HEART
ANATOMY
• Plan : 1 Introduction in angiology.
•
2 The arterial system.
•
3 The structure of arteries.
•
4 The structure of veins.
•
5 The structure of heart
•
6 Circulation.
Characteristics and Functions of the Heart
Ensures the unidirectional flow of blood through both the heart and the blood
vessels.
Backflow of blood is prevented by valves within the heart.
Acts like two independent, side-by-side pumps that work independently but at
the same rate. (double circuit)
one directs blood to the lungs for gas exchange
the other directs blood to body tissues for nutrient delivery
POSITION
• Lies within the pericardium in middle mediastinum
• Behind the body of sternum and the 2nd to 6th costal
• cartilages
• In front of the 5th to 8th thoracic vertebrae
• A third of it lies to the right of median plane and 2/3 to
• the left
• Anterior to the vertebral column, posterior to the sternum
EXTERNAL CHARACTERISTICS
• A hollow muscular organ, pyramidal in shape , somewhat larger than
a closed fist; consists of four chambers (right and left atria, right and
left ventricles)
• Cardiac Apex is formed by left ventricle and is directed downwards
and forwards to the left. It lies at the level of the fifth left intercostal
space, 1~2cm medial to the left midclavicular line (9cm from the
midline)
EXTERNAL CHARACTERISTICS
• The apex beat «point of maximum impulse (PMI)», is
the furthermost point outwards (laterally) and
downwards (inferiorly) from the sternum at which the
cardiac impulse can be felt.
• Lateral and/or inferior displacement of the apex beat
usually indicates enlargement of the heart, called
cardiomegaly
• Approximately the size of your fist
• Wt. = 250-300 grams
• Cardiac base is formed by the left atrium and to a small
extent by the right atrium. It faces backward, upward
and to the right
Two surfaces:
1. Sternocostal surface is formed mainly by the right atrium and right
ventricle, and a lesser portion of its left is formed by the left auricle
and ventricle. It is directed forwards and upwards.
2. Diaphragmatic surface is formed by the ventricles – chiefly by the
left ventricle, directed backwards and downwards, and rests upon
the central tendon of the diaphragm.
Three borders:
1. Right border - vertical, is formed entirely by right atrium.
2. Left border - round, is mainly formed by the left ventricle and partly
by the left auricle.
3. Inferior border - horizontal, is formed by the right ventricle and
cardiac apex
GROOVS:
1. Coronary sulcus (circular sulcus) which marks the division between
atria and ventricles, contains the trunks of the coronary vessels and
completely encircles the heart.
2. Interatrial grooves －separates the two atria and is hidden by
pulmonary trunk and aorta in front.
3. Interventricular grooves － anterior and posterior, mark the
division between ventricles (which separates the RV from the LV),
the two grooves extend from the base of the ventricular portion to
a notch called: the cardiac apical incisura.
POSTERIOR VIEW
COVERING OF THE HEART
Pericardiu – a double-walled sac around the heart.
Composed of:
A superficial fibrous pericardium
A deep two-layer serous pericardium
The parietal layer lines the internal surface of the fibrous
pericardium
The visceral layer or epicardium lines the surface of the heart
They are separated by the fluid-filled pericardial cavity called
the pericardial cavity
Protects and anchors the heart
Prevents overfilling of the heart with blood
Allows for the heart to work in a relatively friction-free
environment
LAYERS OF THE HEART WALL
• Epicardium – visceral pericardium
• Myocardium – cardiac muscle layer forming the bulk of the heart
• Endocardium – endothelial layer of the inner myocardial surface
FRONTAL SECTION
ATRIA OF THE HEART
• Atria - receiving chambers of the heart
oReceive venous blood returning to heart
oSeparated by an interatrial septum (wall)
oForamen ovale - opening in interatrial septum in
fetus
oFossa ovalis - remnant of foramen ovale
• Each atrium has a protruding auricle
• Pectinate muscles mark atrial walls
• Pump blood into ventricles
• Blood enters right atria from superior and inferior venae
cavae and coronary sinus
• Blood enters left atria from pulmonary veins
VENTRICLE OF THE HEART
Ventricles are the discharging chambers of the heart
Papillary muscles and trabeculae carnea muscles mark ventricular walls
Separated by an interventricular septum
Contains components of the conduction system
Right ventricle pumps blood into the pulmonary trunk
Left ventricle pumps blood into the aorta
Thicker myocardium due to greater work load
Pulmonary circulation supplied by right ventricle is a much low pressure system
requiring less energy output by ventricle
Systemic circulation supplied by left ventricle is a higher pressure system and
thus requires more forceful contractions
Structure of Heart Wall
• Left ventricle – three times
thicker than right
• Exerts more pumping force
• Flattens right ventricle into a
crescent shape
SEPTUMS/FIBROUS SKELETON
Interatrial septum
• Located between right and left atria
• Contains fossa ovalis
Interventricular septum
• Located between right and left ventricles
• Upper membranous part
• Thick lower muscular part
Fibrous skeleton
• Fibrous rings that surround the atrioventricular,
pulmonary, and aortic orifices
• Composed of dense connective tissue
• Main point of insertion for cardiac muscle
HEART VALVES
• Heart valves ensure unidirectional blood flow through
the heart
oComposed of an endocardium with a connective
tissue core
• Two major types
oAtrioventricular valves
oSemilunar valves
• Atrioventricular (AV) valves lie between the atria and the
ventricles
oR-AV valve = tricuspid valve
oL-AV valve = bicuspid or mitral valve
• AV valves prevent backflow of blood into the atria when
SEMILUNAR HEART VALVES
• Semilunar valves prevent backflow of blood into the ventricles
• Have no chordae tendinae attachments
• Aortic semilunar valve lies between the left ventricle and the aorta
• Pulmonary semilunar valve lies between the right ventricle and
pulmonary trunk
• Heart sounds (“lub-dup”) due to valves closing
o “Lub” - closing of atrioventricular valves
o “Dub”- closing of semilunar valves
Tricuspid valve
• Guards right atrioventricular orifice
• Three triangular cusps: anterior, posterior and septal, the base of cusps are
attached to fibrous ring surrounding the atrioventricular orifice
• Chordae tendineae － fine, white, connective tissue cords, attach margin of
cusps to papillary muscles
Mitral valve
• Guards left atrioventricular orifice
• Two triangular cusps － anterior and posterior with Similar structures to
those of right
Valve of pulmonary trunk
• Guards the orifice of pulmonary trunk
• Has three semilunar cusps – each with free border
CONDUCTING SYSTEM OF THE HEART
• Cardiac muscle tissue has intrinsic ability to:
vGenerate and conduct impulses
vSignal these cells to contract rhythmically
• Conducting system
vA series of specialized cardiac muscle cells
vSinoatrial (SA) node sets the inherent rate of contraction
CONDUCTING SYSTEM OF THE HEART
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
Innervation
Sinuatrial node (SA node)
• Called the pacemaker cell (P cell)
• Located at the junction of right atrium and superior vena cava, upper part of
the sulcus terminalis, under the epicardium.
Atrioventricular node (AV node)
• Located in the lower part of interatrial septum just above the orifice of
coronary sinus, under the endocardium
• Lower part related to membranous part of interventricular septum
Atrioventricular bundle (AV bundle)
• Passes forward through right fibrous trigon to reach inferior border of
membranous part
• Divides into right and left branches at upper border of muscular part of
interventricular septum
MAJOR VESSELS OF THE HEART
Vessels returning blood to the heart include:
• Superior and inferior venae cavae
o Open into the right atrium
o Return deoxygenated blood from body cells
• Coronary sinus
o Opens into the right atrium
o Returns deoxygenated blood from heart muscle (coronary veins)
• Right and left pulmonary veins
o Open into the left atrium
o Return oxygenated blood from lungs
Vessels conveying blood away from the heart include:
• Pulmonary trunk
o Carries deoxygenated blood from right ventricle to lungs
o Splits into right and left pulmonary arteries
• Ascending aorta
o Carries oxygenated blood away from left atrium to body organs
o Three major branches
§ Brachiocephalic
§ Left common carotid
§ Left subclavian artery
BLOOD FLOW THROUGH THE HEART
Pathway of Blood
Through the Heart
and Lungs
Coronary Circulation
• The functional blood supply to the heart muscle itself
• R and L Coronary arteries are 1st branches off the ascending aorta
• Coronary sinus (vein) empties into R. atrium
• Collateral routes ensure blood delivery to heart even if major vessels
are occluded
Coronary Circulation - Arteries
• Right Coronary Artery
o Supplies blood to
§ Right atrium and posterior surface of both
ventricles
o Branches into the
§ Marginal artery - extends across surface of R.
ventricle
§ Posterior interventricular artery
• Left Coronary Artery
o Supplies blood to
§ Left atrium and left ventricle
o Branches into
§ Circumflex artery
§ Anterior interventricular artery
Coronary Circulation - Veins
Coronary sinus
• Vein that empties into right atrium
• Receives deoxygenated blood from:
o Great cardiac vein - on anterior surface
o Posterior cardiac vein
§ Drains area served by circumflex
o Middle cardiac vein
§ Drains area served by posterior interventricular
artery
o Small cardiac vein
§ Drains blood from posterior surfaces of right
atrium and ventricle