Transcript Heart and Circulatio..

THE HEART AND
CIRCULATION
This lesson meets the following DoE Specific Curriculum Outcomes for Biology 11: 116-7 and 317-1
CIRCULATION
• Single celled and simple multicellular
animals don’t possess a circulatory system –
their cells are in direct contact with their
external environments.
• More complex multicellular organisms
(including humans) contain millions of
cells, most of which are not in direct contact
with their external environment.
CIRCULATION
•
The function of a circulatory system is to
connect all cells with their external
environment, to transport nutrients to the
cells and wastes away from the cell.
Types of Circulation in Humans
• A. Pulmonary Circulation
• Carries de-oxygenated blood or blood low
in oxygen and high in carbon dioxide to the
lungs from the right side of the heart
• Involves the right side of the heart, the
pulmonary arteries, both the right and left
lungs and the pulmomary veins
• Carries oxygenated blood back to the left
side of the heart
B. Systemic Circulation
• Carries oxygen to the entire systems of the body
• Involves the left side of the heart, the aorta, all
major arteries, veins and capillaries and the
superior/inferior vena cava
• Carries deoxygenated blood back to the right side
of the heart through the vena cava. Blood pressure
is at its lowest at this point
C. Coronary Circulation
• The arteries and veins of the heart itself
• These blood vessels nourish the heart
providing it with its constant need for food
and oxygen
COMPONENTS OF A
CIRCULATORY SYSTM
1. A fluid in which transported materials are
carried (=BLOOD)
2. A network of tubes through whicn the
fluid flows (=BLOOD VESSELS)
3. A pump to drive the fluid through the
tubes (=HEART)
THE HEART
• The heart is a muscular organ whose
contractions force blood through the
blood vessels.
• Your heart is slightly larger than your
fist and located just to the left of the
middle of your chest cavity.
• The outside of the heart is surrounded
by a tough protective PERICARDIUM.
THE HEART
• Internally, the heart is divided into two
halves by the SEPTUM and is
comprised of four chambers; two
ATRIA (left and right) and two
VENTRICLES (left and right).
• This design allows the heart to act as a
double pump; the right side sends
oxygen-poor blood to the lungs and the
left side pumps oxygen rich blood to the
rest of the body.
THE HEART
• CO2 rich blood returning from the
body (systemic circulation) enters the
right atrium via the two vena cavas.
• This blood then moves into the right
ventricle where it will be pumped out
through the pulmonary arteries to the
lungs (pulmonary circulation).
THE HEART
• Upon its return from the lungs, the 02
rich blood enters the left atrium via
the pulmonary veins.
• The blood then moves into the left
ventricle where it is pumped out
through the aorta to the various
tissues and organs of the body
(systemic circulation).
THE HEART
• The flow of blood through the heart is
controlled by four valves.
• Two of these valves, the
ATRIOVENTRICULAR VALVES (A-V
valves) are located between the atria
and the ventricles (one on the left side
and one on the right).
THE HEART
• The other two valves, the
SEMILUNAR VALVES (S-V valves)
are located between the right
ventricle and the pulmonary artery
and the left ventricle and the aorta.
• The function of these valves is to
insure that blood flows only in one
direction.
THE HEARTBEAT CYCLE
• Since the heart is mostly muscle, its
pumping action results from the alternating
contraction and relaxation of the muscles.
• The periods when the heart muscles are
relaxed is called DIASTOLE.
• The alternate period of contraction is called
SYSTOLE.
THE HEARTBEAT CYCLE
• During diastole, the A-V valves are open
allowing blood to pass from the atria to the
ventricles.
• During systole, a muscle contraction in the
atria cause these chambers to contract
forcing the remaining blood down into the
ventricles.
THE HEARTBEAT CYCLE
• The systole muscle contraction moves in a
wave-like manner from the top of the heart
to the bottom. As it does, it forces shut the
A-V valves and opens the S-V valves of the
aorta and pulmonary artery.
• Finally, as the systole muscle contraction
reaches the ventricles; these chambers
contract forcing blood out through the aorta
and pulmonary artery.
THE HEARTBEAT CYCLE
• When the ventricles are contracting, the
atria are relaxed allowing blood to enter
from the veins and the A-V valves open.
This marks the beginning of a new diastole
period.
• As the heart valves open and close, they
make a “lub-dub” sound that can be heard
through a stethoscope. The “lub” sound is
made by the closing of the A-V valves. The
“dub” sound is made by the closing of the
S-V valves.
The Heart’s Electrical System
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THE HEARTBEAT CYCLE