The circulatory system consists of the heart and blood vessels that circulate blood throughout the body. The heart pumps blood through a network of arteries, capillaries and veins. Arteries carry oxygenated blood away from the heart while veins carry deoxygenated blood back to the heart. Capillaries connect arteries and veins and allow for the exchange of oxygen, carbon dioxide and other materials between the blood and tissues. The circulatory system circulates blood an average of once per minute to deliver oxygen and nutrients to tissues and remove carbon dioxide and waste.

1. The Circulatory System

2. Interesting Facts
• The heart beat is strong enough to squirt
blood 30 feet
• The longer a boy’s ring finger is, the less
likely they are to have a heart attack
(according to one study)
• The human heart beats ~35 million times
per year
• The heart pumps ~1,000,000 barrels of
blood in a lifetime
• Most heart attacks occur between 8-9 a.m.

3. Interesting Facts
• The blue whale has the
largest heart –
it weighs ~ one ton
• The hummingbird has a
heart that beats
1,000 times per minute

4. Interesting Facts
• Your entire volume of blood goes through your
whole body once every minute
• Humans have ~60,000 miles of blood vessels in
their bodies (more than twice the circumference of
the earth!)
• Your heart beats 100,000 times and pumps
~2,000 gallons of blood every day
• Pig and baboon hearts have been transplanted
into humans

5. Exploration
This is a picture of the
bottom of the human tongue.
Take a look at the bottom of your lab
partner’s tongue (if they will let you)
and see if you can find…
◦The veins –thick blue lines
◦The arteries –thick pink lines
◦The capillaries –tiny thin lines

6. The heart!
Questions!
What provides the force to cause the
blood to circulate through the body?
The heart is composed of cardiac muscle
which is part of the autonomic (automatic)
nervous system.
When it beats (flexes) blood is pushed through
the cardiovascular/circulatory system.

7. A collection of
vessels and the
muscles that
control the flow
of blood
through the
body.
What is the Circulatory System?

8. Heart
Function
◦The organ that pumps
blood through the
circulatory system.

9. The Heart
•Atria
Receive blood into heart
and pass it on to the ventricles
•Ventricles
Collect blood from the heart
and pass it on to the lungs, aorta and
push it out into the body
Larger than the atria as more muscle is
needed to
•Why is the left ventricle bigger than the
right ventricle?
Because the right ventricle only has to push
blood out to the lungs which are not very far
away in comparison to the left ventricle which
must push out blood into the rest of the body.
Structure

10. The Heart
• Size of a fist;
• Weighs less than a
pound
• In thorax; flanked
by lungs; rests on
diaphragm
• Top: base
• Bottom: apex

11. Types of Blood Vessels
•Arteries
•Structure
•Arteries are thick walled
and muscular vessels
•Function
•Arteries move oxygen
rich blood away from the
heart (with the exception
of the Pulmonary artery)
•How is the structure of an artery
related to its function?

12. Arteries
• Blood vessels that carry blood away
from the heart.
• They have thick, elastic walls made of
connective tissue and smooth
muscle that can expand in size
• Most carry oxygenated blood (red)
• Damaged arteries spurt in time to heart
beat

13. •Veins
•Structure
•Veins are thin walled
vessels and have flexible
walls. Veins also have one
way valves.
•Function
•Veins bring deoxygenated
blood back to the heart
•How does the structure of a veins
relate to its function?

14. Veins• Blood vessels that
carry blood back to the
heart.
• Carry blood at low
pressure
• Have valves to prevent
backflow of blood
against gravity
• Most carry de-
oxygenated blood
(purple)
• Damaged veins ooze
blood

15. Arterioles
◦Smaller blood vessels that extend from
arteries to capillaries.
Capillaries
◦The smallest vessels in the body. They
are only one cell thick and allow oxygen
and carbon dioxide to be exchanged
from blood to body tissues.
Venules
◦Smaller blood vessels that extend from
capillaries to veins.

16. • Capillaries
• Structure
• Capillaries are only one cell thick and have very
flexible walls.
• Function
• Capillaries connect arteries (arterioles) to veins
(venules) and allow for gas, nutrient and waste
exchange.

17. Capillaries
• Connect arteries and veins
• Walls are one cell thick
• Allow exchange of gases through thin walls
– Drop off oxygen delivered from heart by arteries
– Pick up CO2 and send it to the heart thru veins

18. How Blood Travels thru Vessels
heart artery arteriole capillary venule vein heart

19. Blood Vessels• Arteries: carry
blood AWAY
from the heart
• Veins: carry
blood IN to the
heart
• Capillaries:
connect
arteries to
veins &
exchange
gases with
tissues