ch 19 lecture presentation - Mission...

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PowerPoint® Lecture Slides prepared by Leslie Hendon University of Alabama, Birmingham

C H A P T E R

Copyright © 2011 Pearson Education, Inc.

Part 1

19 The Heart


The Heart •  A muscular double pump •  Pulmonary circuit—vessels transport blood

to and from the lungs •  Systemic circuit—vessels transport blood to

and from body tissues •  (Coronary circuit– supplies blood to the heart

muscle itself) •  Atria—receive blood from the pulmonary and

systemic circuits •  Ventricles—the pumping chambers of the heart that

eject blood from the heart


The Pulmonary and Systemic Circuits

Figure 19.1

Oxygen-rich, CO2-poor blood

Oxygen-poor, CO2-rich blood

Capillary beds of lungs where gas exchange occurs

Capillary beds of all body tissues where gas exchange occurs

Pulmonary veins Pulmonary arteries

Pulmonary Circuit

Systemic Circuit

Aorta and branches Left atrium

Heart Left ventricle

Right atrium

Right ventricle

Venae cavae


Location and Orientation within the Thorax

•  Heart—typically weighs 250–350 grams (healthy heart)

•  Largest organ of the mediastinum •  Located between the lungs •  Apex lies to the left of the midline •  Base is the broad posterior surface


(c)

Superior vena cava

Left lung

Aorta Parietal pleura (cut)

Pericardium (cut)

Pulmonary trunk

Diaphragm

Apex of heart

Location of the Heart in the Thorax

Figure 19.2

Heart

Posterior

Right lung

(b)

Mediastinum

Pericardium (cut)

Fat in epicardium Rib 5

Left lung

Aorta

Mediastinum

Apex of heart (d)

Right auricle of right atrium

Superior vena cava

Right ventricle

Diaphragm

(a)

Rib 2

Midsternal line


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

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Layers of the Pericardium and of the Heart Wall

Figure 19.3

Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Epicardium (visceral layer of serous pericardium) Myocardium Endocardium

Pulmonary trunk

Heart chamber

Heart wall

Pericardium Myocardium


Structure of the Heart—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


Circular and Spiral Arrangements of Cardiac Muscle Bundles

Figure 19.4

Cardiac muscle bundles


Rotating Heart

Heart Chambers

•  Right and left atria •  Superior chambers

•  Right and left ventricles •  Inferior chambers

•  Internal divisions •  Interventricular septa •  Interatrial septa

•  External markings •  Coronary sulcus •  Anterior interventricular sulcus •  Posterior interventricular sulcus

PLAY


Gross Anatomy of the Heart

Figure 19.5b

Left common carotid artery Left subclavian artery Aortic arch Ligamentum arteriosum Left pulmonary artery

Left pulmonary veins

Auricle of left atrium

Circumflex artery

Left coronary artery (in coronary sulcus)

Left ventricle

Great cardiac vein Anterior interventricular artery (in anterior interventricular sulcus)

Apex (b) Anterior view

Brachiocephalic trunk

Superior vena cava

Right pulmonary artery

Ascending aorta Pulmonary trunk

Right pulmonary veins

Right atrium

Right coronary artery (in coronary sulcus) Anterior cardiac vein Right ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava


Right Atrium

•  Forms right border of heart •  Receives blood from systemic circuit •  Pectinate muscles

•  Ridges inside anterior of right atrium

•  Crista terminalis •  Landmark used to locate veins entering right

atrium

•  Fossa ovalis •  Depression in interatrial septum

•  Remnant of foramen ovale

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Right Ventricle

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

•  Pumps blood into pulmonary circuit via pulmonary trunk

•  Internal walls of right ventricle •  Trabeculae carneae : irregular ridges of muscle •  Papillary muscles: connect to ... •  Chordae tendineae: “heart strings”– attach to valve

cusps •  Pulmonary semilunar valve

•  Located at opening of right ventricle and pulmonary trunk


Left Atrium

•  Makes up heart’s posterior surface •  Receives oxygen-rich blood from lungs

through pulmonary veins •  Opens into the left ventricle through •  Mitral valve (left atrioventricular valve or Left

AV valve or Bicuspid valve)


Left Ventricle

•  Forms apex 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)

Rotating Heart Section PLAY


Heart Chambers

Figure 19.5e

Aorta Left pulmonary artery Left atrium


Mitral (bicuspid) valve

Aortic valve Pulmonary valve

Left ventricle Papillary muscle Interventricular septum Epicardium Myocardium Endocardium

(e) Frontal section

Superior vena cava Right pulmonary artery

Pulmonary trunk Right atrium

Right pulmonary veins Fossa ovalis Pectinate muscles Tricuspid valve Right ventricle Chordae tendineae Trabeculae carneae Inferior vena cava


Inferior View of the Heart

Figure 19.5d (d) Inferior view; surface shown rests on the diaphragm.

Aorta

Left pulmonary artery


Auricle of left atrium Left atrium

Great cardiac vein

Posterior vein of left ventricle Left ventricle

Apex

Superior vena cava Right pulmonary artery Right pulmonary veins

Right atrium

Inferior vena cava

Right coronary artery (in coronary sulcus)

Coronary sinus

Posterior interventricular artery (in posterior interventricular sulcus) Middle cardiac vein Right ventricle


Heart Valves— Valve Structure

•  Each valve composed of •  Endocardium with connective tissue core

•  Atrioventricular (AV) valves •  Between atria and ventricles

•  Aortic and pulmonary (semilunar) valves •  At junction of ventricles and great arteries

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Fibrous Skeleton

•  Surrounds all four valves •  Composed of dense connective tissue

•  Functions: •  Anchors valve cusps •  Prevents overdilation of valve openings •  Main point of insertion for cardiac muscle •  Blocks direct spread of electrical impulses

from atria into ventricles


Heart Valves—Valve Structure

Figure 19.6a

Pulmonary valve Aortic valve Area of cutaway Mitral valve Tricuspid valve Myocardium

Tricuspid (right atrioventricular) valve

(a)

Mitral (left atrioventricular) valve Aortic valve

Pulmonary valve

Fibrous skeleton

Anterior


Function of the Atrioventricular Valves

Figure 19.7a

Blood returning to the heart fills atria, putting pressure against atrioventricular valves; atrioventricular valves are forced open. As ventricles fill, atrioventricular valve flaps hang limply into ventricles. Atria contract, forcing additional blood into ventricles. (a) AV valves open; atrial pressure greater than ventricular pressure

Direction of blood flow Atrium

Ventricle

Cusp of atrioventricular valve (open) Chordae tendineae Papillary muscle

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2

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Function of the Atrioventricular Valves

Figure 19.7b

Ventrles cicontract, forcing blood against atrioventricular valve cusps. Atrioventricular valves close. Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria. (b) AV valves closed; atrial pressure less than ventricular pressure

Atrium

Blood in ventricle

Cusps of atrioventricular valve (closed)

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2

3


Function of the Semilunar Valves

Figure 19.8

As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open.

As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close.

(a) Semilunar valves open

(b) Semilunar valves closed

Aorta Pulmonary trunk


Heart Sounds

•  “Lub-dup”—sound of valves closing •  First sound “lub” • The AV valves closing

•  Second sound “dup” • The semilunar valves closing

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Heart Sounds

Figure 19.6a

Pulmonary valve Aortic valve Area of cutaway Mitral valve Tricuspid valve Myocardium

Tricuspid (right atrioventricular) valve

(a)

Mitral (left atrioventricular) valve Aortic valve

Pulmonary valve

Fibrous skeleton

Anterior Copyright © 2011 Pearson Education, Inc.

Heart Sounds

•  Each valve sound is best heard near a different heart corner •  Pulmonary valve—superior left corner •  Aortic valve—superior right corner •  Mitral (bicuspid) valve—at the apex •  Tricuspid valve—inferior right corner


Heart Sounds

Figure 19.9

Tricuspid valve sounds typically heard in right sternal margin of 5th intercostal space

Aortic valve sounds heard in 2nd intercostal space at right sternal margin

Pulmonary valve sounds heard in 2nd intercostal space at left sternal margin

Mitral valve sounds heard over heart apex (in 5th intercostal space) in line with middle of clavicle


Pathway of Blood Through the Heart

•  Beginning with oxygen-poor blood in the superior and inferior venae cavae... •  Go through pulmonary and systemic circuits •  A blood drop passes through all structures

sequentially • Atria contract together • Ventricles contract together


Blood Flow Through the Heart

Figure 19.10

Right atrium

Aorta

To body

To heart

To heart

To lungs

Mitral valve Left ventricle

Left atrium

Left atrium Aorta Left

ventricle Four

pulmonary veins

Right ventricle

Superior vena cava (SVC) Inferior vena cava (IVC)

Coronary sinus Right

atrium Pulmonary trunk

Pulmonary veins

Pulmonary arteries

Aortic semilunar valve

Tricuspid valve

Tricuspid valve

Pulmonary trunk

Right ventricle

Pulmonary semilunar valve

Pulmonary semilunar valve

IVC

SVC

Two pulmonary arteries carry the blood to the lungs (pulmonary circuit) to be oxygenated.

Oxygen-rich blood returns to the heart via the four pulmonary veins.

Oxygen-poor blood returns from the body tissues back to the heart.

Oxygen-rich blood is delivered to the body tissues (systemic circuit).

Oxygen-rich blood Oxygen-poor blood

Mitral valve

Aortic semilunar

valve

Coronary sinus


Heartbeat

•  70–80 beats per minute at rest •  Systole—contraction of a heart chamber •  Diastole—expansion/relaxation of a heart

chamber •  Systole and diastole also refer to

•  Stage of heartbeat when ventricles contract and expand

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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 •  Exerts more

pumping force •  Flattens right

ventricle into a crescent shape

Figure 19.11

Right ventricle

Left ventricle

Interventricular septum


Cardiac Muscle Tissue

•  Forms a thick layer called myocardium •  Striated like skeletal muscle •  Contractions pump blood through the heart

and into blood vessels •  Contracts by sliding filament mechanism


Cardiac Muscle Tissue •  Cardiac muscle cells

•  Short •  Branching •  Have one or two nuclei •  Not fused colonies like skeletal muscle

•  Cells join at intercalated discs •  Complex junctions •  Form cellular networks

•  Cells are separated by delicate endomysium •  Binds adjacent cardiac fibers •  Contains blood vessels and nerves



•  Intercalated discs—complex junctions •  Adjacent sarcolemmas interlock •  Possess three types of cell junctions • Desmosomes • Fasciae adherans—long desmosome-like

junctions • Gap junctions


Fasciae adherens Gap junctions

Microscopic Anatomy of Cardiac Muscle

Figure 19.12

Nucleus Intercalated discs Cardiac muscle cell

(a)

Nucleus

Nucleus

I band A band

Cardiac muscle cell

Sarcolemma

Z disc

Mitochondrion

Mitochondrion

T tubule Sarcoplasmic reticulum

I band

Intercalated disc

(b)

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•  Muscle triggered to contract by Ca2+ entering the sarcoplasm •  Action potential signals along sarcolemma

and t-tubules cause sarcoplasmic reticulum to release Ca2+ ions

•  Ions diffuse to sarcomeres • Trigger sliding filament mechanism



•  Not all cardiac cells are innervated •  These cells will contract in rhythmic manner

without innervation •  They possess an inherent rhythmicity • This is the basis for rhythmic heartbeat


Conducting System

•  Cardiac muscle tissue has intrinsic ability to: •  Generate and conduct impulses •  Signal these cells to contract rhythmically

•  Conducting system •  A series of specialized cardiac muscle cells

that organize the beat of the contractile cells •  Sinoatrial (SA) node sets the inherent rate of

contraction: it beats the fastest, so the rest of the myocardium follows


Conducting System

Figure 19.14

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

Internodal pathway

Superior vena cava Right atrium

Left atrium

Purkinje fibers

Inter- ventricular septum

The impulses pause (0.1 sec) at the atrioventricular (AV) node. The atrioventricular (AV) bundle connects the atria to the ventricles.

The bundle branches conduct the impulses through the interventricular septum. The Purkinje fibers stimulate the contractile cells of both ventricles.

1

2

3

4

5


Thoracic spinal cord

The vagus nerve (parasympathetic) decreases heart rate. Cardioinhibitory

center Cardio- acceleratory center

Sympathetic cardiac nerves increase heart rate and force of contraction.

Medulla oblongata

Sympathetic trunk ganglion

Dorsal motor nucleus of vagus

Sympathetic trunk

AV node

SA node

Parasympathetic fibers Sympathetic fibers Interneurons

Innervation

•  Heart rate is altered by external controls

•  Nerves to the heart include •  Visceral sensory

fibers •  Parasympathetic

branches of the vagus nerve

•  Sympathetic fibers—from cervical and upper thoracic chain ganglia

Figure 19.15 Copyright © 2011 Pearson Education, Inc.

Blood Supply to the Heart

•  Functional blood supply •  Coronary arteries

•  Arise from the aorta •  Located in the coronary sulcus •  Main branches

•  Left and right coronary arteries (these are the first branches off of the ascending aorta) •  --> left coronary artery branches into anterior interventricular*

art. •  and the circumflex artery •  --> right coronary artery branches into marginal art. and •  posterior interventricular* artery

•  (*or descending)

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Blood Supply to the Heart

Figure 19.16

Right ventricle

Right coronary artery

Right atrium

Right marginal artery

Posterior interventricular artery

Anterior interventricular artery

Circumflex artery

Left coronary artery

Aorta

Anastomosis (junction of vessels)

Left ventricle

Superior vena cava

(a) The major coronary arteries

Left atrium

Pulmonary trunk

Superior vena cava

Anterior cardiac veins

Small cardiac vein

Middle cardiac vein

Great cardiac vein Coronary sinus

(b) The major cardiac veins


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

• Occur in episodes characterized by • Anxiety, fatigue, shortness of breath,

palpitations


Development of the Heart

•  Heart folds into thorax region about Day 20–21

•  Heart starts pumping about Day 22 •  Earliest heart chambers are unpaired •  From “tail to head,” the chambers are •  Sinus venosus •  Atrium •  Ventricle •  Bulbus cordis

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•  Sinus venosus—will become •  Smooth-walled part of right atrium, coronary

sinus, and SA node •  Also contributes to back wall of left atrium

•  Atrium—will become •  Ridged parts of right and left atria



•  Ventricle—is the strongest pumping chamber •  Gives rise to the left ventricle

•  Bulbus cordis •  Bulbus cordis and truncus arteriosus give rise

to the pulmonary trunk and first part of aorta •  Bulbus cordis gives rise to the left ventricle


Heart Development

Figure 19.17

(d) Day 28: Bending continues as ventricle moves caudally and atrium moves cranially.

(e) Day 35: Bending is complete.

Atrium

Venous end

Arterial end Aorta Superior vena cava

Inferior vena cava

Ductus arteriosus Pulmonary trunk Foramen ovale

Ventricle

(a)Day 20: Endothelial tubes begin to fuse.

(b) Day 22: Heart starts pumping.

(c) Day 24: Heart continues to elongate and starts to bend.

Tubular heart Ventricle

Ventricle Venous end

Arterial end 4a 4

3 2 1


Congenital Heart Defects

•  Can be traced to month 2 of development •  Most common defect is ventricular septal

defect •  Two basic categories of defect •  Inadequately oxygenated blood reaches body

tissues •  Ventricles labor under increased workload


Congenital Heart Defects

Figure 19.18

Occurs in about 1 in every 500 births


Narrowed aorta


(a) Ventricular septal defect. The superior part of the interventricular septum fails to form; thus, blood mixes between the two ventricles. More blood is shunted from left to right because the left ventricle is stronger.

(b) Coarctation of the aorta. A part of the aorta is narrowed, increasing the workload of the left ventricle.

(c) Tetralogy of Fallot. Multiple defects (tetra = four): (1) Pulmonary trunk too narrow and pulmonary valve stenosed, resulting in (2) hypertrophied right ventricle; (3) ventricular septal defect; (4) aorta opens from both ventricles.


The Heart in Old Age

•  Heart usually functions well throughout life •  Regular exercise increases the strength of

the heart •  Aerobic exercise can help clear fatty deposits

in coronary arteries

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The Heart in Old Age

•  Age-related changes 1.  Hardening and thickening of heart valve

cusps 2.  Decline in cardiac reserve 3.  Fibrosis of cardiac muscle

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