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The Circulatory System
Section 33.1
Functions of the Circulatory
System
• Needed because the body has millions of cells.
• Transports nutrients, oxygen, wastes, other
substances.
The Heart: Structure
• The heart consists of
–
–
–
–
–
4 chambers
Numerous valves
A muscle (cardiac)
Hollow
Septum separates right
from left.
• In the walls of the
heart, 2 thin layers of
connective and
epithelial tissue
sandwich a muscle
called the myocardium.
• Myocardium contracts
and pumps blood
through circulatory
system.
The Heart: Structure
• Diagram
The Heart: Blood Flow
Right
Atrium
Superior/Inferior
Vena Cava
Pulmonary
Veins
Left Atrium
Lungs
Pulmonary
Artery
Mitral
Valve
Tricuspid
Valve
Right
Ventricle
Pulmonary
Valve
Left
Ventricle
Aorta
Aortic
Valve
The Heart: Blood Supply
• Coronary Arteries give blood to heart’s tissue.
– Branch from aorta
– Run through heart tissue
– Narrow
– If blocked, tissue may die=heart attack.
The Heart: Circulation
• Pulmonary
– Right side of heart
pumps to lungs.
– Gas exchange occurs
– Oxygen rich blood
returns to left side of
heart.
• Systemic
– Blood pumped from left
side of heart to body.
– Cells use oxygen
– Oxygen poor blood
comes back to right side
of heart.
The Heart: Heartbeat
• 1. Atria Contract
– Starts in right atrium
– In a small muscle group,
sinoatrial node (SA).
• AKA pacemaker.
– When SA node fires,
electrical impulse
spreads and muscle
contracts.
• 2. Ventricles Contract
– Impulse from SA picked
up by atrioventricular
(AV) node.
– Impulse delayed.
– AV node produces
impulses that spread
through ventricles.
– They contract.
The Heart: Heart Rate
• Varies depending on..
– Activity level
– Oxygen need
• Not directly controlled by nervous system.
– Is influenced though
Blood Vessels: Arteries
• Oxygen rich blood to the tissues of the body
and usually flow with gravity
• Large (superhighways)
• Thick walled…highly pressurized
• Consist of connective tissue, smooth muscle,
endothelium.
Blood Vessels: Capillaries
• Smallest vessels
• Narrow, blood cells move single file
• Thin walls
Blood Vessels: Veins
• Blood flows against gravity
• Large veins near skeletal muscles, push blood
towards heart.
• Veins contain valves
• Consist of connective tissue, smooth muscle,
endothelium.
Blood Pressure
• System always under pressure due to arterial
walls.
• Pressure needed to make blood flow.
• Blood pressure regulated by the nervous
system, also kidneys.