Arteries, Arterioles, Veins,
Venules, & Capillaries
Arteries
• Large hose-like vessels
• Carry blood away from
the heart.
• Have thick, multilayered muscular walls.
• Walls are capable of
stretching to
accommodate the
“pulse” of blood when
the heart beats.
Arteries
• Capable of expanding
and contracting to
change and maintain the
blood pressure.
• NO valves
• Blood spurts
• Blood inside them is
high in oxygen & low in
carbon dioxide except in
pulmonary artery.
Arteries
• Blood inside is bright
red
• Blood inside is under
High pressure
• Examples:
Coronary (heart),
Brachial (arms),
Carotid (head),
Femoral (legs),
Renal (kidney).
Arterioles
• Tiny branches off of the arteries.
• Cannot be seen with unaided eye microscopic
• Thinner, less muscular walls (compared to
arteries)
• Feed blood into the capillaries.
• Narrower than arteries, but wider than
capillaries.
Capillaries
• Flow and pressure of blood
is controlled by sphincters
that are outside of the
capillaries.
• Microscopic vessels ~ 8 µm
in diameter.
• Erythrocytes (rbc’s) pass
through in single file.
• Walls are only one cell thick
(to facilitate diffusion of
materials/exchange).
Capillaries
• Thinness allows for
easy diffusion
outward or inward
through the single cell
layer.
• Form capillary beds networks of vessels
linking arterial and
venous blood.
Capillaries
• Oxygen , nutrients and other materials move
out of the capillaries and into the extracellular fluid and then into cells.
• Carbon dioxide, wastes and other materials
are picked up and move into the capillaries:
(both involve diffusion for the movement).
Venules
• Vessels larger than capillaries but smaller
(i.e. narrower and thinner walls) than veins.
Veins
• Larger inside diameter compared to
arteries
• Take blood towards the heart
• Thinner, less muscular walls than
arteries, but still 3 layers
• No stretching or contracting of walls
except by external muscles.
• Contain valves to help return the
blood to the heart (compensate for
lower venous pressure, less muscle
in walls, and large diameter).
Veins - Valves
Veins
•
•
•
•
•
Blood:
Moves smoothly.
Low in oxygen except
pulmonary circulation.
Dull red.
Low pressure.
Examples: cardiac (heart),
brachial (arms), jugular
(head), femoral (legs),
renal (kidney).
Varicose Veins (copy this)
• When the valves
don’t function
properly, blood
leaks backwards
and pools in veins
• Veins sag, stretch
and swell, creating
bulging knarled
vessels
The END!!