Download Power Point Presentation

CRITICAL CARE CLASS
The Heart
The Heart
• Weighs about 300 – 400 grams
• Function is to pump
• Has both right and left pumps that
work as one
• 4 chambers : 2 atria and 2 ventricles
Basic Structure
•
•
•
•
•
Located in the middle, slightly to the left mediastinum
Wider at the base smaller at the apex
Anteriorly it is protected by the sternum and ribs
Rests on the diaphragm
Three layers surrounded by the Pericardial Sac
Epicardium : outermost layer contains
coronary arteries
Myocardium : muscle
Endocardium : smooth inner layer, smoothness
prevents clot formation
The Atria
The chambers of
the heart
atria are the top
The Ventricles
• The ventricles pump
the blood from the
heart
• Right ventricle pumps
to the lungs to be
oxygenated
• Left ventricle pumps
into the aorta to
deliver blood to the
body
Coronary vessels
• Consists of arteries
• Blood is supplied
to the tissues of
the heart by the
first two branches
of the aorta--right
and left coronary
arteries.
• Left coronary artery has
2 branches :
circumflex and left
anterior descending
• left anterior
descending artery
travels to the anterior
interventricular sulcus
and its branches
supply the walls of
both ventricles.
circumflex artery
follows the coronary
sulcus between the
right and left
ventricle.
Coronary Sinus
• Most of the cardiac veins drain into
coronary sinus, which lies in the
atrioventricular groove.
• It is 2-3 cm long and end in the right atrium
Coronary Sinus
Chordae Tendineae
Blood Flow Through the Heart
• The heart has four chambers. The right and
left sides of the heart are separated by a
muscular wall (septum). This prevents
blood without oxygen from mixing with
blood that contains oxygen. The heart also
contains valves that separate the chambers
and connect to major blood vessels.
• Normally blood flows from the body into the
right upper heart chamber. The blood on the right
side of the heart has been used by the body and
contains little oxygen (oxygen-poor).
• The oxygen-poor blood flows from the right
upper heart chamber through the valve to the
right lower chamber.
• From the right lower heart chamber, blood is
pumped through the valve into the blood vessel
that goes to the lungs (pulmonary artery). This
blood then picks up oxygen (oxygenated).
Oxygen-rich blood flows from the lungs through blood vessels
(pulmonary veins) back to the heart's upper left chamber.
From the upper left heart chamber, blood goes through the valve
and into the lower left chamber.
The lower left heart chamber pumps blood through the valve to a
major blood vessel (aorta) and to the body.
The blood delivers oxygen to the body. Blood is then returned to
the upper right heart chamber through veins and repeats the
cycle.
Blood Flow through the Heart
• Inferior/ Superior Vena cava → Right
Atrium→ Tricuspid Valve → Right
Ventricle → Pulmonary Valve→ Pulmonary
Artery →Lungs→ Pulmonary Vein→ Left
Atrium →Mitral Valve → Left Ventricle
→Aorta
What makes the Blood Flow
• Blood doesn't flow by itself — your heart's
chambers work hard to keep blood moving.
The chambers relax and expand to let blood
flow into them. Then they tighten and pull
inward (contract) to help push blood out.
• When a chamber is relaxed, or expanded, it
is in diastole. When a chamber is
contracted, or small, it is in systole
• Right heart: right atrium and right ventricle
• Left heart : left atrium and left ventricle
• Systole : contraction/squeezing/emptying/ work phase
• Diastole: relaxation/stretching/filling/resting phase
These terms apply to all four chambers
Valves : Act to retain blood in one chamber until the next chamber or
vessel is ready to receive it. Valve function is in response to pressure
changes in the chambers
Atrial-Ventricular Valves and the Semi-Lunar Valves
Heart Sounds are made by vibration.
First heart sound: when AV valves close and ventricles are in systole
Second heart sound: when semilunar valves close and ventricles are in
diastole
Your Heart in Action
See Your Heart in Action.url
Your Heart in Action
Blood supply to the Heart
• Vessels supply blood to heart muscle under
pressure. Vessels encircle the heart, most flow
occurring during diastole when ventricular
muscles release and relieve pressure on the
artery walls, allowing them to fill with blood.
The faster the heart rate, the less time there is
available for coronary artery filling, since
diastolic time is shortened.
Cardiac Output
• The amount of blood moved out by
ventricular contraction per minute
• It is the product of heart rate X stroke
volume
• Normal CO : approximately 4-8 liters per
minute
Regulation of Heart Rate
• Under influence of autonomic nervous system
• Both sympathetic and parasympathetic fibers
innervate the SA and AV nodes
• Sympathetic fibers act on myocardial tissue
• Parasympathetics : affect atrium -> SA node
stimulate = decreased HR, conduction, irritability
• Sympathetics: atrium, ventricle will increase HR<
increase conduction, and irritability
• Reflexes: Aortic and Bainbridge
• SYMPATHETIC
• Affects the atria and the ventricles
• Increases : heart rate, conduction and
irritability
• PARASYMPATHETIC
• Affects only the atria
• Decreases : heart rate, conduction, and
irritability
How Cardiac Output is Determined
• Stroke volume : amount of blood ejected with
ventricular systole
• Preload : How much blood returns to the heart
• Afterload : The pressure the heart pumps against
• Contractility : How effectively the heart pumps
• Frank Starling Mechanism : Affects preload, the
more you stretch the harder the contraction
• Cardiac Output = Stroke Volume X Heart Rate
• The amount of blood the heart pumps out /min is =
to the amount of blood it pumps out per
contraction times the number of contractions /min.
In order to meet tissue demands, the heart must be
able to increase its output several times over.
Peripheral Circulation
• Significance of the cardiovascular system is tissue
perfusion, which supplies cells with oxygen and
nutrients and carries away carbon dioxide.
• Blood flow dependant on MAP, vessel resistance,
vessel length, and blood viscosity
• Blood Pressure = Cardiac Output X peripheral
resistance
• The electrical system in your heart controls the
speed of your heartbeat. The system includes a
network of electrical pathways, similar to the
electrical wiring in your home. The pathways carry
electrical signals through your heart. The movement
of the signals is what makes your heart beat.
• When working properly, your heart's electrical
system automatically responds to your body's
changing need for oxygen. It speeds up your heart
rate as you climb stairs, for example, and slows it
down when you sleep. When your heart rate speeds
up, it means your heart pumps faster and your body
gets more oxygen-rich blood.
• Your heart's electrical system is also called the
cardiac conduction system.
Electrical conduction
• Sa node → AV Node → Bundle of His →
Purkinje Fibers
• Depolarization initiated by impulse from SA
node (atria kick)
• Impulse spreads through both atria
• Impulse reaches AV node
• Impulse transmitted along bundle of His to
Purkinje fibers, activating ventricles almost
simultaneously