660
UNIT 4
Maintenance of the Body
18
lines the internal surface of the fibrous pericardium. At the su-
perior margin of the heart, the parietal layer attaches to the large
arteries exiting the heart, and then turns inferiorly and contin-
ues over the external heart surface as the
visceral layer
, also
called the
epicardium
(“upon the heart”), which is an integral
part of the heart wall.
Between the parietal and visceral layers is the slitlike
peri-
cardial cavity
, which contains a film of serous fluid. Te serous
membranes, lubricated by the fluid, glide smoothly past one an-
other, allowing the mobile heart to work in a relatively friction-
free environment.
Coverings of the Heart
Te heart is enclosed in a double-walled sac called the
peri-
cardium
(per
0
ĭ-kar
9
de-um;
peri
5
around,
cardi
5
heart)
(Figure 18.3)
. Te loosely fitting superficial part of this sac
is the
fibrous pericardium
. Tis tough, dense connective tis-
sue layer (1) protects the heart, (2) anchors it to surrounding
structures, and (3) prevents overfilling of the heart with blood.
Deep to the fibrous pericardium is the
serous pericardium
,
a thin, slippery, two-layer serous membrane that forms a closed
sac around the heart (see Figure 1.10, p. 19). Its
parietal
layer
Heart
Posterior
Left lung
Body of T
7
vertebra
Location of
apical
impulse
Diaphragm
(a)
(b)
(c)
Superior
vena cava
Sternum
2nd rib
Midsternal line
Left lung
Aorta
Parietal
pleura (cut)
Pericardium
(cut)
Pulmonary
trunk
Diaphragm
Apex of
heart
Mediastinum
Figure 18.2
Location of the heart in the mediastinum.
(a)
Relationship of the heart to the
sternum, ribs, and diaphragm in a person who is lying down (the heart is slightly inferior to this
position in a standing person).
(b)
Inferior view of a cross section showing the heart’s relative
position in the thorax.
(c)
Relationship of the heart and great vessels to the lungs.
previous page 694 Human Anatomy and Physiology (9th ed ) 2012 read online next page 696 Human Anatomy and Physiology (9th ed ) 2012 read online Home Toggle text on/off