2. Blood: the fluid of life
In multicellular organisms the medium is called
axtracellular fluid. It contains interstitial fluid, a
liquid found in the spaces between cells.
Blood is a viscuos fluid with a salty taste which flows
inside the vessels of the circulatory system.

3. Composition of blood
Blood is made up of blood cells suspended in a liquid
called blood plasma;
Blood plasma: it’s a substance made up of water
containig dissolved molecues like minerals, nutrients,
waste products, proteins and hormones.

4. Blood cells: Are produced in the bone marrow.

5. Functions of blood
Transports nutrients and oxygen to all cells
Collects waste products released during cell metabolism.
Transports hormones around the body
Helps to regulate temperature
Protects the body from infections
The body uses a lot of mechanisms to prevent blood loss
when a blood vessel is broken
The membranes of red blood cells contain proteins that are
responsible for differences in the blood type of different
people

6. Blood vessels
Blood flows around the body in three types of blood
vessel:
Arteries: They carry the blood away from the heart.
Capillaries: Are blood vessels which branch out from
the arterioles and are found in every body tissue
Veins: Take the blood back to the heart and are
formed by capillaries grouped together.

7. Heart
Hollow organ made of
thick muscle tissue
(myocardium) that
pumps the blood to
make it move around
the circulatory system
with the function of
supply to the cells
nutrients and oxygen.
http://videos.howstuffw
orks.com/health/heart-
videos-playlist.htm

8. Heart’s activity
Heart collects blood
from the veins, pumps it
out into the arteries. The
pumping movement
(heartbeat) occurs
continuously and pushes
blood:

9. Cardiac cycle

10. Circulation through the blood vessels
Ventricular systole pumps the bood to the major arteries,
(elastic).
So they can:
- Dilate when they receive blood, lowering blood pressure.
- Contract back to the normal diameter, pushing the blood
forwards. 

11. Then it travells to the smaller vessels and the
capillaries.
- The blood pressure is higher during syshole
than turning diastole, so blood pressure alternates
between maximun and minimun. When blood
reaches the capillaries (flows slowly) pressure is
lower and facilities the exchanges.
- The blood flows to the venules and veins and
returns to the heart.

12. A double circuit
Pulmonary circulation
The circuit of the blood has two parts:
- Pulmonary circulation: blood starts in the right
ventricle and splits into arteries which each lead
to a lung. The capillaries surrounds the alveoli;
(here gas exchange takes place) they turn into
venules, which join to veins which lead to the left
atrium. The blood flows to the left ventricle,
where systemic circulation begins.

13. Systemic circulation
- Systemic circulation: blood flows along the aorta
and splits into arteries, arterioles and then into
capillaries. These lead to all body (but no to
lungs). Blood provides cell which everything they
need, and takes away waste products. Then
returns to the right ventricle where pulmonary
circulation starts again.

14. Irene Álvarez
Lara Caeiro
Natalia Vázquez
Paula López