Copyright © 2010 Pearson Education, Inc. Marieb Chapter 18 Part A: The Heart CABG.

Copyright © 2010 Pearson Education, Inc.

Marieb Chapter 18 Part A: The Heart

CABG


How Hard Does Our Heart Work?

Copyright © 2010 Pearson Education, Inc. Figure 18.2

Fibrous pericardium

Parietal layer ofserous pericardiumPericardial cavity

Epicardium(visceral layerof serouspericardium)Myocardium

Endocardium

Pulmonarytrunk

Heart chamber

Heartwall

Pericardium

Myocardium


Layers of the Heart Wall

1. Epicardium — visceral layer of the serous pericardium

2. Myocardium - contractile muscle and conduction system

• Fibrous skeleton of the heart: crisscrossing, interlacing layer of connective tissue

• Anchors cardiac muscle fibers

• Supports great vessels and valves

• Limits spread of action potentials to specific paths (non-conductive)

• Provides a framework so muscles don’t affect each other when they contract

3. Endocardium is continuous with blood vessel endothelium

Copyright © 2010 Pearson Education, Inc. Figure 18.4b

(b) Anterior view

Brachiocephalic trunk

Superior vena cava

Right pulmonaryarteryAscending aortaPulmonary trunk

Right pulmonaryveins

Right atrium

Right coronary artery(in coronary sulcus)Anterior cardiac vein

Right ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava

Left common carotidarteryLeft subclavian artery

Ligamentum arteriosum

Left pulmonary artery

Left pulmonary veins

Circumflex artery

Left coronary artery(in coronary sulcus)

Left ventricle

Great cardiac vein

Anterior interventricularartery (in anteriorinterventricular sulcus)

Apex

Aortic arch

Auricle ofleft atrium

Copyright © 2010 Pearson Education, Inc. Figure 18.4e

Aorta

Left pulmonaryarteryLeft atriumLeft pulmonaryveins

Mitral (bicuspid)valve

Aortic valve

Pulmonary valveLeft ventricle

Papillary muscleInterventricularseptumEpicardiumMyocardiumEndocardium

(e) Frontal section

Superior vena cava

Right pulmonaryarteryPulmonary trunk

Right atrium

Right pulmonaryveinsFossa ovalisPectinate muscles

Tricuspid valveRight ventricle

Chordae tendineae

Trabeculae carneae

Inferior vena cava


Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood

Capillary bedsof lungs wheregas exchangeoccurs

Capillary beds of allbody tissues wheregas exchange occurs

Pulmonary veinsPulmonary arteries

PulmonaryCircuit

SystemicCircuit

Aorta and branches

Left atrium

Heart

Left ventricleRight atrium

Right ventricle

Venae cavae

Two Circuits


Pathway of Blood Through Circuits

• Equal volumes of blood are pumped to the pulmonary and systemic circuits

• Pulmonary circuit is a short, low-pressure circulation

• Systemic circuit blood encounters much resistance in the long pathways

• Anatomy of the ventricles reflects these differences (LV size >>> RV size)

• Coronary circuit is a part of the


Rightventricle

Leftventricle

Interventricularseptum


Coronary Circuit

• The functional blood supply to the heart muscle itself

• Arteries connect to other arteries via anastomoses (junctions) (ex: R and L coronary circulations)

• On surface:

• In the muscle:

• RT coronary artery serves:

• L coronary artery serves:

Copyright © 2010 Pearson Education, Inc. Figure 18.7a

Rightventricle

Rightcoronaryartery

Rightatrium

Rightmarginalartery

Posteriorinterventricularartery

Anteriorinterventricularartery

Circumflexartery

Leftcoronaryartery

Aorta

Anastomosis(junction ofvessels)

Leftventricle

Superiorvena cava

(a) The major coronary arteries

Left atrium

Pulmonarytrunk

Copyright © 2010 Pearson Education, Inc. Figure 18.7b

Superiorvena cava

Anteriorcardiacveins

Small cardiac vein

Middle cardiac vein

Greatcardiacvein

Coronarysinus

(b) The major cardiac veins

Copyright © 2010 Pearson Education, Inc. Figure 18.4d

(d) Posterior surface view

Aorta

Left pulmonaryartery

Left pulmonaryveinsAuricle of leftatriumLeft atrium

Great cardiacvein

Posterior veinof 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

Posteriorinterventricularartery (in posteriorinterventricular sulcus)Middle cardiac veinRight ventricle


Homeostatic Imbalances• Angina pectoris

• Occurs because of atherosclerosis in coronary arteries

• Emotion, physical stress, etc. cause HR and contractility to increase

• Clogged arteries can’t meet the demand for oxygen and nutrients

• Thoracic pain results

• Stop activity, take a vasodilator; pain subsides

• No cell death because it is a temporary situation

• Sign of CAD


Homeostatic Imbalances• Myocardial infarction (heart attack)

• Prolonged coronary blockage

• Plaque alone

• Plaque + clot

• Plaque embolizes

• Vessel spasm

• Areas of cell death are repaired with non-contractile scar tissue


What Happens After A MI?

• Dead cells are replaced by non-contractile scar tissue (collagen)

•Non-contractile

•Non-conductive

•Stiffens the heart

• If the heart attack is severe, the heart might go into ventricular fibrillation or not pump well enough to maintain the perfusion of tissues and BP


What Does a MI Look Like?


Heart Valves• Ensure unidirectional blood flow through the heart

• Valves can be damaged by

• Types of damage

• Incompetence/insufficiency

• Stenosis


Heart Valves

Copyright © 2010 Pearson Education, Inc. Figure 18.8a

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valveMitral(left atrioventricular)valveAorticvalve

Pulmonaryvalve

(b)

Pulmonary valveAortic valveArea of cutaway

Mitral valveTricuspid valve

Myocardium

Tricuspid(right atrioventricular)valve

(a)

Mitral(left atrioventricular)valveAortic valve

Pulmonaryvalve

Fibrousskeleton

Anterior


Nucleus

DesmosomesGap junctions

Intercalated discs Cardiac muscle cell

(a)

Microscopic Anatomy of Cardiac Muscle


Microscopic Anatomy of Cardiac Muscle

• Intercalated discs: junctions between cells anchor cardiac cells

• Desmosomes prevent cells from separating during contraction

• Gap junctions allow ions to pass; electrically couple adjacent cells

• Heart muscle behaves as a functional syncytium ( )

Copyright © 2010 Pearson Education, Inc. Marieb Chapter 18 Part A: The Heart CABG.

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