heart anatomy - linkpublishing.com · heart anatomy author: stephen g. davenport created date:...

7/5/02 Stephen G Davenport 1

Heart Anatomy

Copyright 1999, Stephen G. Davenport, No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form without prior written permission.


Overview of Cardiovascular System• Cardiovascular system

consists of heart and vascular system

• Vascular system consists of circuits

• Major circulations include:– Systemic circuit– Pulmonary circuit


Coronary Circulation

• Major supply vessels are the right and left coronary arteries– Arise from base of aorta (just superior to aortic

semilunar valve)– Encircle the heart in atrioventricular groove

• Blood delivery is most efficient when the heart is relaxed– Contraction compresses the vessels– Valve flaps (aortic semilunar valve) which are open

during heart contraction partially block openings to coronary vessels


Location of Heart• Enclosed within mediastinum from 2nd rib

to 5th intercostal space• Rests of diaphragm• Two thirds located to left of mid-sternal

line• Base points toward right shoulder• Apex points toward left hip


Membranes of Heart• Pericardial sac (protects and is a site of

attachment to surrounding structures)– Double walled:

• Fibrous pericardium is outer region• Serous pericardium completely surrounds heart. Its

two regions are the parietal and visceral layers– Parietal layer lines fibrous layer of pericardial

sac– Visceral layer is located on surface of heart

• Pericardial cavity is located between visceral and parietal layers

– Contains serous fluid for reduction of friction


Heart and Pericardial Cavity• Pericarditis

• Inflammation of the pericardium. At onset characterized by friction murmur then followed by effusion of fluid and swelling of precordia (epigastric region and lower thorax)

• Cardiac tamponade (tam"pon-ad')• Acute compression of the heart due to fluid

or blood accumulation in the pericardial cavity


Heart Wall• Wall of heart consists of three layers:

– 1. Epicardium is the visceral layer of the serous pericardium

– 2. Myocardium is a layer of cardiac muscle and its associated connective tissues

• Cardiac muscle is contractile tissue and individual fibers (cells) are electrically coupled with gap junctions. End junctions are called intercalated discs.


Heart Wall 2. Myocardium (continued)

Fibrous skeleton of the myocardium is formed by fibrous connective tissues: – anchors the cardiac fibers (cells)– organizes the muscle into spirally and circularly arranged

bundles– supports the attachment of major blood vessels– forms the framework of the heart’s valves– forms an electrical barrier; thus, the heart has its own

conduction system3. Endocardium is innermost layer

– Endothelium (simple squamous epithelium and its basement membrane)

– Lines the muscle, valves, and is continuous with endothelium of blood vessels


Four Chambers of the Heart• Atria (right and left) are receiving chambers

– Right atrium receives blood low in oxygen from the body by way of the superior and inferior venae cavaeand from the heart’s myocardium by way of the coronary sinus

– Left atrium receives high oxygen blood from the lungs by way of the right and left pulmonary veins

• Ventricles (right and left) are discharging chambers– Right ventricle pumps blood to lungs (pulmonary

circulation) by way of pulmonary trunk– Left ventricle pump blood to body (systemic

circulation) by way of aorta (ascending)


Atria• The term atrium applies to a receiving chamber of

the heart (atria is pleural)• The term auricle applies to the wrinkled muscular

wall of an atrium• The atria are separated by an interatrial septum.• A slight depression called the fossa ovalis is

located within the interatrial septum. The fossa ovalis is a remnant of a fetal opening called the foramen ovale. In fetal circulation the foramen ovale allowed some blood to pass directly from the right atrium into the left atrium.


Ventricles• Wall of ventricles make up most of the

mass of the heart• Trabeculae carnae are extensions of the

myocardium that forms ridges and bundles associated with the internal ventricular walls

• Papillary muscles are extensions of the myocardium that are associated with the atrioventricular valves


Valves of the Heart

Valves prevent the backflow of bloodValves open and close in relation to blood

pressure gradientsTwo sounds result from valves closure

– Lub is first sound and results when AV valves close

– Dub is second sound and results when SL valves close


AV Valves • Two atrioventricular (AV) valves each located

between an atrium and its respective ventricle• Tricuspid (three cusps) on right side

– Opens when r. atrial pressure is greater than r. ventricular– Closes when r. ventricular pressure is greater than r. atrial

• Bicuspid (two cusps), commonly called mitral, on left side– Opens when l. atrial pressure is greater than l. ventricular– Closes when l. ventricular pressure is greater than l. atrial


AV Valves (continued)

• Sound associated with closure of AV valves is called the first heart sound, lub

• Each AV has chordae tendineae (tendinous cords) that connect to extensions of myocardium called papillary muscless.

• Papillary muscles do not pull the AV valves open. Along with their attached chordae tendoneae they provide a mechanism to keep the cusps in a closed position


SL Valves of Heart• Semilunar (SL) valves

– Each located between a ventricle and the major vessel that exits the respective ventricle

– They do not have chordae tendineae nor papillary muscles

– Each consists of three crescent moon shaped cusps (semilunar)

• Pulmonary semilunar valve is located on right side between right ventricle and pulmonary trunk. It prevents backflow of blood from pulmonary trunk into right ventricle

• Aortic semilunar is located on left side and prevents backflow of blood from aorta into left ventricle


Heart : Contraction, Valves, Sounds

• Which side of the heart is shown?

• Which (if any) chamber is contracting?

• When will the AV valve close?

• When will the semilunar valve open?

• What produces heart sounds?


Heart: Contraction, Valves, Sounds

• Which side of the heart is shown?

• Which (if any) chamber is contracting?

• When did the AV valve close?• When did the semilunar valve

open?• What produces heart sounds?

heart anatomy - linkpublishing.com · heart anatomy author: stephen g. davenport created date:...

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