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The ___ circuit sends deoxygenated blood to the lungs to pick up oxygen and unload carbon dioxide.


The ____ circuit sends oxygenated blood and nutrients to all body cells and removes wastes.

thoracic, diaphragm

The heart is a hollow, cone-shaped muscular pump that lies within the __ cavity and rests on the ___.

mediastinum, lungs, sternum

The heart is within the ___, bordered laterally by the ___, posteriorly by the vertebral column, and anteriorly by the ___.


The __ of the heart, which attaches to several large blood vessels, lies beneath the second rib.


Protective sac enclosing the heart composed of two layers with fluid between

fibrous pericardium

Membrane of dense connective tissue that is lined by the parietal pericardium

visceral pericardium

The innermost of the two layers of the pericardium


The visceral pericardium doubles back on itself to become the ___ pericardium.

parietal pericardium

The tough outermost layer of the pericardium that is attached to the diaphragm and the sternum.


The ___ protects the heart by reducing friction.


Outer wall of the heart.


Wall of the heart that pumps blood out of the heart chambers.


The inner wall of the heart.


The Purkinje fibers are located in the ___.


Chambers that receive blood returning to the heart.


Chambers that receive blood from the atria and contract to force blood out of the heart into arteries.

right atrium

The ___ ___ receives blood from the superior vena cava and the inferior vena cava.

coronary sinus

Drains blood into the right atrium from the myocardium of the heart itself.


Valve that lies between the right atrium and right ventricle.


Valve that permits blood to move from the right atrium into the right ventricle and prevents backflow.

chordae tendineae

"heart strings" are tiny white collagenic cords that anchor the cusps to the ventricular walls.

papillary muscles

Chordae tendineae originate from small mounds of cardiac muscle tissue called ___ ___.


The papillary muscles contract when the ___ contracts.


The right ventricle has a ___ muscular wall than the left ventricle.

left ventricle

The ___ ___ has to force blood out to greater areas than the right chamber.

increasing, tricuspid

When the muscular wall of the right ventricle contracts, the blood inside its chamber is put under __ pressure, and the ___ valve closes.


Arteries that lead to the lungs.


Valve that allows blood to leave the right ventricle and prevents backflow into the ventricular chamber.

left atrium

The ___ ___ receives blood from the lungs through 4 pulmonary veins.


Blood passes from the left atrium into the left ventricle through the ___ valve.


When the left ventricle contracts, the bicuspid valve closes passively, and the only exit is through the ___.


The mitral and tricuspid valves are called ____ valves because they are between the atria and ventricles.


The pulmonary and aortic valves are called ____.

low, high, right, venae cavae

Blood that is __ in oxygen and __ in carbon dioxide enters the __ atrium through the __ __ and coronary sinus.,


As the right atrial wall contracts, the blood passes through the __ valve and enters the right ventricle.

closes, pulmonary, pulmonary, arteries.

When the right ventricular wall contracts, the tricuspid valve __, and blood moves through the __ valve to the __ trunk and its ___.

capillaries, alveoli

From the pulmonary arteries, blood enters the ___ associated with the __ of the lungs.


Freshly oxygenated blood returns to the heart through the __ veins that lead to the left atrium.


The left atrial wall contracts, and blood moves through the __ valve and into the chamber of the left ventricle.

aortic, aorta

When the left ventricular wall contracts, the mitral valve closes and blood moves through the __ valve and into the ___.

coronary arteries

First two branches of the aorta that supply blood to the tissues of the heart.


The heart must beat continually to supply blood to the body tissues. To do this, __ cells require a constant supply of freshly oxygenated blood.


Branches of the coronary arteries feed the many capillaries of the ___.


Detours in circulation that may supply oxygen and nutrients to the myocardium when a coronary artery is blocked.


Veins that drain the myocardium.

coronary sinus

Cardiac veins join an enlarged vein on the heart's posterior surface called the __ ___ which empties into the right atrium.

a-v, ventricles

When pressure in the ventricles is low, the pressure difference between the atria and ventricles causes the ___ valves to open and the __ to fill.


About 70% of the returning blood enters the ventricles prior to contraction.

atria, ventricles

When the ___ contract, the remaining 30% of returning blood is pushed into the ___.

increases, close

As the ventricles contract, ventricular pressure __ sharply, and as soon as the ventricular pressure exceeds the atrial pressure, the A-V valves ___.


During ventricular contraction, the __ valves remain closed.


When ventricular pressure exceeds the pressure in the pulmonary trunk and aorta, the __ and ___ valves open.


The lubb sound occurs during ventricular contraction when the A-V valves are ____.

S-A node

A small, elongated mass of specialized cardiac muscle tissue just beneath the epicardium. It's located in the right atrium near the opening of the superior vena cava.


Node that can reach threshold on their own.


Without stimulation from nerve fibers or any other outside agents, the S-A node cells initiate impulses that spread into the surrounding ___.

S-A node

The cardiac conduction system starts with the _ __.

Atrial syncytium

CCS: S-A node ---> ___ ___.

Junctional fibers

CCS: Atrial syncytium ---> ___ ___.

A-V node

CCS: Junctional fibers ---> __ __.

A-V bundle

CCS: A-V node ---> ___ ___

Bundle branches

CCS: A-V bundle ---> ___ ___.

Purkinje fibers

CCS: Bundle branches ---> __ ___.

Ventricular syncytium

CCS: Purkinje fibers ---> ___ ___.

myocardium, cardiac cycle

An ECG is a recording of the electrical charges that occur in the ___ during a __ ___.


Between cardiac cycles, the muscle fibers remain ___ with no detectable electrical changes.

S-A node, atrial

When the __ ___ triggers a cardiac impulse, ___ fibers depolarize, producing an electrical change.

P wave

ECG: Depolarization of the atrial fibers that leads to contraction of the atria.

QRS Complex

ECG: Depolarization of ventricular fibers prior to the contraction of ventricular walls.


When cardiac impulse reaches ventricular fibers, they rapidly depolarize.

T wave

ECG: The electrical changes occurring as the ventricular muscle fibers repolarize slowly.

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