The Circulatory
System – The
Heart
Section 12.1
The Heart
 Contracts
and relaxes rhythmically and
involuntarily without becoming tired.
 Made
 Keeps
up of cardiac muscle.
blood flowing (by pumping) In one
direction only which keeps the oxygen-rich blood
separate from the oxygen-poor blood.
Heart Structure
 Four
chambers – a top and bottom each on the left
and right sides.
 Atria
– the top chambers will with blood returning
from the body or the lungs.
 Ventricles
– bottom chambers receive blood from
the atria and pump it out to the body or lungs.
 Septum
– muscular wall that separates the atria
and ventricles.
The right Side of the heart
 Receives
blood coming back from the body and
pumps it out to the lungs.
 Vena
cava (2 large blood vessels) open into the
right atrium.
 Superior Vena
Cava collects oxygen-poor blood
coming from tissues in the head, chest, and arms.
 Inferior Vena
Cava collects oxygen-poor blood
from the tissues elsewhere in the body.
The right Side of the heart
 The
oxygen-poor blood flows from the right
atrium into the right ventricle and then out into the
pulmonary trunk.
 It
then travels to the pulmonary arteries and then to
the lungs for gas exchange.
 The
pulmonary arteries carry blood from the heart
to the lungs and are the only arteries to carry
oxygen-poor blood.
The left side of the heart

Receives oxygen-rich blood from the left and right
lungs and pumps it out to the body.

Pulmonary veins carry oxygen-rich blood from lungs to
the left atrium. They are the only veins that carry
oxygen-rich blood.

The left atrium pumps blood into the left ventricle
where the blood going to the body leaves through the
aorta.

The aorta is the largest vessel in the body.
Heart valves

The heart has four valves inside of it to ensure the
blood flows the correct direction.

Atria and ventricles are separated by atrioventricular
valves.



Right side is called the tricuspid valve because it has 3
flaps.
Left side is called bicuspid valve because it has 2 flaps.
Other valves are called semi-lunar valves because of
their half-moon shape. They carry blood away from the
heart. (pulmonary arteries and aorta)
Blood vessels
 Arteries


Carry blood away from the heart.
Smaller-diameter arteries are called arterioles.
 Veins


Carry blood toward the heart.
Smaller-diameter veins are called venules.
 Capillaries


Joins the arteries and the arterioles with venules and
veins.
One cell thick and facilitate gas exchange.
Arteries
 Elastic
walls allow arteries to expand as a wave of
blood flows through it during the contraction of
the ventricles and then snap back when the
ventricle relaxes.
 When
you measure your pulse, you’re feeling the
rhythmic expansion and contraction of an artery as
blood passes through it.
Veins

Have thinner walls than arteries and lager inner
circumference.

Veins are less elastic than arteries.

Muscle contractions keep blood flowing through veins.
(not contractions of the veins)

Have one-way valves to keep blood flowing in one
direction. (very important in legs because they ensure
blood moves up your leg against gravity.)
The Mammalian Circulatory
System
 Called
a double-circulatory system.
 Blood
is pumped through one circuit between the
heart and the lungs and it’s pumped through a
second circuit between the heart and the rest of the
body.
 https://www.youtube.com/watch?v=HZ9E
t5TyJXM
Pulmonary Circulation
 The
movement of blood from the heart to the lungs
and then from the lungs back to the heart.
 Lungs
to heart carries waste carbon dioxide (blue)
 As
it passes through lungs, gas exchange occurs
and carbon dioxide is replaced with oxygen.
 Oxygen
rich blood returns to the heart. (red)
Systemic Circulation

The movement of oxygenated blood from the
heart to the tissues and organs throughout the
body.
 After
circulating throughout the body, the blood
returns to the heart carrying waste carbon dioxide
from the body tissues.
 The
blood then re-enters pulmonary circulation.
 80-90%
of your blood is in systemic circulation.
Cardiac circulation
 The
movement of blood through the heart.
Homework
 #2,
7 and 10 P488
 Heart diagram worksheet