Cardiovascular SystemThe Heart
Anatomy Chap. 21
The Cardiovascular system is comprised
of the heart, blood vessels, & blood
 The heart acts as a “pump”, creating
pressure which causes blood to move
through the blood vessels of the body,
allowing O2 & nutrients to be distributed
to, & wastes removed from, body tissues

Heart Anatomy Overview
Play Heart Anatomy video
Anatomical Features of the Heart


The heart lies within the
mediastinum of the thoracic cavity
Hollow muscular organ with four
internal chambers
 (2) atria (lt. atrium & rt. atrium)receive blood from veins
 (2) ventricles (lt. ventricle & rt.
ventricle)- pump blood into
arteries
Superior aspect of heart is the “base” (3rd intercostal
space/sternal angle), where the blood vessels attach;
Inferior is the “apex” (5th intercostal space), which rests
on the relaxed diaphragm

Pericardium

The heart lies enclosed within pericardial
membranes
pericardium (pericardial sac) – outer layer
of dense CT that protects & anchors
 Serous pericardium – double layered membrane
with “pericardial fluid” between
 Fibrous


Parietal pericardium – lines the pericardial sac
Visceral pericardium – covers the heart; also known as
the “epicardium”
Layers of Heart Wall
 Epicardium (a.k.a. visceral pericardium)
 Myocardium
 Endocardium
Cardiac
muscle
tissue
Because of the characteristics of cardiac
muscle tissue & the arrangement of connective
tissue (fibrous skeleton) within the heart, the
heart basically has two functional units:
 the myocardium of the atria (upper chambers)
act as one functional unit
 the myocardium of the ventricles (lower
chambers) act as the other
This allows the atria to contract simultaneously
while the ventricles are relaxed; then the
ventricles contract simultaneously while the atria
relax
External Features
 Auricles
 Coronary sulcus – contains the
coronary sinus
 Anterior interventricular sulcus –
contains coronary vessels
 Posterior interventricular sulcus –
contains coronary vessels
SVC
Interatrial septum
Fossa ovalis
Pulmonary
veins
Lt Atrium
Rt Atrium
Pectinate
muscles
Bicuspid (mitral)
valve
Coronary sinus
(opening)
Chordae tendineae
Tricuspid valve
Papillary muscle
Chordae tendineae
Papillary muscle
IVC
Deoxygenated
blood
Oxygenated
blood
Atrioventricular
(AV) valves
 Tricuspid
 Bicuspid
Aorta (ascending)
Pulmonary artery
Pulmonary trunk
Pulmonary semilunar
valve
Aortic semilunar valve
Trabeculae
carneae
Lt ventricle
Rt ventricle
Interventricular
septum
Semilunar
valves
Left common carotid artery
Brachiocephalic trunk
Left subclavian artery
Ligamentum arteriosum
Aortic Arch
Pulmonary artery
Pulmonary trunk
Pulmonary semilunar
valve
Aortic semilunar valve
Trabeculae
carneae
Lt ventricle
Rt ventricle
Interventricular
septum
Anatomy
Coronary Circulation
 Myocardium receives oxygenated
blood from the left & right Coronary
arteries – branches off the ascending
aorta
 left coronary artery  anterior
interventricular branch &
circumflex branch
 right coronary artery  marginal
branch & posterior interventricular
branch
 Deoxygenated blood is drained
through Cardiac veins (Great,
posterior, middle & small cardiac
veins), which all eventually
merge and drain into the
coronary sinus
Conducting System
 Intrinsic regulating system that
generates “heartbeat”
 comprised of functionally
specialized “autorhythmic
(conducting) cells” – which can
spontaneously generate action
potentials
 SA node (“pacemaker”)  AV
node  AV bundle (of His) 
Bundle branches  Purkinje
fibers
Movement of blood through heart & heart sounds
 The activity of the conduction system results in the contraction (systole)
& relaxation (diastole) of the heart chambers
 atria will contract as ventricles remain relaxed (atrial systole/ventricular
diastole). Blood moves from atria to ventricles
 as atria relax, ventricles begin to contract (atrial diastole/ventricular
systole). The AV valves (tricuspid & bicuspid/mitral) snap shut to prevent
backflow of blood into atria. The closing of the valves makes a sound –
“Lub”
 as blood moves from ventricles to arteries (pulmonary trunk & aorta),
pressure will increase in the arteries and decrease in the ventricles.
Semilunar valves will then shut  “Dupp” as ventricles relax
 all 4 chambers will be in diastole, and then cycle begins again