Fundamentals of Anatomy and Physiology

The Cardiovascular Circulatory System (^325)
(^) Heart (^)
has a specific performs specific (^)
Structure enables Functions (^)
(^) require (^)
See Concept (^)
Map (^)
14 - 1. Ventricular Atrial (^)
contraction^ contraction^
(^) provides (^)
blood for (^)
(^) after (^)
Expulsion (^)
of blood Cardiac Reception (^)
(to output of blood (^)
tissues) (from (^)
tissues) (^)
®^
amount
Lear ni ng^
expelled
is
Cen gage^
(^)
©^
CONCEPT Map 14- 2 The heart.. (^)
because the heart beats about 72 times a minute. It is a
unique organ in that it can contract, rest, and immedia- tely
contract again during our entire lifetime. The system has a
series of valves that prevent blood from backflow-ing
through the blood vessels. It is our pumping heart that helps
keep us alive and healthy.
The Anatomy of the Heart
The heart is positioned obliquely between the lungs in the
mediastinum (Figure 14-1). About two-thirds of its bulk
lies to the left side of the midline of the body. It is shaped
like a blunt cone. It is about the size of a closed fist. It is
approximately 5 inches long (12 cm), 3.5 inches wide at its
broadest point (9 cm), and 2.5 inches thick (6 cm).
It is enclosed in a loose fitting serous membrane known
as the pericardial (pair-ih-CAR-dee-al) sac, which
can also be referred to as the parietal pericardium. The
pericardial sac is made up of two layers (Figure 14-2). The
outermost layer is the fibrous layer or fibrous peri-
cardium (FYE-bruss pair-ih-CAR-dee-um). It is made of
tough fibrous connective tissue and connects to the large
blood vessels that enter and leave the heart (the venae
cavae, aorta, pulmonary arteries, and veins), to the dia-
phragm muscle, and to the inside of the sternal wall of the
thorax. It prevents overdistention of the pumping heart by
acting as a tough protective membrane sur-rounding the
heart. It also anchors the heart in the medi-astinum. The
innermost layer of the pericardial sac is the serous layer or
serous pericardium. This layer is thin and delicate. It is
continuous with the outermost layer of the wall of the heart,
called the epicardium, at the base of the heart. It is also
continuous with the large blood vessels of the heart and is
also known as the parietal layer of the pericardial sac.