The Circulatory System

Interesting Facts

• The heartbeat 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.

Interesting Facts

• The blue whale has the

largest heart –

it weighs ~ one ton

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• The hummingbird has a

heart that beats

1,000 times per minute

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Interesting Facts

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• Your entire volume of blood goes through your whole body once every minute

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• Humans have ~60,000 miles of blood vessels in their bodies (more than twice the circumference of the earth!)

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• Your heart beats 100,000 times and pumps ~2,000 gallons of blood every day

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• Pig and baboon hearts have been transplanted into humans

Exploration

This is a picture of the

bottom of the human tongue.

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Take a look at the bottom of your lab partner’s tongue (if they will let you) and see if you can find…

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◦The veins –thick blue lines

◦The arteries –thick pink lines

◦The capillaries –tiny thin lines

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Questions!

What provides the force to cause the blood to circulate through the body?

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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.

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A collection of vessels and the muscles that

control the flow of blood through the body.

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What is the Circulatory System?

Heart

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Function

◦The organ that pumps blood through the circulatory system.

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The Heart

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

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

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Larger than the atria as more muscle is needed to pump greater volumes of blood

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• 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.

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Structure

Types of Blood Vessels

Arteries

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• Structure
• Arteries are thick walled and muscular vessels

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• Function
• Arteries move oxygen rich blood away from the heart (with the exception of the Pulmonary artery)

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• How is the structure of an artery related to its function?

Arteries

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• 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 heartbeat

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• Veins

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• Structure
• Veins are thin walled vessels and have flexible walls. Veins also have one way valves.

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• Function
• Veins bring deoxygenated blood back to the heart

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• How does the structure of a veins relate to its function?

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

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.

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• Capillaries

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• Structure
• Capillaries are only one cell thick and have very flexible walls.

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• Function
• Capillaries connect arteries (arterioles) to veins (venules) and allow for gas, nutrients, and waste exchange.

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

How Blood Travels thru Vessels

heart artery arteriole capillary venule vein heart

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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