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Human Anatomy, First Edition McKinley & O'Loughlin


Human Anatomy, First Edition McKinley & O'Loughlin Chapter 22 Lecture Outline: Heart * True or False: Both Skeletal and Cardiac muscle are composed of Intercalated ... – PowerPoint PPT presentation

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Title: Human Anatomy, First Edition McKinley & O'Loughlin

Human Anatomy, First EditionMcKinley
  • Chapter 22 Lecture Outline
  • Heart

Functions of the Heart
  • Center of the cardiovascular system, the heart.
  • Connects to blood vessels that transport blood
    between the heart and other body tissues.
  • arteries carry blood away from the heart
  • veins carry blood back(toward) to the heart
  • Arteries carry blood high in oxygen.
  • (except for the pulmonary arteries)
  • Veins carry blood low in oxygen.
  • (except for the pulmonary veins)
  • Which are the GREAT VESSELS?
  • Those vessels that enter and exit the heart

Characteristics and Functions of the Heart
  • Ensures the unidirectional flow of blood through
    both the heart and the blood vessels.
  • Backflow of blood is prevented by valves within
    the heart.
  • Acts like two independent, side-by-side pumps
    that work independently but at the same rate.
  • one directs blood to the lungs for gas exchange
  • the other directs blood to body tissues for
    nutrient delivery
  • Develops blood pressure through alternate cycles
    of heart wall contraction and relaxation.
  • Minimum blood pressure is essential to push blood
    through blood vessels to the body tissues for
    nutrient and waste exchange.

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Pulmonary and Systemic Circuits
  • The pulmonary circuit consists of the chambers on
    the right side of the heart (right atrium and
    ventricle) as well as the pulmonary arteries and
  • conveys blood to the lungs via pulmonary arteries
    to reduce carbon dioxide and replenish oxygen
    levels in the blood before returning to the heart
    in pulmonary veins
  • The Systemic circuit
  • Returns blood to the left side of the heart
  • consists of the chambers on the left side of the
    heart (left atrium and ventricle), along with all
    the other named blood vessels.
  • carries blood to all the peripheral organs and
    tissues of the body

Pulmonary and Systemic Circuits
  • Oxygenated blood from the left side of the heart
    is pumped into the aorta, the largest systemic
    artery in the body, and then into smaller
    systemic arteries.
  • Gas exchange in tissues occurs from capillaries.
  • Systemic veins then carry deoxygenated blood
    (high in carbon dioxide) and waste products.
  • Most veins
  • merge and drain into the
  • superior and inferior venae cavae, which drain
    blood into the right atrium.
  • There, the blood enters the pulmonary circuit,
    and the cycle repeats .

Anatomy of the Heart
  • Size of Heart clenched fist.
  • it weighs about 250 to 350 grams
  • Located left of the body midline posterior to the
    sternum in the middle mediastinum.
  • Rotated such that its right side or border (right
    atrium and ventricle) is located more anteriorly,
    while its left side or border (left atrium and
    ventricle) is located more posteriorly.

Anatomy of the Heart
  • The posterosuperior surface of the heart, formed
    primarily by the left atrium, is called the base.
  • The pulmonary veins that enter the left atrium
    border this base.
  • The inferior, conical end is called the apex.
  • It projects slightly anteroinferiorly toward the
    left side of the body.

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  • Heart is contained in a fibrous, serous sac held
    in place within the mediastinum by connective
    tissue that supports the great vessels external
    walls superior to the heart and the diaphragm
    inferior to it.
  • Function of
  • Restricts heart movements so that it doesnt
    bounce and move about in the thoracic cavity, and
    prevents the heart from overfilling with blood.
  • Outer portion is a tough, dense connective tissue
    layer called the fibrous pericardium.
  • attached to both the sternum and the diaphragm
  • Inner portion is a thin, double-layered serous
    membrane called the serous pericardium.
  • parietal layer
  • visceral layer

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Heart Wall Structure
  • Heart wall consists of three distinctive layers
  • external epicardium
  • middle myocardium, and
  • internal endocardium
  • Epicardium is the outermost heart layer and is
    also known as the visceral layer of serous
  • As we Get older
  • more fat is deposited in the epicardium, and so
    this layer becomes thicker and more fatty.

Heart Wall Structure
  • Myocardium is the middle layer of the heart wall
    and is composed chiefly of cardiac muscle tissue.
  • Myocardium is the thickest of the three heart
    wall layers.
  • it lies deep to the epicardium and superficial to
    the endocardium
  • Internal surface of the heart and the external
    surfaces of the heart valves are covered by a
    thin endothelium called the endocardium.

Cardiac Muscle Tissue
  • Fibers are relatively short, branched fibers that
    usually house one or two central nuclei and
    numerous mitochondria for ATP supply.
  • Fibers are arranged in spiral bundles and wrapped
    around and between the heart chambers.
  • Resembles skeletal muscle in that fibers in both
    muscles are striated, with extensive capillary
    networks that supply needed nutrients and oxygen.
  • Fibers contract as a single unit because muscle
    impulses are distributed immediately and
    simultaneously throughout all fibers either of
    the atria or of the ventricles.
  • Specialized cellcell contacts called
    intercalated discs electrically and mechanically
    link the fibers together and permit the immediate
    passage of nerve impulses.

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External Anatomy of the Heart
  • Composed of four hollow chambers two smaller
    atria and two larger ventricles.
  • Atria are thin-walled chambers that are located
  • anterior part of each atrium is a wrinkled,
    flaplike extension called an auricle
  • Atria receive blood returning to the heart
    through both circulatory circuits. UPPER
    CHAMBERS are
  • right atrium receives blood from the systemic
  • left atrium receives blood from the pulmonary

External Anatomy of the Heart
  • Ventricles are the inferior chambers.
  • Blood that enters an atrium is passed to the
    ventricle on the same side of the heart.
  • Two large arteries, the pulmonary trunk and the
    aorta exit the heart at the basal surface.
  • The pulmonary trunk carries blood from the right
    ventricle into the pulmonary circuit.
  • The aorta conducts blood from the left ventricle
    into the systemic circuit.

External Anatomy of the Heart
  • Atria are separated from the ventricles
    externally by a relatively deep coronary sulcus
    (or atrioventricular sulcus) that extends around
    the circumference of the heart.
  • On both the anterior and posterior surfaces of
    the heart, the anterior interventricular sulcus
    and the posterior interventricular sulcus are
    located between the left and right ventricles.
  • These sulci extend inferiorly from the coronary
    sulcus toward the heart apex.

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Functions of the Fibrous Skeleton of the Heart
  • The fibrous heart skeleton is located between the
    atria and the ventricles, and is formed from
    dense irregular connective tissue.
  • separates the atria and ventricles
  • anchors heart valves by forming supportive rings
    at their attachment points
  • provides electrical insulation between atria and
  • insulation ensures that muscle impulses are not
    spread randomly throughout the heart, and thus
    prevents all of the heart chambers from beating
    at the same time
  • Provides a rigid framework for the attachment of
    cardiac muscle tissue.

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Internal Anatomy of the Heart
  • There are four heart chambers
  • right atrium
  • right ventricle
  • left atrium
  • left ventricle
  • Each plays a role in the continuous process of
    blood circulation.
  • Valves permit the passage of blood in one
    direction and prevent its backflow.

Right Atrium
  • Receives venous blood from the systemic circuit
    and the heart muscle itself.
  • Three major vessels empty into the right atrium.
  • superior vena cava drains blood from the head,
    upper limbs, and superior regions of the trunk
  • inferior vena cava drains blood from the lower
    limbs and trunk
  • coronary sinus drains blood from the heart wall
  • The interatrial septum forms a wall between the
    right and left atria.

Right Atrioventricular (AV) Valve
  • Separates the right atrium from the right
  • Also called the tricuspid valve.
  • has three triangular flaps
  • Venous blood flows from the right atrium, through
    the valve into the right ventricle.
  • Is forced closed when the right ventricle begins
    to contract, preventing blood backflow into the
    right atrium.

Right Ventricle
  • Receives deoxygenated venous blood from the right
  • An interventricular septum forms a wall between
    the right and left ventricles.
  • The internal wall surface of each ventricle has
    three cone-shaped, muscular projections called
    papillary muscles, which
  • anchor chordae tendineae
  • attach to the cusp of the right AV valve and
    prevent everting and flipping into the atrium
    when contracting

Pulmonary Trunk
  • At its superior end it narrows into a
    smooth-walled, conical region called the conus
  • The pulmonary semilunar valve marks the end of
    the right ventricle and the entrance into the
    pulmonary trunk.
  • Pulmonary trunk divides shortly into right and
    left pulmonary arteries.
  • carry deoxygenated blood to the lungs
  • Note this is a blue vessel on the heart

Semilunar Valves
  • Location
  • within the walls of both ventricles immediately
    before the connection of the ventricle to the
    pulmonary trunk and aorta.
  • Function
  • Allow blood to exit the ventricles
  • Each is composed of three thin, pocketlike
    semilunar cusps.
  • As blood is pumped into the arterial trunks, it
    pushes against the cusps, forcing the valves
  • When ventricular contraction ceases, blood is
    prevented from flowing back into the ventricles
    from the arterial trunk by first entering the
    pockets of the semilunar valves between the cusp
    and the chamber wall.
  • causes the cusps to inflate and meet at the
    artery center, effectively blocking blood

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Left Atrium
  • Once gas exchange occurs in the lungs, the
    oxygenated blood travels through the pulmonary
    veins to the left atrium.
  • Smooth posterior wall of the left atrium contains
    openings for approximately four pulmonary veins.
  • Has pectinate muscles along its anterior wall as
    well as an auricle.

Left Atrioventricular (AV) Valve
  • Separates the left atrium from the left
  • Also called the bicuspid valve or the mitral
  • Left AV valve has chordae tendineae similar to
    those of the right AV valve.
  • Oxygenated blood flows from the left atrium into
    the left ventricle.
  • Is forced closed when the left ventricle begins
    to contract
  • prevents blood backflow into the left atrium

Left Ventricle
  • Largest of the four heart chambers.
  • Wall is typically three times thicker than the
    right ventricular wall.
  • Why is this?
  • Requires thick walls in order to generate enough
    pressure to force the oxygenated blood from the
    lungs into the aorta and then through the entire
    systemic circuit.
  • right ventricle only has to pump blood to the
    nearby lungs

Left Ventricle
  • Trabeculae carneae in the left ventricle are more
  • Two large papillary muscles attach to the chordae
    tendineae that help support the left AV valve.
  • At the superior end of the ventricular cavity,
    the aortic semilunar valve marks the end of the
    left ventricle and the entrance into the aorta.

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Cardiac Cycle
  • The inclusive period of time from the start of
    one heartbeat to the initiation of the next.
  • All chambers within the heart experience
    alternate periods of contraction and relaxation.
  • Contraction of a heart chamber is called systole.
  • forces blood either into another chamber (from
    atrium to ventricle) or into a blood vessel (from
    a ventricle into the attached large artery)
  • Relaxation phase of a heart chamber is termed
  • myocardium of each chamber relaxes between
    contraction phases, and the chamber fills with

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Conduction System of the Heart
  • Exhibits autorhythmicity what is that?
  • meaning that the heart itself (not external
    nerves) is responsible for initiating the
  • Certain cardiac muscle fibers are specialized to
    conduct muscle impulses to the contractile muscle
    cells of the myocardium.
  • Specialized cells are part of the hearts
    conduction system.
  • SA Node
  • AV Node

Conduction System of the Heart Sinoatrial (SA)
  • Heartbeat is initiated by the cardiac muscle
    cells of the sinoatrial (SA) node.
  • located in the posterior wall of the right
    atrium, adjacent to the entrance of the superior
    vena cava
  • Act as the pacemaker.
  • rhythmic center that establishes the pace for
    cardiac activity
  • Initiates impulses 70 - 80 times per minute.
  • Like the first engine on the train

Conduction System of the Heart Atrioventricular
(AV) Node
  • Muscle Impulse travels to both atria, stimulating
    atrial systole.
  • And via an internodal conduction pathway through
    an opening in the fibrous skeleton to the
    atrioventricular (AV) node.
  • located in the floor of the right atrium between
    the right AV valve and the coronary sinus
  • Like the second engine on the train

Conduction System of the Heart Atrioventricular
(AV) Bundle
  • Cardiac impulse then travels from the AV node to
    the atrioventricular (AV) bundle(bundle of His).
  • extends into the interventricular septum and then
    divides into one right and two left bundle
  • Conduct the impulse to conduction fibers called
    Purkinje fibers in the heart apex.
  • Purkinje fibers are larger than other cardiac
    muscle fibers.
  • Muscle impulse conduction along the Purkinje
    fibers is extremely rapid, consistent with the
    large size of the cells.
  • The impulse spreads immediately throughout the
    ventricular myocardium.

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Innervation of the Heart
  • Innervated by the autonomic nervous system.
  • Consists of both sympathetic and parasympathetic
  • referred to as the coronary plexus
  • Autonomic innervation by autonomic centers in the
    hindbrain doesnt initiate heartbeat, but it can
    increase or decrease the heartbeat.
  • Sympathetic innervation increases the rate and
    the force of heart contractions.
  • Parasympathetic innervation decreases heart rate,
    but tends to have no effect on the force of
    contractions, except in special circumstances.

Coronary Circulation
  • Left and right coronary arteries travel in the
    coronary sulcus (atrioventricular groove) of the
    heart to supply the heart wall.
  • the only branches of the ascending aorta
  • Openings for these arteries are located
    immediately superior to the aortic semilunar
  • The right coronary artery typically branches into
  • marginal artery
  • supplies the right border of the heart
  • posterior interventricular artery
  • supplies both the left and right ventricles

Coronary Circulation
  • Left coronary artery typically branches into the
    anterior interventricular artery.
  • also called the left anterior descending artery
  • supplies the anterior surface of both ventricles
    and most of the interventricular septum
  • Circumflex artery.
  • supplies the left atrium and ventricle
  • Arterial pattern can vary greatly among

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