Fundamentals of Anatomy and Physiology

Laboratory Exercise: The Cardiovascular System

PERICARDIUM^

Fibrous

pericardium

Serous

pericardium

(parietal layer)

Space

Epicardium

(visceral layer)^

(serous pericardium

of the heart)

MYOCARDIUM

(muscle layer)

ENDOCARDIUM

(inner endothelial

lining covering

trabeculae)

(^) ®
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Figure 14- 2 The layers of the pericardial sac (left) and the layers of the walls of the heart
(right).
Myocardium
Endocardium
Myocardium
Epicardium
(^) ®
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Figure 14- 3 The walls of the heart.
The Chambers of the Heart
The inside of the heart is divided into four chambers that
receive blood from various parts of the body (Figure 14-4).
The two upper chambers are called the right atrium
(RITE AY-tree-um) and the left atrium. Each atrium has
an external appendage called an auricle (AW-rih-kl),
named because of its similarity to the ear of a dog (see
Figure 14-1). The auricle increases the volume of the
atrium. The lining of each atrium is smooth, except for
the anterior atrial walls and the lining of the two au-ricles,
which contain projecting muscle bundles called the
musculi- (MUSS-kyoo-lye) pectinati (pek-tin-NAY-tye)
that give the auricles their rough appearance. The two atria
are separated from each other by an internal inter-atrial
septum.
The lower two chambers are called the right ventricle
(RITE VEN-trih-kl) and the left ventricle. The two ventri-
cles are separated from one another by an internal inter-
ventricular septum. The irregular ridges and folds of the