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17.5: Internal Structures of the Heart

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    53779
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    Internal Structures of the Heart

    The heart is divided into four chambers: right atrium, right ventricle, left atrium, and left ventricle. The atria are the two superior chambers of the heart and the ventricles are the two inferior chambers of the heart. The right side of the heart and the left side of the heart are isolated from each other (each belongs to a separate circuit - see the Circulation Through the Heart section below). The right and left sides are separated by septa. Between the right and left atria is tissue called the interatrial septum and between right and left ventricles is tissue called the interventricular septum.

    Diagram of the chambers and valves of the heart. Aorta, Pulmonary Artery, Pulmonary Valve, Right Atrium, Tricuspid Valve, Right Ventricle, Aortic Valve, Left Atrium, Mitral Valve, Left Ventricle

    Above: Chambers and valves of the heart.

    Heart Chamber

    Location

    Blood flowing into this chamber

    Blood flowing out of this chamber

    Associated valves

    left atrium

    superior left side of the heart

    from pulmonary veins; oxygen-rich blood

    to the left ventricle

    mitral valve (aka left atrioventricular valve; aka bicuspid valve) drains blood from the left atrium when it is open during ventricular diastole

    left ventricle

    inferior left side of the heart

    from left atrium; oxygen-rich blood

    to the aorta

    blood moves into this chamber through the mitral valve (aka left atrioventricular valve; aka bicuspid valve) during ventricular diastole; blood moves out of this chamber through the aortic valve during ventricular systole

    right atrium

    superior right side of the heart

    from superior vena cava and inferior vena cava; oxygen-poor blood

    to the right ventricle

    tricuspid valve (aka right atrioventricular valve) drains blood from the right atrium when it is open during ventricular diastole

    right ventricle

    inferior right side of the heart

    from right atrium; oxygen-poor blood

    to the pulmonary trunk

    blood moves into this chamber through the tricuspid valve (aka right atrioventricular valve) during ventricular diastole; blood moves out of this chamber through the pulmonary valve during ventricular systole

    There are four valves in the heart: two that separate the atria from the ventricles on both the right and left sides (atrioventricular [AV] valves), and two that separate the ventricles from their associated arteries (aortic valve and pulmonary valve). The aortic valve and pulmonary valve are sometimes called semilunar valves since they are composed of three crescent-shaped cusps. The AV valves are also called the tricuspid valve and the bicuspid valve (aka the mitral valve); these names describe the number of cusps that make them up (tri= 3 cusps; bi= 2 cusps). Heart valves are either open or they are closed based on whether the heart muscle of the ventricles is contracting, ventricular systole, or the heart muscle of the ventricles is not contracting, ventricular diastole. Both systole and diastole are equally important for moving blood effectively though the heart and through the blood circulation circuits.

    Beating heart with the ventricles shown open.

    Above: Animated heart pumping with the ventricles shown open.

    Heart Valve

    Location

    During ventricular systole

    During ventricular diastole

    How it Works

    aortic valve

    between the left ventricle and the aorta

    open

    closed

    valve is closed unless pressure inside the ventricle pushes it open

    mitral valve (left atrioventricular [AV] valve; bicuspid valve)

    between the left atrium and the left ventricle

    closed

    open

    valve is open unless pressure inside the ventricle pushes it closed; papillary muscles and chordae tendineae prevent the valves from flipping open during ventricular systole (prolapse)

    pulmonary valve

    between the right ventricle and the pulmonary trunk

    open

    closed

    valve is closed unless pressure inside the ventricle pushes it open

    tricuspid valve (right atrioventricular [AV] valve)

    between the right atrium and the left ventricle

    closed

    open

    valve is open unless pressure inside the ventricle pushes it closed; papillary muscles and chordae tendineae prevent the valves from flipping open during ventricular systole (prolapse)

    Diagram of internal structures of the heart

    Above: Internal structures of the heart. (Left) Anterior view of the internal heart and (right) superior view of the valves of the heart with the atria removed.

    Internal Heart Structure

    Location

    Function/Description

    chordae tendineae

    connecting the cusps of AV valves with the papillary muscles

    "heart strings" aid in holding AV valves closed to prevent valve from flipping open during ventricular systole

    fossa ovalis

    indentation in the right atrium along the interatrial septum

    location where a hole used to be during fetal development (foramen ovale); since fetal lungs are non-functional, the pulmonary circuit of circulation is extraneous and therefore blood is allowed to pass through foramen ovale from the right atrium to the left atrium; a flap closes over foramen ovale after birth and eventually seals up

    interatrial septum

    tissue between the right and left atria

    separate the right and left atria; keeps oxygen-poor blood on the right side of the heart from mixing with oxygen-rich blood on the left side of the heart

    interventricular septum

    tissue between the right and left ventricles

    separate the right and left ventricles; keeps oxygen-poor blood on the right side of the heart from mixing with oxygen-rich blood on the left side of the heart

    papillary muscles

    muscles on the internal heart wall connected to chordae tendineae

    aid in holding AV valves closed to prevent valve from flipping open during ventricular systole (prolapse)

    trabeculae carneae

    ridges along the inside wall of the ventricles

    aid in holding AV valves closed to prevent valve from flipping open during ventricular systole (prolapse)

    Cadaver images of the right atrium and left ventricle

    Above: (Right) Inside of the right atrium of the heart, superolateral view. (Left) Inside the left ventricle, anterior view.


    This page titled 17.5: Internal Structures of the Heart is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.

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