science 9

1. BLOOD
VESSELS

2. WHAT IS A
BLOOD
VESSEL?
 Blood vessels are intricate
networks of hollow tubes that
transport blood throughout the
entire body so that it can deliver
valuable nutrients to and remove
waste from cells via
the cardiovascular system.

3. Blood is the circulating medium in the
cardiovascular system. It flows
continuously through the different
types of blood vessels.

5.  Arteries
 Veins
 Capillaries
 Flow of blood starts
from the: heart, to the
artery, to arteriole, to
capillary, to venule, to
vein, and goes back to
heart.

6.  The walls of arteries are thicker than veins to
withstand pressure as the blood is being
pumped throughout the body.
 Capillaries are extremely small vessels located
within the tissues of the body that transport
blood from the arteries to the veins. Fluid and
gas exchange between capillaries and body
tissues takes place at capillary beds.

7.  Arteries –moves blood
away from heart
 Veins –moves blood
towards the heart
 Capillaries –connects
arteries and veins as the
blood in arteries gives off
oxygen in body tissues
and carries carbon
dioxide as it travels to
veins going back to heart

8.  Arteries (red) carry
oxygenated blood
away from the heart
to different parts of
the body.
 Veins (blue) carry
deoxygenated blood
from different parts
of the body going to
the heart. Have
valves to prevent
backflow of blood.

9. The walls of blood vessels have coats or tunics,
namely tunica interna (innermost coat), tunica media
(central coat), and tunica externa (outermost coat).
Arterial walls are strong enough to withstand the
pressure of the blood coming from the heart. By
contrast, veins withstand low blood pressure and thus
have thinner walls.

10. NOTE: Arteries generally carry oxygenated blood
(blood with oxygen), whereas veins carry
deoxygenated blood (blood without oxygen).
 The flow of blood in the arteries is away from the
heart, whereas in veins, the blood flows toward the
heart. Thus, veins have valves to prevent the backflow
of blood.

11.  The pressure or force that blood exerts against the walls of the
blood vessels. It rises and falls as the heart contracts and relaxes.
 Systolic pressure is the pressure in the arteries when the
ventricles are contracting. Meanwhile, Diastolic pressure is
the pressure in the arteries when the ventricles are relaxing.
 A blood pressure reading of 120 over 80 means a systolic
pressure of 120 and diastolic pressure of 80.
 Stethoscope is used to detect blood pressure while
sphygmomanometer is used to measure blood pressure.