Chapter 22 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for...

Chapter 22

*Lecture Outline

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

*See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint

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Chapter 22 Outline• Overview of the Cardiovascular System• Anatomy of the Heart• Coronary Circulation• How the Heart Beats: Electrical Properties of

Cardiac Tissue• Innervation of the Heart• Tying It All Together: The Cardiac Cycle• Aging and the Heart• Development of the Heart

Overview of the Cardiovascular System

• The heart propels blood to and from most body tissues via two basic types of blood vessels called arteries and veins.

• Arteries are defined as blood vessels that carry blood away from the heart.

• Veins are defined as blood vessels that carry blood back to the heart.

• The arteries and veins entering and leaving the heart are called great vessels.

General Characteristics and Functions of the Heart

• Blood flow through the heart is unidirectional because of four valves within the heart.

• The heart is functionally two side-by-side pumps that work at the same rate and pump the same volume of blood.– One pump directs blood to the lungs.– One pump directs blood to most body tissues.

General Characteristics and Functions of the Heart

• The heart generates blood pressure through alternate cycles of the heart wall’s contraction and relaxation.

• Blood pressure is the force of the blood pushing against the inside walls of blood vessels.

• A minimum blood pressure is essential to circulate blood throughout the body.

Pulmonary and Systemic Circulations

The cardiovascular system consists of two circulations:1. Pulmonary—right side of the heart and the pulmonary arteries and veins; conveys blood to the lungs and back to the left side of the heart2. Systemic—left side of the heart and arteries and veins; conveys blood to most body tissues and back to the right side of the heart

Cardiovascular System

Figure 22.1

Position of the Heart

• Slightly left of midline deep to the sternum in a compartment of the thorax known as the mediastinum

Figure 22.2


• During development, the heart rotates such that the right side or right border (primarily formed by the right atrium and ventricle) is located more anteriorly.

• The left side or left border (primarily formed by the left atrium and ventricle) is located more posteriorly.


• The posterosuperior surface of the heart is mainly the left atrium and is called the base of the heart.

• The superior border is formed by the great arterial vessels and the superior vena cava.

• The inferior conical end is called the apex.• The inferior border is formed by the right

ventricle.


Figure 22.2

Pericardium• The heart is enclosed within a tough sac

called the pericardium• Restricts heart movements so that it moves only slightly within the thorax

Figure 22.2

Pericardium

Composed of two parts:1. Fibrous pericardium—outer covering of

tough, dense connective tissue2. Serous pericardium—composed of two

layers:• parietal layer—lines the inner surface of the

fibrous pericardium• visceral layer (epicardium)—covers the outer

surface of the heart– the small space between the parietal and visceral layers is

called the pericardial cavity

Pericardium

Figure 22.3

Anatomy of the Heart Wall

The heart wall consists of three distinctive layers (from superficial to deep):1. Epicardium—consists of the visceral layer of the serous pericardium and areolar connective tissue2. Myocardium—cardiac muscle; thickest of the three layers3. Endocardium—internal surface of the heart chambers and external surface of the heart valves

Anatomy of the Heart Wall

Figure 22.4

External Heart Anatomy

• Composed of four hollow chambers: two smaller and superior atria (sing., atrium) and two larger inferior ventricles

• The anteroinferior borders of the atria form a muscular extension called the auricle

• The atria and ventricles are separated from each other by a relatively deep groove called the coronary sulcus

• The anterior interventricular sulcus and posterior interventricular sulcus are located between the right and left ventricles and run from the coronary sulcus toward the apex of the heart

External Heart Anatomy

Figure 22.5

Internal Heart Anatomy:Chambers and Valves

The heart possesses four chambers:1. Right atrium2. Right ventricle3. Left atrium4. Left ventricle

The heart also possesses four valves:1. Right atrioventricular (tricuspid)2. Pulmonary semilunar3. Left atrioventricular (bicuspid or mitral)4. Aortic semilunar

Right Atrium

Receives venous blood from heart, the muscles, and systemic circulation; three veins drain into the right atrium:

1. Superior vena cava

2. Inferior vena cava

3. Coronary sinus

Separating the right atrium from the right ventricle is the right atrioventricular valve (tricuspid valve)

Right Atrium

Figure 22.6


Ascending aorta

Right pulmonary artery

Right pulmonary veins

Right atrium

Right auricle

Right atrioventricular valve


Chordae tendineae

Papillary muscle

Right ventricle

Ascending aorta

Right auricle

Right atrium

Fossa ovalis

Pectinate muscle

Papillary muscle

Trabeculae carneae

Interventricular septum

Pulmonary semilunar valve

Left ventricle

Pulmonary trunk

Ligamentum arteriosum

Aortic arch

Right coronary artery

Right ventricle

Chordae tendineae

Left pulmonary artery


Pulmonary trunk

Left pulmonary veins

Left atrium

Aortic semilunar valve

Left atrioventricular valve

Left ventricle

Septomarginal trabecula

Trabeculae carneae


Aortic arch

Descending aorta

Coronal section, anterior view

Interatrial septum

Superior vena cava

Fossa ovalis

Interatrial septumOpening for coronary sinus

Opening for inferiorvena cava

Inferior vena cava

Superior vena cava


Pulmonary semilunarvalve

© The McGraw- Hill Companies, Inc./Photo and Dissection by Christine Eckel

Right Atrium

• Deoxygenated venous blood flows from the right atrium to the right ventricle through the right atrioventricular valve.

• The right atrioventricular valve 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 atrium

• An interventricular septum forms a thick wall between the right and left ventricles

• The inner wall of each ventricle displays large, irregular muscular ridges called trabeculae carneae

Right Ventricle

Figure 22.6


Ascending aorta



Right atrium

Right auricle



Chordae tendineae

Papillary muscle

Right ventricle

Ascending aorta

Right auricle

Right atrium

Fossa ovalis

Pectinate muscle

Papillary muscle

Trabeculae carneae



Left ventricle

Pulmonary trunk


Aortic arch


Right ventricle

Chordae tendineae



Pulmonary trunk


Left atrium



Left ventricle


Trabeculae carneae


Aortic arch

Descending aorta


Interatrial septum

Superior vena cava

Fossa ovalis



Inferior vena cava

Superior vena cava




Right Ventricle

• There are typically three cone-shaped muscle projections inside the right ventricle called papillary muscles.

• The papillary muscles anchor thin strands of strong connective tissue made up of collagen fibers called chordae tendineae.

• The chordae tendineae attach to three cusps of the (tricuspid) right atrioventricular valve.

• Cusps are triangular flaps that hang down into the ventricle.

• The chordae tendineae prevent the cusps from prolapsing into the right atrium when the right ventricle contracts.

Right Ventricle

Figure 22.6


Ascending aorta



Right atrium

Right auricle



Chordae tendineae

Papillary muscle

Right ventricle

Ascending aorta

Right auricle

Right atrium

Fossa ovalis

Pectinate muscle

Papillary muscle

Trabeculae carneae



Left ventricle

Pulmonary trunk


Aortic arch


Right ventricle

Chordae tendineae



Pulmonary trunk


Left atrium



Left ventricle


Trabeculae carneae


Aortic arch

Descending aorta


Interatrial septum

Superior vena cava

Fossa ovalis



Inferior vena cava

Superior vena cava




Right Ventricle

• At the superior end or roof of the ventricle is a smooth area called the conus arteriosus.

• Beyond the conus arteriosus is the pulmonary semilunar valve, which marks the end of the ventricle and the beginning of the pulmonary trunk.

Semilunar Valves

• Two of them: pulmonary and aortic• Located in the roof of right and left ventricles,

respectively• Each valve is composed of three thin, half-

moon-shaped, pocketlike semilunar cusps• When ventricles contract, blood pushes cusps

against the arterial trunks• When ventricles relax, some blood flows back

toward the ventricles, enters the pockets of the cusps and forces them toward midline, thus closing the valve

Valves of the Heart

Figure 22.7

Left Atrium

• Oxygenated blood from the lungs travels through the pulmonary veins to the left atrium.

• The left atrium is separated from the left ventricle by the left atrioventricular valve, which is also referred to as the bicuspid or mitral valve.

• This valve only has two triangular cusps.• This valve is forced shut when the left ventricle

contracts in a similar fashion to the closing of the right atrioventricular valve.

Left Ventricle

• The wall is typically three times thicker than the right ventricular wall.

Figure 22.8

Left Ventricle

• The left ventricle has to pump blood to the entire body, except for the lungs, and therefore has to generate a greater blood pressure.

• At the superior end or roof of the left ventricle is the aortic semilunar valve, which marks the end of the left ventricle and the beginning of the aorta.

Valves of the Heart

Coronary Circulation

• The right and left coronary arteries travel within the coronary sulcus and supply the heart wall muscle with oxygen and nutrients.

• The coronary arteries are the only branches given off by the ascending aorta just superior to the aortic semilunar valve.

Coronary Arteries

Figure 22.9

Right Coronary Artery

Branches into two arteries:

1. Marginal artery—supplies the right border of the heart

2. Posterior interventricular artery—supplies the posterior surface of the left and right ventricles

Left Coronary Artery

Branches into two arteries:

1. Anterior interventricular artery—also called the left anterior descending artery, supplies the anterior surface of both ventricles and most of the interventricular septum

2. Circumflex artery—supplies the left atrium and ventricle

Coronary Veins

Venous return of blood from the heart wall muscle occurs through three major veins:1. Great cardiac vein—runs alongside the anterior interventricular artery2. Middle cardiac vein—runs alongside the posterior interventricular artery3. Small cardiac vein—travels close to the marginal artery

All three of the above veins drain into a large vein called the coronary sinus that drains into the right atrium.

Coronary Veins

Figure 22.9

Conducting System of the Heart

• The myocardium is composed of cardiac muscle fibers.

• Cardiac muscle fibers contract as a single unit because they are all connected with low resistance cell-to-cell junctions called gap junctions.

• Gap junctions comprise the intercalated discs shared by adjacent cardiac muscle fibers.

• Therefore, an electrical impulse is distributed immediately and spontaneously throughout the myocardium.

Comparison of Cardiacand Skeletal Muscle

Structure of Cardiac Muscle

Figure 22.10


Nucleus

Sarcolemma

Mitochondrion

Myofibrils

StriationsIntercalated discs

Intercalated disc Intercalated disc

Sarcolemma

Desmosome

Gap junction

Mitochondrion

Cardiac muscle cell

Nucleus

(c) Longitudinal section of cardiac muscle

(b) Cardiac muscle cell, longitudinal view

(a) Cross section of cardiac muscle cell

LM 1000x

Openings oftransverse tubules

Sarcoplasmicreticulum

Transversetubule

Sarcomere

Z disc Z discH zone

M lineI band I band

A band

c © Dennis Drenner/Visuals Unlimited


• The heart exhibits autorhythmicity, which means it is capable of initiating its own heartbeat independent of external nerves.

• The electrical impulse that initiates the heartbeat comes from specialized cardiac muscle cells called the sinoatrial (SA) node or the pacemaker.

• The SA node is located on the posterior wall of the right atrium adjacent to the opening of the superior vena cava.

• The SA node generates 70–80 impulses per minute under parasympathetic control.


• Impulses from the SA node travel to the left atrium and the atrioventricular (AV) node located in the floor of the right atrium.

• Electrical activity then leaves the AV node into the atrioventricular (AV) bundle (bundle of His), which extends into the interventricular septum.

• Once within the septum, the AV bundle divides into left and right bundles.


• These bundles pass the impulse to conduction cells called Purkinje fibers that begin at the apex of the heart.

• The Purkinje fibers spread the impulse superiorly from the apex to all of the ventricular myocardium.


Figure 22.11


1 2

3 4 5

Superior vena cava

Sinoatrial node (pacemaker)Internodal pathway

Atrioventricular node

Right bundle

Left bundlesPurkinje fibers

Purkinje fibers

Left atriumRight atrium

Purkinje fibers

Atrioventricular bundle(bundle of His)

Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria andto the atrioventricular node by the internodal pathway.

Atrioventricular node cells delay themuscle impulse as it passes to theatrioventricular bundle.

Atrioventricularbundle

InternodalpathwayAtrioventricularnodeInterventricular

septum

Atrioventricularbundle

Left and rightbundle branches

Interventricularseptum

The atrioventricular bundle (bundle of His) conducts the muscle impulseinto the interventricular septum.

Within the interventricular septum, theright and left bundles split from theatrioventricular bundle.

The muscle impulse is delivered to Purkinjefibers in each ventricle and distributedthroughout the ventricular myocardium.

Innervation of the Heart

• The heart, like most other organs, is innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system.

• The anatomical components of both divisions make up the coronary plexus.

• Autonomic innervation does not initiate a heartbeat, but it can increase or decrease the rate of the heartbeat.

Innervation of the Heart

Figure 22.12

Sympathetic Innervation

• Starts with neurons located in T1–T5 segments of the spinal cord

• Preganglionic axons enter the sympathetic trunk and synapse on ganglionic neurons.

• Postganglionic axons project from all three cervical ganglia and travel to the heart via cardiac nerves.

• Sympathetic input to the heart increases the rate and force of heart contractions.

Parasympathetic Innervation

• Starts with neurons in the medulla oblongata via the left and right vagus nerves (CN X)

• Decreases heart rate but generally has no effect on force of contraction

Coordinated Sequence of Heart Chamber Contractions

1. SA node generates an impulse.

2. Both atria contract almost simultaneously (systole) while ventricles are relaxing (diastole).

3. Impulse goes to AV node and then to the ventricles.

4. Ventricles contract (systole) while atria relax (diastole).

Ventricular Systole and Diastole

Figure 22.13


Right ventricle Left ventricleSemilunar valves open

Transverse section

Left ventricle

(a) Ventricular Systole (Contraction)

Atrioventricular valves closed

Aortic arch

Anterior

Posterior

Pulmonarytrunk

Blood flow intopulmonary trunk

Leftatrium

Ventricles contract, forcingsemilunar valves to open andblood to enter the pulmonarytrunk and the ascending aorta.

Ventricular contraction pushesblood against the open AVvalves, causing them to close.Contracting papillary musclesand the chordae tendineaeprevent valve flaps fromeverting into atria.

Blood flow intoascending aorta

Ascendingaorta

Blood flow intoright atrium

Rightatrium

Cusp ofsemilunarvalve

Cusp ofatrioventricularvalve

Blood inventricle

Left AVvalve (closed)

Right AVvalve (closed)

Rightventricle

Pulmonarysemilunarvalve (open)

Aortic semilunarvalve (open)

Ventricular Systole and Diastole

Figure 22.13


Right ventricle Left ventricleSemilunar valves closed

Right ventricle

Transverse section

Left ventricle

Blood

(b) Ventricular Diastole (Relaxation)

Atrioventricular valves open

Aortic arch

Atrium

Anterior

Posterior

Ventricles relax and fill withblood both passively andthen by atrial contraction asAV valves remain open.

During ventricular relaxation,some blood in the ascendingaorta and pulmonary trunkflows back toward theventricles, filling the semilunarvalve cusps and forcing themto close.

Blood flow intoleft ventricle

Leftatrium

Blood flow intoright atrium

Rightatrium

Blood flow intoright ventricle

Cusps ofsemilunarvalve

Cusp ofatrioventricularvalve

Chordaetendineae

Papillarymuscle

Left AVvalve (open)

Right AVvalve (open)

Aortic semilunarvalve (closed)

Pulmonarysemilunarvalve (closed)

Cardiac Cycle

Figure 22.14


Atria relax

Atria contract

1

Atria relax

2

Atria relax

3

Atria relax

5 4

Phase

Structure

Contract

ContractRelax

Relax

Relax

Relax

Open

Closed

Open

Closed

Closed

Open

Atria

V entricles

A V valves

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Semilunarvalvesopen

AVvalvesclosed

Allvalvesclosed

AVvalvesopen

Ventricles contractVentricles contractVentricles relax

Atrial systoleAtria contract; AV valves are open,semilunar valves are closed

Late ventricular systoleAtria continue to relax; ventricles contract;AV valves remain closed; semilunarvalves are forced open

Early ventricular systoleAtria relax; ventricles begin to contract;AV valves are forced closed (lubbsound); semilunar valves still closed

Lateventricular

diastole

Earlyventricular

diastole

Lateventricular

systole

Earlyventricular

systole

Atrialsystole

Semilunarvalves

Time(seconds)

Semilunarvalves closed

Allvalvesclosed

AVvalvesopen

Early ventricular diastoleAtria and ventricles relax; AV valvesremain closed and semilunar valves close(dupp sound); atria continue passivelyfilling with blood

Late ventricular diastoleAtria and ventricles relax; atria continuepassively filling with blood; AV valvesopen and ventricles begin to passively fill;semilunar valves remain closed

Ventricles relaxVentricles relax

0.0

Blood Flow Through the HeartCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Right atrium

Right atrium

Left atrium

Left atrium

Systemic veins

Blood Flow Through the Heart

Superiorand inferior

venae cavaeRightatrium

Rightatrioventricular

valveRight

ventricle

Pulmonarysemilunar

valve

Pulmonarytrunk andarteries

Gas exchangein the lungs

Gas and nutrientexchange

in peripheraltissues

Systemicarteries

AortaAortic

semilunarvalve

Leftventricle

Leftatrioventricular

valve

PulmonaryveinsLeft

atrium

Right ventricle

Left ventricle

Pulmonary veins

Superior vena cava, inferior venacava, coronary sinus

Ascending aorta (blood entersvessels of systemic circulation)

Left ventricle

Pulmonary trunk (blood entersvessels of pulmonary circulation)

Right ventricle


Left AV valve


Right AV valve

Chamber of the Heart Receives Blood From Sends Blood To Valves Through Which BloodFlows

Table 22.3

Development of the Heart

Figure 22.15


Figure 22.16

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