© 2014 pearson education, inc. the human heart. © 2014 pearson education, inc. the heart the heart...

© 2014 Pearson Education, Inc.

The Human Heart


The Heart

• The heart is a muscular double pump

• Two functions

1. Pulmonary circuit: Right side receives oxygen-poor blood from the body and

pumps it to the lungs

2. Systemic circuit: Left side receives oxygenated blood from lungs and pumps throughout

the body


The Heart

• Atria

• Receive blood from the pulmonary and systemic circuits

• Ventricles

• The pumping chambers of the heart


Figure 19.1 The heart as a double pump.

Capillary bedsof lungs wheregas exchangeoccurs

Aorta andbranches

Pulmonaryarteries

Left atrium Pulmonary

veins

Right atrium

Right ventricle

Left ventricle

Venaecavae

Capillarybeds of allbody tissueswhere gasexchangeoccurs

Heart

Pulmonary Circuit

Systemic Circuit

Oxygen-rich,CO2-poor blood

Oxygen-poor,CO2-rich blood


Figure 19.2 Location of the heart in the thorax.

Midsternal line

Rib 2

Diaphragm

Mediastinum

Heart

Right lung

T8

Posterior

Diaphragm

Apex ofheart

Pericardium(cut)

Left lung

Pulmonarytrunk

Parietalpleura (cut)

Aorta

Superiorvena cava

Mediastinum

Aorta

Left lung

Fat inepicardium

Rib 5

Pericardium(cut)

Apex of heart

Rightventricle

Right auricleof right atrium

Superiorvena cava


Structure of the Heart—Coverings

• Pericardium—two primary layers

• Fibrous pericardium

• Strong layer of dense connective tissue

• Serous pericardium

• Formed from two layers

• Parietal layer of the serous pericardium

• Visceral layer of the serous pericardium


Figure 19.3 The layers of the pericardium and of the heart wall.

Pericardium

Myocardium

Pulmonarytrunk

Heart chamber

Endocardium

Myocardium

Heartwall

Epicardium (viscerallayer of serouspericardium)

Pericardial cavity

Parietal layer of serouspericardium

Fibrous pericardium


Layers of the Heart Wall

• Epicardium

• Visceral layer of the serous pericardium

• Myocardium

• Consists of cardiac muscle

• Muscle arranged in circular and spiral patterns

• Endocardium

• Endothelium resting on a layer of connective tissue

• Lines the internal walls of the heart


Heart Chambers

• Right and left atria

• Superior chambers

• Right and left ventricles

• Inferior chambers

• Internal divisions

• Interventricular septa

• Interatrial septa


Figure 19.5b Gross anatomy of the heart.

Anterior view

Right atrium

Right ventricle

Left ventricle

Auricle ofleft atrium

Brachiocephalic trunk

Superior vena cava

Right pulmonary artery

Ascending aorta

Pulmonary trunk

Right pulmonary veins

Right coronary artery(in coronary sulcus)

Anterior cardiac vein

Right marginal artery

Small cardiac vein

Inferior vena cava

Apex

Anterior interventricularartery (in anteriorinterventricular sulcus)

Great cardiac vein

Left coronary artery(in coronary sulcus)

Circumflex artery

Left pulmonary veins

Left pulmonary artery

Ligamentum arteriosum

Aortic arch

Left subclavian artery

Left common carotid artery


Path of Blood Flow Through Heart


Right Atrium

• Forms right border of heart

• Receives oxygen-poor blood from systemic circuit through these vessels:

• Superior vena cava

• Inferior vena cava


Right Ventricle

• Receives blood from right atrium through the right atrioventricular valve (tricuspid valve)

• Pumps blood into pulmonary circuit the pulmonary trunk


Right Ventricle

• Internal walls of right ventricle

• Trabeculae carneae

• Papillary muscles

• Chordae tendineae

• Pulmonary semilunar valve (pulmonary valve)

• Located at opening of right ventricle and pulmonary trunk

Papillary muscle


Left Atrium

• Makes up heart’s posterior surface

• Receives oxygen-rich blood from lungs through pulmonary veins

• Opens into the left ventricle through

• Left atrioventricular valve (bicuspid valve)

• Mitral valve is another name for the left AV valve

• Bicuspid valve is another name for this.


Left Ventricle

• Forms apex (lower tip) of the heart

• Internal walls of left ventricle

• Trabeculae carneae

• Papillary muscles

• Chordae tendineae

• Pumps blood through systemic circuit via

• Aortic semilunar valve (aortic valve)


Figure 19.5e Gross anatomy of the heart.

Superior vena cava


Pulmonary trunk


Fossa ovalis

Pectinate muscles

Tricuspid valve

Chordae tendineae

Trabeculae carneae

Inferior vena cava

Right atrium

Right ventricle

Frontal section

Left ventricle

Left atrium

Endocardium

Myocardium

Epicardium

Interventricular septum

Papillary muscle

Pulmonary valve

Aortic valve

Mitral (bicuspid) valve



Aorta


Left atrium

Right atrium

Aorta



Auricle of left atrium

Great cardiac vein

Posterior vein ofleft ventricle

Superior vena cava



Inferior vena cava

Coronary sinus

Right coronary artery(in coronary sulcus)

Posterior interventricularartery (in posteriorinterventricular sulcus)

Middle cardiac vein

Apex

Left ventricle

Right ventricle

Inferior view; surface shown rests on the diaphragm.

Posterior View


Heart Valves—Valve Structure

• Each valve composed of

• Endocardium with connective tissue core

• Atrioventricular (AV) valves

• Between atria and ventricles

• Right AV valve tricuspid valve

• Left AV valve bicuspid (mitral) valve

• Aortic and pulmonary valves

• At junction of ventricles and great arteries


Figure 19.7a Function of the atrioventricular valves. (1 of 2)

Ventricle

Direction ofblood flow

Atrium

Cusp ofatrioventricularvalve (open)

Chordaetendineae

Papillarymuscle

AV valves open; atrial pressure greater than ventricular pressure

Blood returning to theheart fills atria, pressingagainst the AV valves. Theincreased pressure forcesAV valves open.

As ventricles fill, AV valveflaps hang limply into ventricles.

Atria contract, forcingadditional blood into ventricles.

1

2

3


Figure 19.7b Function of the atrioventricular valves. (1 of 2)

Atrium

Cusps ofatrioventricularvalve (closed)

Blood inventricle

AV valves closed; atrial pressure less than ventricular pressure

Ventricles contract, forcingblood against AV valve cusps.

Papillary musclescontract and chordaetendineae tighten,preventing valve flaps fromeverting into atria.

AV valves close.

1

2

3


Figure 19.8 Function of the semilunar valves.

Aorta

Pulmonary trunk

Semilunar valves open

Semilunar valves closed

As ventriclescontract andintraventricularpressure rises,blood is pushedup againstsemilunar valves,forcing them open.

As ventricles relaxand intraventricularpressure falls,blood flows backfrom arteries,filling the cuspsof semilunarvalves and forcingthem to close.


Heart Sounds

• “Lub-dup”—sound of valves closing

• First sound: “lub”

• The AV valves closing

• Second sound: “dup”

• The semilunar valves closing


Figure 19.10 The heart is a double pump, each side supplying its own circuit.


Heartbeat

• 70–80 beats per minute at rest

• Systole—contraction of a heart chamber

• Diastole—expansion of a heart chamber

• Systole and diastole also refer to

• Stage of heartbeat when ventricles contract and expand


Structure of Heart Wall

• Walls differ in thickness

• Atria—thin walls

• Ventricles—thick walls

• Systemic circuit

• Longer than pulmonary circuit

• Offers greater resistance to blood flow


Structure of Heart Wall• Left ventricle

• Three times thicker than right ventricle

• Exerts more pumping force

Rightventricle

Leftventricle

Interventricularseptum


Cardiac Muscle Tissue

• Not all cardiac cells are innervated

• Will contract in rhythmic manner without innervation

• Inherent rhythmicity- autorhythmic


Conducting System- The heart is AUTORHYTHMIC!! • Cardiac muscle tissue has intrinsic ability to

• Generate and conduct impulses

• Conducting system

• A series of specialized cardiac muscle cells

1. Sinoatrial (SA) node sets the inherent rate of contraction INTERNODAL PATHWAY

2. Atrioventricular (AV) node

AV bundle bundle branches Purkinje Fibers


Figure 19.14 The intrinsic conducting system of the heart. (1 of 2)Superior vena cava Right atrium

Left atrium

Subendocardialconductingnetwork (Purkinje fibers)

Inter-ventricularseptum

Internodal pathway

1

2

3

4

5

The sinoatrial (SA)node (pacemaker)generates impulses.

The impulsespause (0.1 sec) at theatrioventricular(AV) node.

The atrioventricular(AV) bundle connects the atriato the ventricles.

The bundle branches conduct the impulsesthrough theinterventricular septum.

The subendocardialconducting network stimulates the contractilecells of both ventricles.


Innervation

• Heart rate is set by SA node but altered by 2 extrinsic mechanisms….


Innervation

• Parasympathetic fibers (Cardioinhibitory center in medulla of brain)

• Branches of vagus nerve

• Decrease heart rate

• Restricted to

• SA node, AV node, coronary arteries


Innervation

• Sympathetic nerves (Cardioacceleratory center in medulla of brain)

• Travel to heart from cervical and upper thoracic chain ganglia

• Innervate SA node, AV node, coronary arteries—as parasympathetic

• Also innervate cardiac musculature throughout the heart

• Increase heart rate and strength of contraction


Figure 19.15 Autonomic innervation of the heart.Dorsal motor nucleusof vagus

Cardioinhibitorycenter

Medulla oblongataCardioacceleratorycenter

Sympathetictrunkganglion

Thoracic spinal cord

Sympathetic trunk

The vagus nerve(parasympathetic)decreases heart rate.

Sympathetic cardiacnerves increase heart rateand force of contraction.

SAnode

AVnode

Parasympathetic fibers

Sympathetic fibers

Interneurons


Circulation to the heart…not by the heart. How does the heart itself get

nutrients and oxygen?


Blood Supply to the Heart

• Coronary arteries

• Blood supply to the muscular walls and tissues of the heart

• Right coronary artery

• Left coronary artery

• Arise from base of the aorta and run in the coronary sulcus


Blood Supply to the Heart

• Left coronary artery (LCA)

• Branches into anterior interventricular artery and circumflex artery

• Left anterior descending artery (LAD) is the clinical name for anterior interventricular artery


Blood Supply to the Heart • Right coronary artery (RCA) descends in

coronary sulcus

• Branches to form the marginal artery

• Later braches into the posterior interventricular artery. Clinically called posterior descending artery (PDA)


Cardiac Veins

• Carry deoxygenated blood from the heart wall to the right atrium

• Coronary sinus—runs in the posterior part of the coronary sulcus

• Returns majority of venous blood from the heart to the right atrium

• Three tributaries of coronary sinus

• Great cardiac vein, middle cardiac vein, small cardiac vein


Figure 19.16 Coronary circulation.

Superiorvena cava

The major cardiac veins

The major coronary arteries

Small cardiac vein Middle cardiac vein

Great cardiac vein

Coronary sinus

Anteriorcardiacveins

Right ventricle

Right atrium

Anastomosis(junction ofvessels)

Superiorvena cava

Aorta

Pulmonary trunk

Left atrium

Left ventricle

Rightmarginalartery

Rightcoronaryartery

Posterior interventricular artery

Anterior interventricular artery

Left coronaryartery

Circumflex artery


Disorders of the Heart

• Coronary artery disease

• Atherosclerosis—fatty deposits

• Angina pectoris—chest pain

• Myocardial infarction—blocked coronary artery

• Heart attack

• Silent ischemia—no pain or warning


Disorders of the Heart

• Heart failure

• Progressive weakening of the heart

• Cannot meet the body’s demands for oxygenated blood

• Congestive heart failure (CHF)

• Heart enlarges

• Pumping efficiency declines

• Pulmonary arterial hypertension

• Enlargement and potential failure of right ventricle


Disorders of the Conduction System

• Arrythmias—variation from normal heart rhythm

• Ventricular fibrillation

• Rapid, random firing of electrical impulses in the ventricles

• Results from crippled conducting system

• Common cause of cardiac arrest


Disorders of the Conductory System

• Arrythmias (continued)

• Atrial fibrillation

• Impulses circle within atrial myocardium, stimulating AV node

• Promotes formation of clots

• Leads to strokes

• Occurs in episodes characterized by

• Anxiety, fatigue, shortness of breath, palpitations

© 2014 pearson education, inc. the human heart. © 2014 pearson education, inc. the heart the heart...

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