between 90 and 120 millimeters of mercury,
-
1:10 - 1:14and diastolic pressure between 60 and 80.
-
1:14 - 1:20Taken together, a normal reading is a bit
less than 120 over 80. -
1:20 - 1:22The blood traverses
the landscape of the body -
1:22 - 1:25through the pipes
of the circulatory system. -
1:25 - 1:26In any plumbing system,
-
1:26 - 1:30several things can increase the force
on the walls of the pipes: -
1:30 - 1:32the properties of the fluid,
-
1:32 - 1:33extra fluid,
-
1:33 - 1:35or narrower pipes.
-
1:35 - 1:36So if the blood thickens,
-
1:36 - 1:41a higher pressure is needed to push it,
so the heart will pump harder. -
1:41 - 1:45A high-salt diet will lead
to a similar result. -
1:45 - 1:47The salt promotes water retention,
-
1:47 - 1:51and the extra fluid increases the blood
volume and blood pressure, -
1:51 - 1:54and stress,
like the fight or flight response, -
1:54 - 1:58releases hormones, like epinephrine
and norepinephrine -
1:58 - 2:01that constrict key vessels,
-
2:01 - 2:05increasing the resistance to flow
and raising the pressure upstream. -
2:05 - 2:09Blood vessels can usually handle
these fluctuations easily. -
2:09 - 2:14Elastic fibers embedded in their walls
make them resilient, -
2:14 - 2:19but if your blood pressure
regularly rises above about 140 over 90, -
2:19 - 2:22what we call hypertension,
and stays there, -
2:22 - 2:24it can cause serious problems.
-
2:24 - 2:27That's because the extra strain
on the arterial wall -
2:27 - 2:28can produce small tears.
-
2:28 - 2:31When the injured tissue swells up,
-
2:31 - 2:33substances that respond
to the inflammation, -
2:33 - 2:37like white blood cells,
collect around the tears. -
2:37 - 2:41Fat and cholesterol floating
in the blood latch on, too, -
2:41 - 2:44eventually building up to form a plaque
-
2:44 - 2:48that stiffens and thickens
the inner arterial wall. -
2:48 - 2:50This condition is called
atherosclerosis, -
2:50 - 2:53and it can have dangerous consequences.
-
2:53 - 2:57If the plaque ruptures, a blood clot
forms on top of the tear, -
2:57 - 3:00clogging the already narrowed pipe.
-
3:00 - 3:01If the clot is big enough,
-
3:01 - 3:07it can completely block the flow of
oxygen and nutrients to cells downstream. -
3:07 - 3:08In vessels that feed the heart,
-
3:08 - 3:10that will cause a heart attack,
-
3:10 - 3:15when oxygen-deprived cardiac
muscle cells start to die. -
3:15 - 3:18If the clot cuts off
blood flow to the brain, -
3:18 - 3:20it causes a stroke.
-
3:20 - 3:23Dangerously clogged blood vessels
can be widened -
3:23 - 3:26by a procedure called
an angioplasty. -
3:26 - 3:29There, doctors thread a wire
through the vessel -
3:29 - 3:31to the obstructed site,
-
3:31 - 3:35and then place a deflated
balloon catheter over the wire. -
3:35 - 3:39When the balloon is inflated,
it forces the passageway open again. -
3:39 - 3:42Sometimes a rigid tube
called a stent -
3:42 - 3:45is placed in a vessel
to held hold it open, -
3:45 - 3:47letting the blood flow freely
-
3:47 - 3:50to replenish the oxygen-starved
cells downstream. -
3:50 - 3:54Staying flexible under pressure
is a tough job for arteries. -
3:54 - 3:57The fluid they pump
is composed of substances -
3:57 - 3:59that can get sticky and clog them,
-
3:59 - 4:03and your typical healthy heart
beats about 70 times a minute, -
4:03 - 4:08and at least 2.5 billion times
during an average lifetime. -
4:08 - 4:11That may sound like an insurmountable
amount of pressure, -
4:11 - 4:15but don't worry, your arteries
are well suited for the challenge.
- Title:
- How blood pressure works - Wilfred Manzano
- Description:
-
View full lesson: http://ed.ted.com/lessons/how-blood-pressure-works-wilfred-manzano
If you lined up all the blood vessels in your body, they’d be 60 thousand miles long. And every day, they carry the equivalent of over two thousand gallons of blood to the body’s tissues. What effect does this pressure have on the walls of the blood vessels? Wilfred Manzano gives the facts on blood pressure.Lesson by Wilfred Manzano, animation by Fox Animation Domination High-Def.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:32
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