Transcript Cardio Presentation

The Heart
Unfortunately, “heart” in this case is meant in the
anatomical sense, not the metaphysical one –
which is much more interesting.
Outline of the Heart
Pulmonary Veins
•These terms will
be explained in
depth later
•If the terms are
not circled in
BLUE, you do not
need to know
them for IB
Categorizations of Heart Parts
(aka, “Stereotypes Aren’t Always Bad: Sometimes They Help You Pass Biology”)
• There are five types of parts in the heart: Atria, Ventricles ,
Valves, Arteries , and Veins
• The Atria (singular Atrium) are the small upper chambers
which receive blood from either the vena cavae or the
pulmonary veins and pump it to the ventricles
• The Ventricles are the larger lower chambers which receive
blood from the atria and pump blood out of the heart
Categorization (cont.)
• The valves are flaps of connective tissue which keep the blood
moving in one direction (and prevent backflow)
– Atrioventricular (AV) valves are located between the atria and ventricles
– Semilunar valves are located at the two exits of the heart (the aorta and the
pulmonary artery)
– A heart murmur is a condition in which the valves are damaged and allow
blood to squirt backwards. Despite the name, this actually sounds like a hiss.
• Arteries carry blood away from the heart
– The largest arteries associated with the heart are the aorta, which carries
oxygenated blood to the body and the pulmonary artery, which carries
deoxygenated blood to the lungs
• Veins return blood to the heart
– The largest veins associated with the heart are the pulmonary veins, which
bring oxygenated blood from the lungs, and the vena cavae (singular vena
cava), which bring deoxygenated blood from the body
What the darn thing actually looks like
(in a 64-year-old man)
Not so pretty, is it?
Composition of the Heart
• Some of you may have noticed that the last picture looks
like an uncooked piece of meat…that’s because it is
• It is hollow, but the heart’s walls are composed entirely of
cardiac muscle
– This is involuntary striated muscle, and is found only in the heart
• This muscle tissue moves independently of conscious thought, meaning
the heart beats without you actively thinking about it
– That is why the heart was still beating when the Aztecs cut it out of sacrifice victims
• The muscle is noticeably darker at the bottom half of the
heart
– This is because the muscle comprising the ventricular walls is
thicker than that which makes up the atrial walls…we will
explain this later
What does this thing actually do?
• Put simply, the heart is a dual-action pump that
gets blood to everywhere else in your body
• First, the heart pumps deoxygenated blood to the
lungs so the red blood cells can pick up oxygen.
The blood then returns to the heart
• The blood then passes through the chambers and
is pumped out of the heart to the rest of the body
• The full circulatory process will be explained later.
This presentation only covers the role of the heart
When Blood Shows Up…
• Blood enters the heart (without
oxygen) through the vena cavae
– Blood from the head, neck, and arms enter
through superior vena cava
– Blood from the trunk and legs enter through
the inferior vena cava
• This blood passes through the vena
cavae to the right atrium
• The blood flows down from the right
atrium through the tricuspid valve (an
AV valve) to the right ventricle
• The R. ventricle then pumps the blood
through the pulmonary valve and into
the pulmonary arteries to the lungs,
where it picks up oxygen (more on the
lungs in the next presentation)
When It Comes Back…
• The newly-oxygenated blood returns
to the heart through the pulmonary
veins and into the left atrium
• The blood flows through the mitral
valve into the left ventricle
• The L. ventricle then pumps the
blood though the aortic valve into
the aorta (the big artery)
• The blood exits the heart through
the aorta and goes off into the new
exciting world known as the
circulatory system (tune in
tomorrow for the exiting conclusion)
IN CONCLUSSION…sorta…
The Top Student Will Recognize That…
(Info about this process which better explains what we just said)
• The atria pass incoming blood to the ventricles as their walls contract and
push the blood through the AV valves
• The ventricles do the real “pumping”
– Remember we said there is more muscle around the ventricles?
– This is because the ventricle walls must contract much more powerfully than the atria.
Remember that while the atria only have to push blood to an adjacent chamber, the
ventricles must force blood out of the heart and around the body
• The ventricles pump blood in a multi-step process
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The blood flows in from the atrium and the AV valve remains open
The ventricle walls violently contract, causing a temporary rise in ventricular pressure
This pressure causes the AV valve to close, so the blood cannot flow back into the atria
The semilunar valve opens, and the pressure forces the blood out through the artery
As this happens, the atria begins to once again fill with blood
When the ventricle pressure becomes lower than that in the atrium, the semilunar
valve closes, the AV valve opens, and the process begins again
• Both ventricles contract and relax simultaneously
The Heart’s Cyclical Structure…er, Operation
• As anyone who has felt their heartbeat knows, the heart pumps blood in a
rhythmic cycle of contractions and relaxations. This is the cardiac cycle.
– When the heart (meaning ventricles) contracts and expels blood, this is known as
systole
– When it relaxes and fills with blood, this is known as diastole
•Cardiac output is the volume of blood per minute pumped by the L. ventricle
– This depends on two things: the number of beats per minute (heart rate) & the amount
of blood pumped by the L. ventricle per contraction (stroke volume)
– The average stroke value is 75 mL and the avg. heart rate is 70 bpm. Thus, the average
cardiac output is 5.25 L/min (this is roughly the total volume of blood in the body)
And because we Bio kids don’t like math:
Cardiac Output = Stroke Volume × Heart Rate
“Without a pulse, you’re dead.
And that’s why were the most important section in this band.”
• As we mentioned earlier, the heart beats in regular, rhythmic intervals
– The sound (which is often written as “lub-dub”) you hear when you listen to someone’s
heartbeat has two parts. The first (“lub”) is the result of the blood hitting closed AV
valves. The second (“dub”) is the blood recoiling against closed semilunar valves.
• The pulse is the rhythmic stretching of arteries as the ventricles force blood
through them
– Pulse is always roughly in sync with heartbeat (give or take a fraction of a second’s delay)
• Heartbeat is controlled by the sinoatrial (SA) node (for IB, pacemaker)
– The SA node is made of specialized muscle tissue
– It is located in the right atrial wall, near the vena cava superior
– It sends electrical impulses like nerve cells, but operates independently of the N. system
• Remember, the heart does not need nerve endings to pump (¡Recuerda Las Aztecas!)
– Because it is located inside the heart in mammals (whereas arthropod heartbeats are
controlled from outside the heart and rely on the nervous system), mammalian hearts
are sometimes called myogenic hearts
But What About the Heart?
We often get so caught up in remembering how much good the heart does for the rest
of the body that we almost forget that it also needs to care for itself. No, this is not
Stephen’s way of lashing at out the overabundance of governmental social programs
Basically, how does the heart get blood? Or does it even matter? The heart is full of
blood, so does it really need to receive it’s own dose of blood?
As clearly indicated by the fact that we have this slide up, yes it is necessary. While
the chambers are indeed hollow, the muscles that cause them to contract still require
oxygen, and thus blood. Coronary arteries and veins (and the resulting capillaries) are
found along the outside of the heart along the muscle. Like all other parts of the
circulatory system, this is fed with blood from the aorta.
And for those of you who realize we’re
just not destined to be teachers…
We (or at least Stephen) are very sorry
if you were expecting a completely
serious presentation. We (meaning
Stephen) assumed that it would be
very difficult for anyone to take us
seriously if we actually tried to be
serious.
So we (read “Stephen”)
designed this PowerPoint to be
ridiculous so that you could laugh at
us (or if no one else, Stephen), and
thus learn about the heart.